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Advanced Structured Materials
Ferdiansyah MahyudinHendra Hermawan Editors
Biomaterials and Medical DevicesA Perspective from an Emerging Country
Advanced Structured Materials
Volume 58
Series editors
Andreas Öchsner, Southport Queensland, AustraliaLucas F.M. da Silva, Porto, PortugalHolm Altenbach, Magdeburg, Germany
More information about this series at http://www.springer.com/series/8611
Ferdiansyah Mahyudin • Hendra HermawanEditors
Biomaterials and MedicalDevicesA Perspective from an Emerging Country
123
EditorsFerdiansyah MahyudinDr. Soetomo HospitalAirlangga UniversitySurabayaIndonesia
Hendra HermawanCHU de Quebec Research CenterLaval UniversityQuebec CityCanada
ISSN 1869-8433 ISSN 1869-8441 (electronic)Advanced Structured MaterialsISBN 978-3-319-14844-1 ISBN 978-3-319-14845-8 (eBook)DOI 10.1007/978-3-319-14845-8
Library of Congress Control Number: 2016930548
© Springer International Publishing Switzerland 2016This work is subject to copyright. All rights are reserved by the Publisher, whether the whole or partof the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations,recitation, broadcasting, reproduction on microfilms or in any other physical way, and transmissionor information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilarmethodology now known or hereafter developed.The use of general descriptive names, registered names, trademarks, service marks, etc. in thispublication does not imply, even in the absence of a specific statement, that such names are exempt fromthe relevant protective laws and regulations and therefore free for general use.The publisher, the authors and the editors are safe to assume that the advice and information in thisbook are believed to be true and accurate at the date of publication. Neither the publisher nor theauthors or the editors give a warranty, express or implied, with respect to the material contained herein orfor any errors or omissions that may have been made.
Printed on acid-free paper
This Springer imprint is published by SpringerNatureThe registered company is Springer International Publishing AG Switzerland
ToAmélie and Maïka (Hermawan)Dhila and Hani (Mahyudin)And our beloved country Indonesia
Preface
In September 2012, about two hundred Indonesian scientists working in the bio-materials field gathered at the first national symposium on biomaterials hosted byBogor Agricultural University in Bogor, Indonesia. A year later, the IndonesianBiomaterials Society1 was officially launched. One of the strong wishes of thisnewly born society was to publish a book as a way to introduce and disseminate theworks of Indonesian biomaterials scientists worldwide. After facing some chal-lenges during the publication process, we finally present this book, “Biomaterialsand Medical Devices: A Perspective from An Emerging Country.”
The book covers the current development and future direction of biomaterialsand medical devices in Indonesia, including the government policies and directives.In particular, it highlights the unique needs of Indonesian healthcare service, theabundant potential for natural resource for biomaterials, and the challenge formedical devices development. Indonesia, with its 255 million population, 900billion USD of GDP with 5 % annual growth, and 72 years of life expectancy is anemerging country having great economic potential. The government has launched anew pro-public universal healthcare program, which at one point stimulates thedevelopment of biomaterials aiming for national independency on producingmedical devices. The book is written by selected Indonesian experts from aca-demics, clinics, and government agencies. It should be viewed as a reference forresearchers directing their research, for industries developing and marketing theirproducts, and for the government setting new policies. The perspectives and thelessons learned from Indonesia could be then adopted for the development ofbiomaterials and medical devices in other emerging countries facing similarchallenges.
1Indonesian Biomaterials Society (Masyarakat Biomaterial Indonesia), is an independentnot-for-profit professional society having an orientation toward the development of science andtechnology of biomaterials and medical devices in Indonesia. Further information can be found at:http://biomaterial.or.id.
vii
We start the book’s coverage with the chapter “Structure and Properties ofBiomaterials” which introduces the structure and properties of biomaterials as anopening to understand the science and technology of biomaterials. Chapter“Naturally Derived Biomaterials and Its Processing” covers biomaterials processingwith special focus on various unconventional methods for synthesizing naturalbiomaterials, where its sources are abundant in Indonesia. The biocompatibilityissues of biomaterials that include cytotoxicity, genotoxicity, in vitro and in vivomodels, and some biocompatibility data extracted from many cases in Indonesia ispresented in chapter “Biocompatibility Issues of Biomaterials.” It is followed by thechapter “Animal Study and Pre-clinical Trials of Biomaterials” reviews the animalstudy and clinical trials of biomaterials, which include animal models for bioma-terial research, ethics, care and use, implantation study and monitoring, andexperiences on animal study of medical implants in Indonesia. Chapter“Bioadhesion of Biomaterials” covers the bioadhesion aspect of biomaterials as oneof the fundamental sciences to understand implant–host interaction. Chapter“Degradable Biomaterials for Temporary Medical Implants” describes degradablebiomaterials as a new generation of materials for temporarily needed medicaldevices, which may find its suitability for lowering the overall cost of implantsurgical procedures. Chapter “Biomaterials in Orthopaedics” covers biomaterialsfor orthopedic applications with special focus on the most common surgicalintervention and type of implants used in Indonesia. Meanwhile, biomaterials indentistry are covered in the chapter “Biomaterials in Dentistry” including its currentstate and development in Indonesia. Chapter “Tissue Bank and Tissue Engineering”covers tissue bank and tissue engineering with the latest status of its institute inIndonesia. And finally, the chapter “Indonesian Perspective on Biomaterials andMedical Devices” concludes the book with a general overview of the IndonesianGovernment policies and directives on biomaterials and medical devices, and thechallenge and opportunity for the development of biomaterials in Indonesia.
We acknowledge Prof. Andreas Öchsner of Griffith University, Australia, aneditor at Springer, who has facilitated the publication process of this book with thepublisher. We sincerely thank all the authors, and the people around them, for theircommitment and tireless efforts in writing their chapters to finally realize our book.We will continue to collaborate and keep our synergy in answering the Indonesianhealthcare challenges via research and development of effective and low-costbiomaterials and medical devices. Hopefully, this book inspires more scientists inIndonesia and other emerging countries to proudly present their high quality worksat the international stage and be the champions beyond their native niche(Indonesian proverb: tidak cuma jago kandang).
Ferdiansyah MahyudinHendra Hermawan
viii Preface
Contents
Structure and Properties of Biomaterials . . . . . . . . . . . . . . . . . . . . . . . 1Sulistioso Giat Sukaryo, Agung Purnama and Hendra Hermawan
Naturally Derived Biomaterials and Its Processing . . . . . . . . . . . . . . . . 23Raden Dadan Ramdan, Bambang Sunendar and Hendra Hermawan
Biocompatibility Issues of Biomaterials . . . . . . . . . . . . . . . . . . . . . . . . 41Widowati Siswomihardjo
Animal Study and Pre-clinical Trials of Biomaterials . . . . . . . . . . . . . . 67Deni Noviana, Sri Estuningsih and Mokhamad Fakhrul Ulum
Bioadhesion of Biomaterials. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103Siti Sunarintyas
Degradable Biomaterials for Temporary Medical Implants . . . . . . . . . . 127Ahmad Kafrawi Nasution and Hendra Hermawan
Biomaterials in Orthopaedics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161Ferdiansyah Mahyudin, Lukas Widhiyanto and Hendra Hermawan
Biomaterials in Dentistry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183Margareta Rinastiti
Tissue Bank and Tissue Engineering . . . . . . . . . . . . . . . . . . . . . . . . . . 207Ferdiansyah Mahyudin and Heri Suroto
Indonesian Perspective on Biomaterials and Medical Devices . . . . . . . . 235Ferdiansyah Mahyudin, Sulistioso Giat Sukaryo,Widowati Siswomihardjo and Hendra Hermawan
ix
Editors and Contributors
About the Editors
Ferdiansyah Mahyudin is lecturer and head of theDepartment of Orthopaedics and Traumatology,Faculty of Medicine, Airlangga University (UniversitasAirlangga or Unair),2 Indonesia, as well as orthopedicsurgeon (musculoskeletal oncology consultant) at Dr.Soetomo General Hospital in Surabaya. He completedhis MD at Sebelas Maret University, orthopedic surgerytraining, and Ph.D. (2010) at Unair and Diploma ontissue bank (2001) at National University of Singapore.His research interests include orthopedic implants,oncology, tissue bank, and stem cells. He is the chair-man of the Indonesian Musculoskeletal Tumor Society.
e-mail: [email protected] or [email protected].
Hendra Hermawan is assistant professor at theDepartment of Materials Engineering with jointappointment at the Axis of Regenerative Medicine,CHU de Québec Research Center, Laval University,Canada. He received his BS and MS from Institute ofTechnology of Bandung (Institut Teknologi Bandungor ITB),3 Indonesia, and Ph.D. (2009) from LavalUniversity. He spent 6 years of industrial postdocand academic works in Europe and Asia beforejoining the present affiliation in 2014. His research
2More about Universitas Airlangga: www.unair.ac.id.3More about Institut Teknologi Bandung: www.itb.ac.id.
xi
interest focuses on metals for biomedical applications. He serves as aneditorial board member of Journal of Orthopaedic Translation (Elsevier). e-mail:[email protected].
About the Contributors
Sri Estuningsih is a veterinarian and lecturer at the Faculty of VeterinaryMedicine (FVM), Bogor Agricultural University (Institut Pertanian Bogor orIPB),4 Indonesia. She obtained her DVM and MS from IPB, and Ph.D. (2001) fromIPB-Justus Liebig Universität, Germany (Sandwich Program). Her research interestfocuses on veterinary pathology including immunosuppression and radiation.e-mail: [email protected]
Ahmad Kafrawi Nasution is lecturer at the Department of MechanicalEngineering, Muhammadiyah University of Riau, Indonesia. He completed his BSat Bung Hatta University, MS at ITB, and Ph.D. (2016) at University ofTechnology of Malaysia (UTM), Malaysia. He has a broad expertise which rangesbetween metallurgy, failure analysis, and metal welding. e-mail:[email protected]
Deni Noviana is a veterinarian and full professor in Surgery and Radiology,FVM IPB. He accomplished his DVM at IPB and Ph.D. (2004) at YamaguchiUniversity, Japan. His expertise lies in diagnostic imaging, echocardiography,ultrasonography, and radiology. He is the executive director of the FVM IPBAnimal Teaching Hospital. e-mail: [email protected]
Agung Purnama is an NSERC postdoctoral fellow at Politecnico di Milano.He received his BS from ITB and Ph.D. (2014) from Laval University. Hehas developed a cross-disciplinary expertise comprising materials engineering,electrochemistry, cardiology, tissue engineering, and molecular biology. e-mail:[email protected]
Raden Dadan Ramdan is lecturer at the Department of Materials Engineering,ITB. He completed his BS at ITB, MS at UTM, and Ph.D. (2009) at KobeUniversity, Japan. His research interests include phase-field simulation, surfacetreatment, and coating for biomaterials, especially the coating of hydroxyapatite ontitanium alloy by high-velocity oxy-fuel processes. e-mail: [email protected]
Margareta Rinastiti is lecturer at the Faculty of Dentistry, Gadjah MadaUniversity (Universitas Gadjah Mada or UGM),5 Indonesia. She completed herDDS, MS, and Specialist in Conservative Dentistry at UGM and Ph.D.(2010) at University of Groningen, Netherlands. Her research interests include
4More about Institut Pertanian Bogor: www.ipb.ac.id.5More about Universitas Gadjah Mada: www.ugm.ac.id.
xii Editors and Contributors
conservative dentistry, minimally invasive dentistry, and composite materials.e-mail: [email protected]
Widowati Siswomihardjo is dentist and full professor at the Faculty of Dentistry,also coordinator of the Department of Biomedical Engineering, School of GraduateStudies, UGM. After finishing her Ph.D. (1999) at Unair, she did a postdoc atUniversity of Melbourne, Australia. Her major interest is in the biocompatibility ofbiomaterials where she collaborates closely with the Faculty of Dentistry,University of Hong Kong. She is one of the leaders in the Indonesian nationalmedical devices projects. e-mail: [email protected]
Sulistioso Giat Sukaryo is researcher in the Center of Science and Technology forAdvanced Materials, National Nuclear Energy Agency of Indonesia (Badan TenagaAtom Nasional or BATAN).6 He completed his BS and MS at ITB. His researchinterest focuses on materials for medical implants ranging from metals, polymers,ceramics to composites, and degradable biomaterials. He utilizes various nucleartechniques for microstructure characterization and mechanical propertiesimprovement of polymers. e-mail: [email protected]
Siti Sunarintyas is lecturer at the Faculty of Dentistry with joint affiliation with theDepartment of Biomedical Engineering, School of Graduate Studies, UGM. Sheobtained her BS from UGM, and MS and Ph.D. (2002) from Unair. Her researchinterests include adhesive materials and fibers for biomedical applications. e-mail:[email protected]
Bambang Sunendar is full professor at the Department of Engineering Physics,ITB. He received his BS from ITB, and MS and Ph.D. (2001) from KeioUniversity, Japan. His research interests are advance material synthesis, biomate-rial, controlled release, and surface modification. He is the head of the advancedmaterials processing laboratory in ITB and a member of the National ResearchCouncil of Indonesia. e-mail: [email protected]
Heri Suroto is lecturer at the Department of Orthopaedics and Traumatology,Faculty of Medicine, Unair, and orthopedic surgeon (hand and microsurgery con-sultant) at Dr. Soetomo General Hospital. He obtained his MD, orthopedic surgerytraining and Ph.D. (2011) from Unair. He is the director of the RegenerativeMedicine and Stem Cell Center in Surabaya and focuses his research on naturallyderived biomaterial, nerve tissue engineering, tendon tissue engineering, and bra-chial plexus injury. e-mail: [email protected]
Mokhamad Fakhrul Ulum is a veterinarian and lecturer at the FVM IPB. Hereceived both his DVM and MS from IPB and Ph.D. (2016) from UTM. He hasdeveloped multidisciplinary expertise comprising in vitro and in vivo testing ofbiomaterials, biomedical imaging, microfluidics, analytical biochemistry, andapplied diagnostics. e-mail: [email protected]
6More about Badan Tenaga Atom Nasional: www.batan.go.id.
Editors and Contributors xiii
Lukas Widhiyanto is lecturer at the Department of Orthopaedics andTraumatology, Faculty of Medicine, Unair, and orthopaedic surgeon atDr. Soetomo General Hospital. He completed his MD and orthopaedic surgerytraining at Unair (1999), fellowship in Spine surgery at Samsung Medical Center,Korea (2013), and Dokkyo Medical University Hospital, Japan (2015). e-mail:[email protected]
xiv Editors and Contributors
Structure and Properties of Biomaterials
Sulistioso Giat Sukaryo, Agung Purnama and Hendra Hermawan
Abstract Biomaterials are materials from which medical devices are made. Basedon their chemical composition, they can be polymers, metals, ceramics or com-posites. Metals are still the most used biomaterials mostly due to their superiormechanical properties and can be found in orthopedic, cardiovascular and dentalimplants. However, many type of implants can only work properly when polymersor ceramics are also used in pair with metals such as in total knee or hip arthro-plasties. Nowadays, biomaterials are no longer seen as inert substances supportingor replacing dysfunctional tissues or organs. They are now required to promote thehealing process and self-disintegrate once the process is completed. All the effortsin searching ideal biomaterials are paid to improve the wellness and health ofhuman beings. This chapter is intended to give a brief introduction to the structureand property of biomaterials.
Keywords Biomaterials � Ceramic � Metal � Polymer � Property � Structure
1 Introduction
In general understanding, biomaterials is defined as any substance, other than adrug, synthetic or natural in origin, which can be used for any period of time, whichaugments or replaces any tissue, organ, or function of the body, in order to maintainor improve the quality of life of an individu (Dee et al. 2003). The use of bio-materials in the modern age was prominent during the World War II following the
S.G. Sukaryo (&)National Nuclear Energy Agency of Indonesia, Tangerang Selatan, Indonesiae-mail: [email protected]
A. Purnama � H. Hermawan (&)Laval University, Quebec City, Canadae-mail: [email protected]
A. Purnamae-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_1
1
need to treat wounded soldiers. Since then, the concept of biomaterials has evolvedconsiderably.
The development of biomaterials involves various disciplines of science. Itengages multidisciplinary fields including material science and engineering, med-ical science, biophysics, chemistry and biology. Biomaterials are now mostlydeveloped under the research in material science and engineering. Metal and alloys,polymer, ceramics and composites are vastly explored and characterized in theeffort to find specific properties that match the requirements of a particular bio-material (Ratner et al. 2013). The development of biomaterials is directed bymedical science as the user of biomaterials. It gives information of what devicesneed to be developed together with their physical, mechanical, chemical, andbiological characteristics. The development of biomaterials is also supported bybiophysics studying the compliance of biomaterials and conducting physicalproperties testing such as, magnetic properties, electrical properties, phase analysisand heat properties. Moreover, the development of biomaterials are strongly relatedto the field of chemistry suggesting the nature of elemental reactivity useful forpredicting the behavior of biomaterials towards their surroundings. Chemistry alsoprovides important idea on surface functionalization and coating of biomaterials.The interaction of cross-disciplinary expertise supporting biomaterials is presentedin Fig. 1.
The translation of biomaterials from bench (laboratory) to bed (patient) requiresa long and rigorous process. Starting from the formulation of specific needs, thesynthesis of materials, design and manufacture of prostheses and clinical testing topass all requirements determined by regulatory agencies such as the United StatesFood and Drug Administration (FDA) or European conformity (CE) agency(Vallet-Regí 2010). The proposed biomaterials will be either granted PremarketApproval (PMA) if substantially similar to one used before (the “me too” devices),or have to go through a series of guided biocompatibility assessments. Figure 2shows the general path of the biomaterials and implants development.
Fig. 1 Diagram of multidisciplinary contribution to biomaterials
2 S.G. Sukaryo et al.
The early generation of biomaterials was designed to be inert, hence providingonly physical support with minimum requirement of compatibility. Nowadays, theconcept of biomaterials has shifted significantly. Biomaterials are now seen asactive substances, not only inert, that support the healing process of an injuredtissue. They come in various forms such as a complex hybrid of composites ormetals coated with different polymers. Usually, a single material goes for a specificapplication. In the early development of biomaterials, there was a limited concernabout how a material would interact with human body since they were consideredinert. However, as the demand for biomaterials kept increasing, the development ofnon-inert biomaterials added a new layer of complexity. Consequently, the need ofa systematic study to assess the compatibility of various materials become impor-tant, permitting a standardized assessment to compare new biomaterials with thepreviously existing ones. The term of biocompatibility was then introduced in thefield. Biocompatibility refers to the ability of a material to perform a particularfunction within living tissues followed by appropriate host responses, minimuminflammatory and toxicity reactions both locally and systematically (Ratner et al.2013). It is thus a complex function of materials, design, applications, hostresponses, etc. Biological properties of biomaterials refers to the biocompatibilityand can be determined using in vitro and in vivo test systems. However, bothapproaches are limited to the results obtained from models, which are not com-pletely represent the human system.
Biomaterials consist of metals, polymers, ceramics, and composites. Eachmaterial possess a unique building block, which determines their biological andmechanical properties. While biological properties are mainly influenced by thesurface property of materials, mechanical properties play significant role in satis-fying the structural requirements of specific biomaterials or implants. Therefore,this chapter serves as a brief introduction to biomaterials focused on the materialsstructure and their mechanical properties.
Fig. 2 A biomaterials development path from basic science to clinical applications. Adapted from(Ratner et al. 2013)
Structure and Properties of Biomaterials 3
2 Metals
Metals are exploited as biomaterials mainly due to their superior mechanicalproperties. They have been widely used in various forms of implants providing therequired mechanical strength and corrosion resistance. They account for 70 %implants including orthopaedic: knee joint, total hip joint, bone plates, fracturefixation wires, pins, screws, and plates; cardiovascular: artificial heart valves,vascular stents, and pacemaker leads (Niinomi et al. 2012). Figure 3 shows twocoronary stents as example of implant made of metal. Although pure metals arewidely used, alloys provide improved strength and corrosion resistance. The maincriteria in choosing metals and alloys for biomedical applications are biocompati-bility, appropriate mechanical properties, good corrosion resistance in body fluid,durable and cost effectivity (Dee et al. 2003).
2.1 Structure and Properties
Metals consist of metallic bonds in which free electrons circulating among theatoms. The circulating electrons provide the transfer of electrical charge and ther-mal conductivity. The movements of free electrons act as the binding force to holdthe positive metal ions together. The strong binding by a close-packed-atomicarrangement results in high specific gravity and high melting points of most metals.Since the metallic bond is essentially unidirectional, the position of the metal ionscan be altered without destroying the crystal structure resulting a plastic deformablesolid (Callister and Rethwisch 2014). Atomic structure of metals resembles blocksof atoms which is ambulatory to each other. When stress is applied, these blocks aredisplaced until the yield stress is reached and large blocks of atoms slip and pass
Fig. 3 Photograph ofcoronary stents (before andafter expansion) made ofstainless steel as an exampleof metal implant (Courtesy ofBiosensors International,Singapore)
4 S.G. Sukaryo et al.
each other. The plane along which movement occurs is called the slip plane. Slipplane movement depends on density of the atom in the slip plane, and depends ofthe crystal system in the metal. Two different crystal systems: face-centered cubic(FCC) and hexagonal close-packed (HCP) structures are shown in Fig. 4.Considering the number of the slip plane, FCC has higher density of slip plane thanother crystal systems and thus more ductile.
Chemical composition is one of the basic ingredients or characteristics of metalswhich determines the formed microstructure and phases, thus their properties suchas physical and mechanical properties. For instance, the addition of aluminum(Al) and vanadium (V) into pure titanium (Ti), to form the Ti-6Al-4 V alloy, greatlyincreases the tensile strength of Ti. Metallurgical state is another characteristic thatdetermine mechanical properties, for example annealed condition offers betterductility than that of cold worked. Finally, metal processing also affects theirmicrostructure and properties. For example, cast metal implants usually possesslower strength than those made by forging. Up to now, the three most used metalsfor implants are stainless steels (notably the 316L type), cobalt-chromium (Co-Cr)alloys and Ti alloys (Niinomi et al. 2012). Table 1 lists common applications ofmetals as biomaterials and Table 2 shows the properties of some metallicbiomaterials.
Fig. 4 Illustration of two crystal structures: a HCP, and b FCC
Table 1 General applications of metals as biomaterials
Alloy type Applications
Stainlesssteels
Joint replacements (hip, knee), bone plate, fixation, dental implant, toothfixation, heart valve, stents, spinal instruments, screws, dental root implant,pacer, fracture plates, hip nails, shoulder prosthesis
Co-Cr alloys Total hip and knee joint replacement, bone plate, fixation, screws, dental rootimplant, pacer, and suture, orthopedic prosthesis, mini boneplates, surgicaltools, dental implants, stents
Ti and itsalloys
Total hip and knee joint replacement, dental implants, tooth fixation, screws,suture, parts for orthodontic surgery, bone plate, screws, artificial heart valvesand heart pacemakers, stents, cochlear replacement
Structure and Properties of Biomaterials 5
2.2 Stainless Steels
Austenitic stainless steels were first used for implants in 1936, as fracture fixationand joint replacement and have scored the longest record of practical use ever since(Jaimes et al. 2010; Niinomi et al. 2012). The advancement in steel refining andalloying technology elevated the grade of 18-8 type stainless steel to the widelyknown AISI 316L (SS316L), which is highly recommended for implant applica-tions since quite long time (Smethurst 1981).
Although the 316L type has adequate physical and mechanical properties andwide availability in various shapes and sizes, some works were done to improve itsbiocompatibility. Electrochemical observation on Fe-Cr-Ni alloys found that thebody environment contributed to some changes in the composition and structure ofthe passive layer formed on the surface, such as Cr2O3 (Jaimes et al. 2010). Thesechanges make the passive layer susceptible to localized corrosion and stress cor-rosion cracking (Talha et al. 2013). Molibdenum (Mo) contributes to stabilize thepassive film and improve the corrosion resistance in chloride solution. However, thebreakdown of passive layer allows the release of metal ions contained in the metals,such as nickel (Ni) and Cr ions. Ni ion is potentially harmful to the human body andmay cause allergic reactions in tissues and also toxicity (Niinomi et al. 2012). Giventhe potential detrimental effect of Ni on the human body, experts recommended tolimit its content in stainless steel for medical applications. In 1992, a new steel,ASTM F1586 (ISO5832-9) was introduced as an orthopedic implant material.
Table 2 Properties of some metallic biomaterials
Material Alloying composition(wt%)
Density(g/cm3)
E(GPa)
YS(MPa)
UTS(MPa)
ε(%)
SS316L max 0.03 C; 13–15 Ni; 17–19Cr; 2.25–3 Mo; balance Fe
7.96 205–210
190 490 40
CoCrMo max 0.5 Ni; 27–30 Cr; 5–7 Mo;balance Co
8.4 227 450 655 8
Ti grade 4 max 0.4 O; max 0.5 Fe; balanceTi
4.5 105 483 550 15
Ti6Al4V 5.5–6.5 Al; 3.5–4.5 V; balanceTi
4.4 110 760–795
825–860
8–10
Ti6Al7Nb 5.5–6.5 Al; 6.5–7.5 Nb; balanceTi
4.52 110 800 900 10
Ti35Nb5Ta7Zr(TNTZ)
35.3 Nb; 5.1 Ta; 7.1 Zr; balanceTi
5.85 55 530 590 21
NiTi 54.5–57 Ni; balance Ti 6.45 20–110
50–800
755–960
10–15
TiNb 40 Nb; balance Ti 6.73 69 616 1421 37.3
Note E = elastic modulus, YS = yield strength, UTS = ultimate tensile strength, ε = elongation.Data compiled from: ASTM F67, ASTM F75, ASTM F136, ASTM F138, ASTM F139, ASTMF1295, ASTM F2063 and (Long and Rack 1998; Calin et al. 2014; Davidson et al. 1994; Navarroet al. 2008; Taarea and Bakhtiyarov 2004)
6 S.G. Sukaryo et al.
This Ni-free alloy contains a high nitrogen (N) and manganese (Mn) to stabilize theaustenitic structure of stainless steel and to improve mechanical properties, corro-sion resistance and biocompatibility (Talha et al. 2013).
2.3 Co-Cr Alloys
Co-Cr alloys are characterized by their high corrosion and wear resistances (Yan et al.2007). They have been widely used for artificial knee joints, artificial hip joints anddental applications (Patel et al. 2012). These alloys can be processed via severalroutes including casting, forging, and powder metallurgy. The most used and com-mercially available alloys are Co-28Cr-6Mo (ASTM F75) for casting version whereasforging versions are named as ASTM F90, ASTM F562, ASTM F799 and ASTMF1537. Further improvement on their wear and corrosion resistance can be achievedby heat treatment and hard surface coating, such as by using laser and electron beamthat produces non-equilibrium microstructures via rapid heating and cooling of thesurface (Walker et al. 2013).
Heat treatments and modification of elemental content could change themicrostructure and alter the electrochemical and mechanical properties of theCo-Cr-Mo alloy. However, cast Co-Cr-Mo alloys have coarse grain and microporosity and brittle σ phase (HCP) formed along the interdendritic region whichdeteriorates their mechanical properties. Therefore, γ phase (FCC) should suppressthe σ phase in order to increase ductility of the Co-Cr-Mo alloys. Adding N sta-bilizes the γ phase and inhibits the σ phase similar to what happened in the FeCrsystem (Lee et al. 2011).
In recent years, the reliability of the mechanical properties of these alloys such astensile strength and fatigue properties has increased considerably through advancesin alloy design and optimization of the deformation process. This reliabilitybecomes so important because of the increasing life expectancy of patients afterartificial knee joint or artificial hip joint surgeries. Currently, joint replacementsurgery is not only performed in elderly but also in younger patients. Thus, theability to engage in sports and fitness activities after undergoing surgery becomes amajor challenge to the failure of artificial joints (Mitsunobu et al. 2014).
It is generally agreed that the important factors affecting the longevity oforthopedic implants are the release of metal ions from the implants and the for-mation of debris which provokes tissue inflammation, bone loss and implantloosening. About 20–30 % of implant material loss were caused by the combinedaction of wear and corrosion known as tribocorrosion (Doni et al. 2013). Thismechanically-assisted electrochemical process constitutes a major concern in theclinical aspects of metal implants. Recent in vivo studies showed that metal ionsand particles are separated due to the friction on Co-Cr-Mo implant and furthercaused damage to the soft tissue (Walker et al. 2013).
Structure and Properties of Biomaterials 7
2.4 Ti and Its Alloys
Originally, Ti and its alloys are developed as an aircraft structural materials, but thecurrent research and development of these alloys is also directed toward biomedicalapplications by reducing the elastic modulus and improving the biological prop-erties (Calin et al. 2014). Ti and its alloys show excellent corrosion resistance andhigh strength to weight ratio compared to stainless steels and Co-Cr alloys. A stableand coherent Ti oxide (TiO2) thin film is formed on Ti surface providing superiorcorrosion resistance. Ti is an allotropic metal where between room temperature and882 °C forms α-phase with HCP structure and above that it transforms to β-phasewith body-centered cubic (BCC) structure (Brandes and Brook 1992). Pure Ticannot be hardened by heat treatment therefore must be alloyed with other elementsto grow precipitates in the single phase matrix. Moreover, they are very attractiveimplant materials because of their high strength to weight ratio and better bio-compatibility compared to other metallic biomaterials. The most known Ti alloy,the Ti-6Al-4V, is considered as having excellent tensile strength and pitting cor-rosion resistance. When alloyed with Ni, Ti-Ni alloy or better known as Nitinol,possesses shape memory effect which is another interesting property used forexample in dental restoration wiring. Ti is featured by its light weight, with densityonly 4.5 g/cm3, compared to 7.9 g/cm3 for 316L stainless steel and 8.3 g/cm3 forcast Co-Cr-Mo alloys (Brandes and Brook 1992). Ti and its alloys for medicalapplications were covered in ASTM standards F67, F136 and F2063.
Ti and its alloys are grouped into: α type, α + β type with elastic modulus of110–120 GPa, and β type with elastic modulus of 60-85 GPa (Niinomi et al. 2012).However, the elastic modulus values are still too high compared to those of humanbone, 10–30 GPa (Calin et al. 2014). This difference can hinder load transferbetween implant and the surrounding bone, known as stress shielding effect. Thiseffect can lead to implant loosening due to the poor bone growth around the implantor the need for revision surgery (Rack and Qazi 2006). Concerns over stressshielding have led to the development of Ti alloys with lower elastic modulus.Alloying with tantalum (Ta), zirconium (Zr), silver (Ag), platinum (Pt), Al, tin (Sn),copper (Cu) and boron (B) improves super-elastic behavior of Ti alloys, whereasadding oxygen (O) or N gives similar effect to Ni-free Ti alloys (Niinomi et al.2012). Lately, addition of indium (In) into Ti-Nb alloy remarkably decreases theelastic modulus (Calin et al. 2014). Single crystal texture of TNTZ alloy possesselastic modulus as low as 35 GPa (Niinomi et al. 2012).
2.5 Other Metallic Biomaterials
Precious metals and alloys such as gold (Au), Ag and Pt and their alloys are mostlyknown in dentistry due to their good castability, ductility and resistance to corrosion.Dental alloys such as Au-Ag-Cu system, Au-Ag-Cuwith the addition of zinc (Zn) and
8 S.G. Sukaryo et al.
tin known as dental solder, and Au–Pt-Pd system used for porcelain-fused-to-metalfor teeth repairs (John 2000).
Ta and amorphous alloys are among other metals used for implants. The excellentX-ray visibility and low magnetic susceptibility of Ta, makes it often used for X-raymarker on stents. Porous Ta, which can be made by using high power lasers, has beenproposed for orthopedic implants claiming a better tissue acceptance (Balla et al.2010). Amorphous alloys show interesting properties compared to its crystallinecounterparts whereas they exhibit a higher corrosion resistance, wear resistance, tensilestrength and fatigue strength. Amorphous alloys like that of Zr-based (Wang et al.2011) with its low Young’s modulus is prospective for miniaturizing metal implants.
3 Polymers
A polymer is a macromolecule composed of many repeated subunits. It has a broadrange of properties and play an essential role in our current daily life. Polymers rangefrom synthetic plastics such as poly(styrene) to natural biopolymers such as DNAand proteins. Due to a large molecular mass relative to small molecule compounds, itproduces unique physical properties, including toughness, viscoelasticity, and atendency to form amorphous structures rather than crystals. Thanks to these features,polymers have been widely used as substitute materials to metals. Figure 5 shows aset of total knee replacement implants as an example of implant with part made ofpolymers. The articulating surface is made of ultra high molecular weight poly(ethylene) (UHMWPE) as its has low coefficient of friction, good chemical resis-tance, resistance to environmental stress cracking, high notched impact strength andhigh energy absorption at high stress rates. However, wear is considered as one ofthe major problems that shorten the life of an UHMWPE artificial knee joint andproduce debris that is responsible for osteolysis (Brach del Prever et al. 2009).
Fig. 5 A set of total knee replacement implants and its fixation (Courtesy of Dr. Soetomo GeneralHospital, Surabaya)
Structure and Properties of Biomaterials 9
3.1 Chain Structure
Both natural and synthetic polymers are created via polymerization of many smallmolecules (monomers) forming a chain structure. Based on its chain structure,polymers are classified as linear, branch, cross-link and network, as seen in Fig. 6.Chemical bonds in a polymer consist of primary and secondary bonds. The primarybonds involve two atoms sharing electrons hence called covalent bonds. The sec-ondary bonds include van der Waals forces, hydrogen and ionic bonds. Primarybonds are 10–100 times stronger when compared to secondary bonds. (Callister andRethwisch 2014). The average length of the polymer chain can be seen from themolecular weight of a polymer which is essentially the sum of the weight of itsmonomer.
The cross-linking structure can be formed by a number of techniques, includinghigh energy radiation. The advantages of radiation processing include the absent ofany chemical residues as no chemical additives are requires to initiate the reactions,applicable at all temperatures, can be targeted on specific area or surface only, and itoffers a combination of synthesis/modification of materials with sterilization(Darwis et al. 2015). Nuclear radiation, such as γ-ray generated from Co60, pro-duces free radicals which lead to break down of chain and cross-linking formationbetween adjacent molecules. The dose of γ radiation is one of the most importantparameters where its increase makes crystallinity decreases and drops significantlyat 100–150 kGy (Lewis 2001). This radiation technique has been applied tocross-link UHMWPE to control the degree of crystallinity thus increase itsmechanical properties and prevent wear.
Unlike metals, polymers in general are amorphous and they are not crystalline innature. However, polymers can be engineered so that its structure can have crys-talline regions, both in the process of synthesis and deformation (Callister and
Fig. 6 Types of polymers chains: linear (1), branch (2), cross-link (3), and network (4)
10 S.G. Sukaryo et al.
Rethwisch 2014). The magnitude of the crystalline regions within a polymer isexpressed as degree of crystallinity. It influences mechanical properties such asstiffness, hardness, and ductility; and physical properties such as optical and densityof the polymers. The degree of crystallinity can be engineered by controllingprocess parameters such as the rate of solidification, although obtaining 100 %value is rather difficult. Polymers with branched chain structure have a lower degreeof crystallinity when compared with unbranched structures. The structure of chainthat contains mixture of amorphous and crystalline is called semi crystallinestructure. As illustrated in Fig. 7, semi crystalline polymers possess crystallineregion where chains are aligned and amorphous regions where chains are ratherforming network.
3.2 Thermal and Mechanical Properties
Based on its thermal properties, polymers are divided into: (1) thermoplastic whichis soft and viscous when it is heated up and become hard and rigid when it is cooleddown, and this process can be done repeatedly; (2) thermoset which melts whenfirst heated and then hardens permanently when cooled, but when it is heated again,the polymer will be destroyed. Thermoplastic polymers are mostly soft and veryductile due to its linear, branch and cross-link structures. While thermoset is typ-ically harder and rigid due to its three dimensional network (Callister andRethwisch 2014). The summary of thermoplastic and thermoset properties are listedin Table 3.
The term mechanical properties is commonly used to denote stress-strain rela-tionship for polymer systems which unlike metals these relationships depend notonly on temperature but also time dependence. The mechanical properties of
Fig. 7 Illustration of semicrystalline structure ofpolymers
Structure and Properties of Biomaterials 11
polymers depend on the strain rate, temperature, and environmental conditions.They can be brittle, plastic and highly elastic (elastomeric or rubber-like). Theirtensile strengths are orders of magnitude smaller than those of metals, but elon-gation can be up to 1000 % in some cases. It has been long-known that mechanicalproperties change dramatically with temperature, going from glass-like brittlebehavior at low temperatures to a rubber-like behavior at high temperatures (Fig. 8).
The solid state deformation of polymers is time-dependent and nonlinear. Itresembles some combination of elastic and viscous responses, known as vis-coelastic behavior. An immediate consequence of the viscoelasticity of polymers isthat their deformations under stress are time dependent. Different to the deformationon metals where the end point of elastic deformation is either fracture or plasticflow, imposed mechanical stress on polymers results into strain that increases withtime (i.e. polymer creep). When a constant deformation is imposed, the inducedstress will relax with time (stress relaxation) (Ward and Sweeney 2012).
Table 3 Comparison of thermoplastic and thermoset polymers
Thermoplastic Thermoset
Few cross-linking More cross-linking (10–50 % of mers)
Ductile Hard and brittle
Soften with heating Not soften with heating
Examples: poly(ethylene), poly(propylene),poly(carbonate), poly(styrene)
Examples: vulcanized rubber, epoxies,polyester resin, phenolic resin
Fig. 8 The influence of temperature to the tensile behavior of poly(methyl methacrylate)(Carswell and Nason 1944)
12 S.G. Sukaryo et al.
Generally, decreasing the strain rate has the same influence on the strain-strengthcharacteristics as increasing the temperature where the material becomes softer andmore ductile. The strength of polymers can be increased by increasing molecularweight, cross-linking and crystallinity which all makes the secondary bondingenhanced as the molecular chains are closely packed and parallel. Similar to strainhardening in metals, pre-deformation by drawing increases strength by orienting themolecular chains. While for undrawn polymers, heating increases the tensilemodulus and yield strength, and reduces the ductility—opposite of what happens inmetals (Landel and Nielsen 1993). Mechanical properties of some polymers arelisted in the Table 4.
3.3 Examples of Most Used Polymeric Biomaterials
Polyurethanes are one of the most commonly used materials for blood contactingmedical devices due to their superior bio- and blood-compatibility. They are used ascatheters, heart valves, total artificial heart, and artificial blood vessels. They pos-sess superior durability, elasticity, elastomer-like character, fatigue resistance, andcompliance (Zdrahala and Zdrahala 1999). Large family of polyurethanes providesextensive structure and property diversity with the common characteristic of ure-thane linkages along the large molecular chains. Generally, urethane linkages areformed by the reaction of isocyanates and alcohols accompanied with the formationof various bonds such as allophanate, biuret, acylurea, and disocyanurate leading tofurther branching and crosslinking thus affecting their physical and chemical
Table 4 Mechanical properties of some polymers (Kalpakjian 2008)
Material UTS (MPa) E (GPa) Poisson’s ratio
Acrylonitrile butadiene styrene 28–55 1.4–2.8 –
Acetal 55–70 1.4–3.5 –
Acrylic 40–75 1.4–3.5 –
Cellulosic 10–48 0.4–1.4 –
Expoxy 35–140 3.5–17 –
Flurocarbon 7–48 0.7–2 0.46–0.48
Nylon 55–83 1.4–2.8 0.32–0.40
Phenolic 28–70 2.8–21 –
Poly(carbonate) 55–70 2.5–3 0.38
Poly(ester) 55 2 0.38
Poly(ethylene) 7–40 0.1–0.14 0.46
Poly(propylene) 20–35 0.7–1.2 –
Poly(stirene) 14–83 1.4–4 0.35
Poly(vinyl chloride) 7–55 0.014–4 –
Note UTS = ultimate tensile strength, E = Young’s modulus
Structure and Properties of Biomaterials 13
properties as well as their biocompatibility (Burke and Hasirci 2004). In their earlydevelopment, polyurethanes were obtained by the reaction of diisocyanates andglycols applied as rigid foams, adhesives, resins, elastomers, and coatings.However, their application as medical devices was limited to the degradation andcalcification. For this reason, polyurethanes are often derived from polyether whichprovides great number of linkage determining the properties of polyurethanes. Thisnew type of polyurethanes are virtually insensitive to hydrolysis thus very stable inthe physiological environment (Zdrahala and Zdrahala 1999).
The shift in biomaterials paradigm from biostable to bioactive has led thedevelopment of biodegradable polymers. Polymers are now expected to help thebody to repair and regenerate the damage tissues through the degradation process.They are widely applied as a platform in the biomedical technologies such as tissueengineering, regenerative medicine, gene therapy, controlled drug delivery andnanotechnology (Middleton and Tipton 2000). One of the most commonbiodegradable polymers in biomedical application is polylactides. They exist in twooptically active forms: L-lactide and D-lactide. The former is naturally occurringisomer, a building block of poly(L-lactide) (PLLA) with the degree of crystallinityaround 37 % (Maurus and Kaeding 2004). PLLA possesses good tensile strength,low extension, and high modulus (around 4.8 GPa) making it ideal biomaterial forload bearing applications such as orthopaedic fixation devices (Leinonen et al.2002). The degradation rate of PLLA depends on the degree of polymer crystallinityas well as the porosity of the matrix. High molecular weight PLLA degrades between2 and 5.6 years total resorption in vivo. PLLA is known to loose its strength after6-months of hydrolization eventhough there is no significant changes in mass occurfor extensively long period of time (Miller et al. 1977). For this reason, glycolides orD-lactide are often added as copolymers allowing superior property modulation.Poly (DL-lactide) is an amorphous polymer due to the random distribution of L- andD-lactide units. Hence, it shows lower strength (around 1.9 GPa) compared to poly(L-lactide) and it losses its strength within 1–2 months when hydrolyzed andundergoes complete mass loss within 12–16 months (Middleton and Tipton 1998).
4 Ceramics
4.1 Bonding and Structure
Ceramics are compounds between metallic and non-metallic elements and they arecomposed of more than one elements such as silica (SiO2) and alumina (Al2O3).Ceramics bonding is partially or totally ionic bonding, covalent bonding, or com-bination of both. This bonding is tighter compared to metallic bonding (Callisterand Rethwisch 2014). The interatomic bonding in ceramics results in long range ofthree-dimensional crystalline structure. Most ceramics have polygranularmicrostructure while some are amorphous, similar with structure of metallic alloys.
14 S.G. Sukaryo et al.
The characteristics of ceramics is determined by the characteristics of itsmicrostructure, including the size of the grain, porosity, type and phase distributionin each particles (Carter and Norton 2007; Narayan et al. 2015). This microstructurecan be manipulated through thermal processing techniques.
In contrast to metallic bonding, the electron in ionic and covalent bonds ofceramics are localized between the constituent ion/atoms. Consequently, ceramicsare insulator to electrical and thermal. However, ions with the same electric chargerepel each other, therefore moving the plane of atoms is difficult. The planes ofatom cannot slide before they slip past one another making ceramics as hard andbrittle material, as illustrated in Fig. 9.
4.2 Processing and Properties of Ceramics
Ceramics are often fabricated by mixing fine particles with water and an organicbinder then pressed them into one mold. They are subsequently heated or sintered athigh temperature. This process densities the particles through evaporation andcondensation. Similar to casting of metallic alloy, microstructure of ceramicdepends on the variables of the processed. For example, strength is determined byboth of the size of the grain and porosity. Grain size can be controlled by the initialsize of the particles where it will increase during the process while the porosity willdecrease (Carter and Norton 2007; Narayan et al. 2015).
Ceramics typically characterized with little creep, limited plastic deformationand are sensitive to the presence of cracks or other defect. These are the reason whyceramics have low tensile strength compared to the compressive strength (Hollinger2006). Although ceramics and glasses have good resistance to corrosion, they aresusceptible to other forms of degradation when exposed to physiological environ-ment such as in body fluids. The mechanism and rate of degradation depend on the
Fig. 9 The illustration of sliding in ceramics
Structure and Properties of Biomaterials 15
specific types of ceramics. In alumina, the degradation may cause a preferentialdissolution of impurities resulting cracks propagation, which subsequently leads tofracture (Narayan et al. 2015).
In general, ceramics biomaterials (bioceramics) are expected to possess desirablemechanical properties and biocompatibility. Calcium-phosphate is one of the mostimportant family for bioceramic materials. It is mainly applied for hard tissue repairdue to their similarity to the minerals in natural bone as well as their excellentbiocompatibility and bioactivity (Sakka et al. 2012). They are established materialsfor augmentation of bone defects. Moreover, calcium-phosphates such as hydrox-yapatite, fluorapatite, tricalcium phosphate have been used for medical and dentalapplications (Hollinger 2006). Unfortunately, they possess relatively poor tensileand shears properties. In practice, the strength of the calcium phosphate is lowerthan that of bone and teeth (Ratner et al. 2004). In addition to their inherentbrittleness, their application is restricted to non-load bearing defects or pure com-pression loading. Common applications include the treatment of maxilla-facialdefects or deformities, cranio facial repair, and augmentation of spine and tibialplateau. Tricalcium-phosphate is one of the most important family members and itis widely used as bone substitute materials due to their chemical similarity to that ofmammalian bone and teeth. However, it is considered to be brittle and it has poorfatigue resistance hence it is not suitable for many load-bearing applications (3–5 MPa). Its poor mechanical behaviour is even more evident when applied as highlyporous ceramics. For this, metal oxides ceramics such as alumina (Al2O3) andtitania (TiO2) have been explored as bioceramic components of tricalcium phos-phate (Sakka et al. 2012).
The formation of bone-like apatite layer is the main requirement for calcium-phosphate materials to be bioactive and bond to living bone. Calcium-phosphatepossesses the ability to attract osteoblast and osteoclasts (Thamaraiselvi andRajeswari 2004). Within in vitro model, human and animal osteoblast cells anchor tothe material surface within 2 h incubation period and their proliferation depends ontheirmicrostructure.When implanted in an osseous site, bone bioactivematerials suchas hydroxyapatite provides an ideal environment for cellular interaction and colo-nialization by osteoblast cells. This leads to a tissue response called osteoinduction inwhich bone grows on and bonds to the implants (LeGeros 1993). A vast experimenthas been conducted extensively to improve the properties and performance ofcalcium-phosphate based implants. In physiological solution, hydroxyapatite showsmore stability compared to tricalcium-phosphate as it has lower solubility. However,the application of tricalcium-phosphate as a bone substitute has received considerableattention due to its remarkable biocompatibility within living bodies when replacinghard tissues and its biodegradable properties. Consequently, tricalcium-phosphate hasbeen used as bone graft substitutes in many surgical fields such as orthopaedic anddental surgeries (Elliott 1994).
16 S.G. Sukaryo et al.
4.3 Type of Bioceramics and Their Use
Bioceramics are used to repair or replace defects in tooth or bone, to coat metallicbiomaterials and to reinforce composites. They are used mostly in orthopedicimplants such as components for arthroplasty joints with superior durability com-pared to metals, substitutes of bone grafts, and as osteoconductive coating (Park andLakes 2007). Bioceramics are classified into: bioinert, bioactive and bioresorbable.
Bioinert ceramics generates minimal response in the body. Their chemical andphysical are not altered when placed in human body (Saenz et al. 1999). Typically,these materials have a high compression strength and resistance. Alumina (Al2O3),zirconia (ZrO2) and pyrolytic carbon are some examples of bioinert ceramics.Figure 10 shows dental implant made of zirconia as example of implant made ofceramics. Bioactive ceramics will react (i.e. chemically bond) with the living tissue.Typically, they are characterized with good osteoconduction properties but havelower mechanical strength compared to bioinert counterparts. Meanwhile, biore-sorbable ceramics can be absorbed in the body and replace the tissue. They possessgood osteoconductivity although the interface between the ceramic and the bones isrelatively unstable (Hollinger 2006). Examples of bioresorbable ceramics are β-tricalcium phosphate, hydroxyapatite, carbonate, calcium carbonate (Hench andWilson 1993).
One particularity of bioceramics (including bioglass) is its osteoconductiveproperties due to chemical similarity with the main mineral in bone, especiallycalcium phosphate (CaP) compound such as hydroxyapatite (Ca10(PO4)6(OH)2).Therefore, CaP is widely used as coating on metallic biomaterials for bone implants.Table 5 lists different CaP compounds with different ratio of calcium to phosphate.
Fig. 10 Examples of dental implants made of bioceramics (Courtesy of Faculty of Dentistry,UGM)
Structure and Properties of Biomaterials 17
5 Composites
Composites are combination of two different types of material or more withoutreaction occurs between the respective elements (Callister and Rethwisch 2014).The structure and properties of the composites depend on the structure of eachconstituent forming the composite and at the same time on their combination.Composites materials is designed to provide improved mechanical properties or tocreate materials with functional and structural properties at the same time. Forinstance, in polymers-ceramics composite, polymer can act as the matrix andceramics act as its filler (reinforcement). The properties of these composite will beductile, yet hard, without a change in their respective structure (Chawla 2012).
Composites are considerably attractive materials for orthopedic application sincethey are modifiable to have good biocompatibility, reliable mechanical properties,biodegradability and ability to bond with the bone (Hollinger 2006). Secondaryreinforcing phase (i.e. fibers and ceramic particles) can be added making them ashard as cortical bone and improving the bone-bonding activity. A combination ofpolymers and drug compounds has been applied for soft-tissue treatment as wounddressings, which consists of polymer fibers filled with medication to support thehealing process. In this case, polymer fibers provide structural matrix while themedication serves as a functional material (Park and Lakes 2007).
In metal-matrix composites, the metal acts as matrix and ceramics act as filler. Inthe application of biodegradable metal for bone fracture fixation, Fe or Mg iscombined with CaP particles as filler. The CaP acts as the functional material thatwould promote the growth of new bone cells while the metal will be the structuralmaterial in bone fixation (Ulum et al. 2014). Another example of compositesincludes the mixture of magnetite (Fe2O3), hydroxyapatite (HA), and hydroxy-propyl-methyl-cellulose (HPMC). The mixture is intended for the treatment ofosteoporosis and cancer therapy. Magnetite generates heat when radiated within
Table 5 Calcium phosphate with different Ca/P ratio (Saenz et al. 1999)
Name Ca/P ratio Chemical formula
Monocalcium phosphate monohydrate 0.5 Ca(H2PO4)2·H2O
Monocalcium phosphate anhydrate 0.5 Ca(H2PO4)2Dicalcium phosphate dehydrate (brushite) 1.0 CaHPO4·2H2O
Dicalcium phosphate anhydrate (monetite) 1.0 CaHPO4
Octacalcium phosphate 1.33 Ca8(HPO4)2(PO4)4·5H2O
α-tricalcium phosphate 1.5 α-Ca3(PO4)2β-tricalcium phosphate 1.5 β-Ca3(PO4)2Amorphous calcium phosphate 1.2–2.2 Cax(PO4)y·nH2O
Calcium-deficient hydroxyapatite 1.5–1.67 Ca10-x(HPO4)x(PO4)6-x(OH)2-x[0 < x < 1]
Hydroxyapatite 1.67 Ca10(PO4)6(OH)2Tetracalcium phosphate 2.0 Ca4(PO4)2O
18 S.G. Sukaryo et al.
electromagnetic field and thus applied to kill cancer cells through hyperthermiaprocess (Iwasaki et al. 2013). When the mixture is injected into the bone, HA andHPMC form gel-like structure providing matrix to magnetite (Sakka et al. 2012).
6 Summary
Biomaterials are aimed to improve the quality of life. Its requirement has beenevolved significantly from inert materials to bioactive materials providing supportfor the tissue healing process. Biomaterials extends from polymers, metals,ceramics, and composites. They are selectively chosen according to their uniqueproperties in order to meet the desired requirements for a particular application.Nowadays, metals are still widely used as biomaterials due to their superiormechanical properties and their workability. Metallic bonds provide by free cir-culating electrons which confer metals as good electric and thermal conductors.Metals are often alloyed in order to modify their microstructures adjusting thedesired properties. They are widely used for making load bearing implants inorthopedic, cardiovascular and dental applications. Similarly, polymers have beenapplied as biomaterials due to their workability and wide selection of mechanicalproperties due to their modifiable structure. Polymers are lightweight and relativelyinexpensive. Their polyvalent applications including artificial knee joint, tibial tray,surgical sutures, coating materials and drug carriers. When it comes to superiordurability, ceramics stand out from other type of biomaterials. This property isattributely related to the solid mixture of metallic and non-metallic elements boundtogether in both covalent and ionic bonds. Paired with good osteoconductivity,ceramics are used for arthroplasty joints, substitute of bone graft, and osteocon-ductive coating material. Newer generation of biomaterials incorporates bothstructural and functional properties together in a single material. This so calledcomposite is formed by mixing two or more different types of material. Theproperties of composite materials depend on the constituents materials. Metals,polymers, and ceramics have been incorporated to form different composites forvarious biomaterial applications ranging from bone fracture fixation to hyperther-mia treatment for cancer therapy.
The development of biomaterials is now at the same pace as the research fordrug discovery. Biomaterials are no longer seen as inert materials supportingdysfunctional tissues or organs. They are now required to promote the healingprocess and self-disintegrate once the process has been completed. Moreover,specific desired properties for particular application are on the hunt through engi-neering process in an accelerated pace. All the effort is paid to improve the wellnessand health of human beings.
Acknowledgment We acknowledge the financial supports from Indonesian Ministry of Research,Technology and Higher Education (SGS), CHU de Québec Research Center (HH), and NaturalScience and Engineering Research Council (AP).
Structure and Properties of Biomaterials 19
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Naturally Derived Biomaterials and ItsProcessing
Raden Dadan Ramdan, Bambang Sunendarand Hendra Hermawan
Abstract The rich Indonesian biodiversity has been viewed as an infinite resourceof naturally inspired and derived biomaterials. The utilization of these naturalmaterials for biomaterial applications necessitates additional steps to the currentlyestablished conventional synthesis methods. Some of these steps have been suc-cessfully developed at a lab scale with suitable controlling parameters resulting intoan optimum overall synthesis processes. Further optimization and fine tuning on theparameters are required to translate the innovation into a commercialization. Moreefforts from biomaterial researchers and a supportive policy from the Governmentare essentially needed to foster the development of biomaterial and its appliedtechnology resulting into low-cost yet effective medical devices to support thenational health care program. This chapter concentrates its discussion on selectednaturally derived biomaterials, their sources and their processing which have beendeveloped in Indonesia. These include synthesis of hydroxyapatite from coral, landsnail and egg shells via precipitation reaction, sol-gel, hydrothermal and biomimeticmethods, new synthesis of membrane and encapsulation using template derivedfrom a flower plant, and synthesis of zirconia for dental restoration.
Keywords Biomaterials � Biomimetic � Coral � Natural � Precipitation � Sol-gel
R.D. Ramdan (&) � B. SunendarInstitute of Technology of Bandung, Bandung, Indonesiae-mail: [email protected]
B. Sunendare-mail: [email protected]
H. Hermawan (&)CHU de Quebec Research Center, Laval University, Quebec City, Canadae-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_2
23
1 Introduction
In one definition, a biomaterial is any substance (other than a drug) or combinationof substances synthetic or natural in origin, which can be used any time, as a wholeor as a part of a system which treats, augments, or replaces any tissue, organ orfunction of the body (Von Recum and Laberge 1995). By this definition, naturalproducts can be applied as biomaterials of natural in origin which its historical usedates back to 3000 BC when the ancient Egyptians used sutures made from animalsinew, coconut shells, wood and ivory to repair injured skulls and replace teeth(Ratner et al. 2004). Theoretically, any material natural or man made can be abiomaterial as long as it serves the stated medical and surgical purposes for ulti-mately safely implantation in or on the human body. Nature has provided a range ofmaterials (mainly polymers and minerals) with remarkable functional properties.Natural was defined as something that is present in or produced by nature and notartificial or man made, and most often the definition is assumed to mean somethinggood or pure (Fratzl 2007). Among the advantages of using natural materials forimplants is that they are similar or familiar (biomimetics) to materials in the bodysystems.
Indonesia is the largest archipelagic country in the world having undeniablerichness in species and ecosystems from its more than 17,000 islands with largerainforest, 87,000 km2 of coral reefs and 24,000 km2 of mangrove areas. Thearchipelago (Fig. 1) is the heart of the Coral Triangle, the global hotspot for marinelife and the world’s richest coral species biodiversity. In June 2010, a group ofseven international research institutions has founded the Indonesian BiodiversityResearch Center (IBRC) with headquarter located in Bali. The Center aims topromote biodiversity stewardship in Indonesia through collaborative research andeducational programs, to increase biodiversity research in Indonesian scientificcommunities, and to build lasting research networks between Indonesian and USresearch centers. The Indonesian Ministry of the Environment estimates that morethan half of Indonesia’s species are still unrecorded while there is still much to bediscovered.
In this chapter, we concentrate our discussion on selected naturally derivedceramic biomaterials, their sources and their synthesis or processing which requiredadditional steps rather than the conventional processes for synthetic origin. Specialattention is given to natural biomaterials and processes developed in Indonesia.These include, among all, synthesis of hydroxyapatite (HAp) from coral, land snailand egg shells via precipitation reaction, sol-gel, hydrothermal and biomimeticmethods, new synthesis of membrane and encapsulation using template derivedfrom a flower plant, and synthesis of zirconia from abundant raw materials found inIndonesia for dental restoration.
24 R.D. Ramdan et al.
2 Natural Source of Ceramic Biomaterials
Ceramic biomaterials (bioceramics) have been used as active biomaterials forpromoting regeneration of tissues, healing of traumatic disease, or restoring phys-iological functions. They found the applications in dental restorations, filling ofbony defects, rebuilding bone at facial, cranial and other parts (Hench 1991).Bioceramics are mostly produced from synthetic raw materials, but natural sourcesare also available such as corals and shells which are found abundant in manyplaces in Indonesia.
2.1 Corals
Due to its porous nature and high content of calcium carbonate, coral and its derivedHAp have been used as bone grafts, spinal fusion, bone filler and orbital implantssince 30 years ago with proven biocompatibilty and resorbability (Guillenium et al.1987; Ige et al. 2012). Its porous structure is a range similar to that of cancellousbone (150–500 μm) and thus makes it ideal for ingrowth of blood vessels(Ben-Nissan 2003). Apart of their exoskeleton structure, coral grafts can act as acarrier for growth factors thus improving their osteoinductivity or osteogenicity(Louisia et al. 1999). The use of coral derived bone graft prevents the transmission ofhuman immunodeficiency virus, hepatitis B, hepatitis C and other similar diseases(Suzina et al. 2005). There are many commercial brands of coralline HAp availablein the market since decade ago, such as Biocoral, Pro-osteon and Interpore (Damienand Revell 2004). Figure 2 shows example of bone graft produced from coral.
Fig. 1 The Indonesian archipelago (Google)
Naturally Derived Biomaterials and Its Processing 25
Production of bone grafts from natural coral for medical applications, such asorthopaedic and cranio-maxillo-facial surgeries, needs a set of rigorous protocols ofpreparation and purification. As part of conservation efforts, only dead coral fromPoratidae family (Porites or Goniopora species) is usually harvested as rawmaterials for the production of coralline HAp (Damien and Revell 2004). The coralmaterial is cut into smaller pieces (blocks and granules) then chemically treatedfollowed by freeze drying and radiosterilized before subjected to a series of bio-compatibility tests (Suzina et al. 2005). There are several techniques widely utilizedto synthesis HAp directly from corals, including hydrothermal and microwaveprocesses, and sol-gel coating (Balázsi et al. 2007).
In a simple hydrothermal method, the coral is subjected to a temperature of 900 °Cto decompose all carbonate phases and remove all organic materials. The preheatedcoral, calcium carbonate, is then converted into HAp by chemical exchange reactionwith diammonium phosphate resulting in pure coralline HAp powders with botharagonite and calcite phases (Sivakumar et al. 1996). Under a controlledhydrothermal exchange process, a mix product of calcite (CaCO3) and β-tricalciumphosphate (β-TCP) can be derived from coral sand grains with retaining porousstructures, making them suitable as bone scaffolds (Chou et al. 2007). The use of amineraliser (KH2PO4) can accelerate the exchange process and eliminate the for-mation of intermediary phases, while without the mineraliser, aragonite is convertedat high temperature and pressure into calcite, which was subsequently converted toβ-TCP and finally to HAp. The use of mineralizer gives a better retention of theoriginal structure of the coral such as the pore interconnectivity (Xu et al. 2001).
2.2 Shells
Numerous shells are found in nature and some of them have been evaluated forpossible biomaterials. As an example, cockle shell which has almost similar mineralcomposition to that of coral suggesting its potential to be used as a material fororthopaedic applications (Awang-Hazmi et al. 2007). The nature of the mollusc
Fig. 2 a Porite coral, b chemically treated pieces of coral, c coralline HAp bone graft
26 R.D. Ramdan et al.
shell, in-terms of both mineral composition and porous structure, makes it an idealbioceramic materials candidate with exceptional mechanical properties (Rodríguez-Navarro et al. 2006). Apart of marine mollusc, there are thousands of land snailspecies, including helix aspersa, helix pomatia and achatina fulica which can beeasily found in Indonesia. Their shell is rich in calcium carbonate thus can be usedas a source for bioceramic production. Figure 3 shows images of achatina fulica, itsshell and HAp powders.
In view of utilizing the abundant source (and waste product) of land snail shells,various Ca-phosphates powders, specifically monetite, fluorapatite, have beenproduced from helix pomatia shells via a simple economical method. The emptyshells were washed, dried, crushed and ball milled to obtain 100 µm size powders,then stirred at 80 °C while reacted with drops of H3PO4 for 8 h. The liquid part wasthen evaporated in an incubator at 100 °C for 24 h to finally collect theCa-phosphates powders (Kel et al. 2012). Another HAp synthesis can be done fromachatina fulica shells by a reflux method. It is started with drying and milling theshells to obtain powders continued by deproteinization in basic solution, followedby reflux in weak acid solution and ended by heat treatment and gelatinization.
3 Synthesis of Naturally Derived Bioceramics
3.1 Hydroxyapatite Powders
One important bioceramics that is progressively developed by many researchers isHAp, Ca10(PO4)6(OH)2, a bioceramic material with chemical composition similarto that of mineral in bone and tooth. It has excellent biocompatibility and can bedirectly attached to the bone and does not pose toxicity. In addition, apatitestructure accommodates ion exchange by substituting hydroxyl ion (OH−) with
Fig. 3 a Achatina fulica snail, b its shell, c HAp powders
Naturally Derived Biomaterials and Its Processing 27
other ion. Therefore it can also be used for filter application, such as for sorption ofbivalent metal (Río et al. 2006).
Based on its chemical composition, one of the requirements for the synthesis ofHAp is by providing calcium donor which can be taken from natural resources. It isexpected that by taking calcium donor from natural resources, we can decrease thecost of HAp production. There are many potential raw materials for calcium donor,one of them is achatina fulica shells which are provided in the huge amount inIndonesia. Another natural resource material for calcium donor that is provided inthe huge amount in Indonesia is egg shells. Egg shell contains 50.2 % calcium,12 % magnesium and 21 % natrium (Freire et al. 2000) thus is highly prospected ascalcium donor for the synthesis of HAp. However, there is limited study reported onthe synthesis of calcium from these natural resources. Both shells are commonlytreated as waste product, therefore, synthesis of calcium from this natural sourcescan support the green environment program in the country.
Calcium from achatina fulica shell is provided in the form of two types ofcalcium carbonate (CaCO3): aragonite and calcite. Aragonite and calcite has similarcomposition but different crystal structure. The former is easier to be dissolved insea water and is considered as metastable structure. Therefore, if both of thesecarbonates exist in the same shell, it is preferable to have calcite at the outer whilearagonite at the inner of the shell. However, since the outer shell is normally coatedwith a protein namely periostracum, the dissolution of this calcium sources can beavoided.
One pertinence method for HAp synthesis from achatina fulica shells is thereflux method. It is considered as the development of distillation method andinvolves the condentation of vapors that is followed with returning of condensate tothe origin system. This reflux method is started with drying the shell that is fol-lowed with milling to obtain the appropriate raw materials size. This step is veryimportant, because fine particles are required for optimum interface reaction duringreflux process. Therefore after milling process, shieving for filtering the appropriatesize of the shell powder is required. After that deproteinization is performed by basesolution and followed with reflux in weak acid solution. The last step is heat treatmentand gelatinization. Heat treatment is important step in reflux method and influences themorphology, crystallinity and surface area of the particles (Khalid et al. 2013).Figure 4 shows the flow chart of HAp synthesis from achatina fulica shells.
On the other hand, one option to synthesize HAp from egg shell as calciumdonor is by solution combustion method. This method is one of chemical approachfor the fabrication of nanomaterials by mixing the oxidizer and fuel and heating upthis mixing and ended with calcination of the heated powder. In the beginning, eggshell solution is made with HNO3 and is followed by mixing the solution withphosphate and other solution (i.e. acid or base). Result of these steps is a transparentgel of HAp. The last step is heat treatment of HAp gel to transform it into powders.In the solution combustion method, common parameters to be optimized are thefuel type, the fuel to oxidizer ratio and initial furnace temperature (Ghosh et al.2011). Different fuel type might affect on the morphology of the product, whereas
28 R.D. Ramdan et al.
different fuel to oxidizer ratio affect the heating temperature and in turn lead toagglomeration of the product. On the other hand, initial temperature has significanteffect on the existence of unburnt layer of the synthesan during the process.Figure 5 shows the flow chart of HAp synthesis from egg shell.
3.2 Hydroxyapatite Membranes
Among the important biomaterial membranes is scaffold membrane which isessential for many biological activities. This membrane also important element forthe bone transplantation and normally in order to increase the performance of themembrane for this purpose, other materials is required for the growth initiation ofnew cell, such as by HAp membrane. As in the case of HAp synthesis, it isimportant to provide raw material for its production in the huge amount in nature, tokeep sustainability of production as well as to support the green environmentprogram. Additional important reason related with membrane scaffold application isthe egg shell has complex structures that consist of protein fibers, porous structureand connected each other. This raw material is also provided in a huge amount andtherefore progressively developed as template for anorganic materials growth.
One of the method to grow HAp membrane utilizing egg membrane as thetemplate is by biomimetic method, a method that imitates model, system or elementin nature. In biomimetic synthesis, synthesis of target molecule through a series ofreaction and requires intermediate structure. In this case, HAp is the target moleculewhereas the egg membrane is the intermediate structure. HAp source can be pre-pared from SBF solution, where egg membranes are immersed for certain periodand through it HAp membranes grow. SBF is a solution with similar chemicalcomposition and concentration to human blood plasma with other condition such as
Fig. 4 Flow chart of HAp synthesis from achatina fulica shells
Fig. 5 Flow chart of HAp synthesis from egg shells
Naturally Derived Biomaterials and Its Processing 29
pH and temperature are also kept identical with this plasma. The solution releasescalcium and phosphate during immersion of egg membrane and induces the for-mation of HAp on the egg membrane. The growth of HAp on the membrane isindicated by the increase of fiber diameter that becomes in order of severalmicrometres.
Normally, more HAp grows on the egg shell as a function of immersion periodin the SBF solution. Several important parameters that affect the formation of HApmembrane by biomimetic method are pre-treatment, heat treatment and template.Among important pre-treatment that accelerate the formation of HAp is by NaOHtreatment (Miyazaki et al. 2002). For the case of egg membrane, immersion of eggmembrane in NaOH solution increases the porosity size of the membrane. On theother hand, the membrane template might influence the mechanism of formation ofthe apatite (Sun et al. 2006).
Another way to synthesize HAp membrane is by mixing alginate-chitosan as themembrane template and followed with the growth of HAp on the membrane.Alginate is a substance extracted from seaweed and refer to alginic acid and itsderivatives. For the alginate extraction, seaweed is dissolved in a hot solution ofsodium carbonate for hours resulting into dissolved sodium alginate and undis-solved substance (cellulose) that is subsequently removed. Chitosan is a biobasedpolymer and produced by deacetylation of chitin. The source of this material isexoskeleton of crustacean, such as crabs and shrimps. This material is biodegrad-able and biocompatible in nature and can be synthesized into various type ofmorphology such as membranes, sponges, gels, scaffolds, microparticles,nanoparticles and nanofibers (Anitha et al. 2014). Chitosan has potentiality forvarious applications such as drug delivery and tissue engineering. Alginate andchitosan have opposite charges, with positive for chitosan and negative for alginate.Therefore, mixing of these substances might create a stable structure with a strongchemical bonding and can produce a membrane template relatively fast with con-trollable porosities.
For membrane template applications, it should be considered that the membranehas interconnected porosity in order to support cell migration, gas diffusion,nutrition and other functions. The growth of HAp on alginate-chitosan membranetemplate will increase biocompatibility of the membrane, and therefore improve celladhesion, the growth and formation of new tissue. As has been explained previ-ously, HAp can be made from SBF solution, such as the famous Kokubo solution(Kokubo et al. 2004). This solution is acellular solution with inorganic ion con-centration approaching the extracellular solution in human body. The solution canbe prepared by dissolving NaCl, NaHCO3, KCl, K2HPO4·3H2O, MgCl2·6H2O,CaCl2 and Na2SO4 in distilled water, whereas pH of this solution kept at 7.4 andtemperature at 36.5 °C (Hayakawa et al. 2000). By this method, immersion timemight affect degree of crystallinity of the product, whereas pH of the solutioninfluences the kinetic of HAp formation.
Another potential raw material for HAp membrane template is hibiscus tiliaceus,a species of flowering tree which is commonly found in Indonesia. HAp membranesynthesis from this source is started by cleaning the hibiscus tiliaceus raw material,
30 R.D. Ramdan et al.
which is then heated at certain temperature (such as 500–700 °C) for several hoursin order to create active carbon membrane support. HAp formed on this membraneby impregnation the membrane in the SBF solution, in the similar way as the caseof egg shell and alginate-chitosan membrane previously explained.
4 Other Naturally Derived Biomaterials Processes
4.1 Micro-Capsules
Controlled release of drug in the textile application has been progressively devel-oped in recent years for the purpose of skin care and medication. Coating is themethod implemented for this application with a controllable release kinetics by thenumber of layers in the system (Martin et al. 2013). In addition, initial surfacecondition of textile fiber should be considered related with incorporation of drugand its release kinetic (Labay et al. 2014). For the purpose of skin care and woundprevention, textile lubrication should also be considered in order to reduce frictionagainst the skin (Gerhardt et al. 2013).
Recently for the controlled released application, textile is coated withmicro-capsule that contain active compound. Micro-capsule is a product ofencapsulation, where one compound, either in the form of solid, liquid or gas, iswrapped by other compound such as thin film of polymer (Jackson et al. 1991).Commonly, active compound such as drug is wrapped inside the capsule (shellmaterial). Active compound is released through porosities on micro-capsule, whichcan be due to differences in pH, osmosis pressure, temperature and air pressure. Therelease can also be due to mechanical loading and self reaction of the activecompound, which is a function of time.
Silica is one of raw materials that can be used for micro-capsule due to itsbiocompatibility characteristics. One of the methods to produce micro-capsule fromsilica is by mixing emulsion and sol-gel. In this method, three main stages shouldbe performed: precursor preparation, emulsification of precursor and solidificationof micro-capsule. As an example, precursor for silica micro-capsule can be madefrom tetraethyl orthosilicate (TEOS), HCl, dan tetrahydroxybenzophenone (THBP)solutions that are emulsified in siklohexane with the addition of sorbitan monos-tearate (span 60) as surfactant. HCl is used as acid catalyst whereas THBP is activecompound to be encapsulated. The volume of TEOs precursor and the rate ofemulsification have significant effect on the morphology and micro-capsule particlesize. In addition, increasing TEO concentration might increase the particle size. Onthe other hand, the addition of surfactant has significant effect on the morphology ofsilica particle product. Emulsification step will produce micro droplet that in turn issolidified by sol gel reaction. The final product of these processes is encapsulationactive compound in the micro-capsule.
Naturally Derived Biomaterials and Its Processing 31
One potential application of micro-capsule in drug delivery is for hyperthermiacancer therapy. At this method, cancer tissue is heated within 44–45 °C, temper-ature at which cancer cell can be destroyed with minimum damage to the normaltissue. For this purpose chemotherapy active substance is attached on nanomagneticparticle and encapsulated by micro-capsule. One requirement for nano-magneticparticle for this application is sufficient biocompatibility. Therefore for this purpose,this nano-magnetic particle is encapsulated with polymer that has sufficient bio-compatibility and biodegradability. As an example is producing nano-magneticparticle from NiCl2·6H2O precursor and encapsulated with alginate and chitosanshell.
For drug delivery applications, core-shell structure of micro-capsule offer varietyof advantages in the released controlled of the active substances. One of the famousmethods for producing miro-capsule with core-shell structure is by sol-gel methodthrough Stober route utilizing silica template. Stober route process was found in1968 and obtained by series of reaction between silica precursors with alcohol andwater as well as alkali catalyst, which were used to produce homogeneous silicaparticle in the size of micro-capsule (Stober et al. 1968). In certain case, in order toincrease the homogeneity of the silica particle, dispersion particle such as chitosanis added. Chitosan has excellent biocompatibility and increases the absorption ofdrug and has been applied in various applications such as tissue engineering, drugdelivery system, encapsulation and wound healing.
There are various methods to produce micro-capsule such as polymer encap-sulating bioactive antioxidant by electrospinning method in the food industries(Fernandez 2009). Another method is electrostatic dry powder coating which can beused in the production of drugs in the pharmaceutical industry, with the particlecores lower than 1 mm (Szafran 2012). In order to coat membranes on the activeparticles or catalyst and produce micro/mesoporous structure (MembraneEncapsulated Catalysts or MECs), fluidized bed film coating is viewed as apotential method. As an example of this method is by film coating of sphericalzeolite particles with a suspension of nano-alumina in hydroxylpropyl cellulose(HPC) to create MECs (Capece 2011).
In addition to the above method, microfluidic technique is a method to encap-sulate living cell. Example of micro-capsule for this purpose is alginate hydrogelmicroparticles which is obtained from double-emulsion template that is producedusing microcapillary device (Martinez et al. 2012). Another method is the pres-surized carbon dioxide anti-solvent co-precipitation process. As an example of thismethod is the encapsulation of propolis in the micro-capsule of water soluble poly(ethylene glycol) or PEG (Yang et al. 2014). In addition, another encapsulation inthe food industry area is encapsulation of antioxidant and aromas which is usuallyexist in oil and easily oxidized such as the encapsulation of vegetable oil in powderof maltodextrin and acacia gum by spray drying method (Fuchs et al. 2006).
32 R.D. Ramdan et al.
4.2 Bioactive Glass for Cancer Treatment
Another important development in biomaterials is bioactive glass for cancer celldetection with the help of Magnetic Resonance Imaging (MRI) apparatus. Bioactiveglass such as α-Fe2O3 can be used for cancer cell detection due to its paramagneticcharacteristics that will be detected by MRI. Bioactive glass is made of raw glassmaterials such as SiO2, CaO, Na2O dan P2O5 and are added with Fe2O3. Heatingthese compounds up to their melting temperatures produces calcium ferrite(CaFe4O7) and α-Fe2O3 as bioactive glass ceramic. The process is relatively simplewithout the need for high-tech apparatus and nano size particles.
There are several steps used to produce bioactive glass starting from mixing rawmaterials as mentioned above. The mixing composition is then heated up to liquidstate and then followed with fast cooling outside the furnace to obtain glass state ofthe mixing. The next step is milling to produce fine particles of bioactive glass andfollowed with two stages of heat treatment. The first step of heat treatment is for thenucleation of bioactive glass and the next step is for the growth of the glass, whereit is expected that Fe2O3 crystallizes become α-Fe2O3. Heat treatment can be per-formed near the glass transition temperature in an oxidizing atmosphere (Eun-TaeKang et al. 2013). Figure 6 shows the process step to produce bioactive glassmaterial. In the case of laboratory work, for the purpose of simulating the releasedof α-Fe2O3 in the body fluid, the resulted bioactive glass materials is immersed forcertain period in SBF. After this immersion, the weight loss of bioactive glass ismeasured to indicate the released of the glass. During its application, it is expectedthat the body fluid carries the glass on the cancer cell then covering the cell, bywhich it can be detected under the MRI. Immersion in the SBF solution can also beused for detecting the biocompatibility of the glass which is indicated by theformation of bioapatite on the glass surface for the bioactive materials.
4.3 Dental Biomaterials
One of the challenge in dental biomaterials is improving the biocompatibility andmechanical property of composite resin. HAp as previously described has excellentbiocompatibility but its mechanical property is considered insufficient for com-posite resin dental application. Therefore, HAp is mixed with other materials suchas zirconia-alumina-silica to form a composite of HAp-zirconia-alumina-silica thuscan be used as filler in the composite resin dental restoration.
Fig. 6 Production process of bioactive glass material
Naturally Derived Biomaterials and Its Processing 33
The above composite is synthesized started from preparing each component.Zirconia is prepared from zirconium chloride precursor with isopropyl alcohol assolvent, while alumina is from aluminum nitrate nano-hydrate precursor withaquadest as solvent. Silica is synthesized from tetraethyl orthosilicate (TEOS)precursor with aquadest as solvent. Each precursor is mixed using a template suchas acacia mangium pulp, then stirred at a controlled pH, aged for hours up to days,cleaned and dried. The last step of this synthesis is sintering with variationtemperature and holding time. For the case of HAp, similar process is appliedwith different precursor, such as (NH4)2PO4 precursor and aqua dm as solvent.These three components are mixed with coupling agent (i.e. mixing oftrimethoxypropylsilane and chitosan) to increase the adhesion of filler with polymerdental restoration matrix. The last step is mixing the fillers with coupling agent anddental restoration matrix. Figure 7 shows the step of production of dental restorationmaterial.
There are several important parameters affecting the quality of filler materialparticles such as concentration and type of coupling agent, pH of mixing colloidand crystallinity of the composite substances. The addition of coupling agent, suchas chitosan induces a better binding between filler materials and the matrix.Crystallinity of the composite substances significantly affects the mechanicalproperties of the filler composite, such as hardness, compressive strength, elasticmodulus and stiffness. While pH and composite concentration significantly affectthe resulted particle size and in turn affect the mechanical properties of the com-posite particles.
Related to the material resources in Indonesia, zirconia is provided in a hugequantity. However it is still rarely developed for biomaterials purpose due to lack ofresearch on this material. In addition for the perfect application of this material asbiomaterial it is preferable to mix with other materials as stabilizer, such as Y2O3,CaO, MgO, La2O3, and CeO in order to increase the mechanical properties of thematerial. The result of these composite mixing can also be used for filler in dentalrestoration applications.
One of the methods to produce nano-particle zirconia with stabilizer such asMgO is by sol-gel method. Zircona can be taken from ZrCl4, while MgO source isMgSO4 with aquadest as the solvent. In order to increase particle distribution, othersubstances such as chitosan can be added. The mixture is then aged and dried,followed by calcination process. The last step is homogenization of the powder bymortar milling or ultrasonic homogenizer. Figure 8 shows the step of process toproduce nano-particle zirconia with stabilizer. Among important parameters that
Fig. 7 Production steps of dental restoration material
34 R.D. Ramdan et al.
affect the quality of nano-particle zirconia are calcination temperature, particledistribution and stabilizer composition. Calcination temperature should be deter-mined in order to obtain appropriate particle size, whereas particle distribution isimportant for the homogeneity mechanical properties. Stabilizer composition affectsthe particle size of zirconia composite and in turn determines the mechanicalproperties as well.
4.4 Surface Treatment
Various metals with excellent oxidation resistance such as titanium alloy have beenused as implant materials. Additional surface treatment and coating are oftenapplied on its surface to further improve its biocompatibility. Among them aresol-gel and thermal spray methods with HAp, carbon, titania and hydrogel titanateas the coating materials.
For the HAp coating, one of new potential thermal spray methods ishigh-velocity oxy fuel (HVOF) process (Ramdan 2014). The method is expected togive better degree of crystallinity of HAp and increase the bonding strength with themetal surface (Lima 2005; Gaona 2007). Intermediate layers such as titania andcarbon nanotube, are often used to facilitate this bonding. In order to coat HAp onmetal implant by HVOF method, a careful surface preparation is required. A seriesof grinding, polishing or sand blasting is normally performed in order to create flatsurface with sufficient roughness to allow a good mechanical interlocking. Theoxide layer on titanium alloy should be removed to enhance adhesion property. Thiscan be done by chemical etching that also gives additional contour on the metalsurface. Apart of the surface preparation, the precursor for coating, HAp powders,should have sufficient flow ability in dry condition.
HAp coating with HVOF process is very fast and can be accomplished in 10 s.Therefore no diffusion of HAp will take place into the metal substrate leaving thepossible bonding mechanism only for mechanical interlocking. In order to increasethe bonding strength between HAp and the metal substrate, post-annealing treat-ment can be performed subsequently. This additional treatment might induce adiffusion of HAp into the metal substrate. Figure 9 shows one optional of HApcoating on the metal substrate by HVOF process.
Fig. 8 Production steps of nano-particle zirconia with stabilizer
Naturally Derived Biomaterials and Its Processing 35
Another surface treatment to increase biocompatibility of metal implant is bycoating with carbon layer. It can be done by dip coat the metal in a carbon sus-pension. Before the process, as in the case of HVOF coating, several substratepreparation should be done such as grinding, ultrasonic cleaning and an optionalimmersion in a coupling agent such as chitosan that enhances the adhesion ofcarbon layer on the metal surface. After that, coating is performed by dipping themetal substrate into the carbon suspension followed by drying. The last step issintering the coated sample in order to create adhesion between the substrate andcarbon. The carbon coated metal surface will allow an easier growth of HAp duringbiomimetic process in SBF compared to non-coated metal. Figure 10 shows a flowchart of HAp coating by biomimetic process with carbon as intermediate layer.
Another pre-treatment that can be done to enhance HAp biomimetic coatingprocess is by introducing hydrogel titanate intermediate layer through alkali treat-ment. For the alkali treatment, metal substrate is immersed in NaOH solution toproduce hydrogel titanate (HTiO3
−·nH2O) that is obtained from the reactionbetween TiO2 and hydroxyl ion from NaOH. After the immersion process, themetal is heat treated to dehydrate the hydrogel titanate and form a stable sodiumtitanate (Na2Ti6O13). Heat treatment can also induce better bioactivity of the alkalitreated layer (Lu et al. 2012). After that, immersion in SBF is performed to growHAp layer on the treated metal surface. Figure 11 shows a flow chart of biomimeticcoating of HAp with substrate preparation by alkali treatment.
Fig. 9 Flow chart of HAp coating on metal substrate by HVOF method
Fig. 10 Flow chart of biomimetic coating of HAp on metal substrate with pre-treatment bydipping in the carbon suspension
36 R.D. Ramdan et al.
5 Perspective
The undoubtful rich Indonesian biodiversity, both its rainforests and coral reefs, hasbeen viewed as the unlimited source of naturally inspired and derived biomaterials.The authors’ view on utilization of this biodiversity is not as the source forindustrial exploitation of biomaterials synthesis, but rather for learning from theNature in finding useful biomaterials for the benefit of humanity. This biodiversitymust be used wisely and intelligently. It must be conserved. The tragic rapid loss ofIndonesia’s biologically wealthy rainforests and the increase of threatened nativemammals and the destructive exploitation of coral reefs must be prevented.
The utilization of natural resource materials, which are specific yet abundantlyavailable in Indonesia, for biomaterial applications necessitates additional steps tothe currently established conventional synthesis methods. These steps have beensuccessfully developed at a lab scale with suitable controlling parameters resultinginto the optimum overall synthesis processes. Further optimization and fine tuningon the parameters are required to translate the innovation into a commercial scale.More efforts from biomaterial researchers and a supportive policy from theGovernment are essentially needed to foster the development of biomaterial and itsapplied technology resulting into low-cost yet effective medical devices to supportthe national health care program.
Acknowledgment The authors acknowledge the support from the Indonesian Ministry ofResearch, Technology and Higher Education (RDR, BS) and the CHU de Québec Research Center(HH).
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Naturally Derived Biomaterials and Its Processing 39
Biocompatibility Issues of Biomaterials
Widowati Siswomihardjo
Abstract The history of biomaterials started with gold and ivory, when thesematerials were used by the Egyptians and Romans before the twentieth century.Biomaterial is defined as any non-vital materials used in medical devices, intendedto interact with biological systems. An important property that differentiates abiomaterial from other material is its biocompatibility. It is a term that is referred toas the appropriate host response to biomaterials. The understanding of biocom-patibility is becoming an interdisciplinary study, since the biocompatibility ofbiomaterials is a critical issue in limiting device longevity and functionality.Biocompatibility is a multifactorial property, and it can be illustrated as a dynamicand an ongoing process. Some materials, such as amalgam, acrylic resin, andbis-GMA have been used for years in dentistry. On the other hand controversiesstill arise to debate the biocompatibility of those materials. Measuring the bio-compatibility of a material is very complex. It is based on three levels of tests. Sincethere is no guarantee that a material is 100 % safe, all regulations and standards arerelated to the risk and safety of the materials. It is a challenge for biomaterialsscientists to provide biomaterials with good biocompatibility that are able to servefor the best result of medical treatments. Gadjah Mada University as a leadinguniversity in Indonesia pays a great interest in the field of research. Some studies indeveloping local biomaterials and medical devices conducted by researchers ofGadjah Mada University are presented in this chapter.
Keywords Biomaterials � biocompatibility � biological response
W. Siswomihardjo (&)Gadjah Mada University, Yogyakarta, Indonesiae-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_3
41
1 Introduction
In the history of human life, the first biomaterials used were gold and ivory. Thesematerials were used by the Egyptians and Romans who lived along time before thetwentieth century. Biomaterials are defined as non vital materials used in medicaldevices, intended to interact with biological systems. In the last few years thebiocompatibility of biomaterials has been developing into a complex and com-prehensive study. Medical treatments are related very much with the use of bio-materials, whereas ‘all materials are poison, and nothing is without poison—onlythe dose permits something not to be poisonous’—as stated by Paracelsus, thefather of toxicology. Biocompatibility is a term which is extensively used inmaterials science—it is the ability of a material to elicit an appropriate biologicalresponse in a given application in the body. Biocompatibility of a material can beillustrated as a multifactorial property, with a dynamic and ongoing process. Of thebiological responses to materials, toxicity test is the first screening test used foralmost all materials. Nowadays using humans as research subjects without previoustests of the biocompatibility of the developed material is considered unethical. Theunderstanding of the biocompatibility of materials is not only important for clinicalpractitioners but also manufacturers who are responsible for providing safe mate-rials on the market. This chapter describes the basic concept of biocompatibility ofbiomaterials and illustrates it with some research in developing new materialsconducted especially in Indonesia.
2 Biocompatibility of Biomaterials
The study of biomaterials is a wide-ranging field, covering aspects of biology,medicine, engineering and materials science (Temenoff and Mikos 2008). At thebeginning of the twenty first century, biomaterials are widely used throughoutmedicine, dentistry and also biotechnology. Previously the word “biomaterial” wasnot used, as the forms of biomaterials today were not yet in existence (Ratner et al.2004). In the history of human life, the first biomaterials used were gold and ivoryfor the replacements of bone defects, and these materials were used by theEgyptians and Romans who lived along time before the twentieth century (Bergmanand Stumpf 2013). Biomaterials are defined as any non-vital materials used inmedical devices, intended to interact with biological systems (Schmalz andArenholt-Bindslev 2009). Materials that are inserted into the human body are thusreferred to as biomaterials and include ceramic, polymers, metals and composites.One of the major concerns of biomaterial scientists is the biological response to thechosen material, since it will determine the biocompatibility (Temenoff and Mikos2008). The clinical success of a biomaterial depends on many properties of thematerial. The most important property that differentiates a biomaterial from othermaterial is its ability to exist in contact with tissues of the human body without
42 W. Siswomihardjo
causing any harm to the body (Williams 2008). Biomaterials serve to restore health,function and esthetic appearance of patients. To fulfill these objectives, biomaterialsare designed to work intimately with their hosts (Tang 2014).
All materials intended for the application in human body, will initiate tissueresponses when implanted into the living tissues (Anderson 2001). When a materialis inserted into living tissue, interaction with the surrounding biological system willoccur and produce biological response (Wataha 2001). Biocompatibility is a termthat is used extensively in the science of biomaterials. It describes the relativeability of a material to elicit an appropriate biological responses in a given appli-cation in the body (Sakaguchi and Powers 2012). Biocompatibility is referred to asthe appropriate host response to biomaterials (Tang 2014).
Many implants conducted prior to 1950 did not succeed, due to a poor under-standing about the biocompatibility of biomaterials (Ratner et al. 2004). In the lastfew years, the biocompatibility of biomaterials has been growing into an increas-ingly sophisticated and complex field of study. The understanding of biocompati-bility is becoming an interdisciplinary study that draws on knowledge from biology,materials science, biomechanics, engineering as well as aspects of clinical practiceand the specific condition of the host. It can be said that to test new materials priorto clinical use is quite recent, but the historical use of the biocompatibility ofbiomaterials extends back to the time of Hippocrates. The biocompatibility ofbiomaterials becomes a critical issue in limiting device longevity and functionality(Onuki and Bhardwaj 2008). Nowadays using humans as research subjects indeveloping new materials without preliminary testings on the biological propertiesof the new material is considered as unethical (Anusavice 2003). As no biomaterialis absolutely save and free from any potential risk of harm, biocompatibility testingsare listed as first priority in developing new biomaterials. The main purpose ofbiocompatibility testings is to protect the safety of not only the patients but also theclinical staff and laboratory technicians (Temenoff and Mikos 2008). Since the wayin which the mutually acceptable co-existence of biomaterials and tissues isdeveloped, has been of great interest for many years to many biomaterials scientists(Williams 2008).
Related with the definition of the biocompatibility of materials, it can beunderstood that a single material may not be biologically acceptable in all appli-cations (Sakaguchi and Powers 2012). For example, a material that clinically isacceptable as a root canal sealer may not be acceptable as a dental implant (Fig. 1).
In the case of a bone implant, the requirement for a biocompatible material is thatthe material should integrate with the bone (Fig. 2). In this condition the appropriatebiological response for the implant material is what we call osseointegration.Whereas materials for root canal sealer, the expectation is that the material will notinitiate inflammation, and thus osseointegration is not the appropriate biologicproperty. Whether a material is biocompatible or not for a specific function, dependsmuch on the clinical and physical function for which the material will be used. It alsodepends on the biological response that will be required from the material(Sakaguchi and Powers 2012). Thus, in choosing a material, it is important to firstclearly define the purpose for which the material will be used.
Biocompatibility Issues of Biomaterials 43
Another example is the biocompatibility of the impression material (Fig. 3).There are many kinds of impression materials, such as alginate, agar, ZOE andsilicon. Some concerns about the biological response of impression material is thepotential for inflammation and causing hypersensitivity. A biocompatibility prob-lem might happen when some of the materials are trapped in the patient’s gingivalsulcus (Fig. 4). A foreign body of impression material is known to elicit gingivalinflammation, which might also disturb the tooth preparation (Anusavice et al.2013). Therefore, it is important to clean the gingival sulcus directly after taking theimpression to minimize the possibility of hypersensitivity.
Fig. 2 Illustration of osseintegration between a metal implant and the alveolar bone
Fig. 1 Illustrations for a fully filled root canal with biocompatible sealer where it fills the apicaland lateral canal and a non compatible sealer which is not able to fill the accessories canals
44 W. Siswomihardjo
3 Factors and Nature of Biocompatibility
The traditional concept of biocompatibility is understood as a lack of significantadverse reaction between material and the oral tissues (Browne 1988).Unfortunately, nowadays it is recognized that there are only few materials that donot elicit a significant interaction with the host tissues (Browne 1994). Based onthat fact, an updated concept of biocompatibility becomes the ability of materials toinduce an appropriate and also an advantageous host response during its intendedclinical usage (Murray et al. 2007).
Fig. 4 Possible entrapment of impression material in the sulcus gingivalis
Fig. 3 Alginate impression material (Courtesy of Faculty of Dentistry, UGM)
Biocompatibility Issues of Biomaterials 45
Biocompatibility is a multifactorial property (Fig. 5) which will interact with itssurrounding environment. The biological response of the material will alter if thereare changes occured in host condition or the material itself (Sakaguchi and Powers2012). The biocompatibility of a material is not stable nor absolute (Wataha 2001)and also very individual; it can be said to be like color (Fig. 6). A material’s colordepends on the character of the light source, how the light interacts with thematerial, and how the observer interprets the reflected light. In this sense a mate-rial’s color depends on its environment, similar to the biocompatibility of materials(Sakaguchi and Powers 2012).
Fig. 5 Biocompatibility as a multifactorial property
Fig. 6 The biocompatibilityof material is like the colorreflection of material thatdepends on the interaction ofmaterial with light andobserver’s interpretation ofthe reflected light
46 W. Siswomihardjo
Factors that influence the occurence of biological response of biomaterials(Wataha 2001; Sakaguchi and Powers 2012; Anusavice 2003; Anusavice et al.2013) are as listed below:
1. The chemical nature of the material’s components2. The physical nature of the material’s component3. The types and locations of patient tissues that will be exposed to the material4. The duration of the exposure5. The surface characteristics of the material6. The amount and nature of substances eluted from the material7. The forces and conditions placed on the material8. The physical function for which the material will be used9. The design of the device
The biocompatibility of a material can be illustrated as a dynamic, and anongoing process. A material device that is today placed in the body as biocom-patible, may not be biocompatible in the future. The general condition of the hostmay alter through exposure to diseases or aging. On the other side, the materialsdevice itself may change through corrosion or fatigue, or the loads placed on thematerial may change through alterations in the occlusion or diet. The interactionamong host, materials function and materials properties (Fig. 7) will continue overtime (Wataha 2001). Some materials device may develop complications, theadverse interactions of host with the material, or vice versa. Complications occurmostly as a consequence of biomaterial and tissue interactions (Ratner et al. 2004).
Any material device that is placed in the body can cause local or systemic bio-logical responses. These two responses are influenced by the components that mightbe released from the material. The nature, severity and location of these effects aredetermined by the distribution of the released components (Anusavice et al. 2013).Local biological responses might be influenced by: (1) the ability of material com-ponents to be distributed to these sites, (2) the concentration of the material com-ponents, and (3) the exposure times of those components which may occur fromseconds even to years (Anusavice 2003). Similar to a local biological response, thesystemic side effect from the components of materials are also a function of the
Fig. 7 The interaction amonghost, materials function andmaterials properties
Biocompatibility Issues of Biomaterials 47
distribution of those components released from the materials. Local toxicity or a localbiological response is based on the chemical interaction between a toxic componentand biologically relevant molecules (Schmalz and Arenholt-Bindslev 2009). Thesystemic biological response depends on: (1) the duration and concentration of theexposure of the released components, (2) the excretion rate of the components, and(3) the site of the exposure.
4 Biocompatibility of Selected Biomaterials
4.1 Amalgam
One of the most interesting issue related with clinical dentistry today, is the use ofamalgam as restorative material. It is the most important filling material in thehistory of dental materials, as it has been used continuously for almost 200 years toreconstruct decayed teeth (Soni et al. 2012). In many countries, dental amalgam isstill of great importance as restorative material. However, it is a fact that the overalluse of dental amalgam is decreasing, due to its content of mercury, known as a toxicsubstance.
The amalgam used today are mostly based on the formulation which is publishedby G.V. Black in 1895. Modifications of the basic formulation were subsequentlyintroduced in the early 1960s (Anusavice et al. 2013). Amalgam is an alloy whichcontains mercury as one of its components. Mercury is liquid at room temperatureand it can be alloyed with solid metals (Anusavice 2003). Amalgam alloys containspredominantly silver and tin. It may also contain concentrations of other compo-nents such as copper, zinc, gold and mercury. To produce dental amalgam, mercuryis mixed with the powder of the amalgam alloy.
The amount of alloy and mercury to be used can be described as themercury/alloy ratio, which signifies the number of parts by weight of mercurydivided by the number of parts of alloy to be used for the particular technique. Themercury content is about 50 % by weight and that for spherical alloys is 42 % byweight (Anusavice et al. 2013). Free mercury (Hg) is known to be a cause ofcontact dermatitis and mercury vapor is about ten times more toxic than lead onhuman neurons and with synergistic toxicity to other metals (Mutter 2011). Cellculture tests have demonstrated the toxicity of the free Hg in dental amalgams. Withthe addition of copper (Cu), dental amalgams have become toxic to cells in culture, butlow-Cu amalgams do not inhibit cell growth (Mallineni et al. 2013). High-Cu amal-gams cause severe reactions when in direct contact with the tissue (Lawrence et al.1972). Dental amalgam when handled correctly, it has a high durability (Schmalz andArenholt-Bindslev 2009).
Oral amalgam pigmentations or amalgam tattoos (Fig. 8) are relatively commonclinical lesions caused by unintended deposition or displacement of amalgamparticles into the oral soft tissue during dental operative or surgical treatments
48 W. Siswomihardjo
(Schmalz and Arenholt-Bindslev 2009). Amalgam tattoos are harmless and asymp-tomatic. Seen as discoloration of the gingival or buccal membrane, nowadays theprevalence of amalgam tattoos remains high as the general population continues tohave existing amalgam fillings replaced by the newer composite fillings (Lundin et al.2013).
A review article on the biocompatibility of dental amalgams (Ucar and Brantley2011) stated that: (1) mercury released from dental amalgam restorations does notcontribute to systemic disease or systemic toxicological effects, (2) allergic reac-tions to mercury from dental amalgam restorations have been demonstrated, butthese are very rare. While the general public remains concerned about amalgamfillings (Fig. 9) as they contain 50 % mercury (Pleva 1994), they are neverthelesswidely used due to the fact that they have not been found to cause disease orharmful effects (Duplinsky and Cicchetti 2012). This controversy means that dentalprofessionals around the world continue to debate the potential risk of dentalamalgam to our health (Schmalz and Arenholt-Bindslev 2009). For decades, thedental professions have sought aesthetic restorative materials to replace the tradi-tional amalgam alloy for stress-bearing restorations (Mallineni et al. 2013).
4.2 Acrylic Resin
The use of polymers have revolutionized the biomedical industry ever since theirdiscovery. Many prostheses made from polymers have been in use for the last threedecades (Bhola et al. 2010). Since the mid of 1940s, polymethyl methacrylate(PMMA) has become the most common material for the fabrication of denture
Fig. 8 a Amalgam filling;b amalgam tatoo, adiscoloration of the gingivalmucosa (Courtesy of Facultyof Dentistry, UGM)
Biocompatibility Issues of Biomaterials 49
bases. Most resin systems used in dentistry as denture bases are based on methylmethacrylates (MMA) (Gautam et al. 2012). Around ninety-eight percent of alldenture bases are still constructed from methyl methacrylate (Phillip 1989). Itscolor, optical properties, and dimensional characteristics remain stable under nor-mal intraoral conditions, and its physical-mechanical properties have proven to beadequate for dental applications (Anusavice et al. 2013).
Polymerization is the chemical reaction in which monomers of a low molecularweight are converted into chains of polymers with a high molecular weight. Recentyears have seen controversy emerge regarding the possible complications andnegative side effects from the use of acrylic resin denture bases. Despite its satis-factory aesthetic properties and, ease of processing, PMMA denture bases have thepotential to elicit irritation, inflammation or allergic reaction in the oral mucosa(Ozen et al. 2006). Many in vitro and in vivo experiments were conducted onacrylic based resins or on their leached components, and results showed them tohave cytotoxic effects (Gautam et al. 2012). A study conducted by Pradeep andSreekumar (2012) proved that monomer MMA is indeed cytotoxic even in very lowconcentrations. Atoxic compound which exists in the chemical composition asmonomer, can cause allergies in dental laboratory staff and denture wearers priorand after the polymerization (Lassila et al. 2001). Regarding leaching componentsfrom PMMA, two aspects are of particular importance—the monomer polymerratio and the residual monomer concentration (Gautam et al. 2012). Polymethylmethacrylate is one of the most widely used polymer for denture bases, but dentistsand laboratory staff should be very careful in handling the acrylic resin. Techniquesshould be employed to reduce exposure to MMA in order to reduce the risks(Fig. 10) of possible complications (Leggat and Kedjarune 2003).
Denture stomatitis has been found to be a common problem related with denturebases. Candida albicans is a normal commensal in the oral cavity. There is always arisk of the development of Candida associated denture stomatitis (CADS) forpatients who are wearing denture (Bhat et al. 2013). Candida albicans is not onlyable to adhere to the mucous surfaces, but may also stick to the acrylic resins(Fig. 11) of dental prostheses (Salerno et al. 2011).
Fig. 9 a Amalgamrestoration; b toxic reaction ofbuccal mucosa close to therestoration (Courtesy ofFaculty of Dentistry, UGM)
50 W. Siswomihardjo
4.3 Titanium
Metal alloys are important materials as replacement of non-functional parts of thebody, but unfortunately many alloys are prone to corrosion (Singh and Dahotre2007). Since the 1960s, titanium has become a very popular metallic biomaterial
Fig. 11 a Healthy mucosa of the upper jaw; b mucosa with denture stomatitis caused by infectionwith Candida albicans (Courtesy of Faculty of Dentistry, UGM)
Fig. 10 a Allergic reaction to MMA in denture base material; b same patient after substitution ofMMA containing denture base material with polycarbonate material (Courtesy of Faculty ofDentistry, UGM)
Biocompatibility Issues of Biomaterials 51
because of its excellent properties for many medical applications. Both titanium andtitanium alloys, based on their physical, chemical and biological properties, appearto be suitable for implants and prostheses (Ozcan and Hammerle 2012).
Many practioners accepted titanium to be relatively inert substance with minimalside effects (Lugowwski et al. 2000). It is generally considered as a safe metal touse in implantation but on the other hand some studies have suggested that par-ticular titanium might cause health problems (Fig. 12), or produce further sideeffects such as dark staining in the tissue around the titanium (Frisken et al. 2002).
Fig. 12 Complication caused by: a titanium metal plate; b, c orthopaedic plate (Courtesy of Dr.Sardjito General Hospital, Yogyakarta)
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The exact mechanism for titanium release is not clear, but some reports have shownthat ionization of all metals occurs to some extent and titanium may be released inrelatively large concentrations into surrounding tissues (Woodman et al. 1984).A biocompatible titanium base which is alloy suitable for bone implant should meetat least these requirements (Mehta 2015): (1) potentially toxic elements should beavoided completely, (2) elements that may have potential toxicological problems,should be used only in minimal amounts, (3) the alloy should have high corrosionresistance, (4) the alloy should have at least low modulus, high strength, be smoothand notched fatigue strength, (5) the alloy should have good workability andductility. Factors that can influence the failures and complications that might occurwhen using metal implants, (1) the skill of the operator, (2) condition of patient, and(3) anatomic (Chee and Jivraj 2007).
4.4 Bisphenol a Glycol Dimethacrylate (bis-GMA)
During the first half of the twentieth century, silicates were the only tooth-coloredaesthetic materials available for cavity restoration. Although silicates releasefluoride, they are no longer used for permanent teeth because they become severelyeroded within a few years. Since the early 1970s, resin-based composite systemshave become the material of choice for direct aesthetic (Fig. 13) anterior restora-tions (Anusavice 2003).
In dentistry, resin composites have been used with increasing frequency asrestorative materials as a result of the demand for both aesthetic restorations andconcerns over the adverse effects of mercury from amalgam (Sweeney et al. 2012).There are three major structural components in resin-based composite: matrix, fillerand coupling agents (Anusavice et al. 2013). Current dental resin systems are
Fig. 13 Composite resins as direct aesthetic restoratios: a before; b after restoration (Courtesy ofFaculty of Dentistry, UGM)
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generally based on dimethacrylate monomers. Several restorative materials avail-able on the market contain the monomer bis-GMA (Kostoryz et al. 1999).
Composite resins are extensively used in dentistry due to their aesthetic andgood physical and mechanical properties (Tuan Rahmi et al. 2012). The develop-ment of fiber-reinforced composite (FRC) has served the dentists the possibility offabricating restorations with an excellent appearance (Zhang and Matinlinna 2012).Next to that, FRC provides a metal-free tooth restorations for single and multipleteeth replacement (Garoushi et al. 2011).
Although the physical properties of resin composites are constantly beingimproved, result of in vivo studies have shown that their use is often related withnecrosis or irritation of the pulp or the adjacent periodontium (Nalcaci et al. 2006).This cytotoxicity is the result of residual uncured monomer (Sideridou et al.Sideridou et al. 2004), indeed bis-GMA has been found to be cytotoxic in many cellculture systems (Wataha et al. 1994).
5 Concept of Assessing Biocompatibility
The increasing use of biomaterials in clinical medicine to replace failing organfunction has heightened the need to apply relevant tests to study the safety ofmaterials of new medical devices (Kirkpatrick et al. 2005). One of the importantprerequisites for the clinical usefulness of biomaterials is a high level of biocom-patibility (van Tienhoven et al. 2006). All biomaterials used in human beings haveto be tested for their biocompatibility before defining their clinical performance(Illeperuma et al. 2012). Biocompatibility of a biomaterial refers to the extent towhich the material does not have toxic or harmful effects on biological system(Keong and Halim 2009). The use of biomaterials may result in damage to varioustissues. Therefor measuring the biocompatibility of a material is very complex,involving a number of steps to test interactions between the material and its sur-rounding tissues. Historically, new materials were simply tested in humans to assesstheir biocompatibility. However, current materials must be extensively screened forbiocompatibility before they are used in humans (Sakaguchi and Powers 2012). Theassessment of the biocompatibility of a material is a very complicated procedurethat may involve several biological tests, tests of physical and mechanical prop-erties and also risk-benefit analysis (Wataha 2001). Even if the risk of damagecaused by a new material is considered to be acceptable, it has to be understood thatsome people may get problems based on specific conditions. In other words, it isrelated to the problem of individual compatibility (Schmalz and Arenholt-Bindslev2009). Biocompatibility of material is measured based on three levels of tests:(1) in vitro, (2) in vivo, (3) clinical tests (Table 1).
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5.1 In Vitro Test
In vitro test is the initial step to evaluate the harmful effects of new materials thatmay occur (Illeperuma et al. 2012). It is defined as an experiment that is performedin test tubes, cell-culture dishes, or outside of a living organism. These experimentsneed the placement of a material or a component of a material in contact with a cell,enzyme or any other isolated biological system. Based on the objectives, in vitrotests can be divided into those that measure the cytotoxicity or cell growth andthose that measure the effect on the genetic material in a cell (Craig and Powers2002). The advantages of in vitro tests are their being experimentally controllable,fast, and relatively simple and there is no need to consider about the ethical andlegal issues. The primary disadvantage is their questionable relevance to the use ofthe material for human (Wataha 2001). It is important to understand, that sincein vitro tests are performed outside of living organism, the interactions that createbiological response in the body are not present.
5.2 In Vivo Test
The animal test or in vivo tests for biocompatibility are different than in vitro testsbecause the tested material will be placed into an animal. For example, the materialmay be implanted into a mouse or placed into the tooth cavity of a rat (Wataha2001). In vivo tests are distinct from clinical tests, in that the material is not placedin the animal with regards to its final use. The use of an animal allows the inter-action between host and material to occur. The biological responses in animal tests
Table 1 Advantages and disadvantages of biocompatibility tests (Sakaguchi and Powers 2012)
Tests Advantages Disadvantages
In vitro Quick to performLeast expensiveCan be standardizedGood experimental controlExcellence for mechanisms interaction
Relevance to in vivo isquestionable
In vivo Allow complex systemic interactionsResponse more comprehensive than in vitrotestsMore relevant than in vitro tests
Relevance to use is questionableExpensiveTime consumingDifficult to controlDifficult to interpretLegal and ethical concerns
Clinical Relevance to use of material is assured Very expensiveVery time consumingCan be difficult to controlDifficult to interpret and quantifyMajor legal and ethical issues
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are more comprehensive and relevant than in vitro tests. Nevertheless, the relevanceof these tests is still unclear, especially in estimating the appropriateness of ananimal to represent a human (Craig and Powers 2002). The perspectives that shouldbe considered in the in vivo assessment (Anderson 2001):
1. Involving the utilization of the tests to determine the general biocompatibility ofthe newly developed materials for which some knowledge will be necessary forfurther research
2. Regarding the test of medical devices focuses on the biocompatibility of thefinal product, that is the medical device and its component materials in thecondition in which it is implanted.
5.3 Clinical Test
Clinical tests are experiments conducted in clinical research, it can be performed inanimals or in human volunteers. It is mandatory especially for materials that areconsidered to be of high risk (Anusavice et al. 2013). Such studies are mainlydesigned to clarify specific questions about new treatments or interventionsincluding the use of new materials. The tests require that the developed materialshould be placed in a situation identical to its intended clinical use. The importanceof clinical tests for predicting biocompatibility because they imitate the clinical useof the material in all aspects, including duration, location, and the placementtechnique. Clinical tests are the gold standard in predicting biocompatibility as theresult will provide a definitive answer as to whether a material is biocompatible andclinically useful or not (Craig and Powers 2002). Details and protocols on clinicaltests are provided completely in ISO standards, such as ISO 14971 (Anusavice et al.2013). However, clinical tests have many complications and problems, next to thatthese trials can be quite costly. The tests are very time consuming, extremelydifficult to control, difficult to interpret, quite expensive, and are legally and ethi-cally very complex (Wataha 2001). Finally decision for market clearance is thenapproved by many sides, such as manufacturers, governmental agencies or privateorganizations (Anusavice et al. 2013).
5.4 Cytotoxicity Test
Among the many biological responses to materials, toxicity was the earliest responsestudied. Now that biocompatibility testings has evolved significantly, the firstscreening test used for almost all new developedmaterial is the cytotoxicity test. It is atest that assesses the toxicity of amaterial bymeasuring the cell number or growth afterexposure to amaterial (Craig and Powers 2002). Two types of cells can be used for thein vitro assays, the primary and the continuous cells. Fibroblasts are very common for
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conducting cytotoxicity tests especially for dental materials, since they are in closeproximity with many restorative materials in the oral cavity (Moharamzadeh et al.2007). Some assays have been developed to test the cytotoxicity of materials.A commonly used method is the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) and the tryphan blue dye exclusion assay. The dye exclusionassay in that the tryphan blue is a vital stain used to selectively color dead cells bluebased on the principle that viable (live) cells actively pump out the dye by effluxmechanism,whereas dead cells do not. TheMTT testwillmeasure the viability of cellsbased on themetabolic activity (Chintalwar et al. 2012). If the cell is able to reduce theMTT, the resulting formazan is blue and insoluble and deposits in the cell. The amountofformazan formed is proportional to the enzymatic activity (Craig and Powers 2002).
In many countries, materials for medical devices are subjected to legal regula-tions. Since there is no guarantee that a material is 100 % safe (Wataha 2001), allregulations and standards are related to the risk and safety (covering biocompati-bility) of the materials (Table 2). To assess the biocompatibility of materials,
Table 2 ISO 10993 a standard which governs the use of materials
ISO Standard Title
ISO 10993—1: 2003 Evaluation and testing within a risk management process
ISO 10993—2: 2006 Animal welfare requirements
ISO 10993—3: 2003 Tests for genotoxicity, carcinogenicity and reproductive toxicity
ISO 10993—4: 2002 Selection of tests for integrations with blood
ISO 10993—5: 1999 Tests for in vitro cytotoxicity
ISO 10993—6: 2007 Tests for local effects after implantation
ISO 10993—7: 1995 Ethylene oxide sterilization residuals
ISO 10993—9: 1999 Framework for identification and quantification of potential degradationproducts
ISO 10993—10: 2002 Tests for irritations and delayed type hypersensitivity
ISO 10993—11: 2006 Tests for systemic toxicity
ISO 10993—12: 2002 Sample preparation and reference materials
ISO 10993—13: 1998 Identification and quantification of degradation products from polymericmedical devices
ISO 10993—14: 2001 Identification and quantification of degradation products from ceramics
ISO 10993—15: 2000 Identification and quantification of degradation products from metals andalloys
ISO 10993—16: 1997 Toxicokinetic study design for degradation products and leachables
ISO 10993—17: 2002 Establishment of allowable limits for leachable substances
ISO 10993—18: 2005 Chemical characterization of materials
ISO 10993—19: 2006 Physicochemical morphological and topographical characterization ofmaterials
ISO 10993—20: 2006 Principles and methods for immunotoxicological testing of medical devices
Biocompatibility Issues of Biomaterials 57
distinctions have been drawn from the standards (Schmalz and Arenholt-Bindslev2009):
1. Horizontal standards are valid for all medical devices2. Semihorizontal standards are valid for groups of products3. Vertical standards are valid for individual materials.
6 Development of New Biomaterials in Indonesia
Gadjah Mada University (Universitas Gadjah Mada or UGM) in Yogyakarta,Indonesia is a leading and the oldest university in the country. Within its eighteenfaculties, researchers are collaborating to develop new biomaterials through inter-disciplinary studies funded by the Government. The following are examples oflocal biomaterials and medical devices which have been developed by UGM and itspartners.
6.1 Orthopaedic Metal Plates
The enormous need of orthopaedic implants such as osteosynthesis plates is difficultto fulfill in developing countries like Indonesia (Dewo et al. 2008). A heavyearthquake with a magnitude of 6.3 on the Richter scale, struck the Indonesianisland Java in the early morning of May 27, 2006. The earthquake caused 5,782deaths and 36,299 people were injured. While the tsunami of 26 December 2004 inAceh caused 186,983 deaths and injured 125,000 people (Dewo et al. 2008).Earthquake and tsunami casualties were mainly suffering from musculoskeletalinjuries, especially fractures. Osteosynthesis plates are used in orthopaedic traumasurgeries to provide fixation and positioning of a fractured bone (Dewo et al. 2012).Unfortunately for such large numbers of causalities there were not enough boneplates in the local hospitals. The lack of bone plates were caused by: (1) all boneplates are imported, means they are very expensive, (2) donated bone plates fromoverseas were very late in their arrival, (3) local suppliers did not have enough boneplates in stock. In order to overcome the shortage of surgical implants, implants canbe re-used after appropriate cleaning (Magetsari et al. 2006). Another alternative isutilization of local products, because locally produced bone plates are much cheaperand can be obtained faster than from abroad. Mechanical properties of Indonesian—made osteosynthesis plates have shown to be improved by the application of sur-face mechanical attrition treatment (SMAT), as they become comparable to themechanical strength of the standard plates (Dewo et al. 2008, 2015).
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6.2 Bone Grafts
For bone substitution purposes, bio-inspired design is a very important key toinduce new bone formation within physiological condition. In this sense, hardtissue is regarded as carbonate-substituted hydroxyapatite (CHA) because carbonateis one of the most abundant impurity ions and its content is about 4–8 wt%(Barraletet et al. 2000; Landi et al. 2005). This is the reason for the extensivedevelopment of CHA for the last decade (Ana et al. 2010; Sunarso et al. 2013).Researchers at UGM have been successful in developing and fabricating humanbone apatite or CHA composite as reliable construct scaffold for bone substitution.It is now in the process of translating this from the laboratory onto the market, incollaboration with an Indonesian pharmaceutical company managed by the uni-versity holding company (Fig. 14).
6.3 Ventriculoperitoneal Shunts
Insertion of a shunting device for the treatment of hydrocephalus patients hasbecome a routine surgical procedure in neurosurgical practice. However, shunt
Fig. 14 A package of GAMA-CHA developed by UGM (ID P 0036890)
Biocompatibility Issues of Biomaterials 59
complications are frequent problem for pediatric neurosurgical service, most ofwhich are mechanical complications and infection (Scott 1990). To overcome theseproblems a neurosurgeon from the Faculty of Medicine at UGM has designed asemilunar slit valve shunt and a free mobile cylindrical antisiphon valve. It isproved that the semilunar valve shunt has the ability to maintain a normally neg-ative intracranial pressure for children in sitting position. The semilunar valve shunt(Fig. 15) has more advantages especially in the mechanism of opening and closingof the valve, compared to other valve designs (Sudiharto 2002).
6.4 Bone Substitutes
Palatoschisis is a birth defect in human and animals. It is caused by a failure of theelevation, apposition or fusion of the lateral palatine processes, resulting in thepersistence of a slit-like opening between the oral and nasal cavities (van denBerghe et al. 2010). Data from Dr. Sardjito General Hospital in Yogyakarta illus-trates a significant number of palatoschizis patients, with 85 cases in 2013.Palatoschizis (Fig. 16) is a serious esthetic and functional problem that causesdifficulty in chewing, swallowing and also speaking. Since there is no syntheticmaterial for bone substitute, to reconstruct the roof of the oral cavity, plastic surgerycan take place or a denture combined with an obturator can be fabricated(Dandekeri et al. 2012).
Dentistry and orthopaedic applications deal a lot with hydroxyapatite (HAp) dueto its good biocompatibility, osteoconductivity, and the bone-bonding properties(Simon et al. 2005). HAp has been studied for several years as bone substitute
Fig. 15 Ventriculoperitoneal shunt with semilunar valve system for hydrocephalus child
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material (Triyono et al. 2015). A team of researchers from UGM proved that localgypsum, from the area of Tasikmalaya Indonesia was synthesized into HAp bymicrowave-hydrothermal method (Pujiyanto et al. 2006). Based on this research, itcan be showed that the sintering process at the temperature of 1450 °C did notsignificantly effect on the cytotoxicity properties of local HAp powder (Pujiyantoet al. 2013). Pure HAp has chemical composition, biological and crystallographicproperties which are highly similar to bone and teeth (Herliansyah et al. 2006).
Bulk HAp exhibits poor mechanical properties, therefore there is a need toimprove its mechanical properties (Wang et al. 2004). Zirconia (Fig. 17) is one ofthe important fillers that has been used to increase the strength of many ceramics(Nayak et al. 2008). In bone surgery zirconia has shown very wide applications(Quan et al. 2008). One of the major drawbacks in the use of biomaterials is theoccurence of biomaterial-centred infections (Gottonbos 2001). It is proven that localHAp with 20 % zirconia has been an effective concentration in inhibiting thegrowth of S. epidermidis (Siswomihardjo et al. 2012).
Fig. 17 SEM images of: a HAp structure; b HAp with zirconia fill in the pores
Fig. 16 a Palatoschizis patient reconstructed with; b denture combined and with; c obturator(Courtesy of Faculty of Dentistry, UGM)
Biocompatibility Issues of Biomaterials 61
7 Perspective
The biocompatibility of biomaterials has developed into a very complex disciplineof materials science, since the term ‘biocompatibility’ has an important role withrespect to the safety of materials. In the last decade there is a rush in new productsof materials. On the other hand there is a high percentage of occurence in theadverse reactions to materials, not only to patients but medical personnel as well. Ithas understood that there are various ways in which materials and tissues caninteract to each others which will result in a specific biological response. It is thenbecoming a challenge for biomaterials scientists to search for strategies how toimprove the biocompatibility of biomaterials, with final goal provide biomaterialsthat are able to serve for the best performance of medical devices.
Acknowledgement My special thanks goes to my colleagues P. Sudiharto, H. Dedy Kusuma, B.Primario Wicaksono, MG. Widiastuti, Punto Dewo, Ika Dewi Ana, H. Agung Pribadi, Purnomoand Y. Novian Paramarthanto who supported me with pictures, references, suggestions and fruitfuldiscussions in completing this chapter.
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Biocompatibility Issues of Biomaterials 65
Animal Study and Pre-clinical Trialsof Biomaterials
Deni Noviana, Sri Estuningsih and Mokhamad Fakhrul Ulum
Abstract An in vivo study is one of the most important steps in the process oftranslating biomaterials to clinical applications. It is mostly conducted to confirmin vitro results before going further to clinical trials. Appropriate use of animalmodels in the in vivo studies of biomaterials and medical devices is mandatory andshould meet the approved regulations and ethics as defined by both local andinternational regulatory bodies. These studies involve the use of various approachesand protocols in order to know the body responses both local and systemic and tofind out the short- and long-term responses of the body toward the implantedbiomaterials or devices. This chapter describes complete procedures and practicesof in vivo studies starting from selection of appropriate animal model,pre-implantation, surgical procedure and post-implantation, and monitoring ofmaterial-host responses. Some experiences of in vivo studies done by Indonesianresearchers and the development of new implants are also presented.
Keywords Biomaterials � Biocompatibility � Animal testing
1 Introduction
The use of animal models in the in vivo testing phase is unavoidable in order tomeet the achievement of product security for human being. Various kind of animalmodels used in the research must be treated appropriately in accordance with therules and regulations of animal welfare and eligibility nationally and internationally.The consideration of an appropriate animal model and the preparation procedure,
D. Noviana (&) � S. Estuningsih � M.F. UlumBogor Agricultural University, Bogor, Indonesiae-mail: [email protected]
S. Estuningsihe-mail: [email protected]
M.F. Ulume-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_4
67
implantation, monitoring of the bio-information result of animal response duringand after the implantation is discussed in this chapter. This chapter also presentsvarious experiences of in vivo study done by Indonesian researchers, the devel-opment of biomaterial implant in order to meet the national biomedical product forthe independence of nation.
Animal models are animals chosen representatively for biocompatibility testingof a material developed for human beings (Pearce et al. 2007; Shanks et al. 2009).Biomaterial that has been proven safe in vitro does not necessarily show a goodresponse when it tested in vivo in the form of implantation in animal models. Thestages of in vivo testing using animal models in the research of biomaterialdevelopment become unavoidable matters. Various kinds of animal models whichare appropriate to use in the research must be treated morally and ethically well inorder to get the more representative response that has good validity to the appli-cation that supports human tissue recovery (Grimm 2014; Shanks et al. 2009). Theanimal models used in the research must be ruled which is appropriate to theeligibility and welfare of animals internationally, and the local regulation of acountry (Beauchamp and Childress 2001; Marie 2005). These clauses are made asthe reference; therefore, the treatment given to the animals does not harm either tothe animals or the result of the research itself. Implant is a need in the medical fieldwhich can improve the quality of human health, however, the implant remainscategorized as a foreign object that will be responded by the immune system.Therefore, the study of the body response to the implants is an absolute must donebefore they are applied to humans.
This chapter focuses on animal’s model for biomaterial research, ethics, care anduse, implantation study and monitoring, and experiences on animal study ofmedical implants in Indonesia. The consideration of an appropriate model animalselection and preparation procedure of animal suitability, animal uniformity,implantation process until the monitoring of animal during and post implantation isdiscussed in this chapter. This last chapter also presents various experiences andin vivo study done by Indonesian researchers in order to develop the biomaterialimplantation so that the independence of the nation in the need of fulfilment ofnational biomedical products can be reached.
2 Animal Model for Biomaterials Research
2.1 Common Animal Models
Animal models are commonly used in biomedical research especially for validatingresults of in vitro testing (Muschler et al. 2009; Pearce et al. 2007) before appli-cation to human. They are used due to a similarity of the organ function and organsystem owned by human body (Shanks et al. 2009). The response showed byanimal model towards the therapy or treatment and certain diseases is like the
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response showed by human body (McGonigle and Ruggeri 2014). Animal modelshave a shorter life span compared to human body. Moreover, they have a fastermetabolic rate so that the analysis of long-term implantation response can be pre-dicted better. Types of animal models used in the research are mostly rodent ani-mals (95–98 %), like mice and rats, while the rests are other species (about 2–5 %),such as rabbits, small ruminants, dogs and other species (Harkness et al. 2013). Thereaction and effect occurring in implantation and its influence in the process oftissue recovery was examined deeply, and the results showed a good reaction forthe human.
2.2 Appropriate Animal Models
Appropriate animal models are the main factors in in vivo test (Mardas et al. 2014).The suitability of animal models in terms of functionality and application of bio-logical response generated after the implantation into the main target in the research(Table 1). The selection of appropriate animal models in the test process keepsdeveloping along with the development and modification of biomaterial implants inorthopedic and dentistry (Pearce et al. 2007). Some of animal models that arecommonly used in in vivo material test in orthopedic and dentistry implants aresmall-size animals (Mapara et al. 2012), for example mice (Freilich et al. 2008;Yang et al. 2011), rats (Piccinini et al. 2014) and rabbits (Mapara et al. 2012).Whereas large animals (Gardel et al. 2013; Pearce et al. 2007), like sheep (Ulum et al.2014a), goat (Li et al. 2007), dog (Baas 2008), and pig (Ruehe et al. 2009) are alsoused in in vivo test. Large animals have loading functionality and bone structurewhich are similar to human beings. Therefore, they are often used as animal models(Gardel et al. 2013).
2.3 Target Achieving Bio-Information from Animal Models
Biocompatibility is the major target in the development of biomaterial implants.The properties of biocompatibility can be analyzed by using various approach inorder to know the local response as well as the systemic response and to know theshort and long response after it implanted in animals model (Table 2). The extra-cellular fluid in the surrounding implantation site is the sample example that can betaken to determine the local response with the application of microdialysis system(Keeler et al. 2014). The sampling time of extracellular fluid can be done within afew days up to several months adjusted to the study design. Extracellular fluid canbe analyzed at various biomarkers, such as elements, biochemical elements as wellas cytokines—the marker of either good or negative implantation biomaterial in thebody locally.
Animal Study and Pre-clinical Trials of Biomaterials 69
Table 1 Several example of animal models for biomedical implants
Animalmodel
Species Implantationsite
Target analysis References
Mice Balb/C Tibia bone Compatibility test Cheng et al.(2013b); Yanget al. (2011)
Balb/C Tail bloodvessel
Biodegradation andsystemic distribution ofbiodegradable metalsimplant
Mueller et al.(2012)
Ddy FemoralmuscleSubcutaneoustissue
Biocompatibility andbiodegradation ofbiodegradable metalsimplant
Noviana et al.(2012b); Paramithaet al. (2013)
C57BL/6 Femur bone Osteoconductivity ofbioactive-scaffolds
Cheng et al.(2013a)
Rat Sprague-Dawley Femur bone Compatibility boneimplants and osteoporotic
Alghamdi et al.(2014); Alt et al.(2013); Lips et al.(2014)
Mechanical propertiesand integration of implant
Boerckel et al.(2012); Yavariet al. (2014)
Systemic body responsespost-implantation
Lucke et al. (2003)
Tibia bone Gait load implantintegration
Piccinini et al.(2014)
Implant-associatedinfection
Haenle et al.(2013); Lucke et al.(2003)
Systemic body responsespost-implantation
Panjaitan et al.(2014)
Calvarianbone
Bone cement for bonerepair
Schliephake et al.(2004)
Wistar Tibia bone Mechanical loading onperi-implant bone healing
Zhang et al. (2012)
Mandiblebone
Bone cement for bonerepair
Issa et al. (2008)
Wistar-kyoto Calvarianbone
Bone grafting Kneser et al.(2006)
(continued)
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Table 1 (continued)
Animalmodel
Species Implantationsite
Target analysis References
Rabbit New Zealandwhite
Dorsal muscle Biocompatibility Cheng et al.(2013b)
Femur bone Biocompatibility Sennerby et al.(2005); Sul et al.(2002)
Biocompatibility onsystemic and local tissuesresponse
Yu et al. (2012)
Implant for boneinfection
Baro et al. (2002)
Tibia bone Biocompatibility Sennerby et al.(2005); Sul et al.(2002)
Mandiblebone
Biocompatibility of bonescaffold
Wang et al. (2007)
Sheep Thin tailedsheep-Indonesia
Radia bone Biocompatibility andbiodegradation ofbiodegradable metalimplants
Ulum et al. (2014a,2015)
Tibia bone Biocompatibility andbiodegradation ofbiodegradable metalimplants
Ulum et al. (2014a,2015)
Italian massese Tibia bone Autologous bioceramicscaffold
Kon et al. (2000)
Osteointegration of metalimplants
Sachse et al. (2005)
Femur bone Mechanical andhistomorphometric studyof post metal-implantsimplantation
Giavaresi et al.(2003)
Goat Dutch milk goat Paraspinalmuscles
Biological performance Li et al. (2007)
Lumbal bone Biological performance Li et al. (2007)
Spanish-goat Lumbal bone Biological study of bonefusion post-implantation
Brantigan et al.(1994)
Dog Beagle Mandiblebone
Biologic stability ofbone-implant contact
Cha et al. (2010);Cho et al. (2013)
American hound Femur bone Revision of arthroplasty Baas (2008)
Bone allograft andimplant fixation
Barckman (2014)
Tibia bone Bone allograft andimplant fixation
Barckman (2014)
Mongrel-dog Illiac artery Patency and healingcharacteristic of stents
Castañeda et al.(2000)
Aorta artery Patency and healingcharacteristic of stents
Castañeda et al.(2000)
(continued)
Animal Study and Pre-clinical Trials of Biomaterials 71
3 Ethics, Care and Use of Animals
3.1 Bioethics in Biomaterials Research
The ethical and moral in doing research are the norms applying the basic principlesof good interaction that regulate the interaction between human—as the user ofanimals, and the animals that are used in the research (Beauchamp 2008; Grimm2014; Marie 2005). There are four basic principles of bioethics as stated byBeauchamp and Childress (2001), namely (1) the principle of respecting autonomy(respect for autonomy), (2) the principle of doing good deed (beneficence), (3) theprinciple of not doing harm (non-maleficence) and (4) the principle of justice(justice). Animal models are seen as individual or group of research partners thatmust be treated well according to the ethical principles. These principles serve asthe guidance in how humans (the researcher) treat the animal models used in theresearch.
3.2 Principles of “3R” (Three R Principle) and “5F”(Freedoms)
Declaration of Helsinki, 1964 (Rothman and Michels 2000; Bădărău 2013; Holm2013; World Medical Association 2001) mentioned a few principles that containedthe statements about the use of animals in doing research, i.e.: (1) Medical researchinvolving human subjects must conform to generally accepted scientific principles,be based on a thorough knowledge of the scientific literature, other relevant sourcesof information, and on adequate laboratory and, where appropriate, animal exper-imentation; (2) Appropriate caution must be exercised in the conduct of researchwhich may affect the environment, and the welfare of animals used for researchmust be respected.
The ethical use of animals in doing research should follow the instructionand recommendations of international standards (Grimm 2014; Guhad 2005;
Table 1 (continued)
Animalmodel
Species Implantationsite
Target analysis References
Pig Minipig Mandiblebone
Dental implantosseointegration
Joos et al. (2005)
Bone regeneration Ruehe et al. (2009)
Femur bone Mechanical evaluation oforthodontic implants
Pithon et al. (2013)
Miniature swine Vessels Arterial healing poststenting
Nishimura et al.(2012)
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Törnqvist et al. 2014). Russell and Burch (1959) were the first people that stated theidea of the use of animals in doing research which was expected to follow the rulesof 3 R (The “three R principle”). The 3 R principles are (Guhad 2005; Russell andBurch 1959): (1) the use of experimental animals should receive attention in theeffort of finding the replacement (replacement), (2) the reduction in the number ofanimal use to its limit use can be analyzed statistically (reduction), and (3) Theimprovement of animal handling towards the animal is used to reduce the impactthat can be painful and stressful (refinement).
The first principle of Replacement is to avoid the use of animal as much aspossible in doing research (Guhad 2005; Reinhardt 2008; Russell and Burch 1959).Researchers should explore the possibility of using organ culture/tissue/cell as asubstitute for the use of live animals or lower order animals, for example, replacethe use of primates to mice or rats replaced by poultry or poultry replaced by fish,and so on. This replacement principle is basically the biological response expectedfrom the test. This could be represented by a given response from the replacementanimals. The second principle, Reduction, is to develop a strategy of a fewer animaluse to produce the same data adjusted to the research design (Guhad 2005; Russelland Burch 1959). The principles covers the effort to maximize the bioinformationobtained from an experiment without adding the number of animals or the numberof potential treatments towards the pain caused by the treatment in the research so
Table 2 Several example of method to achieving bio-information from animal model
Sample Access Response target of bio-information Analysis
Local Systemic Shortperiod
Longperiod
Extracellularfluid
Microdialysis √ – √ √ Biochemistry, elements,ELISA, biosensor,biomoleculer
Hard tissue(bones)
Biopsy,euthanasia
√ – √ √ Radiology, histology,elements,
Soft tissue(muscles,skin, etc.)
Biopsy,microdialysis,euthanasia
√ – √ √ Radiology, histology,elements, ELISA,biomoleculer
Wholeblood
Venesection,canulation
– √ √ √ Haematopoetic profile,biochemistry, elements,ELISA, biosensor,biomoleculer
Urine Centesis,canulation,pach
– √ √ √ Biochemistry, elements,ELISA, biosensor,biomoleculer
Organtissue(liver,spleen,kidney,etc.)
Biopsy,microdialysis,euthanasia
– √ √ √ Radiology, histology,elements, ELISA,biomoleculer
Animal Study and Pre-clinical Trials of Biomaterials 73
that the researchers can obtain the maximum benefits without adding the pain andthe number of experimental animals. The third principle, Refinement, is an attemptto modify the maintenance management or procedures of research treatment so thatit can improve the animal welfare or reduce or relieve the pain and stress(Buchanan-Smith et al. 2005; Guhad 2005; Russell and Burch 1959).
The 3R principle should be combined with 5F principle (The “five freedoms”) inthe use of animals. The 5F principle tries to place the animal as an object ofresearch with animal welfare principle; therefore, the response given will be rep-resentative enough, and it has a good validity towards the research result that willbe obtained (Marie 2005; Phillips 2008). The animals treated well will give bestresponse if it is compared to those treated badly. Inappropriate treatment will mixup the data obtained; as a result, the data become unrepresentative anymore to theresearch result. This will result in an inappropriate conclusion because the responseobtained bothers the research result.
The 5F principles are: (1) the animals are free from hunger and thirst, (2) theanimals are free from uncomfortable feeling, (3) the animals are free from pain,trauma, and disease, (4) the animals are free from fear and long-term stress, (5) theanimals are free to express their natural behavior, which are given a room andfacility which is appropriate to the environmental enrichment and will not interferewith the research results expected (Suckow et al. 2012).
Ensuring the animal models are free from hunger and thirst by given foodadjusted to the natural condition with a balance nutrition accordance with the needsor research design and drinking water in adequate amounts. The feed is givenaccordance with the needs and drinking water is supplied in ad libitum; moreover,the animals can easily access them. Furthermore, the animals are free from dis-comfort feeling which can be overcome by taking into account the needs of theanimals to a shelter or nest in accordance with the natural conditions on the size,temperature, humidity, ventilation and lighting. The animals are free from pain,injury, and disease that can be done through the established health programs, suchas using non-invasive technique or minimal invasive, pain-reducing medication orconsciousness, and always use a method of euthanasia in accordance with the rulesof ethical use of animals such as providing transition and adaptation to the newenvironment, a new cage officer, a new feed, or a new procedure before the studyperformed. The cage officers or researchers must have expertise and skill in thehandling of animals which are in line with the requirements and implementation ofresearch procedures. The animals used in study will be free to express their naturalbehavior by providing sufficient width cage, good cage quality, and attention tosocialization, specific behavior, as well as enrichment programs. Enrichment pro-gram is given in various forms according to the type of animals, such as a swingingfor primates, woodcarvings for rodents, and so forth.
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3.3 Indonesian Regulations for Animal Use in BiomedicalResearch
The ethical use of animals in research in Indonesia refers to the internationaldocument, like “The Guide for The Care and Use Laboratory Animals” and“Helsinki Declaration” (Garber et al. 2010; Portaluppi et al. 2010; Touitou et al.2004). Then in Indonesia, its implementation refers the ethical code of Indonesianveterinarian in the Articles of Association of Indonesian Veterinary MedicalAssociation (Chapter III Article 18, 19, 21 and 22), as well as Law of the Republicof Indonesia No. 18, 2009 which is completed with the Law of Republic ofIndonesia No. 41, 2014 about Husbandry and Animal Health in which there arearticles (Chapter VI Article 66, Chapter VII Article 71 and 74), that have providedsigns to veterinarian, researcher, and animal user; therefore, they will not harm theanimals.
The implementation of the research using animals is supposed to involve min-imal one skilled and experienced veterinarian to make sure that the animals are in agood condition, healthy and prosperous. A veterinarian is a human resource that hasknowledge and skill related to animal health based on the ethical code of a vet-erinarian and an applied legislation. The articles of Indonesian Veterinary MedicalAssociation in Chapter III contains ethical codes of veterinarian in Indonesiacontaining some responsibilities of a veterinarian towards the patient (animal)namely, (1) treating the patients attentively, and giving affection as the meaning fortheir owner, and using all the knowledge, skill and experience to interests of thepatients, (2) helping the patients in an emergency condition and or providing a wayout if they are not able to refer to other colleagues who are able to do so, (3) withthe consent of his client, the veterinarian can perform euthanasia (mercy sleeping)because he believes that the best acts as the way out for the patients and his clients,(4) prioritizing the animal health and preventing disease expansion that can result inthe economic and social losses.
Related to the animal welfare, the Law of Republic of Indonesia No. 18, 2009and its enhanced within the Law of Indonesian Republic No. 41, 2014 abouthusbandry and animal welfare stated that: (1) animal handling is carried out nor-mally and humanly without any persecution or abuse that dangers the animal,(2) animal handling is performed by animal medical officers that are qualified interms of ethical code and they obey their vow or promise profession, (3) the use ofanimal or part of animal is done under the control of veterinarian based on theethical and veterinarian principles by considering the animal welfare.
3.4 Animal Ethic, Care and Use Committee
The committee of animal ethics is a committee that is responsible for doing thestudy of research or method of animal use in an institution (Grimm 2014; Marie
Animal Study and Pre-clinical Trials of Biomaterials 75
2005). This committee is appointed by the institution to make sure that everyprocedure in animal use has been in line with the principle of animal welfare. Thecommittee of animal ethics in education and research institutions using animal intheir research and education activity in Indonesia is ruled by the decree of theMinister of State for Research and Technology No. 108/M/Kp/IX/2004, theMinister of Health No. 1045/Menkes/SKB/IX/2004 and the Minister of AgricultureNo. 540.1/Kpst/OT.160/9/2004 about the formation of National BioethicsCommittee and Health Research Ethics National Commission—institutions han-dling bioethics and ethics problem in national level.
4 Implantation Study, Live Monitoring and HistologicalAnalysis
4.1 Adaptation and Clinical Health Synchronization
Animal AdaptationAnimal adaptation is an initial step that should be done by researchers before theanimals are used in a series of research. The animals need adaptation process withthe new environment which may be different from the previous one. The adaptationshould be carried out at least in a few days after their arrival because on the way tothe new place, the animals experience stress and distress (Obernier and Baldwin2006); consequently, this influences the (physio biology) condition and the behaviorof the animals (Arts et al. 2012). The condition and environment of the new treat-ment is supposed to be not too different from the previous condition. The animal willadapt several factors, namely physical and chemical factors (Fox et al. 2002). Theexamples of physical factor are temperature, relative humidity, air flow and itscomposition, noisy level, lightning, radiation, cage and its equipment, as well asother physical factors (Fox et al. 2002). Whereas chemical factors, like xenobiotic(biotransformation, feed, and water), pharmaceuticals (drugs, sedation, painkillers,euthanasia drug, antimicrobial drug, and other agents) and pheromones (Fox et al.2002). The time needed by the animal to adapt depends on the type and strain of theanimals; like rodents need around 1–7 days (Obernier and Baldwin 2006).
Clinical Health SynchronizationNext, the health condition of the animal should clinically be treated the samebecause Indonesia is a tropical country. Tropical area has an amazing microbediversity characteristic if it is compared to sub-tropical and non-tropical areas. Theuniformity of the experimental animals can be done by giving some antimicrobialagents to them like ant parasite, antimolds well as other suitable microbe (Morris1995). Geographical area with a different climate has various similarity of pathogenagents; therefore, it becomes a unique challenge for the medical team to giveantibiotic use policy (Campbell et al. 2014). This treatment can be given around
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couple of days until several weeks with a number of treatment, like preventiondosage and or treatment to homogenize the health condition of experimental ani-mals (Table 3).
4.2 Pre-implantation Treatments
Fasting treatment to several experimental animals are various. This depends on thetreatment form of implantation surgery and types of animals. Animal models inresearch with the procedure of implantation surgery will not be given food beforethey experience the process of anesthesia. The pre-medication and pre-anaesthesiatreatment should be given before the anesthesia to perform implantation surgery.
Pre-surgical FastingPre-surgical fasting before the treatment of implantation surgery is done in order toavoid the pulmonary aspiration coming from the remaining food in the digestivesystem (Crenshaw et al. 1999; Maltby 1993). The fasting starts at 2 h before thesurgery to clear the fluid, and it takes 6 h to clear the solid from the digestive system(Ljungqvist and Søreide 2003). Animals with compound stomach (rumen) in thegroup of ruminants (sheep, goat, and cow) should fast for 24–48 h before they getanesthetized to the surgery. Animals with the type of monogastric stomach (dog,cat, pig) should fast for 6–24 h. Rodent’s animals and rabbits (mouse, rat, genuinepig, hamster, and rabbit) do not need to fast because this group has high metabolismlevel. This group does not have gag reflex so that regurgitation will not occurduring the surgery treatment.
Pre-medicationPre-medication is a stage before the animals get anesthetized to the surgery treat-ment. Pre-medication is performed by giving certain medicine to prevent thepre-infection and during the surgery (Bratzler et al. 2005; Bushnell et al. 2008).Although infection is not unavoidable, pre-medication treatment is a good thing todo before the surgery (Martin 1994). Generally, the medicine given is antibiotic as
Table 3 Recommendation for animal health synchronization
Time Drugs type Remark Reference
Day 0–2 No drugs The animals are in a resting condition (recovery)after transportation to adapt new environment
Obernier andBaldwin(2006)Day 3 Anthelmintic Deworming part 1
Day 4–8 Antibiotic Antibiotic
Day 9 Anthelmintic Deworming part 2
Day 10–14 Antibiotic Antifungal or antiprotozoal
Day 15–30 No drugs The animals are in a resting condition (recovery)after the treatment of synchronization beforethey are used in the next stage
Animal Study and Pre-clinical Trials of Biomaterials 77
prophylaxis antibiotic that is given before the surgery (Bratzler et al. 2005;Dale et al. 2004; Morris 1995). The route of antibiotic application in pre-medicationis intravenous (iv), in which the distribution of the antibiotic in the tissue is moreoptimal than that in other route that cannot predict the level and the absorption timeis longer (Martin 1994). The recommended time is minutes before the surgery isperformed. The earlier of the pre-medication given, 120–180 min, the higher risk ofinfection in the surgical site will be (surgical site infection) (Hawn et al. 2013). Inlong duration of surgical treatment, like more than 2 h, the intravenous antibioticapplication must be repeated every 2–3 h once (Hawn et al. 2013; Martin 1994).
Pre-anesthesiaPre-anaesthesia is a certain medication treatment to the animals before anesthesiadrugs given. The treatment of pre-anaesthesia medicine to the animals is intended togive security within the anesthesia, so that the stages of anesthesia becomesmoother and avoid the negative effect (Bosing et al. 2012), avoid myocardialarrhythmias to occur (Romano et al. 2012), avoid the negative effect in the car-diopulmonary system (Bosing et al. 2012; Langan et al. 2000; Schumacher et al.1997), and patient risk with cardiomyopathy (Kato 2014).
The Sterilization of the Implant MaterialSterilization implant material can be done in several ways based on the materialused. Implant material should be packed with a heat-resistant material. Implantmaterial is corrosion resistant and made of a metal that can be sterilized in con-junction with a surgical instrument made of metal. Sterilization material is made ofmetal that can use dry-heat sterilization (oven), heat with high pressure (autoclave)or with radiation energy of gamma rays or X-rays (Fossum 2013; Heaton 1998;Mann et al. 2011). While material that cannot stand with heat can use ultravioletrays, gamma rays or X-rays. Especially for sterilization using ultraviolet light, theimplant material must be exposed directly by light with no obstacles such aspackaging because it can lead to ineffectiveness of the sterilization process.
4.3 Surgical Implantation
AnesthesiaAnesthesia is a major procedure before the process of surgery is performed on theanimal for research need. Anesthesia is an action taken to eliminate some or all ofthe sensation of pain from the body as a result of the presence of drugs that suppressthe sensation of local nerves (peripheral) and central (general) (Fish et al. 2011;Kohn et al. 1997). Anesthesia is limited to the working of the local nerve functiondue to the suppression of local nerve (blockage) or the main branch of the nerve(regional) by the drug. General anesthesia is a form of anesthesia that removes theawareness and sensation of pain and muscle relaxation characterized by thedecreased reflexes. While surgical anesthesia is an elimination of consciousness,sensation of pain and muscle relaxation due to the provision of one kind or
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combination of drugs. This will facilitate the surgical procedure because of the lossof pain sensation and movement of animal.
The stages of consciousness loss in the process of general anesthesia are dividedinto 4 stages (Kohn et al. 1997). The initial phase is characterized by the voluntaryexcitation motors, struggling and ataxia. The second stage is the stage of delirium orinvoluntary excitement in which the animals start to lose consciousness and losevoluntary control. At the end of second stage is marked by the absence of responseto sounds, unconscious and began to lose the sensation of pain. The third stage isthe stage of surgery or called anesthesia surgery that depends on the number ofdoses of the drug given to suppress the central nervous system. The surgicalanesthesia itself is divided into 4 plane, namely plane 1 that is characterized by thepain loss and muscle relaxation. Plane 1 is only appropriate to minor surgicaltreatment with the procedure of non-invasive surgery. Plane 2 is characterized bythe loss of pain sensation and the muscle experience relaxation until this plane isappropriate to whole surgical treatment (both of minor and mayor). Plane 3 is thestage in which the animals lose their nerve reflex total (intercostals muscles). Plane4 is the last plane from anesthesia characterized by the paralysis thoroughly fromintercostals muscles, enlarged pupils, cardiopulmonary function suppression of thefurther level (severe). Stage 4 of the anesthesia is characterized by the cessation ofrespiratory system and circulatory system. This stage is the beginning of deathbecause the respiratory and circulatory systems stop.
The selection of anesthetic agent and the appropriate dose is the key for thesuccess of the surgery. The details of form and type of anesthetic and analgesicselection that fit can be seen in “Lumb and Jones’ Veterinary Anesthesia andAnalgesia” (Grimm et al. 2011; Tranquilli et al. 2013). The anesthesia was given afew minutes (10–20 min) after pre-anaesthesia. Anesthesia can be administeredseveral routes, parenteral e.g. intra-peritoneal, intra muscular, intravenous, andlocal, or per-inhalation according to the type of the surgery and the type of animals.The dose of the drug in mild, moderate or strong conditions is adapted to the type ofsurgery that will be carried out (Garcia 2013).
AnalgesiaAn analgesic agent that serves relieve pain (DeLeo 2006). This dosage is usuallygiven in conjunction with anesthesia in animals undergoing implantation surgery.Certain surgical actions can cause pain even though the animals are in the absenceof consciousness. The pain can trigger the cytokines production that mediatescertain response, such as pain reflexes that are out of control so that it can causedeath in animals (Üçeyler et al. 2007). Pain reflex are suppressed so that the varietyof surgical procedures can be run without the unnecessary reflex motion that canharm the animals and surgical team. The analgesic administration is usually givenuntil a few days after implantation in order to suppress the effects ofpro-inflammatory cytokines (Beilin et al. 2003).
Hair Shaving and Disinfection of Surgical AreaAnimals generally have hair on their body so that the shaving is done in the area ofsurgical orientation and continued by the provision of disinfectant and animal
Animal Study and Pre-clinical Trials of Biomaterials 79
positioning on the operating table for surgery (Fossum 2013; Mann et al. 2011).Disinfection of the surgical area is given by using iodine tincture or using a sterileplastic wrap to cover the surgical area.
ImplantationSurgical implantation can be performed after the animals are completely anes-thetized and do not feel the pain; moreover, they are in the condition of relax(Clarke and Trim 2013). This condition can be achieved in anesthetic condition of 2and 3 stages the surgery is done in accordance with the design of the study wanted(Fig. 1).
The Monitoring of Anesthetized AnimalsThe monitoring of animals during the anesthesia is needed to be done to determinethe stage of the anesthesia process after the administration of anesthesia until theanimals awake again (recovery) (Clarke and Trim 2013; McKelvey andHollingshead 2003). Anesthetized condition is the condition in which the animalsare in the biological stage that is close to death. Therefore, monitoring the status ofanesthetized animal must be done continuously to ensure that the animals are in asafe condition of stage 4 (death) from anesthesia. There are several things thatshould be observed in animals, namely the system of cardiovascular system, res-piratory system, muscle tonus and sense of vision (Table 4) (Garcia 2013).
Fig. 1 The implantation of biomaterials in experimental animals. a The construction of gap in therat femoral bone, b the implantation of stainless steel in the rat femoral bone, c the implantation ofmagnesium rod in the rat femoral bone, d the implantation of polymer membrane in the rat frontalbone, e the implantation of silk suture head in the mice femoral muscle, f the implantation ofporous metal bone graft material with intra-medulla pin on the mice femoral bone
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Post-implantation MonitoringPost implantation of the animals is monitored until they are completely aware. Thepost anesthesia recovery time varies depending on the type of drug used and thesurgical procedures performed (Clarke and Trim 2013). The monitoringpost-implantation should be done within 24–48 h. This is important to determinethe condition of a change in behavior of animals under the normal conditions suchas eating, drinking and their activity (Garcia 2013). Stitching wounds are examinedin the form of a strong knot and the wounds are neatly closed (not open) and there isno bleeding (Fossum 2013). During this monitoring period, antibiotics of postimplantation is given to prevent infection in the surgical area. Once recovered well,the animals are returned to the cage maintenance for further treatment of postimplantation.
4.4 Post-implantation
Post-implantation Pain Killer (Analgesia)Surgery causes tissue damage in animals due to the incision and implantation ofactions that cause the sensation of post-surgical pain (Walker et al. 2011). The painsensation is a major alarm system that inform the damage of the tissue (Sneddon et al.2014). The provision of post implantation analgesia aims to reduce pain and suppressthe negative effects on the release of pro-inflammatory cytokines from the tissuedamaged by surgery (Beilin et al. 2003). Not all animals show the pain sensationclearly (naked eyes) (Fitzpatrick et al. 2006). The methods for analyzing the pain ofthe animals can be done with 3 approaches (Walker et al. 2011; Weary et al. 2006),i.e. by measuring the function of the body through the measurement of food intakeand daily drink or weight, by measuring the physiological response of the body of theblood cortisol concentration profile, and by observing changes in the behavior ofanimals, like the sound produced. The preparations of anti-pain need to be given after
Table 4 Animal observation
Cardiovascularsystem
Respiratorysystem
Muscle tone Eye
Heart rate andrhythmMucousmembranecolorCapillary refilltimeArterial pulseand pressureBodytemperature
Respiratory rateDepth ofbreathingCharacter ofbreathingBlood gasesHemoglobinoxygen saturation(SpO2)
Jaw or limb toneResponse to painfulstimulus (toe or tailpinch)
Position of eye (presenceor absence of movement)Size of pupilResponsiveness of pupilto lightPalpebral reflexCorneal reflexLacrimation
Animal Study and Pre-clinical Trials of Biomaterials 81
the implantation treatment although the sensation of the pain in each animal varies(Nielsen et al. 2009; Tranquilli et al. 2013; Viñuela-Fernández et al. 2007). Theapplication of pain killer (analgesia) is intended to reduce excessive pain sensationthat causes distress to the animals after surgery (Richardson and Flecknell 2005).
Antibiotic post-implantationThe infection after surgery can be so risky in sepsis that it can increase the value ofmorbidity, mortality and additional cost of treatments (Lane et al. 2010). Antibioticsare given in accordance with the purposes, usually given for surgery that lasts formore than 2 h and or patients receiving implant material installation.Post-implantation antibiotics should be given to avoid infection after surgery(Campbell et al. 2014). Generally, antibiotics of post-surgery range in 3–5 dayswith long-acting types of antibiotics with 2 day interval or daily administrationshort-acting (Tables 5 and 6) (Martin 1994).
Suture RemovalSuturing the cut functions to support the tissue so that the distance among the cutscan be made as close as possible in order to make the wound recover well (Bennett1988). Suturing the skin can use silk or nylon thread that can be absorbed by thebody (Altman et al. 2003; Bennett 1988; Vepari and Kaplan 2007). Monitoring oncuts and seams should be done within 48–72 h to make sure that there is noinfection and apart stitches (Fossum 2013). This sewing thread should be takenwithin 3–5 days gradually or no later than 14 days after surgery (Fossum 2013;Mann et al. 2011).
Table 5 Bacteriologic and pharmacokinetic criteria for biomaterials implantation
Bacteriologicproperties
Antibiotic level expected Dose
Rapid anddose-dependentkilling
>Minimum inhibitory concentration(MIC) of organisms for a short period
Large single dose (2–3times the usual dose)
Post-antibioticeffect
No inoculum effect(e.g.,aminoglycosides)
Time-dependentkilling
>Minimum inhibitory concentration(MIC) of organisms Throughout thesurgical procedure
Single dose of a drugswith a long half-life(long-acting)
No post-antibioticeffect
Repeated doses of a drugwith a short half-life(short-acting)Inoculum effect
(e.g., β-lactamantibiotics)
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Implantation Syndrome RisksImplantation syndrome of material should be of concern in the implementation ofthe material implantation. Although the mechanism of syndrome cannot beexplained well, syndrome implantation can cause things outside the desire to deathduring and after implantation (De Maria et al. 2012; Donaldson et al. 2009). Theforms of syndrome were found as bone cement implantation syndrome (BCIS)(Donaldson et al. 2009), coronary syndrome of post-stenting of heart coronaryarteries (Ferrari et al. 2005), blood clotting (Park et al. 2010), Brugada syndrome ofpost cardioverter-defibrillator installation in the heart (Sacher et al. 2006),and infection that occurs after biomaterial implantation (Matsuno et al. 2006;Reefhuis et al. 2003).
4.5 Data Monitoring
Life MonitoringMonitoring data of pre-, peri- and post-implantation in animals can be done inseveral ways, namely the method of non-invasive, minimal invasive and invasive.Samples can be taken, like blood (Fig. 2), urine, tissue, heart and brain electricity,body and tissue temperature, implant stability, and radiology image. Product ofresponse result analyte of tissue interaction with biomaterial can be accessedthrough the biosensor (Wilson and Gifford 2005). The number of biological sam-ples is adjusted to the types and size of animal. Monitoring data for histologicexamination of tissue response in the living animal can be done with biopsy oftissue, muscle, bone and organ (Lehtonen et al. 2001). Implantation biopsy pro-cedure follows the protocol of implantation in accordance with the type of animalsused.
Post-mortem MonitoringMonitoring data of post-mortem is usually performed to design research that hasend-point of animal euthanasia. Some biocompatibility tests of a certain biomaterialon the organ are used for analysis purposes of histologically systemic response ofsome vital organs that can be taken partly or entirely at the end of the test. Suchactions sometimes do not enable the animals to be able to stay alive so that theprocedure of euthanasia is needed (Alper 2008). Euthanasia is a medical procedurethat removes animals’ soul gently and humane (Stokes 2002). Animals are eutha-nized first and then followed by tissue removal. The making of remaining
Table 6 Pharmacodynamics properties of 3 types of antibiotics
Properties β-lactam antibiotics Aminoglycosides Quinolones
Inoculum effect + − ±
Post-antibiotic effect ± + +
Killing rate Time-dependent Dose-dependent Intermediate
Animal Study and Pre-clinical Trials of Biomaterials 83
biodegradable sample or the untouched sample of the non-degradable implant istaken to analyse for the further characteristics (Ulum et al. 2015). The local tissue,such as muscle, bone of implantation area and the sample for systemic reactionfrom inside organs can be taken for histology examination (Paramitha et al. 2013;Ulum et al. 2014b).
4.6 Biomedical Imaging and Its Analysis in Life Animal
Biomedical ImagingBiomedical imaging is a method that seeks to describe a variety of responses thatoccur in implant, peri-implant, tissue around the implant, and other tissue in greaterdistance from the implant or the so-called systemic response. Generally, thebiomedical imaging uses energy of ionizing radiation, such as X-rays, non-ionizingradiation, like magnetic resonance and high-frequency sound waves, ultrasound(Beard and Losh 2006; Davis 2008).
X-ray-based imaging is radiography, tomography, fluoroscopy (Davis 2008).Since X-rays are found, the current development of radiological imaging technol-ogy is growing very rapidly for medical diagnostic purposes as well as for advanceresearch world (Tempany and McNeil 2001). It is necessary to consider that theenergy of ionizing radiation causes negative effects so that imaging is only per-formed in a short time and in certain time (Barrett et al. 2015; Dincer and Sezgin2014). The image of bone and the implant can be analyzed properly in this imaging,both digitally and conventionally. Radiogram implant can be analyzed by usingdensitometer at illuminator (Noviana et al. 2013a; Ulum et al. 2014a). Radiogramon illuminators can be converted into digital images by using a digital camera, andthen it can be analyzed by using software to analyze the picture, like
Fig. 2 Blood sampling in several types of animals of post implantation of biomaterialimplantation: a blood sampling of the mice was taken through the venous sinuses retroorbitalis,b through intacardial or via the tail vein of the mice, c the blood sampling of the rabbit were takenthrough venous auricalis on the ears, and d the sheep were taken through the jugular vein in theneck
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ImageJ. The application of ImageJ software in the analysis has been applied totissue response towards the metal implant that can be absorbed by the body and itexperiences the process of biodegradation (Ulum et al. 2014b).
Magnetic resonance energy-based imaging (MRI) has the ability to image softtissue very well and there is no ionizing radiation (Davis 2008; Hartwig et al. 2009;Jacobson 2005). The MRI imaging was well known for certain time, and it can bedone safely to the animals (Tempany and McNeil 2001); however, there were noeffects that were encountered, namely magnetic resonance energy that can cause abiological effect (Hartwig et al. 2009).
Imaging using high frequency of sound energy is ultrasonography(USG) (Diederich and Hynynen 1999). The imaging that utilized USG can imagereal-time; however, image taking over long time causes an increase in temperatureof surrounding tissue examination hazardous (Jacobson 2005; Teefey et al. 2004).Ultrasound utilizing high frequency sound energy is because of the absence ofionizing radiation; however, imaging taking a long time causes an increase in tissuetemperature around the location of dangerous examination (Liu et al. 2014; Palmeriand Nightingale 2004). The weakness of ultrasound is in the imaging of hard tissue,like bone, the implant and the air. The weakness has developed and can be over-come well so that ultrasound has a diagnostic value (Shiver et al. 2005; Tchelepiand Ralls 2009; Ulum et al. 2015).
Biomedical imaging in animals is different from that in human. Some experi-mental animal need a series of procedures for the restraint and the handling ofanimals is done before imaged. Animal preparation procedure generally needs ananesthetic action as well as the repetition of anesthesia for imaging in a longduration of time. The application of contrast material and the exposure of ionizingradiation influence directly or indirectly towards the physiological function ofanimals (Driehuys et al. 2008).
Animal Handling and RestraintHandling and restraint of animals are an important step prior to the preparation ofimaging. The forms and techniques used will vary on each animal depending on thetype of research and the target data to be taken during the monitoring data.Considering animal movement during imaging is the main thing that bothers if themovement cause noise or inference in an image taken; therefore, the next form ofhandling can be taken by giving tranquilizer, sedation or anesthesia (Hildebrandt et al.2008). Tranquilizer, sedation and anesthesia are handling and restrain forms chemi-cally in the experimental animals to facilitate a variety of procedures in medicaltreatment and research given in accordance with certain rules (Fish et al. 2011; Muirand Hubbell 2014).
Generally, handling and restrain technique of animals can be divided intophysical and chemical forms (Fowler 2011). Physical handling can be done byusing restrain or other tools that can make animals become cooperative during theimaging. Sheep or goat can be handled by using clamp cage or the combination ofrestrain during ultrasound imaging, brain and heart electricity image, blood sam-pling or others. Rodent animals can also be handled by using clamp cage with a
Animal Study and Pre-clinical Trials of Biomaterials 85
special design adjusted to the size of their body. While chemical handling is atreatment using tranquilizer, sedation, or anesthesia drugs depending on the imagetarget that will be taken (Hildebrandt et al. 2008).
Animal Preparation for Biomedical ImagingThe preparation of animals before imaging will be different. This depends on theform of imaging that will be taken. The procedure difference depends on theequipment types and ability in making the image wanted (Johnson et al. 2014). Theanimals should fast before the process of anesthesia in order to avoid animalmovement, and the animals are given ophthalmic ointment during the process ofimaging. The preparation procedures of other animals is like the installation ofprobe electrocardiograph (ECG), installation of cannula at arterious or venousblood channels, the installation of endotracheal tube and others that can be done tothe animals. The installation of intravenous catheter for anesthesia or physiologicalfluid of the body should be done for the imaging procedure about 30–60 min. Smallrodents can be given intraperitoneal or subcutaneous.
Implant ImagingPost-implantation imaging of implanted materials can be conducted in severalapproaches (Davis 2008; Driehuys et al. 2008), such as radiography, tomography,positron emission tomography (PET), single photon emission computed tomogra-phy (SPECT), computed tomography (CT and Micro-CT), Magnetic ResonanceImaging (MRI), Magnetic Resonance Microscopy (MRM) or ultrasonography(USG). Analysis of any implant changes occurring can be analyzed further by usingsoftware that is suitable to the image produced.
Radiology imaging that is available and easily had for researchers in Indonesia isradiography and ultrasound, the conventional or digital ones. Conventional imagecan be made into digital by using digital camera. Next, the digital image is pro-cessed and analyzed further by using software, and computer can be used for thepicture. Advance radiology imaging like tomography (CT-scan) and MRI is stilllimited and it is only available in hospital for human patients only. Radiographyimaging at biomaterial post-implantation can use software tool to analyze the imagelike ImageJ to analyze the image profile of implant opacity and tissue fromradiogram (Fig. 3).
Besides using profile line, the analysis in radiogram density can also be donewith method that is usually used to measure the intensity of image in cellfluorescent coloring (Gavet and Pines 2010; Potapova et al. 2011). Briefly, cellintensities counted with corrected total cell fluorescence formula (CTCF), in whichthe CTCF = Integrated Density—(area of selected cell X mean fluorescence ofbackground readings). The result of the calculation in “Arbitary unit” (a.u.). Fromthe formulation, it can be adopted for radiogram image to become corrected totalintensity (CTI) with grey unit scale (Gray Value) by dividing the value of a.u. with1012 and the last value is made to become absolute so that the number obtained is inscale range of gray value that is 0–256.
In the technique of imaging that uses USG, the area shaving of the animalmodels in the area of imaging should be done (Fig. 4). Probe USG is attached to the
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Fig. 3 Digital radiogram of several metal implant types can be found in the mice femur bone andthe analysis result is “line plot profile”: a, b implant stainless steel and line plot profile, c,d iron-porous and line plot profile, e, f tantalum-porous and line plot profile, g the result analysis ofcorrected total intensity (CTI) implant stainless steel, iron-porous and tantalum-porous. Asterisksign implant, circle bone, broken red line analysis area “line plot profile” using software ofImageJ, red triangle implant analysis area, and yellow line triangle background analysis area, cor.bone cortical bone
Animal Study and Pre-clinical Trials of Biomaterials 87
skin of imaging area by using ultrasound gel in order to get the best image and havediagnostic value. Response interpretation of tissue can be describe in every changeoccurring in implant and tissue around it. Sonogram produced in digital format isthen analyzed by using software to get the best image at biomaterial implant,per-implant and tissue (Noviana et al. 2013b).
Peri-implant ImagingWhat is interesting to the researchers is the reaction that happens in interfacebetween the implant and the tissue. Peri-implant on the implant side and tissue sideas interfaces also can be the image by previous imaging system. Several approachesare performed by adjusting the modality from diagnostic tool that exists to access andcreate the image of interface area reaction like USG (Huang et al. 2007; Nishii et al.2012; Noviana et al. 2013b), radiodensity (Baena et al. 2013; Fonseca et al. 2006),and histology (Sennerby et al. 2005).
Surrounding Tissue ImagingThe imaging of tissue around the implant is done to know the response that happensin millimeter from the interface implant with the tissue. The reaction of the tissuearound the implant can be imaged by using several approaches radiologically. Softtissue and the internal architecture, like muscle, can be seen clearly by using USG—(Noviana et al. 2013b: Ulum et al. 2015), tomography—(Coan et al. 2008; Sofka et al.2006) and MRI-based (Botnar et al. 2004; Hermawan et al. 2010). Figure 5 showsresponse image of metal post implantation of tissue that is absorbed by the body infemur bone of rat using USG. While harder tissue image, like bone, at gold standardstill use x-ray based imaging (Fig. 3).
Systemic Tissue ImagingThe imaging of systemic tissue at organ functions can be well imaged by usingUSG- (Gibbon et al. 2002; Kosonen et al. 2013; Noviana et al. 2012a) andMRI-based (Botnar et al. 2004; Jacobson 2005). This imaging is intended to knowthe indirect influence and long term installation of implant in the body.
4.7 Histological Analysis
Histology Analysis for Biomaterial ImplantsAnalysing the tissue related to the implant interaction can be done by using his-tology approach (Carleton and Drury 1957; Ozawa et al. 2002; Wick 2012).Implant planted in tissue can be processed histologically or it can be released fromthe tissue adjusted to the type of embedding tissue and the target data that will betaken. The series of tissue process starts from the preparation until the coloring andthe tissue analysis in the slide. General analysis of tissue response can be performedby using hematoxylin-eosin coloring (HE) while special response uses stain thatdepends on specific target of response wanted (McLaughlin 1983; Troyer et al.2002).
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Tissue HarvestingTissue of post-implantation for both biopsy and euthanasia that has been taken iskept in the preservative solution like Buffer Normal Formaldehyde (BNF) with10 % concentration or other solution that is suitable (Bancroft and Gamble 2008).The tissue is kept 48 h minimal to give enough time for BNF to infiltrate andpreserve the tissue. Mature tissue is marked by the infiltration from BNF well andthen it is trimmed in accordance with the tissue analysis target wanted.
Fig. 4 Technique of USG imaging of post implantation of sheep foot and its analysis. a Theshaving around imaging area, b USG imaging, c sonogram, d schematics figure sonogram and theanalysis of echogenicity difference along the implant of steel-bioceramic from “line plot profile”that uses ImageJ software e day 14 and f 60 post-implantation. Head arrow sign the formation ofnew bone around the implant, arrow time of liquefaction around the implant, red asterisk implant,circle bone
Animal Study and Pre-clinical Trials of Biomaterials 89
Tissue EmbeddingEmbedding tissue can be done by using two ways, namely by using paraffin (softembedding) (Bancroft and Gamble 2008) and polymer (hard embedding) (Willboldand Witte 2010). Soft embedding of this tissue uses paraffin in which the hardimplant (ceramic and metal) is released from the implantation tissue. Hardembedding of tissue uses polymer in which the implant in implantation tissue is notnecessarily to be released (Cerri and Sasso-Cerri 2003; Willbold and Witte 2010).
Tissue StainingGeneral coloring to analyze the tissue usually uses coloring material,hematoxylin-eosin (Carleton and Drury 1957; Page 1983). Hematoxylin gives violetblue color in constituent elements of main cell. Eosin gives red color at cytoplasm andcell wall. Various occurrences of cellular interaction happening at the tissue can begenerally visualized well by using this general coloring (Cerri and Sasso-Cerri 2003;Mao et al. 2009; Pearce et al. 2007). Special coloring is intended to analyse thespecific response of cellular level or cell product (cytokin) between the implantmaterial and tissue (McLaughlin 1983). Special coloring works through the specificchemical reaction between antigen and antibody targeted in the tissue. Furthermore,special coloring is also intended to the degradation products. This can be used to knowthe distribution of material in local of systemic tissue (Mueller et al. 2012). In ana-lyzing the tissue response to implants which implanted for long periods, there willappear chronic inflammatory response, the body forming a fibrous capsule composedof connective tissue. To visualize the connective tissue well, to make it look distinctwith the surrounding tissue,Masson trichrome staining is commonly used (Kingsbury2008). Tissue analysis of the product due to the occurrence of inflammatory cellmetabolites in response to a foreign body such as implants for tracking of variouscytokines or enzymes (metalloproteinases) using immunohistochemically methodscan be used. Likewise, the existence of specialized cells can be tracked usingimmunohistochemically techniques, such as tracking macrophages, neovasculariza-tion by tracking endothelial cells and so on (Buchwalow and Böcker 2010).
Fig. 5 Sonogram of biodegradable porous metallic implant at rat bone: a the long cutting at USGimaging, b cross cutting at USG imaging. Head arrow sign cavity image filled by fluid, animalimplant, circle femur bone
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5 Experiences on Animal Study of Medical Implantsin Indonesia
Indonesia is a developing country that keep developing dynamically, one of whichis in independence business to fulfill the need of biomaterial in health medicalbusiness. Researchers from higher institutions, national research institution or smallgroup observers and biomaterial developer try to design and make material that issuitable for medical biomaterial need. This is for the need of human being in Asia,especially Indonesia itself. The result of product, prototype and sample materialdevelopment that has been designed and synthesized has been tested throughin vitro biocompatibility test.
The next stage is in vivo test in several animal models in accordance with theaim why the products are made. The analysis performed for orthopedic with heavyfunctionality burden is implant product for artificial hip and joint replacementimplant. While the product for slight orthopedic burden is bone plate, bone screw,and intra medulla implant. Furthermore, the product for almost very less burden iscraniofacial implant (plate and screw). The testing of biocompatibility at the ani-mals with heavy burden is done at small ruminant, like sheep and goat, or pig.While for the slight or almost no burden, the testing is performed at rodents likemice, rats, and rabbits.
Several biomedical implants have been done in vitro and in vivo testing by someresearcher from Indonesia. The bioceramic material from egg shell as dental fillerhas been tested in local dental dog. The stainless steel intramedullary implant thatdeveloped by local industry has been tested at New Zealand White rabbits femoralbone. The stainless steel bone plate tested at mandibular bone of Sprague Dawleyrats and New Zealand White rabbits. Tantalum bone plate implant with bioceramicscoating is done at rat’s femoral bone (Panjaitan et al. 2014). The newest devel-opment of implant that can be absorbed by the body has also been done with steel-and magnesium-based material at experimental animals, mice (Paramitha et al.2013), rat and sheep (Ulum et al. 2015). Furthermore, testing is also performed topolymer implant for the surgery thread suture performed at mice (Ulum et al. 2012),eye tissue at rabbits, and craniofacial and femoral at rat (Panjaitan et al. 2014). Theresult of the testing has been reported partly and the others have been processed forpublication (Table 7). Several examples of implantation process of biomaterialimplant were performed by researchers in Indonesia at some types of animals andexamples of how to analyze the radiology image (radiogram and sonogram) overthe tissue response towards biomaterial as described in Figs. 1, 2, 3, 4 and 5.
Animal Study and Pre-clinical Trials of Biomaterials 91
Table 7 Some experiences on animal study in Indonesia
Animal Biomaterialimplants
Materials Duration(days)
References
Mice Bone implant—rod
Stainless steel 316L 30 Noviana et al. (2012b);Paramitha et al. (2013)
Bone implant—rod
Cr-coatedbiodegradable iron
30 Noviana et al. (2012b);Paramitha et al. (2013)
Bone implant—rod
Biodegradable iron 30 Noviana et al. (2012b);Paramitha et al. (2013)
Surgical suture Natural silk 7 Ulum et al. (2012)
Bone scaffold Biodegradable porousiron
30 Unpublished
Bone implant—rod
Biodegradablemagnesium
30 Unpublished
Bone scaffold Polymer (PLGA)-coated biodegradableporous iron
30 Unpublished
Intramedullaryimplant—rod
Stainless steel 316L 30 Unpublished
Rat Bone implant—plat
Porous tantalum 60 Panjaitan et al. (2014)
Bone implant—plat
HAp-coated poroustantalum
60 Panjaitan et al. (2014)
Craniofacialimplant—plat
Stainless steel 316L 60 Unpublished
Craniofacialimplant—membrane
Pericardium membrane 60 Unpublished
Bone filler HAp 60 Unpublished
Bone implant—plate
Biodegradable porousiron
360 Unpublished
Rabbit Intramedullaryimplant—rod
Stainless steel 316L 60 Unpublished
Craniofacialimplant—plat
Stainless steel 316L 60 Unpublished
Sheep Bone implant Iron-bioceramiccomposite
70 Noviana et al. (2013a, b);Ulum et al. (2013, 2014a, b,2015)
Bone scaffold HAp-TCP 60 Unpublished
Bone cement HAp-TCP 60 Unpublished
Pig Bone implant HAp-TCP 90 Unpublished
Dog Dental filler HAp-TCP 60 Unpublished
92 D. Noviana et al.
6 Perspective
Indonesia is a developing country in various fields that continuously strive toimprove many things for the prosperity of its people, as well as in terms of thedevelopment of biomaterial implants. Several regulations and procedures for theprovision of an animal model for the development of implants are already availableand continue to be addressed in line with the demands of international standards insafe products for its users. Various things have presented above about the abilityand experiences of Indonesian researchers and scientists to gather a wide range ofproducts of the nation’s children were tested both in vitro and in vivo animaltesting. Tests on animals already a done deal and are able to prove the variousprocesses that occur in the animal body with an imaging technique capable ofimaging the things that happened between the materials with the animal’s bodylocally and systemically.
Acknowledgements The authors acknowledge the support of Indonesian Ministry of Educationand Culture-DGHE No. 083/SP2H/PL/Dit.Litabmas/II/2015 and Indonesian-Australia CenterSmall Grant in the year of 2015.
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Bioadhesion of Biomaterials
Siti Sunarintyas
Abstract Biomaterials are widely used in many kinds of medical devices. Thebiomaterials used can be metal, polymer, ceramic or composites. Bioadhesion willbe occured when the medical device contact to biological surface. There are manyconditions where bioadhesion is beneficial and vice versa. The implantation ofmedical devices in the human body is not without risk. It is reported that implan-table medical devices are an ideal interface for microorganisms. There are infec-tions caused mainly by bacteria originating in the body. Some aspects influencebioadhesion of implantable medical devices including surface topography, chemicalinteraction, mechanical interaction and physiological interactions are discussed.The understanding of such aspects hopefully governs medical practitioners incontrolling the medical devices bioadhesion process, then optimizing the desirablebioadhesion and removing the undesirable interactions. To complete the discussionon bioadhesion of biomaterials, it is also described some methods of bioadhesiontesting including surface roughness measurement, contact angle measurement,surface topography evaluation and biofilm formation testing. At last, a perspectiverelated to biomaterials used as medical devices is presented.
Keywords Bioadhesion � Biomaterial � Medical device
1 Introduction
The use of biomaterials has become an integral part of modern health care.Sometimes severe trauma causes the human body to become damaged beyondnatural repair. Often, oncological surgery creates irreparable damage while theresults of wear cannot be repaired by natural processes. Irreparable damage to thehuman body may not be necessarily associated with lost of function and quality oflife. Numerous biomaterial devices are available for the restoration. Biomaterials
S. Sunarintyas (&)Gadjah Mada University, Yogyakarta, Indonesiae-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_5
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have found applications in approximately 8,000 kinds of medical devices that havebeen used in repairing skeletal systems, returning cardiovascular functionality,replacing organs, and repairing senses. There will be bioadhesion when the bio-materials are placed in the body. Bioadhesion is the state in which two materials, atleast one of which is biological in nature, are held together for extended periods oftime by interfacial forces. In the context of medical devices usage, the term ofbioadhesion refers to the adhesion of biomaterials to a biological tissue. Thebioadhesion interaction could be desirable or undesirable. The biological substratcan be cells, bone, dentine, mucus, or biofilm containing matrix protein andmicroorganisms. The biomaterials used can be metal, polymer, ceramic, andcomposites. An understanding of the bioadhesion mechanism principle of medicaldevices used in the body and some aspects influence bioadhesion is important forclinical practitioners in managing their patients. Moreover, this chapter alsodescribes some methods of bioadhesion evaluation. In the last part, it is discussedabout bioadhesion issues related to biomaterials used as medical devices.
2 Bioadhesion: State of the Art
Bioadhesion is said to occur when two materials, at least one of which is biologicalin nature, are held together for extended periods. Bioadhesion has largely remainedwell in the field of biology referring to cellular interactions (cytoadhesion) or tomucosal adhesion (mucoadhesion). Whether it is cell-to-cell, soft or hard tissue, ormucosal adhesion, the phenomenon of bioadhesion involves the formation of abond between two biological surfaces or a biological surface and a synthetic sur-face. Therefore, bioadhesion can be extended to include any type of adhesionprocess in contact with or within the biological milieu. The term bioadhesionincludes the adhesive properties of synthetic components and the natural surfaces(such as cells, tissue, bone, dentin, mucous). Bioadhesion could also refer to the useof bioadhesives material to bond two surfaces together, which is relevant in drugdelivery, dental and surgical applications (Woodley 2001; Mobley et al. 2002;Vaidyanathan and Vaidyanathan 2009). Nowadays, the wide interest in bioadhesionresearch is due to its implications for the development of new biomaterials, ther-apies and technological products.
Bioadhesive systems are reported have been used for many years in the field ofdentistry and orthopaedics (Meuller et al. 2010; Shah and Meislin 2013) as well asin opthalmology (Zhu et al. 2013) and for surgical application (Jeon et al. 2014).There have been also interested in the use of bioadhesives in other areas, such assoft tissue-based artificial replacement, and controlled release systems for localrelease of bioactive agents. Such applications include systems for release of drugsin nasal cavity (Alagusundaram et al. 2010), intestinal administration (Philip andOman 2010), and urinary bladder application (Haupt et al. 2013).
Depending on the chemical composition of biomaterial and its function on thebiological surface involved, bioadhesion may be desirable or undesirable. Examples
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of desirable bioadhesion interactions are shown in Figs. 1 and 2. The use of dentalcomposite resin as filling material (Fig. 1) illustrates bioadhesion interactionbetween email or dentin (biological substance) and the synthetic polymer adhesiverestorative material. The other example of desirable bioadhesion is bone cement asa synthetic substance commonly used to hold implants in bone. Figure 2 shows thebioadhesion of bone cement in joint replacement.
Fig. 2 Joint replacement is fixed with bone cement
Fig. 1 Composite resin usage for filling dental cavity (Courtesy of Faculty of Dentistry, UGM)
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The bioadhesion between materials can also be undesirable. The undesirableinteraction is commonly well known as biofouling (Palacio and Bhushan 2011).A biofilm is an aggregation of microorganisms that form on a solid substrate, whichmay form during the implantation of biomaterials into the body. The formation ofbiofilms on both living (cells) and non living (i.e. cathethers, stents, implants)surfaces has been identified as a cause of disease. An example of biofilm formationis plaque or calculus formation on the surface of dental composite resin fillingrestoration (Fig. 3). Such biofilm formation unsatisfies the patients as decreasingaesthetic appearance and odor.
This chapter describes both of the desirable and undesirable bioadhesion. Thereare many conditions where bioadhesion is beneficial, for example: cell adhesion onimplant devices, the use of bioadhesives for surgical and dental application, andmucoadhesion in drug delivery system. By understanding the aspects influence thedesirable and undesirable bioadhesion, the control of bioadhesion process will beaccurately and there will be ways to optimize desirable bioadhesion interaction andprevent or remove the undesirable bioadhesion.
The undesirable bioadhesion such as biofilm formation, plaque, and calculus willalso be discussed in this chapter. The understanding of such bioadhesion willrespect to infection prevention of permanent implants and devices. Moreover, theevaluation of both desirable and undesirable bioadhesion will be described forcharacterization of biomaterial. Finally, the occurance of both bioadhesion onmetal, polymer, ceramic, and composite devices will be discussed.
Fig. 3 Plaque formation oncomposite resin filling stainedby disclosing solution(Courtesy of Faculty ofDentistry, UGM)
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3 Aspects of Bioadhesion
There are two stages in the formation of bioadhesion (both desirable and unde-sirable). The first part is the contact stage, when two surfaces are brought togetherinto intimate contact and the second one is the consolidation stage, when theadhesive interactions occur. There are several theories explaining how such inter-actions occur based on surface wettability, molecular interpenetration, mechanicalinterlocking, adsorption, fracturing of the adhesive bond, and electron transferacross an interface (Smart 2014). The bioadhesion interaction is usually complexand requires the application of more than one theory.
In brief, there are 4 aspects affect the bioadhesion interaction, namely: surfacetopography, chemical interaction, mechanical interaction, and physiological inter-action. Surface topography relates more to the surface roughness morphology.Chemical interaction includes the electron transfer across the interface of materialsand adsorption processing in the surface of material. Mechanical interaction coverssurface wetting, mechanical interlocking, and macromolecular interpenetrationphenomena. Physiologic aspect includes physiologic interaction of adhesive.Knowledge of such aspects govern clinicians permit a greater understanding of thebioadhesion mechanism and allow the development of more effective systems thatcan be used in medical therapies.
3.1 Surface Topography
Cell adhesion on synthetic biomaterials surfaces is studied due to its direct impli-cations for the design and clinical performance of medical devices. The adhesion ofcells on biomaterials is an example that describes the importance of surfacetopography of a substrate surface where the cells are cultured. There are variousstudies aimed to evaluate the relationship between surface topography and celladhesion (Katsikogianni et al. 2008; Faeda et al. 2009; Ho-Nam et al. 2009;Ansalme et al. 2011; Galasso et al. 2011; Crawford et al. 2012; Huang et al. 2014).The studies of cell–substratum interactions are often complicated by the presence ofdifferent types of surface pattern. Among the studies, surface topographies can begrouped into three general patterns: (i) irregular surface topography, (ii) regularsurfaces topography and (iii) hierarchical surface topography (Ho-Nam et al. 2009).
Research on Three-dimensional surface images of the nonprecious alloy(nickel-chrome based alloy), that were taken after different surface treatments(Faeda et al. 2009), revealed that the airborne-particle abrasion group was irregular,while the 1000 SiC abrasive paper group showed a relatively regular surfacetopography. Titanium surface topography research reports that hierarchicallystructured titanium surface topography with topography-induced inherent antibac-terial capability and excellent osteogenic activity had been constructed. Biologicalevaluation of such topography revealed that antibacterial ability and excellent
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osteogenic activity of samples with optimized hierarchical structure was betterwhen compared to the control group (Huang et al. 2014). Figure 4 showed suchhierarchically titanium surface with different scale.
Researches on surface topography show that the evaluation of the surface ismeasured on surface roughness (Ra). Orthopedic researches reports that surfaceroughness becomes immensely studied by numerous investigators with the goal ofimproving the performance of bone implants (Gittens 2011).
3.2 Chemical Interaction
There are two chemical interaction aspects which are usually discussed in bioad-hesion process of biomaterials, namely the electron transfer across the interface ofmaterials and the adsorption processing. Regarding to the electron transfer there aretwo interactions which are well known: primary bonds (strong bioadhesion) andsecondary forces (weaker bioadhesion). The primary bonds involve ionic, covalent,and metallic bonds. Ionic bonds occur between atoms that have large differences inelectronegativity. Covalent bonds are formed through the sharing of valence elec-trons, rather than complete electron transfer as for ionic bonds. Metallic bonds areformed in two surfaces containing elements that are electropositives (Temenoff andMikos 2008). Secondary forces such as polar (dipole-dipole), hydrogen bonding orvan der Waals interaction (induces dipoles) also play a large role in bonding the twosurfaces. Secondary forces involve attraction between atoms that require neitherelectron transfer nor electron sharing. The attraction occurs between molecules thathave a portion that is slightly positively charged and a portion that is slightlynegatively charged (Temenoff and Mikos 2008; Palacio and Bhushan 2011).
Fig. 4 SEM images of hierarchically titanium surface with different scale
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Illustration on the role of surface chemistry in protein adsorption is described byAndrade et al. (1992). It is assumed that the surface is uniform and the interactionbetween protein and surface is only one type. The strength of the protein adsorptiondepends on the net charge and polarity of the side of protein available foradsorption and the composition of the substrate surface. The protein and substratecould either be predominantly hydrophobic, positively charged, negatively chargedor neutral hydrophilic. The interaction of a neutral hydrophilic side of protein with asurface having a similar polarity tends to lead to weak adsorption. Ionic interactionsbetween proteins and substrate surfaces will lead to relatively moderate adsorption.The interaction between hydrophobic protein part and the substrate lead to strongadsorption. Such illustration (Fig. 5) is only regarding to one interaction. However,proteins contain complex arrangements of hydrophobic, charged and neutralhydrophilic groups which will lead to complex combination interactions.
3.3 Physical and Mechanical Interaction
WettabilityThe physical and mechanical aspects influenced bioadhesion are mostly studiedregarding to the wettability phenomenon and mechanical interlocking interaction.Wettability studies usually involve the measurement of contact angles as the pri-mary data, which indicates the degree of wetting when a solid and liquid interact.Small contact angles (<90°) correspond to high wettability, while large contactangles (>90°) correspond to low wettability. Illustration in Fig. 6 indicates contactangles formed by sessile liquid drops on smooth solid surfaces. For θ < 90o the
Fig. 5 Schematic of a protein adsorbing on surfaces with different net charge and polarity
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liquid wets the wall (e.g. water on glass), for θ > 90o the liquid does not wet the wall(e.g. mercury on glass). Surfaces that have high contact angles and resist wettingwith water are referred to as hydrophobic (water hating). Conversely, surfaces withlow water contact angles are hydrophilic (water loving) (Bauer 2010).
Contact angle is defined as the angle formed by the intersection of theliquid-solid interface and the liquid-vapor interface. A small contact angle isobserved when the liquid spreads on the surface, while a large contact angle isobserved when the liquid beads on the surface. More specifically, a contact angleless than 90° indicates that wetting of the surface is favorable, and the fluid willspread over a large area on the surface; while contact angles greater than 90°generally means that wetting of the surface is unfavorable so the fluid will minimizeits contact with the surface and form a compact liquid droplet. When the contactangle is 0°, it is said that complete wetting occurs. In other condition, superhy-drophobic surfaces show water contact angles greater than 150°, showing almost nocontact between the liquid drop and the surface. Table 1 summarizes the rela-tionship of contact angle to wettability (Bauer 2010). Moreover, contact angles arenot limited to the interface on a solid-liquid, but also to the liquid-liquid interface ona solid. Ideally, the shape of a liquid droplet is determined by the surface tension ofthe liquid. In a pure liquid, each molecule in the bulk is pulled equally in everydirection by neighboring liquid molecules, resulting in a net force of zero.
Fig. 6 Contact angles of liquid drops on a solid surface
Table 1 Relationship of contact angle to wettability, cohesion, and adhesion (Bauer 2010)
Contact angle θ Wettability Adhesion strength Cohesion strength
θ = 0 Perfect wetting Strong Weak
0 < θ < 90 High wettability Strong/weak Strong/weak
90 < θ < 180 Low wettability Weak Strong
θ = 180 Completely non-wetting Weak Strong
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However, the molecules exposed at the surface do not have neighboring moleculesin all directions to provide a balanced net force. Instead, they are pulled inward bythe neighboring molecules creating an internal pressure. As a result, the liquidcontracts its surface area to maintain the lowest surface free (Snoeijer and Andreotti2008).
It is known that small droplets and bubbles are spherical, which gives theminimum surface area for a fixed volume. The intermolecular force to contract thesurface is called surface tension. It is responsible for the shape of liquid droplets. Inpractice, external forces such as gravity deform the droplet. Consequently, thecontact angle is determined by a combination of surface tension and external forces(usually gravity). Theoretically, the contact angle is expected to be characteristic fora given solid-liquid system in a specific environment (Snoeijer and Andreotti 2008).
Mechanical interlockingInterfacial contact and chemical interactions are considered for the initial stages ofbioadhesion. Mechanical interlocking between two molecules of two contactingsurfaces will maintain the adhesive bond. In dentistry, mechanical interlockingprinciple is well known in the application of resin composite filling to restore emailor dentin. Acid etch is used to create micropores on the surface of email or dentin sothat the adhesive resin composite material penetrate to the pores and createmechanical interlocking interaction. The illustration of mechanical interlocking is inFig. 7. Tooth dentin contains tubulus that radiate from the pulp. The tubulusdentinalis structures facilitate the penetration of resin monomers into the dentin andtheir retention once the resin has been polymerized (Asmussen et al. 1991). It isknown that chemical effects play a role in the adhesion between a restoration and
Fig. 7 Mechanicalinterlocking of resincomposite filling to dentin
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dentin. However, the other dimension in this adhesive event is the permeation of theadhesive into the collagen fibrillar network found in tooth dentin (Vaidyanathan andVaidyanathan 2009).
Physiologic interaction aspectBioadhesion can also take place through physiologic interaction. The example ofsuch interaction is fibrin tissue adhesive and lectins adhesive. Fibrin tissue adhesiveis based on the physiology of the blood coagulation process. Thrombin cleaves theprotein fibrinogen during clotting into smaller fibrin subunits, which then gothrough end-to-end and side-to-side polymerization. Factor XIII is responsible forthe cross linking of the subunits into a stable fibrin clot in the presence of calcium(Mobley et al. 2002).
Recently fibrin tissue adhesive has been used by ophthalmic surgeons as alter-native to suture. It is reported that suturing is a time consuming task in ophthal-mology and suture induced irritation and redness. Possible suture relatedcomplications are postoperative wound infection and corneal graft rejection. Toprevent such complications, ophthalmic surgeons are switching to sutureless sur-gery by tissue adhesives as fibrin glue (Panda et al. 2009). Fibrin tissue adhesivehas been used also in patients receiving total knee arthroplasty. Fibrin tissueadhesive reduced blood loss in cementless total knee replacement, therefore reducethe need for blood transfusion. In conclusion, it is said that fibrin tissue adhesive isappropriate to enhance hemostasis and vessel sealing at the operative site incementless total knee replacement, in order to reduce blood loss after surgery andthe risk of complications (Sabatini et al. 2012).
Lectins are carbohydrate-binding proteins, macromolecules that are highlyspecific for sugar moieties. Lectins perform recognition on the cellular andmolecular level and play numerous roles in biological recognition phenomenainvolving cells, carbohydrates, and proteins. Lectins also mediate attachment andbinding of bacteria and viruses to their intended targets. Lectins have the ability tobind specifically to glycosylated cell membrane components. Lectins are beinginvestigated for their ability to transport macromolecules with implication for drugdelivery to the gastrointestinal tract (Lehr 2000).
4 Bioadhesion Testing
4.1 Surface Roughness Measurement
Finishing and polishing procedures may result in differences of surface roughnessof biomaterials, thus possibly affecting the formation and adhesion of proteinadsorbed (Eick et al. 2004). The overall effect of surface roughness is not clear.Some reports suggest that the amount of protein adsorbed is not or very moderatelyaffected by the surface roughness without conformational changes of protein (Caiet al. 2006); while other reports reveal high augmentation of the proteins adsorbed
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and abrupt changes in their conformation upon adsorption (Han et al. 2003). It wasstated also that proteins with dimensions in the same order as the surface roughnessare not conformationally altered by the surface, and proteins with dimensions muchsmaller or much larger change upon adsorption (Galli et al. 2002). However,Fournier (1999) found no linear relationship between the surface roughness andprotein adsorption.
Surface roughness, also known as surface profile Ra, is a measurement of surfacefinish. It is topography at a scale that might be considered “texture” on the surface.Surface roughness is a quantitative calculation of the relative roughness of a linearprofile or area, expressed as a single numeric parameter (Ra). In three-dimensionaloptical profilometry, roughness is usually expressed as surface area roughness (Sa).Profile roughness (Ra) can be extracted as a line through an area. Interestingly, Sa isalso able to report average Ra through a surface by averaging several profiles. Insummary, profiling techniques tend to be more accurate, area techniques tend to befast (Vanburger and Raja 1990).
Optical profilometer and stylus profilometer are suitable for measuring mostsurface roughness applications. Atomic force microscopes (AFM) and electronscanning microscopes (SEM, TEM) have higher resolution and are typically usedfor asperity measurements, but can be destructive of the surface, depending on thematerials. Recently, it is reported that a technique for the measurement of roughnessusing fiber-optics has been developed (North and Agarwal 2009). Another newmethod of surface roughness measurement using microcomputer-based visionsystem has been reported (Luk 1989). The computer is used to analyze the patternof scattered light from the surface to derive a roughness parameter. The parametersare obtained for a number of tool-steel samples which are ground to differentroughnesses. A correlation curve is established by plotting the roughness parame-ters against the corresponding average surface roughness readings obtained from astylus instrument. Similar correlation curves are produced for different materialssuch as brass and copper.
4.2 Contact Angle Measurement
Contact angle value is an important parameter to predict the wettability propertiesof the materials. The wettability properties of the surface are an important parameterto predict the capability of microbial adsorption and colonization on the biomaterialsurface in biologic environment. Previous studies reported that protein wasadsorbed on high (hydrophobic) and low (hydrophilic) energy surface during thebiofilm pellicle formation. However, pellicle on low-energy surface (hydrophobic)was thicker and more loosely bound. Moreover, the surface area of plaque accu-mulation is less on low-energy (hydrophobic) surface than on high-energy (hy-drophilic) surfaces (Andrade et al. 1992; Katsikogianni et al. 2008; Mikhail et al.2013).
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There are various techniques used to measure contact angles. The techniquesinclude the telescope-goniometer method, the Wilhelmy balance method, and themodern developed drop shape method. Most of the techniques can be classified intotwo main groups: the direct optical method and the indirect force method. Notably,studies of small droplets on solid surfaces allow wetting theories to be tested to thenanometer scale, bringing new insight to contact angle phenomena and wettingbehaviour.
The most widely used contact angle measurement method is the conventionaltelescope-goniometer method. The measurement is based on direct measurement ofthe tangent angle at three-phase contact point on a sessile drop profile (Yuan and Lee2013). Over the years, modifications of the equipment have been made to improve theaccuracy and precision. A camera can be integrated to take picture of the drop profileso as to measure the contact angle (Smithwich 1988). The use of high magnificationsenables a detailed evaluation of the intersection profile (Kwok et al. 1996).
The advantageous of direct optical method is on its simplicity. It is only usedsmall amounts of liquid and small surface substrates in the measurement. On theother hand, there is a relatively higher risk of impurities due to the small size of theliquid and substrate. As for accuracy and reproducibility, the measurement relies onthe consistency of the operator in the assignment of the tangent line, which can leadto significant error and inconsistency between multiple users. The limitation ofdirect goniometer method is the measurement of small contact angles (below 20°)cannot be accurately measured due to the uncertainty of assigning a tangent linewhen the droplet profile is almost flat. Moreover, the imaging device only focuseson the largest meridian section of the sessile drop, which means the profile imagereflects only the contact angle at the point in which the meredian plane intersects thethree-phase line (Kwok et al. 1996). Despite all of the issues, the conventionalgoniometer method is considered as the most convenient method if high accuracy isnot needed.
The Wilhelmy balance method is a widely used technique that indirectly mea-sures contact angle on a solid sample. The Wilhelmy balance technique is anindirect force method. It has several advantages over conventional optical methods.First, the task of measuring an angle is reduced to the measurements of weight andlength, which can be performed with high accuracy and without subjectivity.Second, the measured force at any given depth of immersion is already an averagedvalue. Although this feature does not help determine the heterogeneity, it doesautomatically give a more accurate contact angle value that reflects the property ofthe entire sample. In addition, the graph produced by this technique is useful forstudying dynamic contact angles and contact angle hysteresis at different wettingspeeds (Yuan and Lee 2013).
The shape of a liquid drop ideally depends on the effects of interfacial andgravity forces. Surface tension tends to minimize the surface area by making thedrop spherical, while gravity deforms the drop in two ways: (1) by elongating apendant drop and (2) flattening a sessile drop. The balance between surface tensionand external forces (gravity) is reflected in the Laplace equation, which offers the
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possibility of determining surface tension by analyzing the drop shape. In thisanalysis, the liquid drop is assumed to be part of a sphere. Since the work ofBashforth and Adams used the Laplace equation to analyze the shape of dropletprofiles, the task of determining surface tension became simple interpolation (Yuanand Lee 2013). Ever since digital computers became popular, drop shape analysishas been greatly improved, and many new methods have been developed.
Recent study on a new method based on drop profile image analysis shows thatthis method is more technically practice than contact angle goniometer and hasflexibility to be implemented in clinical circumstances (Yulianto and Rinastiti2014). The method involves placing a drop of solvent (water, buffer, nonaqueousliquid) on substrate surface. The contact angle (very high for water if the surfacesare hydrophobic) is determined by a series of photographs of the drop profile image.If the surfaces are hydrophilic, the droplet quickly dissipates, disappearing into thesurfaces. The evaluation measurement uses the linier gradient equation and tan-gential line formula. It is proved that the drop profile image analysis using thetangential line formula is more reliable and sensitive than the linier one.
4.3 Surface Topography Evaluation
Light microscopy is a relatively simple technique that is used as the first approachto gain qualitative information about surface topography or to view thin sections ofa sample. Images can be further analyzed using specialized software to obtain semiquantitative measures of certain colors (Temenoff and Mikos 2008).
Scanning electron microscopy (SEM) is commonly used to visualize the surfacetopography of biomaterial or biomaterial with attached tissue or cells. SEM imagesare produced by recording the production of secondary electrons after an area isbombarded with the primary electron beam. Since the intensity of these electrons isdependent on the surface topography of the sample, SEM is considered a surfaceimaging technique (Temenoff and Mikos 2008).
Atomic force microscopy (AFM) can be utilized to image biomaterial surfaces aswell as those including adsorbed proteins. This technique produces a threedimensional image. The analytical capabilities of AFM are limited to the uppermostatomic layer of a sample because its operation is based on interactions with theelectron clouds of atoms at the surface (Temenoff and Mikos 2008).
4.4 Biofilm Formation Testing
Biofilm are formed on any solid surfaces exposed to a biological environment. It isknown that the initial bioadhesion depends on the surface characteristics, type ofprotein, and fluid interface (Hannig and Hannig 2009). These factors affect thenonspecific protein adsorption by different forces such as electrostatics and van der
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Waals forces, hydrophobic interaction, and conformational rearrangements (Xuet al. 2005; Noh and Voghler 2006). Several researchers investigated the proteinadsorption on surfaces as a function of different parameters: interactions betweenprotein and surface (Xu and Siedlecki 2007), pH, contact time, and wettability (Leeand Park 1994). A variety of techniques have been used to investigate the propertiesof protein adsorption such as ellipsometry (Watanabe et al. 1986), labelling withfluorescence markers and time-of-flight secondary ion mass spectrometry(ToF-SIMS) (Bersmann et al. 2008), scanning force microscopy (SFM) (Mulleret al. 2010).
Regarding to the bacterial adhesion on biomaterials, there are several techniquesused to evaluate such bioadhesion. It should be emphasised, that the in vitroevaluation simplifies measurements might be misleading, as the whole system iscomplex and dynamic. In vivo, the substrate is under a dynamic state, the surfacemay change composition with time and biological fluid flow may interact with thesurface. Moreover, an incoming bacterium may just attach to the surface (re-versibly) or adhere firmly (irreversibly) or release a number of substances or presenta number of adhesive receptors whose specificity, activity and numbers may be afunction of time (Katsikogianni and Missirlis 2004).
The disadvantage of static evaluation is that it is a qualitative orsemi-quantitative test and it registers overall number of bacteria with varyingdegree of attachment. The following statements describe the evaluation of staticstate. First, it is prepared surface overlaid with a suspension of cells for a deter-mined period of time. The non-adherent cells are removed by rinsing and theremaining cells on the surface are counted or examine morphologically by lightmicroscopy or image analysed epifluorescence microscopy, SEM, scanning con-focal laser microscopy, or atomic force microscopy. For viable bacterial countingmethods, it can be use: CFU (colony forming unit) plate counting, radiolabelling,CTC (tetrazolium salt 5-cyano-2,3-ditoly1tetrazolium chloride) staining,spechtrophotometry, coulter counter, or biological markers of ATP (adenosinetriphosphate) (Katsikogianni and Missirlis 2004).
The dynamic evaluation includes: parallel plate flow chamber, parallel-plate flowchambers, rotating disc, atomic force microscopy, Interaction Forces. Theparallel-plate flow configuration is very common. It is simple to construct and thegeneral flow within the chamber can be mathematically analysed easily. The mostcommonly used variation a pump provides a steady-state flow. The fluid entersfrom one side and leaves from the opposite side in a rectangular chamber. Theupper plate is usually a glass coverslip while the bottom is the prepared surface(transparent) on which the cells have been left to settle for a predetermined time.The fluid movement creates a shear stress at the wall, which is calculated fromequation (Bruinsma et al. 2001).
Another technique is radial flow chamber (RFC). RFC consists of two flat disksseparated by a thin gap (200 μm). The fluid dynamics in the RFC has been wellcharacterized. Dynamic flow patterns can be imposed, including pulsatile orreversible steady-state flows. For example angular acceleration of a parallel diskimpart high shear stress transients to attached bacteria (Dickinson and Cooper
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1995). Other fluid shear systems have been used is the rotating disc in liquid(DeJong et al. 2002). In all these systems the major concern is that the measuredadhesion strength of bacteria to substrates is global for bacteria population.
The Atomic Force Microscope has proved useful in imaging the morphology ofindividual microbial cells and bacterial biofilm on solid surfaces, both in dried andhydrated states (Robichon et al. 1999). It is being used increasingly for mappinginteraction forces at microbial surfaces (Alfonso and Goldmann 2003; Dufrene2003). The major advantage of the AFM over other microscopical techniques is thatit can simultaneously provide information on local surface properties and interac-tion forces.
5 Bioadhesion of Medical Devices
5.1 Polymers
Polymer materials play an important role in diagnostic and therapeutic proceduresof modern medicine. Their use as medical devices has rapidly increased. This hasled to medical progress for the benefit of many patients. However, the price to bepaid is the occurance of complications producing new clinical syndromes. Infectionis one of the most frequent and important complications associated with the use ofpolymer foreign bodies. Foreign body associated infections are nowadays clinicalroutine phenomena, although they may have severe consequences for the individualpatient involved.
Phsysicochemical point of view describes bacterial adhesion to polymers can beregarded as the adhesion of colloidal particles to a solid surface in a liquid environ-ment. Besides the hydrodinamic conditions which regulate the transport of the particleto the surface, the bioadhesion is governed by attractive physical interaction includingelectrostatic, van der Waals interaction, dipole-dipole and hydrophobic interaction(Rutter and Vincent 1980). If only electrostatic and van der Waals interactions areconsidered, the DLVO (Derjaguin-Landau-Vervey-Overbeek) theory of lyophobiccolloid stabilization can be applied to bacterial adhesion (Jansen et al. 1988). Forin vivo situations, the DLVO model is not suitable due to other interactions which mayoccur. Another phsycochemical model for describing bioadhesion mechanism is basedupon thermodynamical consideration (Absolom et al. 1982). Again, this approach canonly be applied for in vitro situation.
Specific interactions have been shown to mediate bioadhesion between bacteriaand natural substrate: adhesion of Streptococcus mutans to enamel (Sugarman andYoung 1984), Eschericia coli to uroephitelial cell (Eden et al. 1977). Although notclearly demonstrated for bacterial adhesion to synthetic polymer, it is highly pos-sible that specific interactions play an important role as well.
It is well known that polymers are rapidly coated with proteins or other sub-stances when they are exposed to body fluids (blood, tissue liquid) (Bantjes 1978).
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Bacteria can also become coated by substances from body fluids and undergochanges of their surface properties (Miőrner et al. 1980). A number of studies havebeen done on the influence of adsorbed molecules on the adhesion using serum,plasma, and singular proteins (Fleer and Verhoef 1986). It was found that almost inall studies the presence of serum or plasma leads to a strong decrease in bacterialadhesion. Coating polymer with various proteins like albumin, globulin or othersleads to a decrease in adhesion. It was assumed that the decreased adhesion iscaused by a change in surface properties from more hydrophobic to more hydro-philic. If the polymers are preincubated 1 h with plasma, albumin, or fibrinogen,and adhesion is performed later on in PBS (phosphate-buffered saline), in case ofStaphylococcus epidermidis KH 6 there is an inhibition observed; while in the caseof Staphylococcus epidermidis KH 11 only precoating with albumin leads to aconsiderable reduction of adhesion, whereas on fibrinogen or plasma coatedpolyurethane an increase in adhesion is noticed. This result suggests specificinteractions between Staphylococcus epidermidis KH 11 and receptor like structureson the adsorbed fibrinogen molecule (Jansen et al. 1988). The increase in adhesionof Staphylococcus epidermidis KH 11 on polyurethane preincubated 1 h in plasmamight also be due to interactions with fibrinogen. It was known that the majorprotein adsorbed after 1 h from plasma like synthetic protein solution (Jansen andEllinghorst 1984). This finding is very useful since there is a close relationshipbetween thrombus formation and infection of polymeric devices, especially invascular prostheses and intravenous catheters.
Bacterial adhesion to polymer medical devices is the first important step in thepathogenesis of a foreign body infection. Although the mechanism of bacterialbioadhesion to polymers are not fully clear, the development of antiadhesive andalso antiinfectious polymers seem to be the most reasonable approach for theprevention of foreign body infection (Sutula et al. 2012).
Research of desirable bioadhesion on PLLA (poly-L-lactide) scaffold shows thatPLLA based scaffold demonstrates less cell interaction capability compares toimmobilized sericin protein coated on PLLA. PLLA is a hydrophobic polymer dueto the present of an extra methyl group in lactic acid. Sericin contains a largeamount of amino acids with polar functional groups. The strongly polar groups ofsericin influences the scaffold surface more wettable as indicated by the decreasesof contact angles (Yustisia et al. 2012). By improving the biomaterials surfacehydrophilicity, sericin facilitates the attachment and proliferation of cells, thereforeleads to new tissue formation (Sunarintyas et al. 2011; Sunarintyas andSiswomihardjo 2011).
5.2 Metals
Surface roughness becomes one of the major research in orthopedic with the goal ofimproving the performance of bone implants (Balasundaram et al. 2006).Specifically, compared with smooth surfaces, micron surface roughness (from 1 to
118 S. Sunarintyas
100 μm surface features) on titanium substrates created by sandblasting, etching,machining and the use of micron-sized metal bead coatings has enhanced osteoblastfunctions such as adhesion, proliferation, production of alkaline phosphatase, anddeposition of calcium-containing mineral. Other strategies for improving the bio-compatibility and osteogenic capacity of metal implants include surface modifica-tion with inorganic mineral coatings, particulates, or cements containing a diversityof calcium salts. The idea of these strategies is to make the metal surface moreacceptable to bone cells so that enhances the body into rapid integration of theimplanted structure rather than fibrous encapsulation. Recent studies have providedinformation that nanometer crystalline hydroxyapatite (HA) and amorphous cal-cium phosphate compacts could be chemically functionalized with the arginine–glycine–aspartic acid (RGD) peptide sequence using the aforementioned maleimidechemistry. Results showed that the immobilization of the cell adhesive RGDsequence increased osteoblast adhesion compared to those non-functionalized andthose functionalized with the non-cell adhesive control peptide. In this work variousmodified titanium surfaces were subjected to cell viability studies to measure theircell adhesion properties (Deligianni et al. 2001; Bacakova 2004).
Regarding to metal or alloy implant desirable bioadhesion in the body, it isreported that the efficacy of bone regeneration is determined by surface charac-teristics such as the chemical composition and physical properties of the implantthat controls initial protein adsorption (Balasundaram and Webster 2006). Theseproperties influence the adsorption of proteins which mediate the adhesion ofdesirable (osteoblast) and undesirable (fibroblast) cells. It is believed that the lack ofattention paid to understanding cellular recognition to proteins initially adsorbed onbiomaterial surfaces to date could be one of the key reasons why current implant donot last longer than 15 years. The understanding of common families of proteinadhesion is important. The majority of adhesion molecules can be grouped into:cadherin, immunoglobulin superfamily (IgSF), integrins cell adhesion molecules offocal adhesion contacts, and selectins (Baker and Greenham 1988).
The characteristic feature of the classic cadherins is their ability to mediate Ca2+
dependent homophilic adhesion with specificity being generated by sequence dif-ferences at the adhesive face of the N-terminal domain. Unlike the cadherins, whichessentially mediate homophilic interactions via the antiparallel binding of theN-terminal cadherin repeats with the equivalent domain on neighbouring cells, theIgSF members show a broad range of ligand interactions. Integrins are so calledintegrins cell adhesion molecules of focal adhesion contacts because they ‘integrate’the extracellular matrix with the intracellular cytoskeleton and hence deliver‘outside-in’ signals from the external environment to the cell to modify cellularstructure and functions: cell adhesion, motility, proliferation, apoptosis, inductionof gene transcription and differentiation. The three selectins, E-selectin (CD62E),L-selectin (CD62L) and Pselectin (CD62P), are related both structurally andfunctionally. They have been extensively studied due to their role in the inflam-matory response and their potential use as therapeutic targets (Baker and Greenham1988).
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Previous studies indicate that surface roughness influences bacteria adhesion(Kendall 2004; Quirynen et al. 1993). The cause for this phenomenon may includea rough surface has a geater surface area and the depressions in the roughed surfaceprovide more favorauble for bacteria colonization. However, anothe study showsthat commercially pure titanium (cp Ti) surface roughness produces by 120–1200grit sandpaper polishing shows no effect on number of adhered Staphylococcusepidermidis (An et al. 1995). Such two contrary results need further researches andanalysis regarding to surface area measurement and evaluation of surface config-uration. Further evaluation is necessary as there are various clinical differentprostheses or implant devices which have different surface roughnesses which mayplay a role in bacterial adhesion and implant infection.
5.3 Ceramics
Biofilms are believed to be formed on all surfaces exposed to the natural envi-ronment. Although, initially the biofilm formation on biomaterial surfaces in themouth could appear harmless, its consequences may be much more harmful andsevere. Increased amount of plaque on the rough surfaces of ceramics restoration inthe mouth will exert not only caries-causing virulence, but also a harmful influenceon periodontal tissue. For a full coverage crown or a bridge, caries incidence riskwould be slight, but instead much attention has to be given to the gingival tissues.Previous research (Kawai et al. 2000) reported that more plaque was adhered overglazed surfaces of ceramics as compared with their polished surfaces. This meansthat a glazed surface would not be clinically acceptable from a biologic point ofview. Glazing can produce an undulating and rough surface that has irregularities,inducing more adhesion of bacteria and other substances. Another research alsoconcluded that glazed surfaces are rougher as compared to the polished surfaces(Rashid 2012). Although polished surfaces have been reported to have voids andmicro cracks on the subsurface of porcelain, these superficial defects did notcontribute to the amount of plaque adhesion (Patterson et al. 1992).
An in vitro study proved that the number of Staphylococcus epidermidis increasedin the first 8–12 h after bioceramic implantation. The addition of 20 % zirconia tohydroxyapatite proved to have been an effective concentration in inhibiting thegrowth of Staphylococcus epidermidis. Scanning electron microscopy examinationshowed that zirconia filled in the hydroyapatite pores, whereas the less pores the lessnumber of Staphylococcus epidermidis attached (Siswomihardjo et al. 2012).
5.4 Composites
Study on plaque accumulation on various dental biomaterials showed that poly-ethylene fiber reinforced composite (FRC) as the roughest material promoted
120 S. Sunarintyas
plaque accumulation significantly more than the other smoother materials. Ceramic,having the smoothest surface showed a trend towards less plaque accumulation,although the difference was significant only in comparison with polyethylene FRC.Glass FRC and restorative bis-GMA (bisphenol-A-glicydyl methacrylate) com-posite resin showed very similar plaque accumulation properties. These materialsresemble each other also in their surface physico-chemical properties. They are bothcomposite materials composed of inorganic filler particles in an organic polymermatrix. In the case of glass FRC, glass fibres are the inorganic fillers. Polymermatrices of both composites are commonly based on dimethacrylate monomersystems. Their surface roughness values after polishing are also very similar andsignificantly lower than the roughness of polyethylene FRC (Tanner et al. 2003;Mikhail et al. 2013).
In the oral environment, surface roughness seems to be a governing factor overthe influence of surface-free energy determining the amount of plaque accumulationon dental materials (Quirynen and Bollern 1995). Study on early plaque formationon dental composite and ceramic in vivo showed there was least growth of mutansstreptococci in plaque recovered from ceramic restoration. Seven of the 12 subjectswith mutans streptococci in their plaque had no growth of mutans streptococci onthe ceramic samples, whereas all 12 subjects showed colonisation of mutansstreptococci on polyethylene (Tanner et al. 2005). It was noted that dental biofilmunsatisfied the patients as decreasing aesthetic appearance and odor. Dental plaqueis a biofilm consisting of more than 500 bacterial strains (Coulthwaite and Veran2011). Further research is needed concerning more detail about dental plaquebioadhesion in various biomaterials for medical devices.
6 Perspective
The implantation of medical devices is not without risks. Bacterial or fungalinfections can occur and the body’s strong immune response may lead to therejection of the implanted medical devices. Implantable medical devices are an idealinterface for micro-organisms, which can easily colonize their surface. As such,bacterial infection may occur and lead to an inflammatory reaction. This may causethe implant to be rejected. These infections are mainly caused by bacteria such asStaphylococcus aureus, originating in the body, and Pseudomonas aeruginosa.These infections may also be fungal or caused by yeasts. The challenge presentedby implanting medical devices in the body is preventing the occurrence of theseinfections, which lead to an immune response that compromises the success of theimplant. Antibiotics are currently used during surgery or to coat certain implants.However, the emergence of multi-resistant bacteria now restricts their effectiveness.
Acknowledgment Mrs. Gusnaniar (BME, UGM), Mr. Dedy Kusuma (Dentistry, UGM) and Mr.Bonifasius Primario (Dentistry, UGM) are acknowledged for their kind help in preparing thepictures and literatures for this manuscript.
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Bioadhesion of Biomaterials 125
Degradable Biomaterials for TemporaryMedical Implants
Ahmad Kafrawi Nasution and Hendra Hermawan
Abstract Degradable biomaterials bring possibilities to fabricate medical implantsthat function for a determined period related to clinical events such as healing. Theycan be made on the basis of polymers, ceramics and metals. These metals, whichare expected to corrode gradually in vivo with an appropriate host response andthen dissolve completely upon fulfilling the mission to assist with tissue healing, areknown as biodegradable metals. They constitute a novel class of bioactive bio-materials which supports the healing process of temporary clinical problems. Threeclasses of metals have been explored: magnesium-, zinc- and iron-based alloys.Three targeted applications are envisaged: orthopaedic, cardiovascular and pediatricimplants. Three levels of investigations have been conducted: in vitro, in vivo andclinical trials. Discussion on standardization has been initiated since 2013 withrepresentatives from ISO, DIN and ASTM and drafts of comprehensive standardsare now under preparation. The field of biodegradable metals is exciting andwitnessing more development in the future including new advanced alloys and newreal breakthrough that leads to its clinical translation. This chapter starts with adiscussion on biodegradable polymers to gain important lessons learned foradvancing the research in biodegradable metals, the new emerging research interestin the forefront of biomaterials loaded with full of great expectations.
Keywords Biodegradable � Biomaterials � Corrosion � Metals � Polymers
A.K. NasutionMuhammadiyah University of Riau, Pekanbaru, Indonesiae-mail: [email protected]
H. Hermawan (&)CHU de Quebec Research Center, Laval University, Quebec City, Canadae-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_6
127
1 Introduction
Biomaterials have been widely used to make implants or devices to replace a part ora function of the body in a reliable, safe, physiologically acceptable and economicmanner (Park and Lakes 2007). Examples of such implants are artificial heartvalves, coronary artery stents, total hip replacement, bone plate and screw, anddental implants (Geetha et al. 2009). Biomaterials can be defined as natural orsynthetic materials engineered to interact with biological systems that are used formedical treatment (Ulery et al. 2011). The development of the first medical deviceis based on the principles of medical and scientific acceptable for human use in thelate 1940s and early 1950s (Ratner et al. 2013). The diversity of biomaterials inused today is the result of great advancement in materials technology since nearly40 years ago (Hoffman 1996). Basically, as detailed in Table 1, they can be clas-sified as metals, ceramics, polymers and their composites with 70–80 % of implantswere made of metals (Niinomi et al. 2012).
The development of biomaterials is made possible thanks to strong interdisci-plinary collaboration among clinicians, engineers, chemists, physicists and biolo-gists as the key players (Ratner et al. 2013). Advanced biomaterials developmentrequires the input of knowledge from diverse areas with the ultimate goal to achievethe true biological interaction between the materials and the human body(Vallet-Regí 2010; Ulery et al. 2011). This chapter starts with an overview on thecurrently used biomaterials then focuses further review on biodegradable polymers.The main objective is to gain some lessons from the currently used biomaterials,especially biodegradable polymers, for advancing the research in biodegradablemetals, the new emerging research interest in the forefront of biomaterials loadedwith full of great expectations.
Table 1 Biomaterials commonly used for biomedical applications
Materials Applications Advantages Disadvantages
Metals: stainless steel,Co-Cr alloys, Ti alloys,Mg alloys, etc.
Load bearing implants, jointreplacement, cardiovascularstents, dental implants, etc.
Though,strong,ductile
Non bioactive
Ceramics: alumina,bioglass, calciumphosphate, zirconia, etc.
Orthopaedic and dental implants Bioactive,inert
Brittle, notresilient
Polymers: polyethylene,polyesters, nylon,polylactide, etc.
Blood vessel grafts, hip sockets,sutures, etc.
Bioactive,resilient
Lack of strengthfor load bearingimplants
Composites: amalgam,fiber-reinforced bonecement, etc.
Dental filling, resin bone cement,etc.
Tailormade
Relativelydifficult to make
128 A.K. Nasution and H. Hermawan
2 Overview on Currently Used Biomaterials
Hundreds of type of metals for implants have been clinically used, but in generalthey can be grouped into: (1) stainless steel alloys; (2) Co-Cr alloys; (3) Ti and itsalloys; and (4) precious alloys. These metallic biomaterials are always attractive dueto their nature in offering structural function and inertness, the two key features thatmost implants need. However, as the medical science progresses and the demandfor better implants increases, nowadays it is desirable that an implant also possessesbioactivities or biofunctionalities like blood compatibility and bone conductivity.Therefore, the surface of metals are often modified, for examples: in order toprovide bone conductivity metal surface has been coated with hydroxyapatite(Habibovic et al. 2002), or with poly(ethylene terephthalate) to improve bloodcompatibility (Lahann et al. 1999). Today, development on metallic biomaterialsincludes those composed of nontoxic and allergy-free elements such as Ni-freestainless steel (Yang and Ren 2010) and biodegradable metals which are targetedfor temporary implants (Hermawan and Mantovani 2009).
One important lesson we can learn from inert metallic biomaterials is their highstrength and ductility. Mechanical properties of 316L stainless steel are oftenviewed as the standard reference in developing new metallic biomaterials. This alsoapplies to biodegradable metals to ensure that the mechanical function of a specificimplant, such as coronary stent, remains the same despite its material is changedfrom 316L stainless steel to biodegradable iron (Fe) or magnesium (Mg) alloys.Although designed to be corrosion resistant, aggressive physiological environment,that is not only corrosive but also introduces mechanical loading (static anddynamic), contributes to metallic implant failures such as wear. High concentrationsof chloride and temperature of the human body have also found to induce localizedcorrosion such as pitting, crevice and fretting (Tavares et al. 2010). Figure 1 showsexample of metal implant failure due to corrosion and wear.
Polymeric biomaterials offer main advantage over metals and ceramics in theirease of manufacturability to form various shapes. Basically, these biomaterials canbe divided into: (1) inert polymers such as poly(methyl methacrylate), poly(amide)or nylon, poly(ethylene), etc.; and (2) absorbable polymers such as poly(glycolicacid) and poly(lactic acid), etc. Beside employed in their bulk, they are often madeinto thin layer or coating onto metal surfaces with tailored mechanical and physicalproperties. The recent development exploits absorbable polymers for use as drugdelivery carriers loaded with a specific drug in the form of coating, for exampledrug eluting stents (Jenkins 2007).
Ceramics biomaterials provide inertness, high compressive strength and aes-thetic appearance. They can be classified into: (1) inert bioceramics such as zir-conia, alumina, aluminum nitrides and carbon; (2) bioactive ceramics such ashydroxyapatite, bioglass, etc.; (3) biodegradable/resorbable ceramics such as cal-cium aluminates, calcium phosphates, etc. The inherent surface qualities ofceramics have been exploited to make implants such as dental crowns. The highspecific strength and blood compatibility of carbon makes carbon often used for
Degradable Biomaterials for Temporary Medical Implants 129
Fig. 1 Example of a component of a retrieved total hip implant revised due to adverse local tissuereaction: a modular implants typically provide in large crevice geometries with differential aerationthat will be subjected to micromotion during loading and results result in abrasion and trigger aseries of reactions in the crevice that will lead to events such as cracks, pitting and cracks,b corrosion at the modular neck junction, c corrosion debris (black deposits) is shown in thestem-sleeve mating interface. Adapted from Rodrigues (2014) and Tischler and Austin (2014)
130 A.K. Nasution and H. Hermawan
heart valves leaflets. Many bioceramics have been also applied as coating ontometal surfaces including diamond like carbon, nitrides, bioglasses and hydroxya-patites (Kokubo 2008).
Composite biomaterials can be made with metals, polymers or ceramics as theirmatrix, and reinforced with one of these materials. Composites allow a control overmaterial properties whereas a combination of stiff, strong, resilient but lightweightcan be achieved all together. Bone is a composite of the low elastic modulusorganic matrix reinforced with the high elastic modulus mineral “fibers” permeatedwith pores filled with liquids. Other examples include orthopaedic implants withporous structures, dental filler, and bone cement composed of reinforced poly(methyl methacrylate) and ultra-high molecular weight poly(ethylene) (Ambrosio2009).
3 Biodegradable Polymers
The current trend shows a shift in the use of the permanent prosthetic devices fortemporary therapeutic applications to biodegradable devices that can help the bodyto repair and regenerate damaged tissue (Nair and Laurencin 2007). Basically, theconcept of biodegradable devices is providing a temporary support during thehealing process of diseased tissue and degrading away thereafter, progressively.Precisely, temporary clinical problems need temporary intervention (i.e. temporarypresence of implants) and this can be provided by degradable biomaterials (Li et al.2014). Temporary support is only obtained by using implants made from degrad-able biomaterial (either biodegradable polymers or biodegradable metals) thatallows implant to relegate biologically after fulfilling its function (Barrows 1986;Hermawan 2012). Examples of clinical problems that need temporary support forhealing are narrowed arteries, fractured bones and congenital cardiovascular defects(Hermawan and Mantovani 2009). Some important properties that must be con-sidered in the design of biodegradable biomaterials are summarized in Fig. 2.
Polymeric biomaterials has a long history of applications starting from catheters,syringes, blood contacting extra corporeal devices till matrices for drug delivery,cell encapsulation and tissue regeneration (Shastri 2003). Non-degradable polymerssuch as nylon, poly(methylmethacrylate), poly(ester) and poly(vinyl chloride)began to be used in the medical fieldin the mid-1940s and remain important fornumbers of medical equipment till now (Griffith 2000; Hacker and Mikos 2011).They are used as a component for permanent prosthetic devices including hipimplants, artificial lenses, large diameter vascular grafts and catheters. Meanwhile,degradable polymers adopted for surgery since 40 years ago as a surgical suturematerial and bone fixation devices (Kulkarni et al. 1971). In the last two decadesthere has been a development of new generations of synthetic biodegradablepolymers and natural polymers specifically developed for biomedical applications.
Degradable Biomaterials for Temporary Medical Implants 131
3.1 Natural Biodegradable Polymers
Natural polymers are formed in nature ranging from the growth cycle of allorganisms (Chandra and Rustgi 1998). They can be considered as the firstbiodegradable biomaterials used clinically. In the view of regenerative medicine,natural polymers offer advantages similar to biological macro-molecules (such astissue) and its biological environment (Mano et al. 2007). Other inherent advan-tages include bioactivity, the ability to receptor-binding ligands to cells, suscepti-bility to cell-triggered proteolytic degradation and natural remodeling. While theweakness of natural polymers including immunogenic response and the possibilityof disease transmission (Puppi et al. 2010).
Most natural polymers undergo enzymatic degradation and least undergoeshydrolytic degradation. The enzymatic degradation at in vivo level variesdepending on the site of implantation, the availability and concentration of enzyme(Nair and Laurencin 2007). Hydrolytically biodegradable polymers are polymersthat have a hydrolytically labile chemical bond that influences the level of degra-dation and erosion mechanism (Griffith 2000; Ulery et al. 2011). When the rate ofdegradation at the interface of water-degradable devices on the entire surface isfaster than the diffusion depth of the water, then this indicates surface erosion.Conversely, if the water diffusion is faster than the degradation over the entiresurface and mass loss occurred throughout the bulk of the material, this is called asbulk erosion. These categorizations are extremely important in determining whichmaterial is best for a desired application, for example in drug delivery. Two mostimportant natural polymers used in biomedical field are protein or poly(amino acid),and poly(saccharide).
Fig. 2 Important propertiesto be considered in the designof degradable biomaterials.Adapted from Lloyd (2002)
132 A.K. Nasution and H. Hermawan
Proteins are polymers with amino acid monomers joined by amide bond and arevery common material in the human body. Included into proteins are collagen, poly(amino acid), elastin and elastin-like poly(peptide), albumin and fibrin. Collagen isa protein with significant amounts in human body and is the main component of theligament, cartilage, tendon, skin and bone (Ulery et al. 2011). Collagen has beenstudied for medical applications due to its biocompatibility, mechanical strengthand enzymatic degradability (collagenases and metalloproteinases) (Krane 2008).Collagen has a good process-ability with high solubility in acidic solution to beused as collagen sponges, tubes, sheets, powders and injectable (Matsuno et al.2006; Bushnell et al. 2008; Choi et al. 2009; Liu et al. 2010). The majority of thesestudies focused on the potential use of collagen as a biomaterial for a tissueengineering scaffold, specifically in load bearing applications. Collagen was alsoused as composite materials (hydroxyapatite and collagen) with composition clo-sely resemble to that of bone (Venugopal et al. 2008).
Natural poly(amino acid) is a biodegradable ionic polymers occurs naturally inthree different type: poly(ε–L-lysine), poly(γ-glutamic acid), and cyanophycin(Obst and Steinbüchel 2004). This polymer has characteristic such as biocompat-ibility and complete biodegradability that make this material as an ideal candidatefor applications in human. Poly(l-lysine) is known to have anti-bacterial, anti-viraland anti-tumour activity and is considered to be a potential candidate for developingdrug carrier vehicles (Nair and Laurencin 2007). Poly(γ-glutamic acid) is capable todegrade with the presence of water and developed as drug delivery vehicles, tissueengineering scaffolds and thermo-sensitive polymers (Kishida et al. 1998).Cyanophycin, is a comb-like polypeptide isolated from cyanobacteria that containsα-amino-α-carboxy-linked L-aspartic acid residues representing the poly(α-L-aspartic acid) backbone and L-arginine residues bound to the β-carboxylic groupsof aspartic acids making it a highly poly-disperse polymer (Simon 1971). Syntheticpoly(amino acid) is also studied and showed high crystallinity, low degradation rateand unfavorable mechanical properties (Ulery et al. 2011). Two synthetic bioma-terials derived from poly(amino acids) are poly(L-glutamic acid) with high sus-ceptibility to degradation by lysosomal enzymes and poly(aspartic acid) that is verysoluble in water and easily converted to a hydrogel by high energy radiation (Li2002; Pitarresi et al. 2007).
Elastin is the major protein component of blood vessels and lung tissue (Uleryet al. 2011). In vivo studies showed elastin has little interaction with platelets andhave limitations on the ability to obtain an immune response (Mithieux et al. 2004).With this limitation, a synthetic elastin, elastin-like poly(peptide), was developed.This artificial poly(peptide), although very flexible as elastin, has characteristic thatare biocompatible and non-immunogenic (Ulery et al. 2011). It was studied asdelivery vehicles for chemotherapeutics (Bidwell III et al. 2007), antibiotics(Adams et al. 2009) and proteins (Bessa et al. 2010), beside for the soft tissuesengineering due to its suitable elastic behavior (Nettles et al. 2010).
Albumin is a blood protein that is soluble in water and exists nearly 50 % of thetotal mass of the plasma in the body. Albumin has a function as a carrier ofhydrophobic fatty acids around the blood stream and maintain blood pH (Ulery et al.
Degradable Biomaterials for Temporary Medical Implants 133
2011). The solubility of albumin allowed to be processed into various forms such asfibers (Regev et al. 2010), microparticles (Okoroukwu et al. 2010) and nanoparticles(Shen et al. 2011). Albumin also has been studied as a carrier vehicle for intravenousdrug/gene delivery (Chuang et al. 2002) and as coating materials for cardiovasculardevices (Uchida et al. 2005).
Fibrin is a biopolymer that is similar to collagen and it is the initial biopolymerused as biomaterials. It is characterized by its excellent biocompatibility,biodegradability and inject-ability (Ulery et al. 2011). Fibrin degraded to fibrinol-ysis in the human body in the presence of a complex cascade of enzymes (Erin andRobert 2005). The first product resulting from fibrin is fibrin sealant used clinicallyfor hemostasis and tissue sealing applications in various surgical procedures (Nairand Laurencin 2007).
Poly(saccharide) are macromolecules formed from many monosaccharide unitsjoined together by glycosidic linkages (Ulery et al. 2011). By having good char-acteristic such as biodegradability, process-ability and bioactivity, poly(saccharide)are very promising natural biomaterials. Poly(saccharide) are divided intopolysaccharides of human and non-human origins. Hyaluronic acid and chondroitinsulfate are biopolymers belongs to the poly(saccharide) of human origin.Hyaluronic acid is a linear poly(saccharide), water-soluble and forms highly vis-cous solutions with unique viscoelastic properties (Nair and Laurencin 2007). It hasan important role in various tissues including articular cartilage, the nucleus pul-posus, skin, the cervis, and the glycocalyx of endothelial cells (Nair and Laurencin2007). Half of the total content of hyaluronic acid in the human body is found in theskin, while other sources for its isolation are rooster combs and bovine vitreoushumor (Ulery et al. 2011). Hyaluronic acid can undergo degradation within thebody by free radicals (Rapta et al. 2009), also via digestion by lysosomal enzymesto form mono and disaccharides, which can be further converted into ammonia,carbon dioxide and water via the Krebs cycle (Al-Assaf et al. 2003). Hyaluronicacid plays an important role in tissue repair and drug delivery applications and isvery promising for numbers of regenerative therapies especially in soft tissueengineering (Ulery et al. 2011). Chondrotin sulfate is the major component ofaggrecan, the most abundant glycosaminoglycan found in the proteoglycans ofarticular cartilage (Nair and Laurencin 2007). It can stimulate the metabolicresponse of cartilage tissue and has anti-inflammatory properties (Chan et al. 2005).These showed the importance of these natural polymers used in biomedicalapplications (Kosir et al. 2000).
Other than poly(saccharide) molecules that exists in the human body, there are anumber of similar molecules derived from other sources (poly(saccharide) ofnon-human origin) as promising degradable polymeric biomaterials (Ulery et al.2011). Included in this class are the cationic polymer, chitosan found in crustaceanskeletons and alginate found in brown algae, both used as drug delivery vehicles.
134 A.K. Nasution and H. Hermawan
3.2 Synthetic Biodegradable Polymers
The disadvantages of natural polymers such as immunogenic response and thepossibility of disease transmission (Puppi et al. 2010) has led to the development ofsynthetic biodegradable polymers. Among the first developed synthetic biodegrad-able polymers are the glycolide-based polymers, poly(glycolic acid) and poly(lacticacid), which have been used in products such as degradable sutures since 1960s andboth have received approval by the FDA (Nair and Laurencin 2007). Table 2 listsome of biodegradable polymers that found their application in biomedical field.
Poly(lactic acid) or PLA and poly(glycolic acid) or PGA are poly(α-ester) gradepolymers which are thermoplastic and have characteristic that allows them to bedegraded via hydrolytic action (Nair and Laurencin 2007). PLA is much morehydrophobic than PGA, making the rate of degradation of PLA slower (i.e. remainstable for more than 1 year) (Sinha et al. 2004) compared to PGA, which can bedegraded within few weeks (Nair and Laurencin 2006). PGA are used clinically asan internal fixation device due to its higher rigidity than other degradable polymers(Tormala 1992). It has elastic modulus about 12.5 GPa (Maurus and Kaeding 2004)and very low solubility in organic solvents (Nair and Laurencin 2007). It will loseits strength within 1–2 months and loss its mass within 6–12 months (Nair andLaurencin 2007) and is broken down in vivo into glycine which can be removedthrough the urine (Maurus and Kaeding 2004).
PLA has chiral molecules wherein the polymerization leads to the formation of asemi-crystalline polymer and 4 different forms: poly(L-lactic acid) or PLLA, poly(D-lactic acid) or PDLA, poly(D, L-lactic acid) PDLLA which is a mixture ofPLLA and PDLA, and meso-poly(lactic acid). So far, only PLLA and PDLLA havebeen studied extensively in biomedical research (Ulery et al. 2011) and regarded asan ideal biomaterial for load bearing applications, such as orthopedic fixationdevices with high elastic modulus (about 4.8 GPa) (Middleton and Tipton 2000),while PDLLA has lower elastic modulus of 1.9 GPa (Maurus and Kaeding 2004).PLLA-based polymers replaced the non-degradable fiber (Dacron) for scaffoldsmaterials (Wang et al. 2009). PLLA degradation rate is very low, and was reportedto take between 2 and 5.6 years for the amount of resorption in vivo (Middleton andTipton 2000). The copolymer of lactic acid and glycolic acid, poly(lactic-co-gly-colic acid) or PLGA, degrades via hydrolytic action and its rate depends on variousparameters including ratio LA:GA, molecular weight, shape and structure of thematrix. PLGA degrades in 1–2 months for a ratio of 50:50, 4–5 months for 75:25,and 5–6 months for 85:15 (Nair and Laurencin 2007).
Poly(dioxanone) is a semicrystalline polymer monofilament developed com-mercially under the trade name of PDS and used for several orthopedic applicationssuch as bone fixation screws (Nair and Laurencin 2007). Similar with PGA, PDS isbroken into glycine which can be removed through the urine. PDS has very lowelastic modulus (about 1.5 GPa) compared to PGA, and a decrease in strengthwithin 1–2 months and loss its mass by hydrolytic degradation within 6–12 months(Maurus and Kaeding 2004).
Degradable Biomaterials for Temporary Medical Implants 135
Tab
le2
Somebiod
egradablepo
lymersin
medicine
Polymer
Chemical
structure
App
lications
Poly(glycolic
acid)
Tissueengineering,
drug
deliv
ery
Poly(lactic
acid)
Tissueengineering,
drug
deliv
ery
Poly(lactic-co-glycolic
acid)
Tissueregeneratio
n,drug
deliv
ery
Poly(dioxano
ne)
Ortho
pedicapplications
Poly(caprolacton
e)Tissueengineering
Poly(trimethy
lene
carbon
ate)
Drugdeliv
ery,
softtissueregeneratio
n
Poly(ortho
ester)
Drugdeliv
ery
Poly(anh
ydride)
Drugdeliv
ery,
tissueengineering
Poly(propy
lene
fumarate)
Ortho
pedicapplications
(con
tinued)
136 A.K. Nasution and H. Hermawan
Tab
le2
(con
tinued)
Polymer
Chemical
structure
App
lications
Poly(alkyl
cyanoacrylates)
Drugdeliv
ery
Poly(pho
sphazene)
Tissueengineering,
vaccineadjuvant
Poly(pho
spho
ester)
Drugdeliv
ery,
tissueengineering
Degradable Biomaterials for Temporary Medical Implants 137
Poly(caprolactone) or PCL is a semicrystalline poly(ester) soluble in variousorganic solvents with slow degradation rate of about 2–3 years (Nair and Laurencin2007). Extensive research is ongoing to develop various micro- and nano-sizeddrug delivery vehicles based on PCL (Sinha et al. 2004). PCL has also beenextensively investigated as scaffolds for tissue engineering. PCL has low tensilestrength of about 23 MPa, but has high elongation of >700 % (breakage)(Gunatillake et al. 2006).
Poly(trimethylene carbonate) or PTMC is an elastomeric aliphatic polyester withexcellent flexibility. PTMC has been developed for drug delivery vehicles and softtissue regeneration. The combination of glycolide, trimethylene carbonate anddioxane can reduce rigidity and degrades within 3–4 months (Nair and Laurencin2007). Binding ability of amide hydrogen bonds and biodegradation given by anester bond results the ester co-polymers with good mechanical and thermal prop-erties. Poly(esteramide) or PEA and poly(orthoesters) or POE are thus identified asdegradable polymers suitable for orthopedic applications beside for drug deliveryvehicles (Gunatillake and Adhikari 2003). Preliminary in vivo studies showed thatPOE increased bone growth when compared with PDLGA (Andriano et al. 1999).With the addition of lactide segments as part of the polymer structure, degradationbegan to be achieved from 15 to hundreds of days. The degradation of the lactidesegments produces carboxylic acids, which catalyze the degradation of theorthoester (Gunatillake and Adhikari 2003).
Poly(anhydride) is one of the most extensive biodegradable polymers studiedwith excellent biocompatibility and controlled release characteristics (Gunatillakeand Adhikari 2003). In 1996, this material has been approved by the FDA aspolymers for controlled drug delivery (Nair and Laurencin 2007). Mechanicalproperties and degradation time can vary, depending on the monomers used. Poly(anhydride) is generally classified as surface eroding polymers because of its linearmass loss during erosion (Nair and Laurencin 2007). However, research shows thatthe degradation is not entirely confined to the surface of the polymer matrix andadditional studies tried to explain other parameters that may affect the degradationpolyanhydride (Akbari et al. 1998). The good mechanical property of poly(anhy-dride) was combine with surface-eroding characteristic of poly(imide) resulted intopoly(anhydride-co-imide) specifically used for orthopaedic applications(Gunatillake and Adhikari 2003). This co-polymers has significantly improvementin the mechanical properties, especially the compressive strength of about 50–60 MPa (Gunatillake and Adhikari 2003) compared with poly(anhydride). Thisincrease is based on succinic acid trimellitylimido glycine and trimellitylimidoalanine (Uhrich et al. 1995). Poly(anhydride-co-imide) degraded through hydrolysisof anhydride bonds, followed by the hydrolysis of imide bonds (Uhrich et al. 1997).Another approach to improve the mechanical strength of poly(anhydride) is by theinclusion of acrylic functional groups in the monomeric units to form injectablephoto-cross linkable poly(anhydride) can be used for filling irregularly shaped bonedefects or for soft tissue repairs and can be molded into a desired shape underphysiological conditions (Nair and Laurencin 2007).
138 A.K. Nasution and H. Hermawan
Poly(propylene fumarate) or PPF undergoes bulk erosion through hydrolysis ofthe ester bond and its degradation time depends on several parameters, such asmolecular weight, type of cross-linker and cross-linking density (Nair andLaurencin 2007). PPF injection system was developed as a material for orthopedicimplants (Temenoff and Mikos 2000). Cross-linked PPF was developed byco-polymerization with acrylic monomers such as N-vinyl pyrolidone, using dif-ferent types of polymerization initiators (Gunatillake and Adhikari 2003).
Poly(phosphazene) is a remarkable macromolecules because of its versatileadaptation to a wide range of applications (Lakshmi et al. 2003) where its degra-dation rate can be designed from a few hours to a year by varying the chemical sidegroups (Nair and Laurencin 2007). The application of these polymers as a short-termmedical implants are drug delivery matrices and scaffolds for tissue engineering.Although polyphosphazenes has tremendous potential as a biodegradable matrix, thismaterial is relatively under-utilized (Lakshmi et al. 2003).
3.3 Lesson Learned
Figure 3 shows examples of implants made of biodegradable polymers rangingfrom bone related implants, such as screws and plates, till endovascular implantssuch as the first Igaki-Tamai stent till the most recent Abbot’s bioabsorbable stent.Apart from the ease of fabrication and control of degradation, biodegradablepolymers might not best suited for temporary hard tissue application such as bone,where adequate strength and elastic modulus are required. Polymeric structures are
Fig. 3 Biodegradable polymer implants: a various spine surgical implants made of PGA and PLA(Medscape.com), b Igaki-Tamai stent made of PLLA (Kyoto Medical Planning, Japan),c bioresorbale vascular stent made of PLLA (Abbot Vascular, USA). Note scale bars areapproximatively only
Degradable Biomaterials for Temporary Medical Implants 139
relatively weak and may not achieve sufficient level of the required strength(Yarlagadda et al. 2005; Cheung et al. 2007) and they could suddenly loss theirmass and mechanical integrity due to degradation. Degradation of polymers affectsthe surrounding tissue by lowering the pH and releasing acidic degradation andresorption by-products which triggers inflammatory reactions (Gray et al. 1988;Therin et al. 1992; Rehm et al. 1994; Bergsma et al. 1995; James and Kohn 1996).This is a major concern in orthopaedic applications where implants with consid-erable bulk size are required. Release of small particles during degradation alsotriggers an inflammatory response (Taylor et al. 1994) and affects bone-remodelingprocesses (Conley Wake et al. 1998). When the capacity of the surrounding tissueto eliminate the by-products is low due to the poor vascularization or low metabolicactivity, the chemical composition of the by-products may lead to local temporarydisturbances (Bostman 1991).
The bioactive properties of biodegradable polymers, such as the antibacterial andanticancer properties of poly(peptide), can be further exploited to be combined withbiodegradable metals to develop a strong yet bioactive temporary implants. Thecontrollable hydrolysis of synthetic biodegradable polymers such as poly(lactic-co-glycolic acid) can be formulated as drug carrier and coated onto biodegradablemetals to also provide a strong scaffold with pharmacologic capabilities.
4 Biodegradable Metals
More than 100 years ago, history of bone fracture fixation told us that metals wereused as implants but were then abandoned because of corrosion (Uhthoff et al.2006). At that time, metals were selected on the trial and error basis (Witte andEliezer 2012). With the advancement in materials processing technology, theproblem of corrosion can be controlled by using corrosion resistant alloys asdescribed in the previous chapter. However, clinical reality showed that almost 10–12 % of inert metal implants were removed due to infection, exposure, pain anddiscomfort (Meslemani and Kellman 2012). Some cases on bone fracture fixator(bone screws) showed complications such as reactions of rejection from body(allergic) (Hallab et al. 2001; Kanerva and Förström 2001; Vos and Verhofstad2013) that made most surgeons recommends implants removal once the bone hasunified (Ochs et al. 2012; Williams et al. 2012). Indeed, implants for treating bonefractures are required only temporary during the period of tissue healing (Li et al.2014).
The current promising solution to overcome the disadvantages of the inert (per-manent) implants is the use of biodegradable ones. Presently, the choices can be takeneither from biodegradable polymers or biodegradable metals with both offer eachadvantages and limitations. Biodegradable polymers have biomechanical limitationcompared to biodegradable metals (Suuronen et al. 1992; Henderson et al. 2014).Biodegradable metals have both the strength and the ability to degrade that make themextensively studied and proposed as new temporary implant materials for vascular
140 A.K. Nasution and H. Hermawan
intervention and osteosynthesis (Hermawan 2012; Zheng et al. 2014). In the currentdevelopment, variety of medical devices (or prototypes) have been made (or underresearch and development) from biodegradable metals including bone pins, screwsand endovascular stents as shown in Fig. 4.
Based on materials science point of view, biodegradable metals can be classifiedas pure metals (one metallic element with impurity levels lower than the com-mercial tolerance limits), alloys (various microstructures and one or more alloyingelements) and metal matrix composites. Up to now, Mg, Fe and zinc (Zn) are thethree class of metals have been used in their pure states and as the matrix formaking alloys and composites.
4.1 Basic Concept
The emergence of biodegradable metals oppose the paradigm of implant materialsthat they must be corrosion-resistant and inert within the body (Hermawan 2012;Zheng et al. 2014). Biodegradable metals have been defined as metals that areexpected to corrode gradually in vivo, with an appropriate host response elicited byreleased corrosion products, then dissolve completely upon fulfilling the mission toassist with tissue healing with no implant residues. Furthermore, the major
Fig. 4 Biodegradable metal implants: a Mg alloy cross pin (Drexel University), b Fe alloy stent(Laval University), c Mg alloy stent (Biotronik, Germany), d Mg alloy compression screw(Magnezix®, Syntellix, Germany). Note scale bars are approximative only
Degradable Biomaterials for Temporary Medical Implants 141
component of biodegradable metals should be essential metallic elements that canbe metabolized by the human body, and demonstrates appropriate degradation ratesand mechanism (Zheng et al. 2014).
Ideal biodegradable metal implants will give the required mechanical supportduring the process of tissue reconstruction, and then degrade progressively with anappropriate level of tolerable degradation products in the human body (Zheng et al.2014; Liu and Zheng 2011a, b). In the case of bone fracture, the time required toachieve hard bone union varies greatly depending on the fracture configuration andlocation, status of the adjacent soft tissues, and patient characteristics (Zheng et al.2014). Figure 5 models the degradation rate and the deterioration of mechanicalintegrity of biodegradable metal implants to suit the bone fracture remodelingperiod (Zheng et al. 2014).
Similarly, for endovascular applications, the biodegradable metal implants (i.e.stent) behavior must suit the period of the vessel’s healing process. It starts byinflammation period where platelet deposition and infiltration of inflammatory cellslasts for several days, followed by granulation period where endothelial cellsmigrate to cover the injured surface and smooth muscle cells modulate and pro-liferate for 1–2 weeks, finally remodeling period takes place where extracellularmatrix deposits and continues for months (Zheng et al. 2014). The total healingperiod is not yet fully determined but some argued that the optimal mechanicalintegrity of a stent must be maintained within 6–12 months (Schömig et al. 1994;El-Omar et al. 2001).
Thus, the main issue is the control of degradation rate. Once implanted into thehuman body, biodegradable metal implants are continually exposed to extracellulartissue fluid. Their exposed surface undergoes an electrochemical dissolution of
Fig. 5 Schematic diagram showing ideal behavior biodegradable metal implants for bone fracturefixation where degradation rate keeps low during 3–6 months and increases thereafter, andmechanical integrity which keeps relatively constant during 3–6 months and rapidly deterioratethereafter. Adapted from Zheng et al. (2014)
142 A.K. Nasution and H. Hermawan
material due to interactions with the human body environment that contains water,complex organic compounds, dissolved oxygen, anions, cations and their complex,amino acids, proteins, plasma, lymph, etc. Corrosion initiates at any site on thesurface which has potential difference (electrochemical cells) created from metal-lurgical condition of the metals such as phase variation, grain boundaries, impu-rities, etc., or from geometrical condition such as crevice formation at the interfacebetween a plate and a locking screw. Corrosion is the typical process of degradationfor biodegradable metals. It’s an electrochemical process where oxidation andreduction reactions occurred producing oxides, hydroxides, hydrogen gas, or othercompounds. In the physiological environment, corrosion generally involve thefollowing reactions:
M ! Mnþ þ ne� ðanodic reaction) ð1Þ
2H2Oþ 2e� ! H2 þ 2OH� ðcathodic reactionÞ ð2Þ
2H2OþO2 þ 4e� ! 4OH� ðcathodic reactionÞ ð3Þ
Mnþ þ nOH� ! M OHð Þn ðproduct formationÞ ð4Þ
Beside affecting mechanical integrity, degradation rate also influence the localtissue response and the physiological environment (Witte and Eliezer 2012).Degradation and tissue response interact reciprocally, the implantation causes injuryand the body responses to it by decreasing the pH value around the implantation site(i.e. 5.3–5.6) that may accelerate corrosion process of the implant and reduce thelocal oxygen concentration (Witte and Eliezer 2012). Our knowledge on thiscomplex interaction is still very limited. One of the recommendations of the latestsymposium on biodegradable metals in Italy in 2014 is to encourage more researchto understand in vivo degradation behavior and to determine its relation to thein vitro degradation.
Numerous methods have been used to evaluate the corrosion behavior ofbiodegradable metals in the laboratory, involving either qualitative measurementsof their implants into animals (in vivo) or quantitative electrochemical measure-ments in simulated body fluid (in vitro). These methods so far are adopted fromthose available for corrosion evaluation of inert metallic biomaterials. The in vitroexperiments are designed to closely simulate the in vivo situation even though someimportant variables such as amino acids, proteins and ions at the proper temperatureand pH into the simulated body fluid are often excluded to maintain reproducibilityand minimize variables. Various in vitro degradation assessments are commonlyused from simple mass loss experiments to more complex electrochemical methods,which each has its own unique benefits and limitations (Kirkland et al. 2012).Meanwhile, in vivo assessments used various animal models from small to biggermammals, and different analytical tools from radiographic (X-ray, CT scan, etc.),blood analysis till histology (Dziuba et al. 2013).
Degradable Biomaterials for Temporary Medical Implants 143
4.2 Degradation Assessment Techniques
Three common assessment techniques to measure in vitro degradation rate anddetermine degradation mechanism of biodegradable metals are weight loss, poten-tiodynamic polarization and electrochemical impedance spectroscopy. Weight lossmethod measures degradation rate based on mass difference of specimens before andafter a certain period where the specimens are usually immersed in simulated bodyfluid solution. The ASTM standard G31 (Standard Practice for LaboratoryImmersion Corrosion Testing of Metals) is mostly referred with some modifications.This simple method typically produces accurate results when degradation layer isoptimally removed and when a substantial degree of corrosion is achieved butmultiple replicates are necessary to provide confidence in the results (Kirkland et al.2012). Weight loss experiments reveal how much degradation has occurred, but theydo not reveal the degradation mechanisms or explain why one alloy degrades fasterthan another. Figure 6 shows typical results obtained from the potentiodynamicpolarization and electrochemical impedance spectroscopy techniques.
Different from the weight loss, potentiodynamic polarization method unveils theinstantaneous degradation rate of a metal under a specific condition. In this elec-trochemical method, the metal surface is polarized by applying a range of potentialand in return, the generated current is measured by a potentiostat. Generally, a threeelectrodes system: working, reference and counter electrodes is used and sub-merged in the test solution. The ASTM standard G59 (Standard Test Method forConducting Potentiodynamic Polarization Resistance Measurements) is oftenreferred. The working electrode comprises the specimen with a determined exposedsurface area. Additionally, potentiodynamic polarization is also able to unveildegradation behavior of the metals both thermodynamically and kinetically such aspassivation and activation or concentration controlled process.
Fig. 6 Example of electrochemical corrosion test results: a potentiodynamic polarization curvesfor pure-Fe and Fe coated with hydroxyapatite (HA-Fe) and with composite of poly(caprolactone)and hydroxyapatite (HA/PCL-Fe), b Nyquist plots and a proposed equivalent circuit for pure Mg,pure Zn and cast Zn-3Mg alloy obtained by electrochemical impedance spectroscopy experiment.Adapted from Mohd Daud et al. (2014)
144 A.K. Nasution and H. Hermawan
Electrochemical impedance spectroscopy is a powerful technique for unveilinginformation about surface characteristics of degrading metals. In this method, anAC voltage is applied onto the metal surface, normally from higher to lower fre-quency, followed by the generation of AC current. The two parameters are logged,analyzed and transformed by a frequency analyzer to form impedance. Theexperiment configuration of EIS is similar to that of potentiodynamic polarization.The ASTM standard G106 (Standard Practice for Verification of Algorithm andEquipment for Electrochemical Impedance Measurements) can be further referred.The impedance data can be presented as Nyquist and Bode plots. Some basicinformation can be extracted directly from the Nyquist plot are electrolyte resistance(Re) that represents the internal solution resistance, and polarization resistance (Rp)which is the sum of the resistances caused by the electrochemical process on theworking electrode surface and resistance due to the voltage drop between theworking electrode and counter electrode. Combined with a cross sectional andsurface analysis using microscopy and elemental analysis the characteristics of thedegradation layer formed during degradation process will be optimally revealed.
4.3 Type of Biodegradable Metals
Generally, it is known that the corrosion of Mg and its alloys is considered too fast(Witte and Eliezer 2012); meanwhile, Fe and its alloys corrode relatively too slow(Witte et al. 2005). Therefore, attempts have been made to manipulate theirmicrostructure and surface properties to control their degradation kinetics via diverseadvance material processing and surface modification techniques. In addition,alternative metals have also been explored including Zn and its alloys (Murni et al.2015; Vojtěch et al. 2011). Table 3 summarizes the mechanical and degradationproperties of some metals and alloys used and proposed for biodegradable metals.
Mg and Its AlloysHistory of Mg for use as an implant dated back to 1878, when it was used asligature to stop blood vessels bleeding (Hornberger et al. 2012; Witte 2010).Abandoned due to limited mechanical properties, poor corrosion resistance andhigh cost of production, Mg regained its popularity as innovative biomaterial fortemporary implants (Hornberger et al. 2012). It is a lightweight metal with densityof 1.74 g/cm3 and elastic modulus of *45 GPa (Black and Kohser 2008) which arevery close to those of human bones. It is also an essential element for humanmetabolism and can be found in bone tissue (Saris et al. 2000; Okuma 2001;Vormann 2003; Wolf and Cittadini 2003; Hartwig 2001). Biocompatibility of Mgand its alloys has been confirmed by numbers of studies both in vitro and in vivo(Heublein et al. 2003; Li et al. 2004, 2008; Witte et al. 2007a). However, their fastdegradation rate limits their applications.
Basically, two factors contributing for low degradation resistance of Mg are theinitial galvanic corrosion caused by second phase or impurities and the
Degradable Biomaterials for Temporary Medical Implants 145
quasi-passive hydroxide film formed on the surface (Makar and Kruger 1993). Thecorrosion of Mg follows the overall reactions:
Mg ! Mg2þ þ 2e� ðanodic reaction) ð5Þ
2H2Oþ 2e� ! H2 þ 2OH� ðcathodic reactionÞ ð2Þ
Mgþ 2H2O ! Mg OHð Þ2 þH2 ðoverall reactionÞ ð6Þ
The production of hydrogen (reaction 6) raises a concern as gas bubble formswhen Mg is implanted in vivo (Aghion et al. 2012). New Mg-based metallic glass(Mg-Zn-Ca alloy) was developed and has not exhibited hydrogen evolution inclinical trials (Zberg et al. 2009).
In general, there are two ways to improve the corrosion resistance of Mg and itsalloys: firstly, by tailoring their composition (purification and alloying) andmicrostructure, including grain size (Hoog et al. 2008; Wang et al. 2008) andtexture (Xin et al. 2009) from base material (not only alloys) (Kaesel et al. 2005),through optimal production method (Hort et al. 2010); secondly by employingsurface treatment or coating (Gray and Luan 2002) such as using ceramic, polymer
Table 3 Mechanical and degradation properties of some biodegradable metals
Metal Mechanical properties Degradation rate*(mm/year)E
(GPa)YS(MPa)
UTS(MPa)
ε(%)
Pure Mg (annealed) 45 30 100 7 8
Mg–Al (AZ31, extruded) 175 250 14 2.0
Mg-RE (WE43,extruded)
180 280 10 4.34
Mg-1Ca (extruded) 135 240 10 1.4
Mg-1Zn (rolled) 160 240 7 1.52
Pure Fe (annealed) 200 150 200 40 0.2
Pure Fe (electroformedannealed)
270 290 18 0.75
Fe-35Mn (PM annealed) 230 430 30 0.44
Fe-10Mn-1Pd (forged) 850 1450 10 0.42
Fe-30Mn-6Si (cast) 180 430 17 0.3
Pure Zn 100 – 20 0.3 0.5
Zn-1Mg (cast) – 150 2 0.20
Zn-1Mg (extruded) 170 250 11 0.12
Zn-3Mg (ECAP)** 205 220 6 0.28
Note E elastic modulus, YS yield strength, UTS ultimate tensile strength, ε elongation.*Degradation data were compiled from the most similar experimental set-up (i.e. PDP method,SBF solution), but variation may occur and they may not be directly comparable. **Unpublisheddata. Data compiled from: Moravej et al. (2010a), Hermawan et al. (2008), Schinhammer et al.(2010), Xu et al. (2011), Liu et al. (2011), Gong et al. (2015), Dambatta et al. (2013), Gu et al.(2009) and Vojtech et al. (2011)
146 A.K. Nasution and H. Hermawan
or composite layer (Hornberger et al. 2012). With the achieved improvement, varietyof medical devices were proposed to be made from Mg alloys including ligature wire,pins, screws, plates and endovascular stents (Witte 2010; Henderson et al. 2014;Witte et al. 2005, 2006, 2007b, c; Kim et al. 2008; Zhang et al. 2008; Song 2007;Staiger et al. 2006; Song and Song 2007).
Pure Mg is Mg with other elements (impurities) within tolerance limit. Elementssuch as Fe, Cu, Ni, Co and Be are considered as impurities and their content shouldbe limited to 35–50 ppm for Fe, 100–300 ppm for Cu, 20–50 ppm for Ni, and up to4 ppm for Be (Witte et al. 2008; Makar and Kruger 1993). When the impuritiesexceed their tolerance limits, the corrosion rate will increase (Lee et al. 2009; Li andZheng 2013). More precisely, tolerance limit for Fe was reported as 170 ppm inunalloyed as-cast Mg and 5 ppm in wrought Mg (Kraus et al. 2012; Hofstetter et al.2015). Above this limit, Fe-rich particles are formed and thus electrochemicallyactive cathodic sites exist and accelerate corrosive rate drastically. Addition ofsilicon, which is usually added to improve castability, promotes the formation andgrowth of Fe-rich particles and thus provokes more corrosion (Hofstetter et al.2015). Beside by purification, the corrosion resistance of pure Mg is higher byimproving the grain size through forging or rolling and heat treatment (Li andZheng 2013). The heating temperature and the length of time of the heat treatmentmust be considered properly. Otherwise, it would get the opposite results (Li andZheng 2013). Although pure Mg demonstrated the ability to stimulate new boneformation, but its mechanical properties in general is still considered insufficient fororthopedic applications (Gao et al. 2010; Huang et al. 2007) and consideredunsuitable for vascular stents (Li and Zheng 2013).
Common alloying elements used in Mg for implants are Al, Mn, Zn, Ca, Li, Zr,Yand rare earth elements (RE) (Xu et al. 2007; Witte et al. 2005, 2007c; Kannanand Raman 2008; Rettig and Virtanen 2008; Qudong et al. 2001; Witte et al. 2008;Gu et al. 2009). When viewed from the alloying elements, there are two majorgroups of Mg alloys excluding pure: Al-containing alloys and Al-free alloys (Renet al. 2005; Song and Song 2007; Wang et al. 2008; Witte et al. 2008). Mg alloyswith Al as the main alloying element commonly form complex Mg17Al12 com-pound which strengthens the alloys via solid solution and precipitation strength-ening mechanism (Witte et al. 2008). However, the Mg17Al12 compound has lowmelting point and thus cannot maintain the strength at high temperatures (Witteet al. 2008). The addition of Al decreases the liquidus and solidus lines and thusraises the alloy’s castability, but adding Al more than 2 wt% may result inembrittlement (Housh and Mikucki 1990). The addition of Mn further increases theductility and corrosion resistance as Mn binds to Fe, while addition of Zn alsoprovide a solid solution strengthening (Mordike and Lukáč 2006) and improvecastability. Calcium (Ca) can contribute to strengthen the alloys as it forms Mg2Caand Al2Ca that act as precipitation and grain-boundaries strengthening but cannotbe added more than 1 wt% as it will cause hot tearing during casting (Witte et al.2008). Lithium (Li) is a unique alloying element which can change the latticestructure of the alloy from HCP into BCC (Nayeb-Hashemi and Clark 1988), but itscytocompatibility is questionable.
Degradable Biomaterials for Temporary Medical Implants 147
The current interesting alloying elements for Mg is the RE as they are found tocontribute in the strengthening, raising the creep resistance, and increasing corro-sion resistance (Rokhlin 2003). The RE are divided into two groups: (1) group ofelements with limited solubility such as Nd, La, Ce, Pr, Sm and Eu (Mordike andLukáč 2006), and (2) group of elements with large solubility such as Y, Gd, Tb, Dy,Ho, Er, Tm, Yb and Lu (Nayeb-Hashemi and Clark 1988). Group 1 will form initialintermetallic phases during solidification, while group 2 forms intermetallic phasescomplex with Mg or Al as strengthening precipitates and inhibiting the movementof dislocations at high temperatures (Witte et al. 2008). Examples of Al-containingMg alloys are the types of AZ91, AZ31, AE21, Ca-modified AZ alloys and AE42(Mordike and Lukáč 2006, Housh and Mikucki 1990). LAE442 alloy is a furtherdevelopment of AE42 with low density but with increasing ductility and corrosionresistance (Bach et al. 2003).
Examples of Al-free Mg alloys are the types of WE, MZ, WZ and Mg–Ca alloys(Witte et al. 2008). The addition of elements such as Y, Zr, Zn and RE improvescreep resistance, high temperature stability and forging-ability of the alloys(Mordike and Lukáč 2006; Housh and Mikucki 1990). Currently, the Al-free alloysare the recommended types of Mg alloys for biomedical use in human (Zhang et al.2010, 2012). In addition, the recommended alloying elements for these alloysincludes Ca, Mn and Zn (Song 2007; Xu et al. 2007; Li et al. 2008)
Mg–Ca alloys became the first most studied biodegradable alloys for boneapplications as Mg and Ca are two main elements that exist in human bone andbeneficial for bone healing (Ilich and Kerstetter 2000; Serre et al. 1998). Theirbiocompatibility was tested both in vitro and in vivo where Mg-(1 wt%) Ca pinsgradually degraded after 90 days and formation of new bone was evident (Li et al.2008). Knowing that Zn is also an essential element in the human body, Mg-Znalloys also received attentions (Tapiero and Tew 2003). The in vitro cytocompat-ibiliy of Mg-(6 wt%) Zn alloy was tested with fibroblast cells and showed positiveresults, while the in vivo test in rabbit’s femoral bone showed a relatively slowdegradation rate (2.32 mm/year) without any evidence of toxicity (Zhang et al.2010; Li and Zheng 2013). Mn does not affect mechanical properties of Mg alloys,but it increases corrosion resistance and poses no toxicity (Li and Zheng 2013).Normally, Mn is also added along with Zn and form ternary Mg–Mn–Zn alloys. Anin vivo study showed that after 18 weeks, Mg-1.2Mn-1Zn alloy implants did notcause an increase of serum Mg levels and renal impairment in rats (Xu et al. 2007).
Fe and Its AlloysFe widely involves in a large number of Fe containing enzymes and proteins inhuman body. It involves in the decomposition of lipid, protein and DNA damagesdue to its reactivity to oxygen molecules which might produce reactive speciesthrough Fenton reaction (Mueller et al. 2006). It also plays significant roles intransport, reduction of ribonucleotides and dinitrogen, storage and activation ofmolecular oxygen, etc. (Fontcave and Pierre 1993). The suitability of Fe as abiodegradable implant material has been tested both in vitro and in vivo in varietyof cells and animal models (Waksman et al. 2008; Peuster et al. 2001a, 2003, 2006).
148 A.K. Nasution and H. Hermawan
Even though no toxicity was observed (Peuster et al. 2001b), but the concentrationof Fe ions in the body should not reach higher than 50 μg/ml as my cause toxicityand cell death (Zhu et al. 2009; Siah et al. 2005). Elastic modulus of pure Fe (211GPa) is higher than that of pure Mg (41 GPa) and its alloys (44 GPa) or SS316L(190 GPa) (Song 2007). Obviously, Fe and its alloys possess superior mechanicalproperties and can meet the mechanical requirement that Mg alloys cannot provide(Hermawan et al. 2010a; Niinomi et al. 2012; Schinhammer et al. 2010). However,their slow degradation is unmatched with the tissue healing period and has becomethe major drawback which limit their applications (Peuster et al. 2006; Kraus et al.2014).
Different from Mg, Fe degradation is dependent on oxygen availability.Generally, it degrades via corrosion following reactions:
Fe ! Fe2þ þ 2e� anodic reactionð Þ ð7Þ
2H2OþO2 þ 4e� ! 4OH� cathodic reactionð Þ ð3Þ
2Feþ 2H2OþO2 ! 2Fe OHð Þ2 overall reactionð Þ ð4Þ
The formation of Fe oxides have been identified as the major inhibitor for afaster degradation (Hermawan et al. 2010b; Kraus et al. 2014). Dense degradationproducts such as Fe-hydroxides, Fe-carbonates and Fe-phosphate layers greatlyhinder oxygen transport to the fresh Fe surface (Drynda et al. 2014; Chen et al.2014; Kraus et al. 2014). Attempts to accelerate the degradation kinetics of Fe havebeen explored through alloying, thermomechanical treatment and by makingcomposite of Fe with bioceramics (Ulum et al. 2014, 2015). In the design of Fealloys, several key points must be considered including manufacturing process (i.e.melting temperature of Fe n is higher than that of Mg which associate with cost andequipment), selection of alloying elements (Peuster et al. 2001b, 2006; Hermawan et al.2010a) and heat treatment to control the grain size (Hermawan et al. 2010a;Moravej et al. 2010b; Niinomi et al. 2012).
Moreover, Fe is ferromagnetic in nature, therefore ideal alloying elementsshould change this property to make Fe alloys compatible with high magnetic fieldsuch as that generated by Magnetic Resonance Imaging (MRI) which becomewidely used for post-implantation monitoring and diagnostic (Hermawan et al.2010a). Fe was made via a bottom-up electroforming process that produced finergrain sizes and preferential textures and resulted into a slight increase of corrosionrate (Moravej et al. 2011). By using surface treatment approach, Fe was also coatedwith micro-patterned Au disc arrays and produced a more uniform corrosion withan almost four times higher degradation rate than the uncoated ones (Cheng et al.2015). Another attempt was by making composite of Fe with Fe2O3 to create morephase/grain boundaries which theoretically act as active sites for acceleratingdegradation (Cheng et al. 2014).
Degradable Biomaterials for Temporary Medical Implants 149
Zn and its AlloysZn is an important essential trace element for cell development and growth, immuneand nervous system. It can be found in the bone extracellular matrix where Zn isco-deposited with calcium hydroxyapatite (McCall et al. 2000) and shows a stim-ulatory effect on the growth of new bone tissues (Zhang et al. 2010; Hänzi et al.2010). The dietary intake of Zn for adult varies from 5 to 20 mg/day and its excesswill be excreted by the kidney (Nriagu 2007; Fosmire 1990). The cytocompatibilityof Zn alloy has been comprehensively studied where Zn-3Mg alloy extractexhibited adjustable cytotoxic effects on normal human osteoblast cells and foundsuitable in the view of its applications for bone implants (Murni et al. 2015). In Mgalloys, Zn is often used as a major alloying element such as Mg-Zn, Mg-Zn-Mn-Ca,Mg-Zn-Y, Mg-Gd, Mg-Zn-Si (Vojtěch et al. 2011) and positively affect the cor-rosion resistance and strength of Mg (Vojtěch et al. 2011).
The interest toward Zn alloys began since the work on Mg-Zn-Ca glasses (with*50 wt% Zn) that observed a significant reduction of hydrogen evolution duringin vitro and in vivo studies (Zberg et al. 2009). However, the use of Zn in thecontext of biodegradable implants is relatively new (Bowen et al. 2013;Vojtěch et al. 2011). Alloying Zn with Mg (<4 wt%) was reported to enhance itscorrosion resistance and mechanical properties (Prosek et al. 2008). Zn alloys withup to 3 wt% Mg was recently investigated for bone fixation applications (Vojtěchet al. 2011). Zn alloys could be preferable over Mg alloys since they can befabricated by classical routes such as die casting and hot rolling. Moreover, theyhave lower melting point, lower reactivity, and superior machinability compared toMg alloys. Zn-Mg alloys were found to have a degradation rate that is slower thanMg alloys but faster than Fe alloys (Vojtěch et al. 2011). Similar to Fe, Zndegradation needs oxygen and it generally degrades via the following reactions:
Zn ! Zn2þ þ 2e� anodic reactionð Þ ð8Þ
2H2OþO2 þ 4e� ! 4OH� cathodic reactionð Þ ð3Þ
2Znþ 2H2OþO2 ! 2Zn OHð Þ2 overall reactionð Þ ð9Þ
Pure Zn has alow strength (*20 MPa) compared to Mg, but once alloyed, suchas that Zn-(1–3 wt%)Mg, it can be superior to some Mg alloys (Vojtěch et al. 2011).Beside alloying, mechanical properties of Zn alloy can be further improved by(severe) plastic deformation such as extrusion, equal-channel angular pressing, highpressure torsion, drawing and forging (Zheng et al. 2014; Zhang et al. 2013). Latestreport on hot extrusion of Zn–1 Mg alloy revealed a significant grain size reductionresulting into increase strength twice than that of pure Zn with a much more uniformdegradation behavior (Gong et al. 2015). The cytocompatibility of Zn alloys havebeen comprehensively studied against various cells such as fibroblast, osteoblast andosteosarcoma, with a conclusion that the Zn alloys have potential for bone implantapplications (Murni et al. 2015; Kubásek et al. 2016). However, more works have tobe done on Zn alloys to confirm their suitability as biodegradable metals.
150 A.K. Nasution and H. Hermawan
5 Perspective
The advance of our knowledge in implant-tissue interactions indicates that bio-materials should exhibit bio-functional capability while maintain a superiormechanical property. The study of innovative degradable biomaterials is one of themost interesting research topics at the forefront of biomaterials in the present days.
Biodegradable metals constitute a novel class of bioactive biomaterials whichsupport healing process of a temporary clinical problem. They are expected tocorrode gradually in vivo, with an appropriate host response elicited by releasedcorrosion products, then dissolve completely upon fulfilling the mission to assistwith tissue healing with no implant residues. From the two recent annual sympo-siums on biodegradable metals for biomedical applications, 2014 in Maratea, Italyand 2013 in Umang Island, Indonesia, we witnessed many developments. Threeclasses of metals have been explored: Mg-, Zn- and Fe-based alloys. Three targetedapplications are envisaged: orthopaedic, cardiovascular and pediatric implants.Three levels of investigations have been conducted: in vitro, in vivo and humanclinical trials. Discussion on standardization has been initiated since 2013 withrepresentatives from ISO, DIN and ASTM and a draft of comprehensive standardwas now under preparation. While at least two companies have launched theirbiodegradable metal-based implants into the market: Swiss and Korea.
Although we can feel the high excitement, especially in the industrial side, westill observed the lack of knowledge in this field. At least, two questions remainunanswered satisfactorily: (1) interaction between metals and their degradationproducts with the surrounding implantation sites including the fate of the degra-dation products and its effects on the physiology and body functions, and (2) cor-relation between in vitro and in vivo studies including degradation mechanism andits kinetics that occurred differently. Over all, the field of biodegradable metals isexciting and we will witness more publications in the future reporting advancedalloys and hopefully real breakthrough that leads to the translation toward clinicalpractice.
In Indonesia, research on biodegradable metals was initiated by researchers atthe Faculty of Veterinary Medicine, Bogor Agricultural University in collaborationwith partners from Universiti Teknologi Malaysia and Laval University (Ulum et al.2014, 2015; Nasution et al. 2015). In 2013, we have successfully brought the 5thAnnual Symposium on Biodegradable Metals, which usually held in Europe, toIndonesian exotic beauty of Umang Island. In addition, with the establishment ofthe Indonesian Biomaterials Society in 2012, research potentials on biomaterials inIndonesia become more exposed and initiate more multidisciplinary collaborationsamong researchers within Indonesia and overseas.
Acknowledgment The authors deeply thank Mr. Ng Boon Sing for the discussion on corrosionassessment part, and Miss Zulaika Miswan for the help on the language. We acknowledge thesupport of the Fonds de démarrage from CHU de Québec Research Center, Laval University.
Degradable Biomaterials for Temporary Medical Implants 151
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Biomaterials in Orthopaedics
Ferdiansyah Mahyudin, Lukas Widhiyanto and Hendra Hermawan
Abstract In general knowledge, orthopaedic surgery treats the disease and injuriesof musculoskeletal system including bone fractures, anomalies, degenerative dis-ease, tumor, and infection. Significant difference in orthopaedic cases occursbetween developed and developing countries. In the latter, the majority of cases arecaused by injury and infection. Most surgical treatment needs the use of implantsfor both traumatic and reconstructive procedures. Orthopedic implants can beselected from metals, polymers and ceramics or their combination. In Indonesia,certain type of orthopaedic implants have been produced locally but still cannotfulfill the high demand. The current technology used by local manufacturers hassome limitations in production capacity and product variety mainly for compleximplants like arthroplasty. Collaboration in R&D activities on orthopaedic implantsis on-going between local manufacturers with universities and government insti-tutions under the assistance of orthopaedic surgeons. This collaboration receives afull support from the Indonesian Government as it aligns with the national pro-gramme on supporting local products and the new general health insurance pro-gramme which covers every citizen of Indonesia.
Keywords Biomaterials � Bone implant � Injury � Manufacture � Orthopaedic �Surgery
F. Mahyudin (&) � L. WidhiyantoAirlangga University, Surabaya, Indonesiae-mail: [email protected]
L. Widhiyantoe-mail: [email protected]
H. Hermawan (&)CHU de Quebec Research Center, Laval University, Quebec City, Canadae-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_7
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1 Introduction
Orthopaedic is a branch of medical science that concerns with promotion, pre-vention, investigation, and treatment of disease and injury of musculoskeletalsystem by medication, physical therapy and surgery. Scope of orthopaedic fieldincludes congenital anomaly, degenerative disease, tumor, injury, arthritis andinflammation, infection, muscle weakness and sensory disturbance (Salter 1999).There are significant differences in orthopaedic cases between developed countriesand developing countries. In developed countries, the majority of orthopaedic casesare caused by degenerative diseases such as osteoarthritis and canal stenosis ofspine. On the other hand, in developing countries, most cases are caused by traumaand infection. Orthopaedic surgeon is a profession that frequently applies implantsin their practice. Orthopedic implants consist of traumatic implants, which can beused as internal fixation in trauma cases, and also reconstructive implants, that canbe used to replace damaged bone and joint structure thus recovering the function aswell. The material used for orthopedic implants can be selected from variousoptions such as metals, polymers and ceramics or the combination of two or more.
2 The Most Common Orthopaedic Problems in Indonesia
Currently, the life expectancy in Indonesia has increased. Indonesia is one of thecountries in the world that has rapid industrial and economic growth, as well asincreasing growth in education level. Those changes bring a shift to the pattern ofdiseases in Indonesian. Nowadays, trauma and infectious diseases are still thedominant cases in the field of orthopedics. Trauma cases are closely related to trafficaccidents and occupational hazard, for example in construction work. While, theinfection cases are closely related with the level of environmental health, level ofwelfare and also the level of public education.
In line with the growth of economic and the society welfare, the degenerativedisease that closely links with aging, the metabolic diseases which are influenced bychanges in lifestyle and diet, and cancer are growing and start to become majordiseases in the developing countries including Indonesia. Cause of death has alsochanged. Death caused by heart attacks and cancer have equaled and even exceededdeaths due to infection.
Looking at the tendencies described above, in the not too distant future thepattern of diseases in Indonesia would resemble the case in developed countries,where cases of infection and trauma will be decreased and replaced by degenera-tive, metabolic and cancer diseases. The incidence of orthopaedic cases inIndonesia is high and mostly due to traffic accidents. Most of Indonesian people useprivate vehicle, especially motorcycles (Fig. 1). Mass transport is still not providedvery well therefore cheap and high flexibility vehicle is the best choice. The numberof motorcycles has grown very fast in 10 years and becomes the highest cause oftraffic accidents in Indonesia.
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Accidents are counted for the third death cause in Indonesia that lead to bonefractures and disability. Fractures happen more commonly to men compared towomen under the age of 45 years old. They are often associated with sports, work,or injuries caused by motor vehicles. While in elderly, women are more often thanmen to experience fractures which associate with increasing incidence of osteo-porosis due to hormonal changes at menopause. According to data recorded at theDepartment of Orthopaedic and Traumatology, Airlangga University—Dr.Soetomo General Hospital, Surabaya, from October 2009 to October 2012 therewere as many as 7,134 patients admitted to the emergency room because of frac-tures (Fig. 2).
Fig. 1 Typical traffic condition in Indonesian main cities during rush hours, where motorcyclesslipping around cars risking their own safety (Photo credit: Letterview.com)
Fig. 2 Examples of frequent fracture cases due to traffic accidents: a lower leg fracture; b forearmfracture (Courtesy of Dr. Soetomo General Hospital, Surabaya)
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The increase in the degree of welfare, education and intensive governmenthealthcare program has considerably lowered the incidence of cases of infection inIndonesia although infection is still the second most common case in orthopaedics. Itis mostly caused by mycobacterium infection such as tuberculosis (TB). The secondmost frequent TB infection following the lung TB is an infection of the bone. TB ofthe spine is still a major problem in Indonesia. TB of the spine (Fig. 3) will causedestruction of the bone, causing kyphotic deformities and compression of the spinalcord and eventually paralysis of the extremities. In addition to spinal tuberculosis,there are also infection to the joints, especially the hip joint and the knee.
In line with the increasing life expectancy in Indonesia, there is also an increasedincidence of degenerative cases. Degenerative musculoskeletal diseases that have arelatively high incidence and cause of morbidity in patients is a degenerative jointdisease (osteoarthritis) and osteoporosis (Fig. 4). Osteoarthritis is characterized bysymptoms of joint pain, especially after activity, stiff joints and decrease of range ofmotion. Osteoarthritis can occur in all joints of the body, but the most debilitating isthe one that affects large joints of the body such as the knee joint, hip joint andspine.
Osteoporosis is a disease that occurs due to disturbances in bone mineralization,causing bones to become susceptible to fracture. The disease is common in womenafter menopause. Pathologic fractures due to osteoporosis is most common in thespine, pelvis and wrist joints. The incidence of osteoporosis in Indonesia in age lessthan 70 years for women as much as 18–36 %, while men 20–27 %, for age above70 years for women 53.6 %, men 38 % (Tirtarahardja et al. 2006). Osteoarthritis(OA) is the most common joint degenerative disease in the society, especially inelderly. Indonesia belongs to the 10 countries with a large elderly population.
Fig. 3 Typical MRI pictures of the TB of the spine (Courtesy of Dr. Soetomo General Hospital,Surabaya)
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In 1991, the number of people aged over 60 years was already 16 million, and israpidly increasing. A population-based survey in a rural setting in Indonesiareported that the prevalence of radiographic OA of the knee in subjects aged15 years and above was as high as 15.5 % among men and 12.7 % among women(Soeroso et al. 2005; Darmawan et al. 1992).
3 Surgical Intervention and Implants
3.1 Biomaterials in Orthopaedic Surgery
Biomaterials are commonly used in orthopaedic field. Firstly, it is used for aug-mentation of bone such as in the cases of fracture treatment. Secondly, they are alsoin very good use in replacement and reconstruction of musculoskeletal organs likejoints, ligaments, intervertebral disc, resected bone due to malignancy, and defec-tive joints due to degenerative changes (Grimm 2003). The definition of biomate-rials itself is any material intended to perform the function of an organ or a tissuepartly or completely in living organisms. Those which are usually used in ortho-paedic are commonly called implants (Koksal 2014).
Biocompatibility, appropriate design, manufacturability, mechanical reliability,biological stabilities, special properties such as tensile strength, yield strength,elastic modulus, corrosion and fatigue resistance, surface finish, creep, and hard-ness, resistance to implant wear and aseptic loosening and corrosion of implants areall contributing to characteristic of implants. There are several basic requirementsthat need to be fulfilled in order for the devices to function properly (Patel andGohil 2012). The main biomaterials used in orthopaedic surgery are divided intotwo groups: metals and non-metals.
MetalsThe use of metals for orthopaedic devices started long time ago. In the 17th century,metals have started been used, and later on, in the 18th century a metal screw
Fig. 4 Degenerative cases commonly found in Indonesia: a osteoarthritis of the hip;b osteoarthritis of the knee; c pathological femoral neck fracture caused by osteoporosis(Courtesy of Dr. Soetomo General Hospital, Surabaya)
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implant was used for the first time. Metals have their main applications inload-bearing systems such as hip and knee prostheses and for the fixation of internaland external bone fractures. The metallic implants that are widely used in ortho-paedic surgery are: low carbon grade austenitic stainless steels, titanium (Ti) and itsalloys, and cobalt-chromium (Co-Cr) alloys.
Stainless Steels: Like any steel, it is an iron-carbon alloy. Alloying elementswere added and contributed to the ability of stainless steel to resist corrosion. Thefirst biomedical 18-8 steel alloy contained vanadium (V) but subsequent studiesindicate that it provides the alloy with insufficient corrosion resistance, and there-fore the medical use of vanadium steel has been discontinued (Ivanova et al. 2014).Further study yielded new resistance property in which modern corrosion resistant(stainless) steel is made by adding typically 18 wt% of Cr, which resulting in a thinCr oxide (Cr2O3) film on the surface and 8 wt% of nickel (Ni) which contributes toaustenite phase formation in the alloy. This Cr2O3 film is characterized by its lowchemical reactivity and displays a self-healing capability in contact with oxygen.Based on phase composition, these steels are classified into three categories: aus-tenitic, martensitic or ferritic stainless steels. They considered as the good choicefor number of biomedical applications. In practice, stainless steels are used pre-dominantly in temporary implant devices, such as fracture plates, screws, and hipnails, although stainless steel also is used in some Charnley-style femoral com-ponents for hip replacement. The microstructure of austenitic stainless steels ischaracterized by its gamma (γ) phase with faced-centered cubic structure whichcontributes excellent workability (both forming and machining) and non-magneticproperties. Those belong to this group are the types 302, 316 and the famous 316Lwhich remains popular as an implant material and a low-cost alternative comparedto Ti and Co-Cr alloys (Buhagiar and Dong 2012). Despite its special attributes,there is some downward of stainless steels such as the reported Ni toxicity to thehost organism, and vulnerability of the alloy to pitting and crevice corrosion as wellas stress-corrosion cracking. Therefore, the use of stainless steels is generallylimited to temporary use as biomedical devices despite its role in modern use asorthopaedics and load-bearing implants (Buhagiar et al. 2012).
Ti and its Alloys: They are commonly used for dental and orthopaedic implants.Different alpha and beta structure leads to three different structural types of Tialloys: alpha (α), alpha-beta (α-β), and metastable β and β-phase alloys. Theirexcellent corrosion resistance is a result of inert TiO2 film formation on theirsurface. For dental implants, commercially pure (CP) Ti, typically with single-phasealpha microstructure, is commonly used, while Ti6Al4 V, with a biphasicalpha-beta microstructure, is most commonly used in orthopaedic applications. Thepresence of aluminum (Al) and V alloying elements not only contributes to themechanical stability but also improves the microstructure of alpha-beta in relationto CP Ti. These properties are modulated by heat treatment and deformationalworks. Despite Ti and its alloys combine a range of excellent properties, i.e.mechanical properties, corrosion resistance, fatigue-corrosion resistance, low den-sity and relatively low modulus, their processing is not easy whether it ismachining, forging or heat treating (Navarro et al. 2008). The β-phase in Ti alloys
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tends to exhibit a much lower Young’s modulus than that of the α-phase, thereforeit satisfies most of the necessities or requirements for orthopaedic applications.However, the presence of Al and V in long term use of Ti alloys (especially Ti64)poses potential hazard of toxicity. The release Al and V ions from the alloys hasbeen associated with the potential for Alzheimer and neuropathy disease (Patel andGohil 2012).
Co-Cr Alloys: These alloys, which have been used for many decades, can bebasically categorized into two types: Co-Cr-Mo alloys [Cr (27–30 %), Mo (5–7 %),Ni (2.5 %)] generally used in dentistry and artificial joints; and Co-Ni-Cr-Mo alloys[Cr (19–21 %), Ni (33–37 %), and Mo (9–11 %)] mostly used for making the stemsof prostheses of heavily loaded joints, such as knee and hip (Patel and Gohil 2012).Involvement of heat during processing of Co-Cr-Mo alloys modifies the alloy’smicrostructure and leads to the alteration of electrochemical and mechanicalproperties of the alloys. In term of corrosion resistance, Co-Cr alloys are consid-erably superior to stainless steels as it demonstrates better performance inchloride-rich environment. However, the corrosion products of Co-Cr-Mo, espe-cially the possible release of Cr ions is potentially more toxic than that of stainlesssteel 316L (Chen and Thouas 2015).
PolymersApart from metals, polymers, the organic or inorganic materials that form largechains made up of many repeating units, are extensively used in joint replacementcomponents. Currently the most used polymers in joint replacements are: ultrahighmolecular weight poly(ethylene) or UHMWPE, poly(methyl methacrylate) bonecement or PMMA, thermoplastic poly(ether ether ketone) or PEEK, and bioab-sorbable type of polymers.
UHMWPE: Being used since early 1960s, it is a semi-crystalline polymer withroughly half of its chains is structurally organized in crystalline lamellae and thebalance is entangled in a random amorphous state. At the body temperature, thispolymer behaves between its glass transition temperature and melting point,enabling unique viscous amorphous behavior combined with a solid-like crystallinephase. The microstructural arrangement of UHMWPE provides desirable materialproperties for use in total joint arthroplasty, including wear, strength and fatigueresistance in comparison with other polymeric materials. Therefore, UHMWE isused as a bearing surface in total joint arthroplasty (Ansari et al. 2015). However,UHMWPE is not a perfect material because small amount of fluids can be boundwhich makes discoloration of components as retrieved from infected sites. It issubjected to fatigue failure and displays a tendency to creep for long-term appli-cations, though this is reduced in its highly cross-linked form. Highly cross-linkedand thermally treated UHMWPE is generally acknowledged as the special structurefor hip arthroplasty. Since the introduction of its first-generation, clinical perfor-mance of highly cross-linked implants is generally considered successful, thoughthere has been a small number of reports on the rim fractures of some thinner linersimplanted at high abduction angles. Highly cross-linked UHMWPE is currently lessused in the knee owing to the inherent reduction in ductility and fracture resistance
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as the result of irradiation used to initiate the cross-links, despite its superiormechanical performance (Ong et al. 2014).
PMMA: In 1970s, Charnley introduced the use of acrylic plastic bone cementmade from PMMA (Leong and Lu 2004). PMMA cement is formed by mixingliquid monomer and powdered polymer which produce an exothermic reaction attemperature of 48–56° C in vivo. The monomer component varies a little amongdifferent available preparations while the powder typical contains polymer,copolymers of different molecular weights, initiator, radio-opacifier, accelerator,and antibiotics and dye (Duffy and Shafritz 2011; Webb and Spencer 2007).Antibiotics and barium are added in order to reduce the risk of infection andincrease radiographic visualization, respectively. Being available in bothhigh-viscosity and low-viscosity preparation, PMMA does not adhere to bone ormetal, but rather acts as a grout, interdigitating between the bony trabeculae andincreasing the contact area. Its elastic modulus lies between 1–4 GPa which is closeto that of cancellous (10–2,000 MPa) and cortical (10–20 GPa) bones. PMMA hasviscoelastic properties that demonstrate an increase of stiffness with higher rates ofloading, as well as creep and stress relaxation. It reaches its strongest point undercompression (Wright and Maher 2008).
PEEK: It is a semicrystalline thermoplastic consisting of an aromatic molecularchain interconnected by ketone and ether functional groups. In orthopedic appli-cations, PEEK has been utilized for bearing surfaces, fracture fixation plates, totaljoint arthroplasty parts, and spinal implants. In addition, PEEK is widely used forinterbody fusion cages or components in spine fixation systems. PEEK is radi-olucent which facilitates assessment of the surgical site with plain radiography, CTor MRI (Li et al. 2015). Due to its high quality and imperviousness to degradation,PEEK materials are utilized as a part of a wide assortment of mechanical appli-cations. PEEK can be utilized as a part of an unfilled state, with added substances,for example, carbon or fired strands, or with bioactive added substances, for example,hydroxyapatite. Unfilled PEEK has a flexible Young’s modulus of 4 GPa, but acomposite (filled PEEK) could has a higher elastic modulus than that of Ti alloy (110GPa). By filling 30 % weight with carbon fiber, PEEK composite can reach aversatile modulus of 20 GPa, while at 68 % reaches 135 GPa (Abdullah et al. 2015;Schwitalla and Muller 2013).
Bioabsorbable Polymers: Some polymers are resorbable in their nature and aresuitable for initial fixation and stabilization. In orthopaedic surgery, bioabsorbablepolymers are commonly used when the permanent presence of a device is notneeded or desired, such as sutures, suture anchors, fracture fixation pins, and bonescrews. Over time, these implants will undergo resorption through hydrolysisprocess at a predetermined rate, lose their mechanical integrity and becomes less stiffand loses its ability to support a load. During this process, the load is transferredincreasingly through the healing tissue. Therefore, the rate at which the bioabsorbablepolymer device loses integrity is an important consideration (Burg et al. 2000;Farraro et al. 2014). Bioabsorbable polymers can also provide a mean of releasingdrugs locally to the surgery site. The rate of drug elution can be designed to correspondto the factors affecting healing or bone regeneration process. Some of the most
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frequently used bioabsorbable polymers are poly(glycolic acid), poly(lactic acid), andcopolymers derived from them. The process of natural hydrolysis in the body willdegrade these polymers to yield glycolic acid or lactic acid monomers, respectively(Ulery et al. 2011). Poly(glycolic acid) has higher elastic modulus of 7 GPa comparedto that of 46-poly-L-lactic of 2.7 GPa, but poly(glycolic acid) has shorter degradationtime of 6–12 months compared to that of the latter which degrades after 24 months.Elastic modulus and degradation time can be modulated by varying copolymer for-mulations, for instance, a formulation of half lactic acid and half glycolic acid resultsinto low elastic modulus of 2 GPa and very short degradation time of 1–2 months(Middleton and Tipton 2000).
CeramicsCeramics are polycrystalline materials made of metallic and non-metallic elementsbound by ionic or non-ionic bonds with occasional covalent bond, and are char-acterized by both brittleness and hardness. Many types of ceramic materials areused in practice and they are generally divided into two large groups: inert ceramicssuch as alumina (dense aluminum oxide), zirconia (zirconium oxide), calciumsulfate, and pyrolytic carbon; and bioactive ceramics that are designed to induce areaction from the surrounding tissue such as hydroxyapatite, β-tricalcium phos-phate, and silica-based or calcium-based bioglasses.
Inert Ceramics: Alumina has a very low coefficient of friction when articulatedagainst UHMWPE due to its high wettability that reduces friction and provideself-lubrication during articulation. The combination of low friction, improvedlubrication, and reduced wear has led to the popularity of alumina as a bearingsurface for the femoral head in total hip replacement (Garino 2013; Piconi 2011).Zirconia is stronger and denser than alumina, and it can be polished to a finersurface finish, resulting in lower wear rates than alumina in a laboratory setting.Zirconia is also used as femoral bearing surfaces in total hip implants and inpowdered form as a radiopacifier in some formulations of PMMA bone cement.Unlike alumina, zirconia should not be used in ceramic-on-ceramic articulations.A high rate of early fracture of zirconia heads has led to a large recall, hence theuse of zirconia as bearing surface subsequently decreased. However, newerzirconia-toughened alumina matrix composites have been developed to providegreater strength and fracture toughness than alumina alone (Chang 2014; Heyse et al.2012).
Bioactive Ceramics: These materials possess special characteristic that allows aformation of bonding with living tissue. They take advantage of the tissue’s cellularphysiology and structural component materials to induce bone remodeling, growth,and integration into the implant (Rahaman 2014). An ideal bioactive ceramic wouldactually spur bone growth adjacent to the implant, promote integration of the bonewith the implant structure, and gradually biodegrade as healthy bone tissue replacesthe artificial structure. Calcium-based ceramics (such as calcium phosphate, calciumsulfate, and hydroxyapatite) and bioglasses are two general categories of bioactiveceramics that have been developed. Bioglass is mineral rich structure that can betailored to optimize the tissue response. Hydroxyapatite (Ca10[PO4]6 [OH]2) is a
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logical choice for an osteophilic substrate since it is naturally occurs in bonemineral. Hydroxyapatite coatings have been used for decades both in dental andorthopaedic applications. As commonly occurs with bioactive agents, there wasinitial enthusiasm for coating the entire implant with hydroxyapatite to providestrong fixation to surrounding bone. However, over time it became apparent thathydroxyapatite is best used tactically to enhance regional bone fixation. In total hipreplacement implants, for example, hydroxyapatite coating is best used around theimplant shoulder, which is the most important region for robust bone apposition andimplant fixation (Bose et al. 2015). β-tricalcium phosphate (Ca3[PO4]2) and bio-glasses are usually utilized as a part of basic applications (e.g. filling cancellousbone defects), for bone graft replacement as substitutes or extenders, and especiallyas an aide to fracture repair or fusion in the setting of trauma, orthopaedic oncology,or spine surgery (Goff et al. 2013; Hartigan and Cohen 2005). The fillers areavailable in forms including granules, pastes, and malleable sheets.
3.2 Types and Applications of Orthopaedic Implants
Orthopaedic surgeons are the most common users of implants for treating,improving, or replacing anatomical elements of musculoskeletal system. Variousimplant sizes and shapes are used which are determined by the location and thedisease to be treated. Metal implants consist of many types of plate and screwsystems, intramedullary nail system, pedicle screw system that are used for fractureand reconstruction of bone and spine (Fig. 5). Polymer implants mostly used forbiodegradable screw, while hydroxyapatite ceramic is used as a bone graft toaccelerate bone healing. Certain implants use a combination of biomaterials such as
Fig. 5 Various types of implants used for traumatic purposes: a plates in various types and sizes;b angled-blade plate, commonly used for proximal or distal femoral fractures; c dynamic hipscrew, widely used for cases in proximal femoral fracture; d interlocking nail, suitable for longbone fracture of lower extremity; and e pedicle screw and rod, used for posterior spine stabilization(Courtesy of Dr. Soetomo General Hospital, Surabaya)
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the case of a total joint replacement that combines metal and polymer or ceramic. Ingeneral, implants used by orthopaedic surgeon are divided into: traumatic implantsmainly for fracture fixation; and reconstructive implants which are used to replacebody parts damaged by a disease such as osteoporosis. In Indonesia, the most usedtype is currently the traumatic implants, but gradually the use of reconstructiveimplants also begins to increase with the aging Indonesian population.
Traumatic ImplantsDue to high incidence of trauma cases in Indonesia, traumatic implants are still themost frequent type of implants used in Indonesia. These include screws, plates,nails, and pins either to be used as internal or external fixation of fractures (Fig. 6).External fixator is preferable to be used for open fracture with severe soft tissueinjuries in order to stabilize the fracture comminution and to handle the risk ofpostoperative infection. In the case of extramedullary fixation, plates are combinedwith screws above and below the fracture or using rods or nails inserted intomedullary canal through the fracture site (Ito et al. 2015).
Like any other living tissue, bone responds to environmental and physiologicalchanges. When bone grows, there is an increase of extracellular matrix material tothe endosteum and periosteum layer. This will result in bone growth of both inlength and diameter. Wolff hypothesized in 1892 that under continuous loadingbone will grow better. Bone that does not get enough loading will lose its mass,while bone experiencing greater load will increases its mass in response to reducestress (Frost 1994). Throughout life time, the process of removal and replacementof bone occurs continuously, known as remodelling. In fracture healing, this
Fig. 6 Application of traumatic implants: a angled-blade plate for proximal femoral fracture,b dynamic hip screw for femoral neck fracture, c intramedullary nail used in femoral shaft fracture,d pedicle screw and rod applied for lumbar stabilisation (Courtesy of Dr. Soetomo GeneralHospital, Surabaya)
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process enables the recycling process to occur continuously on the bone and intohealthy tissue to prevent the accumulation of micro fractures that can lead to failureof the bone structure (Grimm 2003).
Fracture can heal with or without the formation of external callus depending onthe mechanical environment supporting the healing process. The one that is fixedmore anatomically and more rigidly will heal without the formation of externalcallus whereas that of being less rigidly fixed will form external callus. In overall,the process of fracture healing requires a suitable and favorable biological andmechanical environment (Cunningham 2001). A higher mechanical resistance ofmetallic implants (i.e. Young’s modulus) compared to cortical bone leads to adecrease in mechanical stress received by the fracture site, known as stressshielding effect. In long-term fixation, this condition will result in increased boneresorption surrounding the implants. This device-related osteopenia or osteoporosisis caused by the increasing activity of osteoclast in respond to stress-shieldingeffect. This effect must be avoided in order to maintain good bone strength and it isadvisable to remove the implant after certain period of bone union especially inweight-bearing bone (Ito et al. 2015).
When an implant is strained under continuous stress, it will reach a point ofultimate resistance which will result in failure when the point is surpassed (Fig. 7).One of the most commonly encountered failure is fatigue where cyclic load, whichdoes not necessary to be massive, cause a repeated stress below ultimate strengthleading to crack propagation and ultimately fracture (Kanchanomai et al. 2008;Mann and Allen 2013). In details, fatigue failure occurs at three stages: crackinitiation, propagation and finally the catastrophic manifestation when the crackreaches a critical length of which the remaining material cannot withstand theapplied stress (Rabbe and Anquez 2013). Under fatigue condition, the number ofstress cycles that the material can withstand is inversely proportional to the mag-nitude of the applied stress; that is, the number of stress cycles the material canwithstand increases as the stress intensity is reduced (Mann and Allen 2013). Whenenvironment is in favor to enhance crack formation, for example in exposure of
Fig. 7 Failure of implants: a fracture of a plate; b fracture on hemiarthroplasty of a hip joint(Courtesy of Dr. Soetomo General Hospital, Surabaya)
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implants to scratches and nicking, the fatigue failure will be more rapidly reach andthe device life span will be greatly reduced. Any factor that arrests or slows downcrack propagation will increase fatigue life. In a certain composite system, a crackpropagates through a fiber-reinforced matrix will stop when it reaches the boundaryof a strong fiber within the matrix. The crack will remain stagnant until enoughdamage accumulates to move the crack through the fiber (Wright and Maher 2008).
The environment inside human body is physically and chemically different fromthe ambient condition. Consequently, a metal that performs well (inert or passive)in the air may suffer a severe corrosion in the body. Corrosion creates two prob-lems: (1) it often leaves behind damaged regions on the surface of orthopaedicimplants that act as stress risers, markedly decreasing implant strength; and (2) itreleases to the surrounding environment corrosion products that can adversely affectbiocompatibility, cause pain, swelling, and destruction of nearby tissue.Orthopaedic implants can be susceptible to several corrosion modes, depending ontheir geometry and manufacturing history, the in vivo conditions under which theyperform, and the presence of surface defects (Chen and Thouas 2015; Wright andMaher 2008). The most common forms of corrosion are uniform corrosion, inter-granular, galvanic, pitting, fatigue corrosion and stress corrosion cracking.Corrosion process is determined by two factors: (1) thermodynamic driving forces,which cause corrosion (oxidation and reduction) reactions; and (2) kinetics, whichdetermines the rate of those reactions. The thermodynamic driving force corre-sponds with the energy required or released during a reaction, while the kineticsbarriers are related to factors that impede or prevent corrosion reactions from takingplace (Jacobs et al. 1998; Manivasagam et al. 2010). Oxide film formed on thesurface of metallic materials plays an important role as an inhibitor for the release ofmetallic ions. During corrosion process, the composition of oxide film changesaccording to reactions at the interface of metal surface and living tissue, and hencethis film plays a very important role, not only for corrosion resistance but also fortissue compatibility (Manivasagam et al. 2010).
Reconstructive ImplantsArtificial joints are indicated for patients with severe destruction of any joints fromthose on small fingers to hips or knees caused by trauma, osteoarthritis or tumors.The affected joints are therefore replaced by prosthetic devices in order to restore itsnormal function and eliminate pain. Figure 8 shows example of various implantsused in reconstructive surgeries. Hip prostheses consists of two separate compo-nents, namely the femoral and acetabular parts. The femoral part itself is furtherconstructed by two main parts which are the head and the stem. Unlike the femoralpart, the acetabular one can be separated into the cup and its liner. Materials usedfor making the components can come from metal alloys such as Co-Cr-Mo or Tialloys, or ceramics and polymers. Since the invention of early prostheses byCharnley in 1970s, the most widely used combination for bearing surfaces is themetal-on-poly(ethylene). This combination is consistently being developed for allthe prostheses to improve its design and techniques of implantation. Themetal-on-poly(ethylene) bearing has become the most favorable and the gold
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standard in hip prostheses as it proved its safety, predictability andcost-effectiveness. However, the risk of complication caused by the presence ofpoly(ethylene) debris remains a major concern and downside. The debris might leadto accumulation of cytokines and proteolytic enzymes which causes peri-prostheticosteolysis. In the end, this process may lead into the most feared complication ofimplant failure due to aseptic loosening. Several measures had been taken tominimize the complication caused by the debris by improving the wear resistancethrough gamma irradiation. However, despite the effort of minimizing the com-plication, there has been shift of interest towards the use of metal-on-metal bearings(Knight et al. 2011).
Due to the risk of metal toxicity, cancer development, hypersensitivity reactionand prosthetic loosening, metal-on-metal bearing was abandoned in 1970s.However, it was later found out that the cause of failure of the early model of thisprosthetic was not due to the nature of the bearing material itself but rather causedby improper design and implantation technique. The metal-on-metal bearing isfavorable than the metal-on-poly(ethylene) since it has better wear resistance (*60times more resistant), lower brittleness of the femoral head component, better jointstability (due to larger possible head diameter), lower incidence of dislocation, andlower osteolytic and peri-prosthetic inflammation reaction. However, there is pos-sible risk from debris released from metal-on-metal bearing. The released metalions increase the Co and Cr ions blood level three to five times higher, even thoughthe long-term effect is still being investigated (Zywiel et al. 2011; Drummond et al.2015).
Due to issue of wear resistance and friction problem in the two previouslymentioned bearings, ceramic-on-ceramic bearing was then introduced by usingalumina and zirconia as the materials. This type of bearing is more superior to metalor poly(ethylene) counterparts in term of hardness, scratch resistance, and inertcharacteristic of the debris. Ceramic bearing is very suitable for active and mobilepatients as it has very good durability and low friction. The low friction comes fromits hydrophilic property which improve lubrication on its surface. However, apartfrom its superiority, the cost of ceramic bearing is higher. The adverse complicationmight occur as a result of loose body presence. This loose body usually originatesfrom chipped parts of the contact surface when improper technique of insertion isapplied or when head dislocation occurs (Zywiel et al. 2011; Macdonald andBankes 2014).
Apart from the characteristic of the bearing surface materials, the interfacebetween bone and prostheses is not less important. There are two kind ofbone-implant fixation: cementless and cemented fixations. Cementless implantsprovide better possibility for revision surgery when needed and they also havebetter soft tissue preservation when being implanted. When cement is not used, theimplants must have special characteristics on their surface to ensure fixation (i.e.porous or grit-blasted surface). The most recent special surface in cementlessprostheses is the use of hydroxyapatite coating that promotes bone growth onto theimplant surface, therefore increases fixation strength. On the other hand, cement isused as space filler rather than as glue. Cemented implants use methacrylate cement
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Fig. 8 Various prosthesesused in reconstructivesurgery: a total hiparthroplasty; b total kneearthroplasty; c megaprostheses for distal femur(Courtesy of Dr. SoetomoGeneral Hospital, Surabaya)
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to improve fixation. In around 1950s, Charnley introduced the used of dentalcement although in later time, the failure of cement shifted the favor of cementedimplants (Khanuja et al. 2011). Comparing the durability of both fixation tech-niques, cemented one has lower durability after 10 years compared to thecementless one, thus causes a higher rate of revision surgery due to aseptic loos-ening. However, without counting the revision surgery, cemented stem performsslightly better than cementless one (Mäkelä et al. 2008).
Wear and osteolysis following total joint arthroplasty occur as a result of acomplex interaction of many variables. These variables include: patient-specificcharacteristics (e.g. weight, activity level and age) which affect the magnitude anddirection of loads across the joint as well as joint kinematics; and implant designand material factors that control how the implant components respond to themechanical burden placed upon them (Gillespie and Porteous 2007; Foran et al.2004). Equally important, surgical factors (e.g. component position and orientation)can also affect joint loads and kinematics. When surgical technique is optimized,the ideal implant position is realized and the best possible wear performance of thetotal joint arthroplasty can be achieved. However, when malposition, damaged, ormisassembled occurred, a specific prosthesis may experience greatly increasedwear. Osteolysis can occur as a response to peri-prosthetic particulate debris thatresults from and is dependent on material type as well as particle size, shape, andamount. In overall, the multiple factors influencing clinical wear performance of hipand knee arthroplasty can be separated into patient specific, implant-specific, andsurgical factors that contribute to wear directly or indirectly (Tsao et al. 2008).
4 Recent Development of Orthopaedic Implantsin Indonesia
4.1 The Rise of Local Implant Industry
Until the era of 1990s, all orthopedic implants required for surgeries in Indonesiaare imported from overseas. There was no local implant industry. Imported implantsare relatively expensive for Indonesian people as most of the population is notcovered by adequate health insurance. Moreover, as the products were mostlyimported from Europe and USA, their size is often too big to fit Indonesian peopleanatomy. These factors has caused orthopaedic service was not optimally deliveredand many patients then looked for alternative therapies such as the service of bonesetter that offers lower price. This condition has been causing a high number ofdisability on orthopaedic patients. Nowadays, in line with the improvement ofIndonesian economic, education and lifestyle, alternative medicine has beenbecoming less popular that hospital (modern) medicine. On the other side, traumaticfracture incidences also increases following the increasing number of motor vehicleaccidents, especially motorcycle. Therefore, the need for implants in Indonesiaespecially the traumatic type is very real.
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This situation has become a trigger for many orthopaedic surgeons at Dr.Soetomo General Hospital, affiliated with the Faculty of Medicine, AirlanggaUniversity in Surabaya, to become the pioneer in producing local implants. In 1993,the first implant manufacturer company was established with the main productsfocused on plates and screws and arthoplasty implants (Fig. 9). The material usedfor producing the implants was mostly type 316L stainless steel sheets, rods andingots imported from the overseas. The manufacturing process involved machiningand casting processes. For fabricating bone plates, the stainless steel sheet was cutand drilled according to the predetermined size (patient specific) and number ofholes, and then finished by polishing. Since the implants are made locally and nearto the hospital, they offer competitive price and deliverability. Beside more rea-sonable price, the implants offer many advantages including adjustable size that fitsto Indonesian people posture, and can be custom-made for specific patient’s need
Fig. 9 Locally made orthopaedic implants: various plates, screws and arthroplasty implants(Courtesy Dr. Soetomo General Hospital, Surabaya)
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and disorder. This local implant industry has received a lot of appreciation frommany users in the country and the implants have been distributed not only in EastJava but started to reach every corner of Indonesia.
4.2 The Challenge and Collaboration
Nowadays there are several implant factories that produce local implants, but stillthey could not fulfill the high demand of implants in Indonesia. Moreover, thetechnology used by local manufacturers still has many limitations including lowproduction capacity and limited product variety (mainly for complex shapedimplants such as arthroplasty). The type of raw materials being used is still limitedto stainless steels as the price for other metals (e.g. Ti and Co-Cr alloys) are stillconsiderably too expensive.
Fig. 10 Investment casting process of bone plates: a implant model; b waxed model; c castproduct with casting system; d pre-finished implants (Courtesy of Dr. Soetomo General Hospital,Surabaya)
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The orthopaedists at Dr. Soetomo General Hospital have been collaborating withmetallurgical scientists and engineers to address the above challenges. They havebeen conducting R&D activities on orthopaedic implants manufacturing technologywith the main purpose to produce high quality implants in large quality at low orreasonable price. Since 2001, the Department of Orthopaedics and Traumatology,Faculty of Medicine, Airlangga University has been collaborating with the Centreof Material Technology, Indonesian Agency for the Assessment and Application ofTechnology (better known as BPPT) in making bone graft from synthetichydroxyapatite. Since 2005, this collaboration has been focusing on developinginvestment casting technology for orthopaedic implants (Fig. 10). This collabora-tion receives a full support from the Indonesia Government as it aligns with thenational programme on supporting local products and the new general healthinsurance programme which covers every citizen of Indonesia.
Acknowledgment The authors acknowledge the supports from Dr. Soetomo General Hospital,Surabaya and the Indonesian Ministry of Health (FM, LW), and the Axis of RegenerativeMedicine, CHU de Quebec Research Center at Saint-François d’Assise Hospital, Québec City(HH).
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Biomaterials in Dentistry
Margareta Rinastiti
Abstract Dental materials are used for the replacement of destroyed or loststructures and for the restoration of disturbed functions of the orofacial organ (hardtooth substance, teeth, and soft tissues of the mouth). Among the main challenges inrestorative dentistry in Indonesia are the caries, recurrent caries due to the leakageor restoration failure that may lead to infection of the pulp and periodontal tissue.Therefore, it is desirable to develop dental materials having ability to seal themarginal interface between material and tooth structure, bioactivity to promoteremineralization and good bonding with tooth structure and antimicrobial capa-bilities. This chapter describes dental materials in restorative dentistry, the mostcommon dental problems in Indonesia, and the development of local bioactivedental materials by utilizing the diversity of natural resources in Indonesia.
Keywords Biomaterials � caries � dental � restorative material � operative den-tistry � natural material
1 The Importance of Oral Health and Dental Problem
The mouth is the gateway to the body, performing dozens of functions that placehigh demands on its unique hard and soft tissues. Oral health is essential to generalhealth and quality of life. Good oral health enhances our ability in speaking,chewing, biting, tasting, swallowing and psychosocial wellbeing. The mostprominent features of the oral cavity are the teeth that are composed of threespecialized calcified tissues, enamel, dentin and cementum that are supported bybone and gingival tissue. The teeth has four major functions: mastication, aesthetic,phonetic and protection of supporting tissue. Normal tooth form and properalignment ensure efficiency in mastication. The teeth cut, tear and grind food in the
M. Rinastiti (&)Department of Conservative Dentistry, Faculty of Dentistry,Gadjah Mada University, Yogyakarta, Indonesiae-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_8
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mouth, enable digestive enzymes greater access to the food material and so assiststheir role in the digestive process. A harmonious form, contour, color, position ofthe teeth are important to a person’s physical appearance. Speech articulation isdependent on the form and alignment of both anterior and posterior teeth.Moreover, form and alignment of the teeth assist in sustaining the teeth in the dentalarches by assisting the developmental and protection of the gingival tissues andalveolar bone that supports them (Heymann et al. 2012). A defect of the tooth willdisturb teeth function and may lead to more serious problems.
There are four conditions that result in defective tooth structure: dental caries,tooth wear, trauma and developmental defects (Fig. 1) (Kidd et al. 2003). Amongthose conditions, dental caries is a major public health problem globally, affecting60–90 % of school aged children and the vast majority of adults (Petersen et al.2009). The development of dental caries is a dynamic process causing progressivedestruction of hard tooth substance (enamel, dentine and cementum) (Yip andSmales 2013). This occurs as an interaction between the biofilm and the toothsurface and subsurface. When the demineralization and remineralization equilib-rium is out of balance, it leads to mineral loss. Remineralization can arrest orreserve progression of disease that lead to change the quality of minerals (Pitts2004). A caries lesion can be progressive and if not treated may expand in size andprogress to the pulp leading to pulp inflammation thus pain and discomfort, and theend result will be loss of vitality and loss of the tooth.
Instead of caries, the loss of dental hard tissue occurs as a result of tooth wear.Tooth wear is a common clinical occurrence and may cause challenges in diagnosisand treatment. The lost of dental tissue may become excessive as a result of erosion,attrition, abrasion or abfraction (Fig. 2). Similar to the effects of dental caries, theseconditions may exhibit dental problems such as: exposure of dentin, notched cer-vical surfaces, sensitivity, pulpitis, loss of vitality and inability to make contactbetween worn incisal and occlusal surfaces in any excursion of the mandible(Heymann et al. 2012). In contrast to caries and tooth wear that arise in slow onset,
Fig. 1 Defective tooth structure: a enamel caries lesion in the buccal fissure of mandibular firstmolar; b dentin caries lesion in the proximal area of maxillary first premolar; c extensive dentincaries lesion with pulp polyp of the mandibular second molar (Courtesy of HA Pribadi)
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traumatic injuries are acquired suddenly and can produce local injuries like lacer-ations, alveolar fracture, root fracture, fracture of the crown and luxation of thetooth (Kidd et al. 2003). Under those circumstances, highly deleterious effects onthe function of teeth will occur. The main issues that arises from tooth wear are poorappearance, poor function, sensitivity, and ongoing concerns about continued wear(Ricketts and Bartlett 2011). Consequently, the defect of the tooth requiresnon-operative or operative intervention as preventive and curative treatment.
2 The Most Common Dental Problems in Indonesia
In 2013, the Indonesian Ministry of Health conducted the epidemiology research onhealth states of Indonesia population, including oral health states. The study cov-ered 33 provinces and 497 regions and generated the prevalence and incidence oforal health, including the assessment of dental caries experienced amongst thepopulation by using DMF-T index. DMF-T was introduced by Klein, Palmer andKnutson in 1938, modified by WHO (World Health Organization). The DMF Indexis applied to the permanent dentition and is expressed as the total number of teeth orsurfaces that are decayed (D), missing (M), or filled (F) in an individual. When theindex is applied to teeth specifically, it is called the DMF-T index, and scores perindividual can range from 0 to 28 or 32, depending on whether the third molars areincluded in the scoring. When the index is applied only to tooth surfaces (five perposterior tooth and four per anterior tooth), it is called the DMFS index, and scoresper individual can range from 0 to 128 or 148, depending on whether the thirdmolars are included in the scoring (Cappeli and Mobley 2007).
The DMF-T index in Indonesia is 4.6 composed of D-T = 1.6, M-T = 2.9,F-T = 0.08. Index 4.6 can be interpreted that in a population of 100 people, there are460 decayed, missing or restored teeth. This index is higher than goals for the year
Fig. 2 Lost of dental tissue: a traumatized maxillary first incisal that has become non-vital;b abfraction lesion involving first and second premolar (Courtesy of L Suprapto)
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2000, which indicated a rate of not more than 3 DMF-T. Based on the data pub-lished by the Indonesian Ministry of Health, in 2013, the DMF-T index of eachprovince in Indonesia can be seen in Tables 1 and 2 below (Department of Researchand Development 2013):
It can be concluded that the linear increases in caries with age in both childrenand adults indicate that caries affect individuals throughout their life. The
Table 1 DMT index of Indonesia provinces
Province D-T M-T F-T DF-T DMF-T
Aceh 1.4 2.6 0.08 0.02 4.0
North Sumatra 1.3 2.3 0.05 0.02 3.6
West Sumatra 1.7 3.1 0.06 0.03 4.7
Riau 1.6 2.3 0.12 0.03 4.0
Jambi 2.3 3.1 0.04 0.01 5.5
South Sumatra 1.9 3.3 0.09 0.03 5.3
Bengkulu 1.3 2.0 0.09 0.03 3.3
Lampung 2.1 2.3 0.07 0.02 4.5
Bangka Belitung 3.0 5.5 0.05 0.01 8.5
Riau Island 1.6 3.2 0.11 0.03 4.9
Jakarta 1.1 2.5 0.32 0.08 3.8
West Java 1.6 2.5 0.08 0.02 4.1
Central Java 1.4 2.9 0.05 0.01 4.3
Yogyakarta 1.3 4.5 0.13 0.02 5.9
Jawa Timur 1.6 3.8 0.08 0.03 5.5
Banten 1.6 2.0 0.09 0.02 3.7
Bali 1.1 3.0 0.12 0.02 4.1
West Nusa Tenggara 0.8 2.1 0.03 0.01 3.0
East Nusa Tenggara 1.5 1.7 0.04 0.01 3.2
West Kalimantan 3.2 2.9 0.10 0.03 6.2
Cental Kalimantan 2.2 2.8 0.13 0.04 5.0
South Kalimantan 2.2 5.0 0.11 0.02 7.2
East Kalimantan 1.9 2.8 0.09 0.02 4.7
North Sulawesi 1.9 3.4 0.06 0.03 5.4
Central Sulawesi 2.0 3.5 0.05 0.01 5.5
South Sulawesi 2.0 4.0 0.05 0.01 6.0
Southeast Sulawesi 1.4 2.8 0.08 0.04 4.3
Gorontalo 1.3 3.0 0.01 0.00 4.3
West Sulawesi 1.5 4.0 0.03 0.01 5.5
Maluku 1.5 2.9 0.07 0.03 4.5
North Maluku 0.9 2.1 0.02 0.01 3.0
West Papua 1.1 1.5 0.02 0.00 2.6
Papua 1.6 1.5 0.11 0.03 3.1
Indonesia 1.6 2.9 0.08 0.02 4.6
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proportion of edentulous adults aged 65 years or more is still high, while the decayteeth of population with ages 33–64 years old revealed the highest index.
Since January 1, 2014, Indonesia has been started to roll out the National HealthInsurance System. Indonesian public awareness of oral health is low, and they tendto seek treatment when there is a specific problem with their tooth. Therefore, thecost of dental treatment is high due to the complexity and advanced nature of theoral health problems. The effective demand of oral health care in Indonesia is low(7 % of the population). Due to the delay treatment, the majority of dental healthcases ended with tooth loss (Dewanto and Lestari 2014). The National HealthInsurance System is expected to raise the dental visits and decrease the number oforal health problems in Indonesia. Moreover, it also conforming to the global goalsfor oral health 2020.
According to the Global goals for oral health 2020, caries needs to be manageddepending on the stage of progress, to prevent new lesions from forming and todetect lesions sufficiently early in the process. By the year 2020 the following willhave been achieved over dental caries baseline: (1) to increase the proportion ofcaries free 6-year-olds by X %; (2) to reduce the DMFT particularly the D com-ponent at age 12 years by X %, with special attention to high-risk groups withinpopulations, utilising both distributions and means; and (3) to reduce the number ofteeth extracted due to dental caries at ages 18, 35–44 and 65–74 years by X %(Hobdell et al. 2003). Based on those goals, the use of appropriate biomaterialshould be considered.
3 Biomaterials in Restorative Dentistry
Dental materials are used for the replacement of destroyed or lost structures, (hardtooth substance, teeth, soft tissues of the mouth) and for the restoration of disturbedfunctions (masticatory, phonetic, esthetic, physiognomic) of the orofacial organ(Tesk et al. 2000). Recently, the market for dentistry materials has been increasingbecause restorative treatment remains the primary work of dentists. Restorativebiomaterials are designed to recover the shape and the function of the teeth, whilepreventive materials are used to prevent oral health problems.
Table 2 Indonesianage-categorized DMF index
Age (year) D-T M-T F-T DF-T DMF-T
12 1.02 0.34 0.04 0.02 1.4
15 1.07 0.34 0.05 0.01 1.5
18 1.14 0.45 0.07 0.03 1.6
35–44 2.00 3.35 0.11 0.03 5.4
45–54 2.13 5.65 0.14 0.04 7.9
55–64 2.15 10.13 0.09 0.03 12.3
65+ 1.84 17.05 0.06 0.02 18.9
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3.1 Preventive Materials
The purpose of modern dentistry is the early prevention of tooth decay rather thaninvasive restoration therapy. The materials that are categorized as preventivematerials are tooth paste, mouth washes, topical application and sealants. There aretwo important principles that should be followed in the treatment of early decay:(1) to reduce the etymological factor, i.e. dental plaque or bacterial biofilm; and(2) to increase the amount of remineralizing substances (Gonzalez-Cabezas 2010).
ToothpasteToothpaste is a colloidal suspension of a mixture of ingredients that must becarefully balanced in order to provide an efficacious, safe, and consumer friendlyproduct. The removal of oral biofilms from a tooth’s hard surfaces is crucial tocaries control and is most effectively accomplished by mechanical brushing withtoothpaste, especially in interproximal regions and posterior teeth along with theuse of adjunctive chemical agents (Sakguchi and Powers 2012). Generally tooth-pastes are composed of colloidal binding agent; humectants; preservatives;flavoring agents; abrasives to remove plaque, stains and calculus; detergents toreduce surface tension and enhance removal of debris and therapeutic agents suchas stannous fluoride. It is widely understood that fluoride is the most importantcomponent of toothpaste. There is strong evidence that daily use of fluoridetoothpaste has a significant caries-reducing effect in young permanent teeth, inhibitthe development of caries 19–27 % and providing remineralization of enamel(Marinho et al, 2009; Twetman et al. 2003). To promote remineralization of pre-viously demineralized enamel relies on calcium and phosphate ions from saliva, 10calcium ions and 6 phosphate ions are required for every 2 fluoride ions to form oneunit cell of fluorapatite ([Ca10(PO4)6F2]) (Reynolds et al. 2008). Therefore, severalnew remineralizing agents have been introduced to supplement and enhance theability of fluoride to restore tooth minerals.
Calcium phosphate formulations have been developed for addition to toothpaste,varnishes, and gum. A milk product, calcium phosphate remineralization technol-ogy based on casein phosphopeptide–amorphous calcium phosphate (CPP-ACP)was effective in remineralizing enamel subsurface lesions (Sakguchi and Powers2012). Casein phosphopeptide forms nanoclusters with amorphous calcium phos-phate providing a pool of calcium and phosphate which can stabilize calciumphosphate on tooth surface, thereby maintaining high concentration gradients ofcalcium and phosphate ions, and promoting remineralization. Additionally, CPPcan also decrease the count of S. Mutans as it has got the ability to integrate in thepellicle. Even though CPP-APP is promising as a preventive material, its use inproducts like fluoride varnishes remains problematic. The total time taken by CPP–ACP for remineralization is still not clearly established and needs further investi-gation (Farooq et al. 2013).
Several commercial toothpastes are branded as treatment for sensitive teeth.A study compared calcium sodium phosphosilicate-containing toothpaste with apotassium nitrate, sodium fluoride, and silica dioxide containing toothpaste, and a
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potassium citrate, sodium monofluorophosphate and silica dioxide containingtoothpaste, showed that those three desensitising toothpastes may be useful prod-ucts for dentine hypersensitivity therapy. However, after immersion in the citricacid solution and artificial saliva the efficacy of tubular blocking was decreased(Wang et al. 2010).
Mouth RinsesMouth rinses are used for a variety of reasons: to help prevent and control toothdecay, to freshen breath, to reduce plaque, to prevent or treat gingivitis, to reducethe speed that calculus forms on the teeth, or to produce a combination of theseeffects. In conjunction with brushing and flossing, the general population often usesthese products as part of a daily oral care regimen (Silverman and Wilder 2006).Typically, mouth rinses contains of active agent as an anti-caries or antimicrobialsuch as bis-biguanides, phenols, quaternary ammonium compounds, oxygenatingcompounds, plant extracts, fluorides, antibiotics and antimicrobial combinations(Walker 1988). The solution generally consists of water, alcohol and preservative;and surfactant, for instance Na laurylsulphate with the ph range from 3.4 to 6.6.
Mouth rinses reduce plaque by between 13–60 % (Barnett 2006), and therebymay reduce the cariogenic bacteria. Since 1960s, mouth rinses have been used as aprophylactic method to prevent the dental caries in children and adolescents and hasshown average efficacy of caries reduction between 20–50 %. Sodium fluoride,stannous fluoride and amine fluoride are commonly used as agents in fluoridemouth rinses to help control dental caries incidence efficiently (Reich et al. 2002).The alcohol-free chlorhexidine used as mouth rinse have been shown to result in asignificant reduction in S. mutans and lactobacilli (Albertsson et al. 2012). Due toits bacteriocidal properties, iodine has been utilized as an antiseptic mouth rinse.Essential oil and herbal mouth rinses have also been introduced to the market. Thecombination of fluoride and essential oils in a mouth rinse may provide anti-cariesefficacy, in addition to essential oils’ established anti-gingivitis efficacy (Zero et al.2004). Although less potent than chlorhexidine, the herbal mouth rinse is a moreeffective antimicrobial agent than the essential oil mouth rinse in inhibiting thegrowth of oral bacteria in vitro. Furthermore, it may serve as a natural antimicrobialmouthrinse alternative for patients who wish to avoid alcohol, artificial preserva-tives, and artificial flavors and colors (Haffajee et al. 2008).
Topical ApplicationTopical application is a preventive treatment by apply varnish or gel containingantimicrobial agent on the surface of tooth to prevent caries. In 2006, the Councilon Scientific Affairs (CSA) of the American Dental Association (ADA) publishedrecommendations for the use of professionally-applied topical fluorides for cariesprevention (American Dental Association Council on Scientific Affairs 2006).Fluoride is the primary agent available for caries prevention. The local availabilityof fluoride to the tooth surface has been shown to prevent caries by primarily threemechanisms: (1) inhibiting demineralization of tooth enamel; (2) enhancing rem-ineralization of tooth enamel prior to lesion progression; and (3) inhibiting theenzyme activity of cariogenic bacteria (Featherstone 2000; Marquis 1995). Fluoride
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varnish and gel can be an effective agent in preventing new caries and in arrestingdental caries in the primary teeth of the children (Weyant et al. 2013).
Topical application containing Chlorhexidine (CHX), the component of bis-biguanides is a promising new treatment for the prevention of dental caries. Overall,the caries inhibiting effect of CHX of around 46 % (van Rijkom et al. 1996). CHXvarnish has a moderate caries-inhibiting effect when applied every 3–4 months.However, after 2 years of application, it seems to diminish (Zhang et al. 2006).Another agent that is used for topical application is xylitol, a five carbon sugaralcohol that looks and tastes like sucrose, thus it is a good sugar substitute.Additionally its beneficial effect is that it is not metabolized by the cariogenicbacteri. It has caries- or MS-reducing effects of in young children and adults(Mäkinen et al. 2013).
Fissure SealantCaries potential is directly related to shape and depth of the pit and fissures.A fissure sealant is a material that is placed in the pits and fissures of teeth in orderto prevent or arrest the development of dental caries. The sealant forms a smooth,protective barrier by covering all the little grooves and dips (pits and fissures) in thesurface of the tooth, forming a micromechanically bonded, protective layer cuttingthe access of caries-producing bacteria from their source of nutrients (Simonsen andNeal 2011). The clinical success of sealings depends on the ability of the material tosolidly adhere to the enamel surface and securely isolate pits and fissures from theoral environment. The application of sealants is often as soon as the emergence ofadult teeth, usually between 6 and 7 years of age. The rest are usually sealed as soonas they appear, which can be any time between 11 and 14. Instead of being used forprimary caries prevention, current evidence indicates that sealants also are aneffective secondary preventive approach when placed on early non-cavitated cari-ous lesions. In clinical situations in which a sealant has ben lost or partiallyretained, it should be reapplied to ensure effectiveness (Beauchamp et al. 2008). It isgenerally accepted that the effectiveness of sealants for caries prevention dependson long-term retention which is related to the biodegradation of materials due to thecaries’ biofilm, acid challenges, salivary enzymes, food and beverage (Beauchampet al. 2008) and biological outcomes such as the absence of caries in pits andfissures after sealant application (Yengopal and Mickenautsch 2009). Therefore anappropriate material should be chosen. The materials that are used to seal the pit andfissure of the tooth, pit and fissure sealant are glass ionomer cement (GIC), resinmodification of glass ionomer and resin composite.
The use of GIC-based restorative materials as fissure sealant is advantageousbecause they bond to dentin and enamel, release fluoride across an extended periodand are biocompatible. They also are technically less sensitive than conventionalresin-based materials. GICs adhere to dentin and enamel via ionic and polarbonding. This action creates an intimate contact that facilitates fluoride ionexchange of the hydroxyl ions in the adjacent enamel apatite (Francisconi et al.2009). However, the clinical effect of fluoride release from glass ionomer cement isnot well-established (Beauchamp et al. 2008).
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According to the results of a systematic review of the literature, sealing withresin-based sealants is a recommended procedure to prevent caries of the occlusalsurfaces of permanent molars (Alonso et al. 2005). Resin modification of GI cement(RMGI) was designed to produce favorable physical properties similar to compositeresins and retaining the features of GIC with a better physical properties, moreaesthetic and less water sensitive then conventional GIC (Sakguchi and Powers2012). The addition of resin likewise should strengthen the relatively poor fractureand wear resistance of RMGI thus increasing the retention rate beyond that of GICsealants (Winkler et al. 1996).
Another type of sealant material used today are resin-based composite adhesiveswith a main component of Bis-GMA, in combination with 37 % phosphoric acid foretching. The composites are lightly filled in order to keep the viscosity low, thusallowing for a deep penetration of the material into pits and fissures (Donly 2002).The action of resin-based materials as fissure sealant relies on the establishment ofan effective mechanical obstacle to the leakage of nutrients to cariogenicmicroorganisms in the deeper parts of fissures (Simonsen 1991). Recently, use offlowable resin composite as fissure sealant has increased due to its beneficialproperties including low viscosity, low modulus of elasticity and ease of handling.Preventive pit and fissure sealing does not seem to require materials with highmechanical properties. A flowable resin composite with lower viscosity has a betterability to flow by itself in small cavities and fissures than composites with a higherviscosity, and hence can facilitate better application of the sealant material(Beun et al. 2012). Flowable resin composite material, in conjunction with atotal-etch, single-bottle adhesive, showed slightly better retention rates than con-ventional resin-based fissure sealant over a 24-month period (Erdemir et al. 2014).
Kantovitz evaluated the degradation of three sealant materials: resin, RMGICand GIC under acid in vitro (Kantovitz et al. 2009). The results showed that acidicsolution lead to fluoride release with both of the ionomeric materials. This phe-nomenon is caused by an accentuated erosion of the polysalt matrix of the glassionomer and because of the dissolution of this material, which increases with lowpH. Typically, the high release of fluoride is followed by the degradation ofmaterials, as a result reduces the retention of ionomeric sealant. It was concludedthat the resin fissure sealant is less susceptible to degradation than RMGIC and GI.Interestingly, when GIC sealant is lost partially or totally, the opening of thefissures remains sealed. It is highly effective because of the isolation of bacteriafrom nutrients in the substrate below early carious lesions that have been sealedand/or the release of fluoride into the dentin (Oong et al. 2008). In contrast,resin-based sealants have been shown to lose almost all of their protective effectonce their retention is lost (Yengopal and Mickenautsch 2009). A 2-year report onthe clinical performance of a RMGI sealant compared to a light-initiatedresin-based sealant showed 0 % complete retention and 38 % complete loss ofthe RMGI sealant, and 32 % complete retention and 10 % complete loss of theresin-based sealant (Smales and Wong 1999). Another researcher reported thatretention rates of GIC sealant ranges from 83 % at 6 months to 70 % at 3 years, withoverall retention at 44.6 % and partial retention was 83.1 % (Komatsu et al. 1994).
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3.2 Operative Dentistry Materials
The operative treatment is chosen when caries or non caries lesions have progressedinto a clinical breakdown of the enamel surface with dentin exposure.
Glass Ionomer CementGlass ionomer cement (GIC) is an appropriate material for use in minimally invasivedentistry (MID). The objective of the dentist in operative dentistry based upon theMID concept is to preserve a healthy set of natural teeth for each patient while aimingto optimally conserve the human body and its function. Glass ionomer cementmaterials, presented in a variety of formulations designed for particular clinicalindications, present unique opportunities to accomplish a variety of clinical objec-tives and consist of three types. Type I is intended as luting cement, type II asrestorative materials, and type III as liners and basis. As lining cement, GICs that canbe used are biological seal and cariostatic. Type II GICs are indicated for area withoutstress bearing, class III and V restorations in adult, class I and II restoration in primarydentition, temporary restorations, restoration of erosive/abrasive lesions withoutcavity preparation, sealing and filling of occlusal pit and fissures, repair of defectivemargins in restorations, minimal cavity preparations in a proximal lesions throughbuccal and occlusal approach (tunnel preparations), core built up, and provisionalrestorations where future veneer crowns are contemplated. The using of GIC forluting purpose because of their fluoride leach which useful in patients with high cariesincidence and its translucency (Kidd et al. 2003; Sakguchi and Powers 2012).
Glass ionomers are water-based cements that are formed by an acid-base reac-tion between a calcium-based fluoroaluminosilicate glass powder and a polyalk-enoic acid liquid. The acid attacks the glass particles, causing a release of calcium,aluminum and fluoride ions. The fluoride ions become incorporated into the matrixand can readily diffuse into the surrounding tooth structure and saliva (Tyas et al.2000). Additionally, it can take up fluoride from the environment, which is pro-vided by exposure to fluoride treatments and toothpaste (Rothwell et al. 1998).
The acid-base reaction involved in the setting mechanism for these materials washydrolytically unstable in its early stages. This meant that they were very sensitiveto water loss and water uptake for at least 1 h after mixing and possible for thecement to dehydrate if left exposed to air. It was subsequently shown that the periodof sensitivity for the restorative esthetic materials is even longer, and it is conve-nient to maintain them in isolation for up to 24 h (Wilder et al. 2000). In spite ofsome shortcomings, the advantages of GICs as restoration material showed verylow polymerization shrinkage and are thermally compatible with tooth structure.These materials can bond to dentin surfaces without removing the smear layer andtheir biological compatibility is well proven (Francisconi et al. 2009). In addition,using the most current formulation of GIC can be placed and finished in a singlevisit and have achieved an aesthetic translucency that is highly desirable.
As a luting cement, GICs fulfill clinical requirements in that: (1) they adherechemically to the tooth structure, providing a sealing of the dentinal surface,(2) they are hydrophilic and, therefore, provide an appropriate compatibility with
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the challenging environment of the mouth, and (3) they are easily cleaned from thesurrounding area after cementation (Francisconi et al. 2009; Kilpatrick 1996). Therationale for using GICs as liners is that they can be easily manipulated into cavitypreparations and provide a release of fluoride thereby reducing the risk of recurrentcaries.
Resin CompositeResin-based composites are increasingly used in dentistry in order to restoredamaged parts of dental tissues or to reconstruct missing teeth. Composites havegood aesthetic properties and by employing adhesive technologies, they allow forminimally invasive interventions which may not always require tooth preparation(Bouschlicher et al. 1997; Gordan et al. 2003). Composites are materials consistingof at least two different classes of materials i.e. metals, ceramics, and polymers withsignificantly different physical and chemical properties. The different materialsremain separated upon mixing. Composite resins consist of an organic resin matrix,inorganic fillers, a coupling agent and additional component, like an initiator, sta-bilizer and pigments to produce the different shades (Ferracane 1995).
The resin component of resin composite is monomer that builds repetitive unitsthat are bound together to form a polymeric matrix. Polymerization occurs throughthe carbon-carbon double bonds of two methacrylate groups (Peutzfeldt 1997). The2,2-bis[4-(2-hydroxy-3-methacryloyloxypropoxy) phenyl] propane: BisGMA ismost commonly used as the organic phase of dental restorative materials because ofits high level of strength and hardness (Amirouche-Korichi et al. 2009). However, ithas drawback properties: very high viscosity, owing to hydrogen bondings betweenthe hydroxyl groups, which limited the incorporation of inorganic fillers and hencea low final DC (Atai et al. 2004). Therefore, a reactive diluent, such as triethyleneglycol dimethacrylate (TEGDMA), ethoxylated bisphenolglycidil methacrylate(Bis-EMA), triethylene glycol methacrylate (TEGMA), and diurethanedimethacrylate (DUDMA) is added to improve the viscosity, reactivity in the finalconversion of the matrix phase (Bowen and Marjenhoff 1992; Eckerman et al.2004; Ferracane 1994).
Filler particles influence the physical and mechanical properties of the com-posite. They reduce the coefficient of thermal expansion, cure shrinkage, provideradio-opacity, improve handling and increase aesthetic results (Labella et al. 1999).The main fillers are silicon dioxide, boron silicate and lithium aluminum silicates(Xu 1999). In some composites, heavy metal particles that are radioopaque such asbarium, strontium, zinc, aluminum or zirconium are added (Hosoda et al. 1990).According to the particle size, a composite can be categorized as: traditionalcomposite (10–20 µm), microfilled (0.01–0.05 µm), hybrid (large particle: 10–20 µm; colloidal silica: 0.01–0.05 µm), microhybrid (0.1–6.0 µm), nanohybrid(microfiller: 0.1–2.5 µm; nanofiller: 20–50 nm) and nanofilled (5–100 nm)(Sakguchi and Powers 2012).
A good adhesion between matrix and filler prevents erosion of the filler surfaceand facilitates stress transfer between those two components, thus increasing themechanical properties of composites (Lin et al. 2000). The filler particles are
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silanated for suitable adhesion to the organic matrix. The organofunctional silanemost commonly used in dental-composites is γ-methacryloxypropyltrimethoxysi-lane (γ-MPS) (Ferracane 1995). Dental composites also contain chemical sub-stances which initiate and promote the polymerization reaction such as benzoyl orlauryl peroxide, various tertiary amines and camphorquinone (Ruyter 1988). Thenewer initiator is called ivocerin. It is capable of absorbing light at a higherwavelength range than acyl phosphine oxide, and can therefore be activated by allcommercially available (halogen, LED) polymerization lights (Todd and Wanner2014). To prevent polymerization during the storage of composite and avoid,butylated hydroxytoluene and hydroquione are usually used in dental composites(Klapdohr and Mozner 2005).
As operative dentistry materials, resin composites are used for a restorativematerials, cavity liners, pit and fissure sealants, cores and build ups, inlays, onlays,crowns, provisional restorations, cements for single or multiple tooth prostheses orcrown, and root canal posts (Ferracane 2011). The development of resin compositeis very progressive. Recently, the size of filler is reduced to get a more easily andeffectively polished material, instead of to improve wear resistance. Hitherto thedevelopment of matrix is not as fast as the development of filler particle, it is knownthat some new resin matrices or combination of monomer have been investigated toreduce polymerization shrinkage and degradation. The latest development is resincomposite bulk fill that enable up to 4- or 5-mm thick increments to be cured in onestep (Ilie et al. 2013), allowing for quicker procedures without impairing propertiessuch as depth of cure, conversion, polymerization shrinkage, and shrinkage stress(Ilie et al. 2013; Moorthy et al. 2012; Ilie and Durner 2013). Nowadays a newsonic-activated bulk-fill system was introduced to the market for posterior bulkrestorations. According to the manufacturer’s data, the Sonicfill system is a unique,sonic-activated bulk-fill system comprised of a specially designed hand piece and anew composite material in unidose tips. The composite is a combination of flowableand universal composites and incorporates a highly-filled proprietary resin withspecial modifiers that react to sonic energy. As sonic energy is applied to the handpiece with five different levels of flowability, the modifier causes the viscosity todrop (up to 87 %), increasing the flowability of the composite. When the sonicenergy is stopped, the composite returns to a more viscous, non-slumping state forcarving and contouring (Jackson 2011).
Compomers and Resin Modified Glass Ionomer CementsCompomer is said to provide the combined benefits of composites (the “comp” intheir name) and glass ionomers (“omer”). It is a polyacid-modified composite resinwhich does not have water in its composition and the majority of components arethe same as for composite resins. Compomers consist of conventional compositeresin monomers (BisGMA or UDMA), together with novel monomers containing asmall number of carboxylic acid functional groups. The filler is similar to theleachable filler on GIC which consists of conventional unreactive silica particles,together with a small amount of acid leachable glass, strontium aluminosilicate orbarium aluminosilicate based, capable of forming glass–ionomer type structures
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within the material (Eliades et al. 1998). The polymerization is activated by lightand followed by an acid–base reaction. The water activates the acid functionalgroups and enables them to react with the strontium or barium glass and the excessbase might act to neutralize lactic acid in clinical active caries. The disadvantage ofcompomer is the sorption to water that will decrease its mechanical properties(Meyer et al. 1998; Nicholson and Alsarheed 1998).
Clinically, compomers are indicated to class II cavities, small clas I and clas IIcabities, root care, high risk patients, deciduous teeth and cervical defects. A highbearing situations such as class II and clas IV is contraindicated. To overcome theproblems of moisture sensitivity and low mechanical strengths of GICs, somehybrid versions of GIC, called resin modified glass ionomer cements (RMGIC)were introduced. These materials maintain the clinical advantages of GIC andinclude a small quantity of resin components such as HEMA or BIS-GMA which ispolymerized by light activation. RMGIC is focused on the matrix by graftingunsaturated carbon-carbon bonds onto the polyalkenoate backbone and/or byincorporating (di)methacrylate monomer(s) into the composition (Randall andWilson 1999; Wilson 1989).
The presence of unsaturated carbon-carbon bonds enables the covalentcross-linking of the matrix via free radical polymerization reactions which signif-icantly improves the mechanical properties RMGIC. The advantage of RMGIC isthe level of fluoride release that is similar to GIC. In addition, the mechanicalproperties of RMGIC are weaker than resin composite but stronger than conven-tional glass ionomer cement (Uno et al. 1996).
MetalsMetals have been used as dental materials for over a century. Generally, most metalsare strong enough to withstand maximum possible oral forces (Upadhyay et al. 2006).Amalgam has been used as a direct filling material for more than a century. It iscreated by mixing elemental mercury (43–54 %) and an alloy powder (46–57 %)composed of mercury with silver and other metals such as tin and copper to give a setmaterial. Amalgam does not adhere to tooth structure and therefore needs to beretained within the cavity by mechanical retention (Kidd et al. 2003). Amalgam isvery strong and lasts a long time, therefore it is indicated to restore those that aresubject to a lot of wear and tear such as molars. Amalgam is relatively inexpensive,generally completed in one visit and resistance to further decay. However, it has somedisadvantages, such as requiring removal of some healthy teeth, its unaesthetic color,that larger amalgam fillings the remaining tooth may weaken and fracture, enhance atemporary sensitivity to hot and cold and contact with other metals may causeelectrical flow (Kidd et al. 2003; Sakguchi and Powers 2012). In addition, a diversityof opinion exists regarding the safety of dental amalgams due to toxicity of mercury.
The mercury could be released when filling is placed and during the functionallife of amalgam restoration (Kidd et al. 2003). However, based on analysis, it hasbeen concluded that the evidence supporting the safety of amalgam restorations iscompelling (Dodes 2001). The American Dental Association (ADA) and Food and
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Drink Administration (FDA) affirmed that amalgam is a safe and durable restorativematerial (Donovan and Heymann 2010). Therefore, it is believed that the use ofamalgam should continue to be taught in dental school. Amalgam restoration is alsopracticed in Indonesia. Another issue with amalgam is safety of the natural envi-ronment. When mercury waste is incinerated, the volatilized mercury precipitates tothe environment and will enter the soil, surface waters, and food chain, thus anappropriate management of amalgam waste have to be taken into consideration.
The dental alloys include noble alloys such as gold and palladium based alloys,Au and Ca alloy combinations (for direct filling and wrought alloys), platinum andplatinum alloys and base metal alloys such as cobalt–chromium casting alloys (forpartial dentures), chromium-containing casting alloys (for crowns and bridges), andtitanium alloys (for implants, partial dentures, crowns, and bridges) (Considine2005; Morris et al. 1992a). Dental cast alloy has good mechanical properties in tinsection to replace lost tissue function. There are two categories of dental alloy:noble alloys (gold and palladium based) and base metal alloys (nickel, iron andcobalt based) (Morris et al. 1992b). These alloys are used for crown, metal ceramiccrown, removable and fixed dentures, inlay and onlay.
CeramicsPorcelain and ceramic materials have been used for fabricating esthetic dentalrestorations since the early 1800s. Glass-ceramics are a popular choice due to theirexcellent aesthetics and ability to bond to tooth structure allowing for a moreconservative approach. Common uses of ceramics are as full coverage crown, inlaysand onlays, bridge, veneering agents, castable ceramic and porcelain-fused-to-metal(PFM) restorations (Leinfelder 2000). All-ceramic restorations are contraindicated forthe region where there is inadequate room for the ceramic to achieve its peak physicalproperties or where tooth structure is inadequate to prepare the tooth (Lowe 2012).
Based on the processing technique, ceramic restoration materials can be clas-sified as: (1) Powder/liquid, glass-based systems, (2) machinable or pressableblocks of glass-based systems and (3) Computer-assisted design/computer-assistedmanufacture (CAD/CAM) or slurry, die-processed, mostly crystalline (alumina orzirconia) systems (Kelly 2004). Based on the main composition, ceramic can becategorized into: predominantly glassy materials, particle filled glasses and poly-cristalline (Kelly 2008).
Predominantly glass ceramics are the best in mimicking enamel and dentin.Optical effects are controlled by manufacturers by adding small amount of fillerparticles. Glasses are three dimensional networks of atoms having no regular pat-tern to the spacing (distance and angle) between nearest or next nearest neighbors,thus their structure is ‘amorphous’ or without form. Glasses in dental ceramicsderive principally from a group of mined minerals called feldspar and are based onsilica (silicon oxide) and alumina (aluminum oxide), hence feldspathic porcelainsbelong to a family called aluminosilicate glasses (Kelly 2004). To improvemechanical properties such as strength, thermal expansion and contraction behav-ior, filler particles are inserted to the base glass composition. Particle filled glasses
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are a product of infiltrating molten glass to partially sintered metal oxides such asalumina, magnesium alumina, and partially stabilized zirconia. They are dividedinto two main groups: leucite-reinforced glass ceramic (LRGCs) and the lithiumdisilicate glass ceramics (LDGCs). LRGCs are recommended for anterior restora-tion, however, due to its high translucency, for the tooth with metal core, the finalshades of the crown are not satisfactory, because this ceramic is unable to hide adark discolored core after endodontic treatment (Kelly 2004; Lowe 2012).Polycrystalline ceramics contain no glass and generally are much tougher andstronger than glass-based ceramics. These ceramics are solid-sintered, monophaseceramics are materials that are formed by directly sintering crystals together withoutany intervening matrix to from a dense, air-free, glass-free, polycrystalline structure(Kelly 2008; Shenoy and Shenoy 2010).
Ceramics are brittle materials and may therefore undergo fracture during func-tion or affects wear opposing dentition and restoration. There are many attempts totoughen the brittle ceramics. Fabrication of interpenetrating phase ceramic com-posites (IPCs) having three-dimensional interconnected microstructure can enhancefracture resistance of the ceramics (He et al. 2011; Yang et al. 2003). An in vitrostudy reported that the polymer-infiltrated ceramic had higher fracture toughnessthan the pre-sintered ceramics preforms. However, the hardness values were lowerthan those in conventional porcelain. Combination of positive characteristics ofceramic and composite resulting in a great strength, high reliability, precise andaccurate restoration (He and Swain 2011).
4 Recent Development on Dental Biomaterialsin Indonesia
Dental practice today utilizes a large number of biomaterials, becoming big busi-ness for the dental industry in manufacturing and marketing materials for use bydentists. Recently, the communication and collaboration between industry,researchers and dental practitioners has been enhanced. The correlation betweenlaboratory and clinical data should be evaluated to increase the quality of bioma-terials. In addition, the dental material research should emphasize the methodologyof bringing problems from the clinic to laboratory and vice versa. Based on theindex of DMF-T in Indonesia, it is clear that demand for restorative materials as thefoundation for replacement tooth structure is high. Moreover, to attain the WorldHealth Organization’s Global goals for oral health 2020, the application of pre-ventive dental material also crucial. Based on the data from Prof. Dr. Soedomo Oraland Dental Hospital, Faculty of Dentistry, Universitas Gadjah Mada (UGM),Yogyakarta, more than 95 % of dental materials used are imported products.Indonesia has an enormous diversity in its natural resources. Therefore, as theleading university on dentistry in Indonesia, many researchers in UGM haveworked on developing locally-sourced dental materials.
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Preventive materials including tooth paste and mouth rinses play an importantrole in the in the prevention of caries. Handajani and colleagues developed toothpaste and mouth rinses containing tea leaves extract (Camelia sinensis). Polyphenols(catecihns) in tea leaves are known to have antimicrobial effects against somebacteria. Epigallocatechin gallate (EGCG) is known as the most polyphenolic of teavarieties. Two types of dentifrice containing of 2 % tea leaf ethanolic extract and0.15 EGCG decreased the level of sIgA in gingivitis patients (Handajani 2006) anddecreased the dental plaque index (Handajani 2009). In addition, the increasing oftea extract in dentrifice heightened the antimicrobial effect against A.Actinomysetemcomitants (Handajani 2012). As a mouth rinse, EGCG showed asignificant decrease in the gingivitis index (Nirmaladewi et al. 2007).
Zeolite, a large group of natural and synthetic hydrated aluminium silicates can befound in 46 locations in Indonesia. The zeolite from the area of Gunung Kidul andKulonprogo was investigated by Irnawati and colleagues as a potential antibacterialand antifungal agent due to its copper content (Cu) (Irnawati et al. 2013). The initial studyshowed that at a range of 0.2–0.25 M concentration Cu concentration in the Cu-naturalzolite influenced the antifungal activity towards C. Albicans (Irnawati et al. 2010).Further research is being undertaken to create a zeolite dental cleanser.
Hydroxyapatite (HAp) has a structure similar to human bone hard tissue and canbe developed for many purposes in medical application. Indonesia has a lot ofnatural resources that can be prepared as synthesis HAp. One of them is calciteminerals extracted from Indonesian mines that is developed by Tontowi and col-leagues (Pujiyanto et al. 2006). Mulyawati and colleagues developed this materialas root canal sealer. The ideal root canal treatment should be able to close hardtissue from the periapical tissues and prevent chronic irritation and foreign bodyreactions to material components. Sealers play an important role in sealing the rootcanal system from foreign microorganisms and filling inaccessible areas of preparedcanals. The filler addition to resin based sealers will enhance the physical propertiesof the polymer. Based on its properties, HAp can be proposed as filler for dentalmaterials. The results showed that epoxy-based-resin sealer with the addition of30 % calcite synthesized HAp satisfy the physical properties of sealer in regards toits contact angle and film thickness. Furthermore, the microhardness of theepoxy-resin based sealer increased (Mulyawati et al. 2015).
Herliansyah and colleagues developed material stake with the concept of func-tionally graded material (FGM) from Ti/40HAp material that is composed of fivelayers with concentrations of HAp from 0–40 % wt through the process of uni-axialpressing followed by sintering at 1200 and 1400 °C in argon gas. This material wasintended as endodontic post after-endodontic treatment. Endodontic posts that arecommercially available have homogenous composition and strength. The rotationalmoment that is transmitted through homogenous endodontic post to dentin mayresult in the fracture of roots. The FGM layer is expected to solve the problem byadjusting the mechanical properties of each post to the nature of the teeth. It wasconcluded that Ti/40HAp200 and Ti/40HAp200 composite materials can be pro-duced by decreasing its hardness as the rising concentrations of HAp in each section(Herliansyah et al. 2013).
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As described above, the current choice of caries treatment is restore the tooth byusing restorative materials. However, the advent of tissue engineering is allowingdentistry to move forward in the use of regeneration as an underlying principle forthe treatment of dental disease. The regenerative dentistry is possible for makingenamel, dentin, dental pulp and the entire tooth (Nör 2006). In this sense, thedevelopment of materials that may heal the injured pulp offers a promising field ofstudy. Ardhani and colleagues investigated an application of combined of gelatinhydrogel film and Platelet Rich Plasma (PRP) to induce functional recovery of thesciatic nerve crushed by injury in the Wistar rat model. It was found that theapplication of gelatin hydrogel film with controlled release manner combined withPRP results faster axonal regeneration (Ardhani et al. 2015). Further research isneeded to confirm the effectiveness of the strategy for pulp nerve regeneration.
Another interesting field of research is the development of the material tominimize the effect of radiography exposure. Radiographic examinations are animportant tool that help dentists to diagnose, plan treatments and monitor bothtreatments and lesion development. According to the UNSCEAR report and IAEARS-G-1.5, dental examinations are the most frequent type of radiological procedure,and account for 21 % of the total worldwide. The estimated annual number ofdental examinations is about 520 million, with a frequency ranging from less thanone to more than 800 per 1000 population per year (Shantiningsih 2015).
Individual doses are small but collective doses cannot be ignored due to the highvolume of procedures. One of the effects of panoramic radiography exposure ismicronucleus apparently in oral mucosa which is seen as a marker of early stagecarcinogenesis mechanism. A betacarotene patch has been developed byShantiningsih and colleagues as radioprotector to prevent the effect of radiationexposure. The ex vivo study resulted that gingival mucoadhesive patch containingbetacarotene had the capability of penetrating through mucous membrane of rabbitplate. This patch is supposed to function as radioprotection agent of panoramicradiography exposure and further investigation has been done by the research group(Shantiningsih 2015).
5 Perspective
Biomaterials are required in most of dental treatment and its development in dentalrestorations represents the main challenge of future research activities. One of themain problem in restorative dentistry is recurrent caries due to the leakage ordamage of restoration. Therefore, a material which is able to seal the marginalinterface between material and tooth structure, to prevent the bacterial invasion todentinal tubulus and the pulp is potential to be developed. Bioactive materials can bedefined as materials that elicit a specific biological response at the interface betweentissues and the material, which results in the formation of a bond (Watson et al.2014). Bioactive material that can promote remineralization without loss of themechanical characteristics, has a good bonding with tooth structure and antimicrobial
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properties is potentially developed as base material. This base material may promotepulpal healing, furthermore it is expected to protect pulp from bacterial invasionwhen restoration leakage is arised. The diversity of natural resources in Indonesia ispotentially evolved as bioactive material.
Acknowledgment The author thanks Dr. Hermawan, Laval University, for the discussion duringthe preparation of this chapter and revision of the final manuscript.
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Tissue Bank and Tissue Engineering
Ferdiansyah Mahyudin and Heri Suroto
Abstract Permanent damage on the tissue or organ are still a major problem andchalenge to be solved in the world of medicine. Humankind has tried to solve theproblem using technologies available in their respective era since long time ago. Wecan read from various literature about the efforts already made to replace andconsequently heal the damaged tissue or organ. Tissue or organ damage caused bywar and many other causes became the main reason of the tissue bank's estabil-ishment in many parts of the earth. Tissue bank strife to provide safe and highquality products to be used as natural biomaterial for damaged tissue reconstructionin patients. Several processes started from procurement, processing, and finallysterilization has been done to guarantee safe and useful products for the patients inneed. In line with the recent technological advancement, especially with theintroduction of stem cell usage, tissue and organ reconstruction has entered a newera that will bring greater hope for patients. If the previous methods that usedbiomaterial only employ dead tissue in the reconstruction procedures, tissue engi-neering will make the combination between stem cell and biomaterial as scaffoldpossible, thus enabling the living tissue to be used in reconstruction. This method,albeit still in the process of research, is expected to yield better results.
Keywords Tissue and organ damage � Biomaterial � Tissue bank � Stem cells �Tissue engineering
F. Mahyudin (&) � H. SurotoAirlangga University, Surabaya, Indonesiae-mail: [email protected]; [email protected]
H. Surotoe-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_9
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1 Introduction
Tissue and organ injuries causing functional damage is the challenge yet to besolved in medical science. In the history of mankind, countless trials and procedureshave been tried to solve this problem. Creating an organ, or at least an artificial one,is a long-life dream of mankind, which started to be realized after so many decadesand technology advancement until now. The legend of transplantation itself wasdepicted in the painting of “Healing of Justinian” by St. Cosmas and St. Damien.The painting describe a lower leg transplantation on a soldier who has been injuredduring war. Cosmas and Damien themselves were Arabic-Christian twin brotherswhose profession are doctors and lived in the area that we call Turkey at present(Meyer 2009; Nather and Zheng 2010; Vacanti and Vacanti 2014).
In 600 BC, Shusruta Samhita from Northern India performed a skin graft forwar victim soldiers and criminals who received nose mutilation as punishment(Nichter et al. 1983; Ang 2005). A Bolognese surgeon named Gaspare Tagliacozzi(1545–1595) published his idea in a book named De Curtorum Chirurgica perInstitionem (Surgery of the Mutilated by Grafting) which describes about forearmflap technique that harvests inner side of forearm to perform reconstruction of thenose and then the termination of pedicle connection several weeks later. The firstallogenic skin graft were performed by Jaqcues-Louis Reverdin in 1869 by usingepidermal grafts which also known now as split thickness grafts. George Pollock ofEngland introduce epidermal graft on combustion injury in 1871. The followingyear in 1872 Louis Xavier Edouard Leopold Ollier reported his success in trans-planting the skin using whole epidermis and part of dermis. And at last in 1886,Karl Thiersch introduce split thickness skin grafting technique to further extendarea of skin graft coverage (Meyer 2009; Nather and Zheng 2010; Phillips 1998a;Vacanti and Vacanti 2014).
The early efforts to replace damaged part of body use metal, ivory, wood andseveral other as biomaterial for reconstruction. On Galileo-Roman period, teethreplacement which is the early phase of dental implant has been performed.Anthropologic discovery of human skull filled with metal on the showed early effortof tissue reconstruction using substitution material (Crubézy et al. 1998). AmbroiseParé (1510–1590) described in his work Dix livres de la chirurgie measures toreconstruct teeth, noses, and other parts of the body (Pare 1634). Early success ofpremolar reimplantation due to trauma were reported by John Hunter (1771) on hisbook titled “The Treatise on the Natural History of the Human Teeth” (Meyer 2009;Nather and Zheng 2010). Reconstruction using donor tissue to cover the defect onmusculoskeletal system were reported by MacEwen in 1880. Lexer reported 23cases of articular cartilage transplantation between 1908 and 1925 and reported50 % success rate. Noyes and Shino began to use allografts in ligament recon-struction in 1981 and have subsequently reported good results. Milachowski wasthe first to transplant a human meniscus in 1984 (Shelton et al. 1998).
There are a lot of materials available at present to be used for defect recon-struction procedure on a tissue or organ to restore its function. The materials used to
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replace the tissue defect are labeled as biomaterials. American National Institute ofHealth describes biomaterial as “any substance or combination of substances, otherthan drugs, synthetic or natural in origin, which can be used for any period of time,which augments or replaces partially or totally any tissue, organ or function of thebody, in order to maintain or improve the quality of life of the individual”.Biomaterial that is being used came from polymers, metals, ceramic, and com-posites whether it is obtained from human or animal (natural) or purposely inventedby human (synthetic). The usage of biomaterial is varied depend on the disease andtissue that need to be restored. On cardiovascular cases, biomaterial is needed toproduce stent in treating coronary diseases, while dentist will need biomaterial fortheir implant to treat the patient. One of the profession that use implant frequently isorthopedic surgeon. Biomaterial in orthopedic are used as internal fixation forfracture of the bone such as screw, plate, and nail system, to replace damaged jointwith artificial one (endoprosthesis), and as bone graft or bone material substitute topromote and stimulation for bone healing (Navarro et al. 2008).
2 Natural Biomaterials
Natural biomaterials refer to organic and inorganic matrix that is obtained fromhuman or animal. The source of biomaterial from human came from tissue or donordonation, or tissue that is being removed after certain procedure such as total jointreplacement and craniotomy. Decellularized extracellular matrix tissue can beobtained from hard tissues such as bone and teeth, or soft tissues such as skin,amniotic membrane, intestine, vascular, heart valve, duramater, cornea, etc. Thereare several advantages using ECM biomaterials as biomaterial ingredients. First ofall, each of molecules in ECM can be broken down by using normal enzymaticprocesses. Another advantage is that the three-dimensional structure and mor-phology of the ECM copies the structure and morphology of the original tissue thatis being transplanted. Lastly, researchers can design a prosthesis that works not onlyon a macroscopic level, but also on the cellular level due to the innate potential ofthe biomaterial. There are, of course, several certain disadvantages using ECM. Itusually triggers immune system of the recipient thus causing severe reactions.There are also many ancillary molecules that change the way the prosthetic willinteract with surrounding recipient tissue when placed in vivo. While there are somemolecules that would promote the regenerative capabilities of the recipient tissue,others might stimulate an immune responses. In the end, there is an abundant ofpotential in ECM biomaterials as well as its problems yet to be solved (Coburn andPandit 2007).
Natural biomaterials that are being used mostly are intact extracellular matrix,collagen, chitosan, hyaluronoic acid and alginate. Collagen is protein that constructa human body the most. More than 30 % protein of human body are collagen(Nimni et al. 1987). Chitosans are the second most abundant biopolymer in natureand represent a family of biodegradable cationic polysaccharides consisting of
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glucosamine and randomly distributed N-acetylglucosamine linked in a β(1–4)manner, and have a chemical structure similar to hyaluronic acid (Dornish et al.2001). Instead of protein, another substance that frequently used as scaffold ismineral hydroxyapatite (HAp). These minerals can be obtained from nature such ashumans, animals, or corrals or made for specific purposes (synthetic). Orthopaedicsurgeon applies mineral HAp as bone graft. Mineral HAp can be obtained frombovine bone and corral as scaffold materials. The preparation of HA will decide thecomposition and structure. First is HA with the organic matrix, unsintered; secondlyis without organic matrix, unsintered; and last one is without the organic matrix andsintered. Sintered and unsintered HA differs in their consistency. Unsintered bonemineral consists of small crystals of bone apatite (carbonate HA), while sinteredbone mineral consists of larger apatite crystals without carbonate when heatedabove 1000 °C. The unsintered material has organic matrix that resembles structurein the context of the three dimensional macro- and microstructure of the bone.Natural HAs possess an interconnecting macroporosity that make the cells penetrateinto the scaffold possible both in vivo and in vitro (Wiesmann and Meyer 2009).
3 Tissue Bank
Transplantation is an effort to move a cell, tissue, or even an organ from a donor toa recipient in order to restore its function. Tissue transplantation differs from organtransplantation, whereby the process is more complicated, more expensive, andusually is a life-saving procedure. Organ transplantation, such as kidney, heart,liver, lung and many other require a healthy and functional donor to replace thedamaged function of the recipient. Consequently, the source of donor organ must bealive or at least in vegetative state in which the function of the organ transplanted isstill functional. After harvesting the donor, the organ must be immediately trans-planted to the recipient in order to prevent death of the organ’s cell. Tissuetransplantation, however, can be harvested from cadaver since it consist ofnon-viable tissue such as cornea, bone, joint, ligament and meniscus. Therefore it isnot necessary to perform the transplantation immediately if it is storage properlyeither in room temperature or deep freezer (Phillips 1998b).
The place to store the donor tissue is called Tissue Bank. Tissue bank, bydefinition, “is an entity that provides or engages in one or more services involvingtissue from living or cadaveric individuals for transplantation purposes. Theseservices include assessing donor suitability, tissue recovery, tissue processing,sterilization, storage, labelling and distribution” (Nather et al. 2007). Tissue bankconnects the donor and recipient that needs the tissue. Main function of tissue bankis to provide various type of high quality and safe tissue for recipients.
Korean War is the first trigger to the establishment of first tissue bank in USA.Huge number of war victims that needed various tissue, especially musculoskeletal,as the result of the war inspired George Hyatt to build Bethesda Naval Tissue Bankin the United States in 1950, with Ken Sell becoming Director in 1965. Almost in
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the same time, Rudolph Klen set up the tissue bank in Hradec Kralove in the oldCzechoslovakia in 1952, and then followed by Frank Dexter who established TheLeeds Tissue bank in 1956, and then The Charité Hospital Tissue Bank in Berlin inthe old East Germany was set up in 1956. Nowadays tissue bank have improvedgreatly worldwide and several regional organization is formed such as AmericanAssociation of Tissue Bank (AATB), European Association of Tissue Bank(EATB), Asia-Pacific Association of Surgical Tissue Banking (APASTB) and LatinAmerican Association of Tissue Banks (ALABAT) (Pfeffer 2009; Phillips 2016). InIndonesia there are three tissue banks located at the National Nuclear ResearchInstitute (BATAN) in Jakarta (1988), Dr. Soetomo General Hospital in Surabaya,East Java (1990) and Dr. M. Jamil Hospital in Padang, West Sumatera.
3.1 Regulation
Availability of the tissue is the main requirement on establishing a tissue bank.Tissue donation is an act of humanity, as it enables one to alleviate the sufferings offellow human beings. Organ donation is a complex situation in which involvingmany aspects such as social, ethic, regulation, medical, infrastructure and skills ofthe doctors in charge. Organ donation aims to obtain potential donor that fill thecriteria and regulation on its own respective country. The aspects mentioned above,unfortunately, cause an imbalance between supply and demand of a tissue,unavoidably causing longer waiting list for a patient to receive a tissue from thedonor (Nijkamp et al. 2008; Anderson and Trias 2009).
Tissue and organ can be obtained from living donor or cadaver. Tissue harvestcan be executed if prior agreement exist. Different countries may have differentregulations regarding this matter. The first is presumed consent or opt-out system,where a deceased individual which fulfill the criteria may have his/her organ har-vested unless there were prior objection from him/herself. The second is informedconsent or opt-in system, where people make their agreement with tissue bankregarding the timing and condition of tissue harvest. Usually the donor receive anID card from tissue bank in exchange. Several countries in Europe adopt opt-outsystem, while USA, UK, and most of Asia except for Singapore adopt opt-in system(Phillips 1998b; Gevers et al. 2004; Rithalia et al. 2009; Douville et al. 2014;Hutchison 2016; Rid and Dinhofer 2009).
Monetary inducement for donation is subject to the following restrictions.Payment to the donor is prohibited. Monetary payment or advantages for thedonation shall not be made to living donors, cadaver donor’s next of kin or anydonor-related party. As regards compensation for donation-related expenses, donorsor their family shall not be financially responsible for expenses related to retrievalof tissues. Anonymity between donor and unrelated recipient shall be strictly pre-served. Anonymity between donor and recipient shall allow tracking of tissues,through anonymous identification numbers (Phillips 2003; Nather et al. 2007).
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The procedure for tissue harvesting varied in every country depend not only bythe consent, but from socio-culture, ethic, religion and nearest family. The role offamily is influential in the decision making. In UK on 2006, refusal of donoragreement caused by the family reach 41 % while Spain record 15 % regarding thesame problem (Rithalia et al. 2009). A certain belief that a deceased must be buriedwith its complete parts of body is the main barrier of tissue harvesting and organdonor in Indonesia. Figure 9.1 illustrate the procedure of human tissue production atthe Cell and Tissue Bank of Dr. Soetomo General Hospital in Surabaya (hereafternamed as Surabaya Cell and Tissue Bank).
3.2 Donors Selection
Main aim of a Tissue Bank is to obtain a safe and high quality tissue to be providedto the patient. Therefore each and every tissue must be examined thoroughly. Donorsuitability for a donation of tissue allograft depend on medical and behavioural,medical records review, physical examination, cadaveric donor autopsy findings(if an autopsy is performed) and laboratory tests (Phillips 2003; Nather et al. 2007;Navarro et al. 2008).
Fig. 9.1 Flow chart of production of human tissue at Surabaya Cell and Tissue Bank
212 F. Mahyudin and H. Suroto
Donor history evaluation includes an interview of the potential living donor orthe cadaveric donor’s next of kin, performed by suitably trained personnel, using aquestionnaire. A qualified physician shall approve the donor evaluation process.According to APASTB Standards for Tissue Bank General Contraindications theuse of tissues for therapeutic purposes:
• History of chronic viral Hepatitis.• Presence of active viral Hepatitis or jaundice of unknown etiology.• History of, or clinical evidence, or suspicion, or laboratory evidence of HIV
infection.• Risk factors for HIV, HBV and HCV have to be assessed by the Medical
Director according to existing National Regulations taking into account nationalepidemiology.
• Presence or suspicion of central degenerative neurological diseases of possibleinfectious origin, including dementia (e.g. Alzheimer’s disease,Creutzfeldt-Jakob disease or familial history of Creutzfeldt-Jakob disease andmultiple sclerosis).
• Use of all native human pituitary derived hormones (e.g. growth hormone),possible history of duramater allograft, including unspecified intracranialsurgery.
• Septicaemia and systemic viral disease or mycosis or active tuberculosis at thetime of procurement preclude procurement of tissues. In case of other activebacterial infection, tissue may be used only if processed using a validatedmethod for bacterial inactivation and after approval by the Medical Director.
• Presence or history of malignant disease. Exceptions may include primary basalcell carcinoma of the skin, histologically proven and un-metastatic primary braintumour.
• Significant history of connective tissue disease (e.g. systemic lupus erythe-matosus and rheumatoid arthritis) or any immunosuppressive treatment.
• Significant exposure to a toxic substance that may be transferred in toxic dosesor damage the tissue (e.g. cyanide, lead, mercury and gold).
• Presence or evidence of infection or prior irradiation at the site of donation.• Unknown cause of death.
Age criteria varied depends on tissue being harvested. There is no age limit formusculoskeletal tissue donor such as cancellous bone. Heart valves and pulmonaryvalve must be harvested under 65 years old, while aortic valve under 50 years oldand mitral valve under 50 years old. Skin tissue is harvested under 75 years old andartery under 50 years old and vein under 60 years old (Phillips 1998c; Nather et al.2007; Navarro 2010).
There is another way to examine medical and social history that hasn’t beenreported previously. A physician will perform a thorough examination to a donorcandidate to find out any sign of risky behaviour or possibility of infection or viraldisease. If any of these signs listed below exist on a donor, it is necessary to ask tothe family or the closest relative about the time the sign shows (e.g. skin piercing,tattoo). The donor shall be rejected if the sign is proved to be critical. The physical
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examination has to be performed systematically in each and every patient with aspecific aim to find the signs mentioned before. There are signs that should bespecifically looked for, such as risk of sexual transmitted diseases: syphilis, ulcers,herpes simples, chancroid, and perianal lesions. Physical evidence of non-medicalpercutaneous drug abuse, acupuncture or tattoos including the presence of ear orbody piercing. Significant enlarged lymph nodes might be present. Oral thrush, bluespots or purple ones characteristics of Kaposi’s sarcoma. Generalized rash that couldpoint to sepsis or unexplained jaundice. Necrotic lesions after previous vaccination.Donor’s physical examination shall be recorded in the donor’s history and collectedby the retrieval team (Phillips 1998c; Nather et al. 2007; Navarro 2010).
The obtained tissues will be tested for transmissible diseases depends on law andpractice in each respectful country. In case of living donors, further procedure forblood testing might be performed. Tests will be performed and deemed legitimateon blood samples from the donor using recognized, licensed tests and according tomanufacturer’s instructions. Tests will be performed by a qualified, licensed lab-oratory and according to Good Laboratory Practice (GLP). There is 24 hours’ timelimit for blood screening on deceased donors after death. Blood screening for livingdonors must be taken at least 7 days before tissue harvesting. For potential tissuedonors who experience more than 50 % hemodilution due to additional fluid such asblood, blood components, or plasma volume expanders within 48 h before death, apre-transfusion blood screening must be done. The physician will be notified ofconfirmed positive result that has clinical significance according to the existing law.Sample of donor blood examination will be securely sealed and stored frozen for5 years after the tissue harvested is expired or in accordance to existing law on eachcountry. Minimum Blood Tests shall include (Phillips 1998c; Nather et al. 2007):
• Human Immunodeficiency Virus Antibodies (HIV-1/2-Ab)• Hepatitis B Virus Surface Antigen (HBs-Ag)• Hepatitis C Virus Antibodies (HCV-Ab)• Syphilis: nonspecific (e.g. VDRL) or preferably specific (e.g. TPHA)
Optional Blood Tests could be necessary for compliance with applicableIntergovernmental, National, Regional and Local Law or Regulation and/or toscreen for endemic diseases (Phillips 1998c; Nather et al. 2007):
• Hepatitis B core antibodies (HBc-Ab): HBc-Ab should be negative for tissuevalidation. Though, if the HBc-Ab test is positive and the HBs-Ag is negative,confirmation cascade should be entered. If the antibodies against the surfaceantigen are found (HBs-Ab), the donor can then be considered to have beenrecovered from an infection and the tissue can be used for transplantation.
• Antigen test for HIV (p24 antigen) or HCV or validated Molecular Biology Testfor HIV and HCV (e.g. PCR), if performed by an experienced laboratory.
• Antibody to HTLV 1: depending on the prevalence in some regions.• Cytomegalovirus (CMV), Ebstein-Barr Virus (EBV) and Toxoplasmosis
Antibodies: for immunosuppressed patients.
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• Alanine Aminotransferase (ALT) for Living Donors: In addition to the generaltesting requirements, testing living donors of tissue for AlanineAminotransferase (ALT) is recommended.
HIV and HCV retest is recommended in living donors in 180 days after priorexamination. Any other method that will yield better result (antigen testing,molecular biology or viral inactivation method) is used rather than retesting with thesame method and the result will be recorded in the same document.
Samples of each obtained tissue will be cultured if the tissues are going to beprocessed without terminal sterilization. Before the tissue exposed to antibioticcontaining solution, representative sample shall be taken. The culture proceduremust enable the growth of both aerobic and anaerobic bacteria and fungi as well. Ifthe harvest is performed on a cadaver, blood culture might be useful in examiningthe condition of the cadaver. They must be examined by the experts of this field. Ifthe result shows low virulence or commonly considered non-pathogenic microor-ganisms growing, the tissue should be distributed after being further processedthrough decontamination. Tissue which shows high virulence microorganismsgrowth is not acceptable for transplantation, unless the decontamination is done torender the microorganism inactivate without harmful potential effects, includingpossibility of residual endotoxins (Phillips 1998c; Nather et al. 2007).
3.3 Tissue Procurement
Tissues can be obtained from either living donors or deceased donors, which can bedivided into vegetative state or heart beating donors, deceased due to cardiopul-monary arrest donors, and non-heart beating donors. The available tissue to beobtained are bone, joint, musculoskeletal tissues (ligament, tendon, fascia lata,meniscus), duramater, heart valve, and skin tissues.
The deceased shall had his/her death pronounced or death certificate signed bydoctors other than those involved in tissue management. All aspect of law regardingdetermination of death shall be respected. The cadaver that is going to be used asdonor must be identified thoroughly before harvesting began. Harvesting shall bedone in adequate facility such as operating room or mortuary with facilities needed.Sterilization of all equipment shall be done between harvests of different cadaver.Tissues may be obtained using aseptic technique, where harvesting process isprepared using a standard surgical technique and resembling standard operatingroom practice. Another way is to perform clean or non-sterile technique, only if thesterilization is adequate to remove all pathogens after the procedure (Phillips 1998c;Phillips 2003; Nather et al. 2007):
• Aseptic technique: aseptic technique shall be observed throughout the pro-curement procedure. Procurement sites shall be prepared using a standard sur-gical technique; all methods shall be consistent with standard operating roompractice.
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• Clean/non-sterile technique: allografts procured using clean/non-sterile tech-niques are suitable for transplantation, if efficient validated sterilizing methodsare used to eliminate pathogens after retrieval.
A sample should be taken for microbiological examination if possible. Aftertissue harvesting, the cadaver must be reconstructed to achieve its previous statebefore the event of funeral. Time needed to obtain the tissue after the death of thedonor is an important issue as well. An optimum time of harvest is between 6 and24 h (if the cadaver if stored at room temperature), or between 12 and 48 h (if thecadaver is kept in a refrigerator at 4 °C before the first 4 h post-mortem). Residualtissues after a therapeutic surgical procedure (e.g. femoral head, skin and amnion)can be obtained for another therapeutic use in other patient or research purposes.Informed consent is required before the residual tissue can be obtained from thedonor.
Potential donor of amnion membrane can be sorted from obstetrician list ofpatient that is going to undergo elective caesarean section deliveries. Inform con-sent for amniotic membrane harvest can be made before the patient get the surgery,therefore the possibility of the patient to agree donating the membrane is higherbecause of longer pre-surgery discussion regarding donation in elective patientcompared to those who undergone emergency caesarean section deliveries. Thesame discussion can also be performed in patient with possible bone donation aftera surgical procedure, although the patient list is made according his/her medical andbehavioural history (Warwick 2010).
3.4 Quarantine
After procurement, the tissue is temporary kept in a −20 °C freezer to wait for thelaboratory test result. If the result is negative, then the process proceeds. If, how-ever, the result is positive, the tissue is deemed unusable and will be terminated.
3.5 Processing of the Tissue
The tissue bank is a storage to keep tissues in non-viable state, which will besterilized later to prevent disease spread from donor to the patient as well ascontamination during processing of the tissue. Non-viable tissue will decrease acuteallograft rejection reaction. Cartilage and cornea are exceptions to this rule. Bothtissue are normally avascular and will not experience vascularization, render it ableto be transplanted in viable condition without causing acute allograft rejectionreaction (Kearney 2010).
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Tissue preservation are meant to avoid matrix tissue damage due to the enzy-matic processes. Enzyme that plays big role in tissue degradation processes isproteolytic. Lipid peroxidation also has great potential to destroy the tissue matrix.Both processes activities mentioned above depends greatly on water availability.Therefore decreasing the amount of water through freeze drying (lyophilisation) orwater immobilization using deep freezing technique is very important to preservethe tissue. The methods for tissue preservation depends on the type of tissue beingprocessed (Kearney 2010). Another process to decrease tissue antigenicity is byremoving all dead cell and their products (Mirsadraee et al. 2007; Vinci et al. 2013).
Bone can be processed by deep freezing and terminal sterilization usingchemical and gamma-irradiation, cryopreservation without irradiation, freeze-driedand demineralized with gamma-irradiation. The obtained bone, both from living ordeceased donor, can be processed using methods mentioned above. On deepfreezing process, the bone will be stored in deep freezer with temperatureof −80 °C. This method will not decrease the mechanical strength of the bone,therefore it is used for large bone graft allograft that will be used as structural bonegraft for large bone defect reconstruction. After all examination yield negativeresult, the bone is wrapped and put into deep freezer. Both cell in the bone and softtissue will necrotize and disappear microscopically in 2 weeks’ time. This processwill significantly reduce tissue antigenicity. It is best for the tissue to be issued fromtissue bank after 1 month to ensure whole process is completed. Freeze drying, onthe other hand, is water reduction process by sublimation where the water willvaporized directly from solid ice state without going through liquid state. The aimof this process is to get biological scaffold that is collagen network containing HAp,decreasing antigenicity, decreasing amount of the microbes, and facilitate steril-ization. This process decreased the amount of water in tissue until 5–8 % bysublimation mean. Freeze drying will decrease bone strength significantly.Therefore small bone allograft will be used on small bone defect as filler to facilitatebone healing. Freeze-dried tissue can only be stored in room temperature (Phillips1998d; Nather and Tay 2010).
Bone demineralization is a chain of process in which soft tissue, blood and fat isremoved from the bone, continued by removal of bone mineral using HCl. Theprocess is halted if the amount of the calcium is decreased to 8 % and will be calledforth as demineralized bone matrix (DBM). This process exposes mineral trappedwithin the bone. DBM is a composite of collagens (mostly type I with some typesIV and X), non-collagenous proteins, various growth factors, few residual calciumphosphate mineral (1–6 %) and some small percent cellular debris. DBM is natu-rally osteoinductive with better potential compared to the unprocessed bone thusprovide better bone healing. Final processing of demineralized bone matrix is freezedrying so the demineralized bone matrix can be keep in room temperature (Natherand Tay 2010; Gruskin et al. 2012).
Musculoskeletal soft tissue allograft such as ligament, tendon, fascia, meniscusprocessed and stored in deep freezer with −80 °C temperature at least 1 month
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before being used. Tissue sterilization is needed to guarantee there is no diseasespreading from the donor to the recipient. Sterilization is needed to ensure there isno proliferating microorganism and to decrease the amount of microorganism untilacceptable level called as sterility assurance level (SAL). Tissue sterilization can bedone either by chemical sterilization or gamma irradiation therapy. Chemicalsterilization is done by using ethylene oxide, glutaraldehyde, and peracetic acid.Each chemical compound have several negative impacts to the tissue therefore itsselection and usage require decent knowledge of characteristic and function of eachcompound to obtain optimal result. Sterilization using gamma ray is usually donewith dose of 25 kGy. Gamma irradiation works directly by causing damage onDNA structure of the microorganism and indirectly by forming free radical that willcause damage to the protein, enzyme and nucleus material of the cell. Gammairradiation might cause decrease on mechanical strength on bone allograft or softtissue allograft, causing some tissue bank refuse to do terminal sterilization process.On these conditions, allograft harvest must be done in aseptic technique andthoroughly monitored to prevent disease spread or contamination (Kearney 2010;Yusof and Hilmy 2010).
3.6 Tissue Bank Products
Product spectrum produced by tissue bank varied depend on the purpose of thetissue bank itself, available facility, and human resources. Tissue that can be pro-duced by tissue bank are bone, joint, skin, amniotic membrane, ligament, tendon,fascia, heart valve, duramater, and many other cell product.
The Surabaya Cell and Tissue Bank was established in 1990. Earlier, it wascalled bone bank since the only tissue obtained from cadaver and donor are bone.With additional human resource and equipment, the bone bank started producinghuman’s soft tissue such as tendon, ligament, duramater and amniotic membrane,hence the name changed into Biomaterial Center—Tissue Bank since 2010. In2014, the Bank began a research of stem cell in collaboration with the RegenerativeMedicine and Stem Cells Center of Dr. Soetomo Hospital, Faculty of Medicine, andInstitute of Tropical Disease of Airlangga University Surabaya. The nameBiomaterial Center—Tissue Bank changed again into Cell and Tissue Bank in thesame year. The Surabaya Cell and Tissue Bank has the signature products such asdeep frozen tissue consist of bone, joint, amniotic membrane, fascia, duramater,tendon and ligament, as well as freeze-dried tissue consist of amniotic membrane,bone, demineralized bone (DBM), and tendon (Figs. 9.2, 9.3 and 9.4). TheIndonesian Ministry of Health has appointed Dr. Soetomo Hospital as center ofservice, education and research for stem cell in Indonesia. According to the regu-lation in Indonesia, clinical trial can only be done using adult stem cells, whileembryonic and animal stem cell are still prohibited.
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Fig. 9.2 a Left and middle, humerus and femur joint for osteoarticular bone allograft and rightshaft of tibia bone for intercalary bone allograft, b various size and shape of freeze dried bone(Courtesy of Dr. Soetomo General Hospital, Surabaya)
Fig. 9.3 Various form of demineralized bone matrix (Courtesy of Dr. Soetomo General Hospital,Surabaya)
Fig. 9.4 a Placenta, b processing of amniotitc membrane, c final product of amniotic membrane(Courtesy of Dr. Soetomo General Hospital, Surabaya)
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3.7 Orthopaedic Applications
Spectrum of disease traded by an orthopedist consist of congenital anomaly,infection and inflammation, trauma, arthritis, tumor, metabolic and degenerativedisease, and also sensory disturbance and muscle weakness. Most of the diseasesmentioned above will cause defect on musculoskeletal system, leading to functionaldisturbance later on. Reconstruction using bone, ligament, tendon, fascia as graft isperformed to treat the defect in musculoskeletal tissue. The tissue graft can beobtained from the patients themselves, which is called autograft, from other person,which is called allograft, and even another species, which is called xenograft. Themost ideal graft came from the patient themselves because there will be no rejectionreaction, rendering perfect incorporation with the body. Autograft, however, hasseveral weakness that is limited source of harvest, unable to reconstruct largedefect, sacrifice some part of normal body structure, need surgical procedure toharvest the graft with risk of pain, infection, and blood loss (Ebraheim et al. 2001;Dimitriou et al. 2011; Loeffler et al. 2012; Shelton and Fagan 2011; Myeroff andArchdeacon 2011). Bone graft is the most tissue transfer transplantation procedureafter blood transfusion. Bone autograft has ideal biologic composition to treat bonedefect that is osteoconductive matrix, in which the graft act as scaffold or trellis thatsupports the growth of new bone; second is osteoinductive proteins, which stim-ulate and support mitogenesis of undifferentiated perivascular cells to form osteo-progenitor cells; and the last one is osteogenic cells, which are capable of formingbone if placed into the proper environment (Finkemeier 2002; Myeroff andArchdeacon 2011). Cancellous bone autograft has osteoconductive, osteoinductiveand osteogenesis properties but no structural strength, meanwhile cortical boneautograft has a structural strength but osteoconductive, osteoinductive and osteo-genesis properties lower than cancellous autograft. Cancellous bone allograft, bothfrozen and freeze dried, osteoconductive properties similar to cortical allograft,osteoinduction properties lower than cortical allograft, but no osteogenesis prop-erties also no structural strength. Frozen cortical bone allograft has similar structuralstrength with cortical bone autograft, osteoconduction lower than cancellous boneallograft and no osteoinduction also osteogenesis properties. Freeze dried cancellousbone allograft has lower structural strength and osteoconduction (same with frozencortical bone allograft) and no osteoinduction also osteogenesis properties.Demineralized bone matrix (DBM) allograft has osteoconductive properties(similar cortical bone allograft), meanwhile osteoinductive properties is similar to cor-tical bone allograft and has no mechanical strength and osteogenesis (Greenwald et al.2001).
Allograft has several advantages compared to the autograft. It doesn’t need anyextra surgical procedure on the patient means that no further morbidity caused, noneed to sacrifice any part of the patient’s body, and it is available with different sizeand shape. With all those advantages, however, it has only osteoconductive andosteoinductive components, therefore it takes longer for the defect to heal and agood processing is required to prevent disease transmission. Frozen allograft needs
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to be stored in −80 °C for a minimum 1 month period. The structural strength willnever decrease along with the decrease of enzyme degradation and host immuneresponse during the process. Due to its strength, frozen allograft is used for largebone defect reconstruction such as joint replacement (osteoarticular) and bone shaftdefect (intercalary). Reports on large bone allograft usage shows satisfactory resultwith excellent allograft survival, although few complication occurred such asfracture of graft, infection, and graft resorption (Muscolo et al. 2006; Bus et al.2014; Bus et al. 2015). Reports from Dr. Soetomo General Hospital in 1990–2010stated that there were 85 large bone allograft procedure performed (Figs. 9.5and 9.6) with 87 % excellent and good functional evaluation with complication of
Fig. 9.5 a Giant cell tumor of distal femur, b tumor after resection, c osteoarticular bone allograft(17 cm), d X-ray after reconstruction of the distal femur including knee joint (Courtesy ofDr. Soetomo General Hospital, Surabaya)
Fig. 9.6 a Malignant soft tissue tumor with ulna bone infiltration, b tumor after bone resection,c intercalary bone allograft (10 cm), d X-ray after ulna bone reconstruction (Courtesy ofDr. Soetomo General Hospital, Surabaya)
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infection in two cases, fracture of bone allograft in two cases, and one case of boneresorption.
Other types of allograft are freeze dried and demineralized bone matrix(Fig. 9.7). Freeze dried bone allograft is processed by decreasing the amount ofwater in the bone until 5–8 %. The objective of freeze drying is to obtain achemically stable product at room temperature and to preserve the properties of thetissue, so that the tissue can be kept easily at room temperature and then distributedto the user after being sterilized. Freeze dried bone allograft has osteoconductiveand minimal osteoinductive properties, but greatly decreased structural strengthinstead (Ferdiansyah 2007). While demineralized bone matrix has better osteoin-ductive properties, structural strength is also decreased, comparable to those offreeze dried bone allograft. Both types of allograft is used to fill small bone defectfor procedures in dentistry, maxillofacial, spinal fusion, etc. (Gruskin et al. 2012).
4 Tissue Engineering
In present days, tissue and organ damage can be treated by reconstruction ortransplantation surgery. Surgical reconstruction procedure has widely implementedon various tissue damage. On musculoskeletal system, orthopedic surgeons haveperformed reconstruction surgeries by using biologic biomaterial (allograft) fromdonor such as bone, joint, meniscus, ligament and tendon. Several other proceduresmight use synthetic biomaterial (implant and endoprosthesis) that is composed frommetal alloy, polymer and ceramic. Reconstruction surgery on cardiovascular,ophthalmology and other medical discipline is also rapidly improving by usingbiologic or synthetic biomaterial as substitute for damaged tissue and eventuallyrestore its normal function. Nevertheless, there are still problems in using biologicbiomaterial that potentially cause morbidity on the patient such as disease trans-mission, infection, inflammation due to reaction against foreign component,
Fig. 9.7 a Left, benign bone tumor, right, after surgery and bone graft; b freeze dried boneallograft; c left fracture of intercondylar femur, right, after surgery and bone graft (Courtesy ofDr. Soetomo General Hospital, Surabaya)
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dislodgment and wear, and also lack of donor (Muscolo et al. 2006; Bus et al. 2014;Bus et al. 2015; Meehan et al. 2014; Illingworth et al. 2013).
Organ transplantation from donor to the recipient is a lifesaving therapy.Transplantable organ are namely kidney, liver, heart, and lung. The technologicaladvancement in medical studies ensured transplantation to be safe and successfulprocedures to maintain the life of the patient. Transplantation, however, mightcause several problems such as immune system process that would lead into chronicrejection and destruction of the organ being transplanted, rendering the recipient toconsume lifelong immunosuppressant with risk of infection vulnerability and ten-dency of tumor formation. The biggest and apparent problem of tissue and organtransplantation is severe discrepancy between available donor and recipients whoneed the organ, as shown by data from Organ Procurement and TransplantationNetwork. Up to mid-2015, there are 122,648 total waiting list patient for life savingorgan transplant, 79,260 of them are on the active waiting list. On January until July2015 18,048 transplantation procedure have been performed with 8,757 people asdonor. It’s displeasing to see 22 patient died each day while waiting for donoravailability. There are 4 fold increase of organ demand in the last 20 years, followedonly by 2 fold increase of transplantation procedure.
Solution is needed to solve the problem of limited organ donor in transplantationprocedures. Tissue engineering might be one of the answers for that. In the late1980, a meeting was held in Keystone, Colorado, sponsored by National ScienceFoundation entitled “Tissue Engineering” which emphasize efforts in manipulatingtissue or combine it with prosthetic material to restore the function. The article“Functional Organ Replacement: The New Technology of Tissue Engineering”published in 1991 issue of Surgical Technology International recorded for the firsttime the term “tissue engineering” is used (Vacanti 2006; Vacanti and Vacanti2014). In the following 25 years, tissue engineering has evolved rapidly not only byusing prosthesis or manipulating tissue, but by also integrating the use of cell andprotein as well. The definition of tissue engineering is still unclear and is oftenmistaken for regenerative medicine. According to National Institute of Health US“Tissue engineering evolved from the field of biomaterials development and refersto the practice of combining scaffolds, cells, and biologically active molecules intofunctional tissues. The goal of tissue engineering is to assemble functional con-structs that restore, maintain, or improve damaged tissues or whole organs”.“Regenerative medicine is a broad field that includes tissue engineering but alsoincorporates research on self-healing—where the body uses its own systems,sometimes with help foreign biological material to recreate cells and rebuild tissuesand organs”. Other definition that is used to identify tissue engineering is “the useof a synthetic or natural biodegradable material, which has been seeded with livingcells when necessary, to regenerate the form and/or function of a damaged ordiseased tissue or organ in a human patient” (Russell and Bertram 2014).
Tissue engineering is a combination of three component known also as tissueengineering triad that is: cell, scaffold and proteins as signaling (Nerem and Schutte2014; Moroni et al. 2015). The aim of tissue engineering is to create a living tissueconstruction to substitute the damaged tissue or organ. The cells can be obtained
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from stem cells or other progenitor cells or even fully differentiated cells. It mightbe a mix of several types of cell, mostly known as primary cell with a partner cell.The scaffolds can be manufactured from either synthetic biomaterial or naturalextracellular matrix. The scaffold is needed for fabrication of a replacement tissueor as a delivery vehicle for the cells being used in a tissue engineering. There arevarious types of signals, including growth factors and chemotactic factors. Thesesignals might be ones secreted by the cells employed (Nerem and Schutte 2014).
Tissue engineering works in replacement, repair and regeneration of the dam-aged tissue. The oldest concept is to replace the tissue rather than repair orregenerate it. Several procedure create a replacement tissue or organ outside of thebody which would be implanted within the body. Some of the initial successes werein this category of replacement. This includes such skin substitutes as Integra, aproduct of Integra Life Sciences and approved by Food and Drug Administration(FDA) in 1996; Apligraf, a product of Organogenesis approved by FDA in 1997;and Dermagraft, a product of Advanced Tissue Sciences approved by FDA in 1999.Dermagraft is now sold by Advanced Biohealing which has been acquired by ShireMedical. Using Integra as an example, the research on this approach was publishedin a journal in 1982 however, as already noted, FDA approval did not come until1996, a gap of 14 years. Furthermore, although all three of these skin substituteswere developed as a ‘replacement’, these products act and categorized as woundhealing implants according to the regulation of the US FDA through the Center forDevices and Radiological Health. Therefore they should be in the repair categoryinstead of replacement. Today these might well be regulated as biologics, and onecan only speculate about the length of time today that would be required for FDAapproval.
4.1 The Cells
Cell is one of major component in tissue engineering to create a fabricated con-struction to become a living tissue construction. The cells can be obtained fromstem cells or other progenitor cells or even fully differentiated cells. A stem cell isdefined as a cell that has the capacity for self-renewal and the potential to differ-entiate into any cell type in the body. Self-renewal is the process by which stemcells divide to make more stem cells, perpetuating the stem cell pool throughoutlife. Self-renewal is division with maintenance of the undifferentiated state. Thisrequires cell cycle control and often maintenance of multipotency or pluripotency,depending on the stem cell (Shenghui et al. 2009). Progenitor cell, however, has theability to generate the exact same cells of the tissue or organ from which it washarvested without ability to change its attributes.
Stem cells have an important role in the process of tissue repair. Manipulatingstem cells for applications in tissue engineering and regenerative medicine hascaught a lot of attention. The differentiation potential of stem cells is described withdifferent functional terminologies (Samadikuchaksaraei et al. 2014).
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• Totipotent stem cells, i.e. the zygote and its descendants up to the eight-cellstage in mammals, which can form the embryo and the trophoblast of theplacenta
• Pluripotent stem cells, such as the inner cell mass of the blastocyst, embryonicstem cells and reprogrammed cells, such as induced pluripotent stem (iPS) cellsthat can differentiate into all the cells of the three embryonic germ layers
• Multipotent stem cells, such as mesenchymal stem cells and several other adultstem cells, which can differentiate into multiple cell lineages like osteoblast,chondroblast and adipocyte, but not all the lineages derived from the three germlayers
• Bipotent stem cells such as mammary gland epithelial stem cells, which candifferentiate into two cell lineages such as myoepithelial and luminal cells
• Unipotent stem cells such as spermatogonial stem cells that can differentiate intoonly one mature cell lineage like male gamete.
Stem cell can be obtained from the patient themselves (autologous) or fromanother person or donor (allogenic). Using autologous stem cell will diminish anyrisk of disease transmission and ensure compatibility with the patient. There aresome disadvantages, however, such as decreasing potential of stem cells in elderlypatient and requiring harvest procedure, which is relatively easy but would stillpotentially causing morbidity for the patient. Allogenic stem cells are obtained fromdifferent individual. It is mainly used for the patient whose stem cells potentialdecreased for any reason. Some risks must be taken into caution while usingallogenic stem cell such as disease transmission and rejection reaction from thehost.
Stem cells are classified into embryonic (human embryonic stem cells, hESCs)and adult stem cells. The hESCs isolated in 1998 for the first time from the innercell mass (ICM) of a pre-implantation human blastocyst in a landmark study byThompson et al. (Thomson et al. 1998). In theory, hESCs have the capability tochange into all tissues of the human body and may provide crucial therapeutictreatment for various diseases. The only method of hESC harvest process in the late1990s/early 2000s involved destruction of a human embryo, and it is considered bysome as the same of terminating a human life. Embryonic stem (ES) cells areconsidered as immortal version of the ICM in culture; they retain high telomeraseactivity and can continue to self-renew indefinitely under appropriate culture con-ditions. When injected into immune-deficient mice, hESC form teratoma tumorsthat contain derivatives of all three germ layers, the most typical ones being bone,cartilage, neural rosettes and epithelium of the airways and gut (Klimanskaya et al.2014). Yamanaka et al. discover that Induced pluripotent stem cells (iPS) is aneffort to make a mature cell into pluripotent cell (Takahashi and Yamanaka 2006).Induced pluripotent stem cells (iPSCs) show similarities to embryonic stem cells(ESCs) that are obtained from many somatic cell types and many animal species.Due to accessibility of somatic cell origin, human iPSCs does not have any problemregarding ethical issues that found in human ESCs due to their embryonic origin,but also enable the easy production of patient-specific pluripotent stem cells.
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Similar to human ESCs, human iPSCs are capable of massive proliferation in vitrowhile retaining the developmental potential to differentiate into various types ofcells.
Adult stem cell can be obtained from bone marrow, adipose tissue, peripheralblood, umbilical cord, placenta and from other tissues or organ of human bodies.Adult stem cells have lower proliferation and differentiation potential compared tohuman embryonic stem cells, therefore the risk of teratoma formation is consid-erably low and diminish the ethical and religion controversy. The most researchedadult stem cells is the one obtained from bone marrow. Beside bone marrow, adultstem cells is usually obtained from adipose tissue and umbilical cord. Adult stemcells from organ are rarely used due to the difficulty in harvesting and higher risk ofmorbidity (Li et al. 2014).
The ideal stem cells in tissue engineering should be: easy to obtain in largenumbers, safe to implant, able to differentiate into the expected cells. It resulted inlimited types of stem cells which might be useful for tissue engineering.Mesenchymal stem cells, hematopoietic stem cells, adipose stem cells, and skin stemcells are easy to obtain and provided in large numbers. They are basically safe for thepatient, being harvested from matured tissues. Although pluripotent stem cells, suchas ES cells and iPS cells, are able to provide massive amount cells due to theirinfinite proliferative potential, one should remember their potential of causing tumorformation, which often prevents their clinical application (Samadikuchaksaraei et al.2014).
4.2 Scaffolds
Scaffold is an important part in tissue engineering that construct the compound intwo or three dimensional shape. Scaffolds will give structural support and shape fornew tissue construction in vitro and/or through the initial period after implantationas cells expand, differentiate, and organize.(Stock and Vacanti 2001; Hollister andMurphy 2011). Materials used in these differ from metals and ceramics, to naturaland synthetic polymers, as well as micro- and nanocomposites. When used in athree dimensional shape, these materials are processed into micro- and/or nano-porous cell carriers, typically known as scaffolds.
All biological materials for scaffold used in medical applications and regener-ative medicine approaches are obtained from naturally materials produced by theresident cells of each tissue and organ; specifically, the extracellular matrix (ECM).The composition of each ECM is specific depends on the tissue, highly dynamic,and crucially important in organ and tissue development, homeostasis, and responseto injury. ECM is consists of separate components such as proteins, gly-cosaminoglycans, glycoproteins, and small molecules or the intact matrix itself, canbe obtained and processed for use as scaffold materials. Individual ECM compo-nents, such as collagen and fibronectin, can be used to alter synthetic scaffoldmaterials to enhance their interaction and integration into host tissues, although they
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have also been used to create both naturally derived scaffold materials andcombination products with synthetic materials as biohybrid devices (Pradhan andFarach-Carson 2010; Kular et al. 2014).
Decellularized tissues or organs can be used as sources of biological ECM fortissue engineering. The advanced research of tissue engineering has showed thatECM components allow the use of xenogeneic materials (often porcine). Manytypes of extracellular matrices have been tried successfully for tissue engineering inanimal models, and products incorporating decellularized heart valves, smallintestinal submucosa (SIS), and urinary bladder matrix have been approved forhuman use. The use of decellularized matrices is preferred due to its ability to retainthe complex set of molecules and three dimensional structure of original ECM. Theright amount in which structural and signaling components are needed depends onthe choices of detergents and enzymes used and the washing conditions used toclear these reagents. Despite many advantages, there are also concerns about the useof decellularized materials. Those are potential for rejection reaction, diseasetransmission, variability among preparations, and the inability to determine thebioactive components of the material expected (Gilbert et al. 2006; Badylak et al.2011).
Biomaterial synthetic scaffolds used to be implemented as temporary prostheticdevices to fill the void spaces caused by necrosis or surgery. Current biomaterialsdevelopment aim to copy the function of natural extracellular matrix (ECM), whichcan support cell adhesion, differentiation, and proliferation. Biomaterial scaffoldsshould be designed considering the following requirements to be considered suc-cessful in copying ECM. First, suitable biomaterials must be selected for certainapplications. This is the same with the effort to build up the target-specific bio-logical scaffolds. Second, biomaterial scaffolds must be a highly open porousstructure with good interconnectivity, while possessing enough structural strengthfor cellular in- or outgrowth. Third, the surface of modified scaffolds must be ableto support cellular attachment, proliferation, and differentiation. Fourth, substanceor cytokine releasing scaffolds are good for tempering tissue regeneration sincecytokines such as growth factors and other small molecules have important roles ingrowing functional living tissues. Fulfilment of the above requirements will ensureexcellent biological scaffolds, therefore producing synergic effects on successfultissue healing (Lee 2011).
There are significant advantages in synthetic scaffolds that closely copy keycharacteristic of the ECM, but it might be manufactured and reproduced more easilythan decellularized organs. Electrospinning has enabled the production of a newgeneration of highly biocompatible micro- and nano-fibrous scaffolds from mate-rials such as poly(epsilon-caprolactone), from diverse matrix proteins such ascollagen, elastin, fibrinogen, and silk fibroin, from polysaccharides, and from car-bon nanofibers (Lee et al. 2009; Szentivanyi et al. 2011). Electrospun materialshave approximately the same fiber diameters with those found in native ECMand display better structural strength than hydrogels. The electrospun scaffoldscan be manufactured using various nano-fibrous structures and can includeadditional essential ECM components such as particular subtypes of collagen,
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glycosaminoglycans, and laminin, either in the spun fibers or as coatings, to pro-mote cell adhesion, growth, and differentiation (Ayres et al. 2010; Shin et al. 2012).
One of the method in producing artificial scaffold for tissue engineering isbioprinting. 3D bioprinting is the process of generating custom cell patternsusing 3D printing technologies, where cell function and viability are preservedwithin the printed construct. The 3D bioprinting is applied to regenerative medicineto fill the need for tissues and organs in suitable shape for transplantation. Itinvolves additional modifications, such as the choice of materials, cell types, growthand differentiation factors, and technical challenges related to the sensitivities ofliving cells and the construction of the tissues. Addressing these modificationsrequires the integrated effort from several fields such as engineering, biomaterialsscience, cell biology, physics and medicine. The 3D bioprinting has already beenused for the generation and transplantation of several tissues, including multilay-ered skin, bone, vascular grafts, tracheal splints, heart tissue and cartilaginousstructures (Murphy and Atala 2014).
4.3 Development of Tissue Engineering in Indonesia
The development of tissue engineering in Surabaya is centered at Dr. SoetomoGeneral Hospital—Faculty of Medicine University Airlangga, beginning withusage of natural biomaterial from the Surabaya Cell and Tissue Bank. Naturalbiomaterial application has helped many patients that require tissue reconstructionprocedure. On several occasion, these procedure might not yield satisfactory resultdue to the nature of material being transplanted which are not a living tissue. Inmassive bone allograft, for instance, the incorporation between the donor andrecipient bone are limited only in the contact surface area, while the middle part ofthe allograft is still considered as dead bone tissue. Consequently, fracture in themiddle of the allograft might occur in the future. The fact that it takes longer time toheal compared to the normal tissue should be taken into consideration in performingsuch procedures. To overcome all of that problems, we need some life constructionsthat use good cell, mature cell, and stem cells.
Tissue engineering triad that consist of cells, biomaterial as scaffold and proteinas signaling (Fig. 9.8) has similar biologic feature compared to the ideal bone graftthat is osteogenesis (possess cells that can produce new bone tissue), osteoinductive(protein to stimulate host cell to produce new bone tissue) and osteoconductive(scaffold as frame for the new bone cell and tissue).
Tissue engineering using stem cells composite along with biomaterial scaffoldmight become a solution, since the transplanted construction is a living construc-tion. The earliest research in 2008 was bone engineering by using bovine HAp asbone scaffold for bone marrow mesenchymal stem cells (BM-MSCs) in critical sizedefect reconstruction on rabbit as shown in Fig. 9.9 (Ferdiansyah 2010). It was thenfollowed by tendon engineering research using tendon allograft and cartilageengineering research using processed bovine cartilage as scaffold for bone marrow
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mesenchymal stem cells (BM-MSCs) as shown in Fig. 9.10 (Suroto 2011). The firstresearch of tissue engineering in Surabaya showed good products rather than justusing only biomaterial.
The above research has triggered more research on stem cells, therapies based onstem cell, and tissue engineering in Indonesia. In order to facilitate the growth ofstem cell research in Surabaya, the Surabaya Regenerative Medicine and StemCenter (SRMSC) was founded in 2011 with a collaboration with Dr. SoetomoGeneral Hospital, the Faculty of Medicine, and the Institute of Tropical Disease,Airlangga University. The SRMSC has two laboratories: (1) in the Institute of
Fig. 9.8 Similarity in the concept of tissue engineering and bone engineering
Fig. 9.9 Bone engineering practice: a Bone marrow aspiration, b culture of stem cells, c bovineHAp, d SEM image of bovine HAp, e stem cells growth inside the bovine HAp, f radiographshows the healing of critical size defect of ulnar bone of rabbit. (Adapted from Ferdiansyah 2010)
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Tropical Disease focuses on basic research, animal and disease model, stem cellbanking and stem cell education; (2) in Dr. Soetomo General Hospital focuses onnatural production of biomaterial, culture and isolation on stem cell for clinical trial,stem cell banking, education for stem cell, and tissue engineering. Now, theSRMSC has done thousands of stem cell researches and has graduated twenty-twodoctors on stem cell studies. In 2014, Dr. Soetomo General Hospital got appointedby Indonesian Ministry of Health as the centre of stem cell educations, researches,and services in Indonesia.
Acknowledgment The authors acknowledge the supports from Dr. Soetomo General Hospital,Surabaya and the Indonesian Ministry of Health. We thank Dr. Hermawan, Laval University forthe discussion and revision during the preparation of this chapter.
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Indonesian Perspective on Biomaterialsand Medical Devices
Ferdiansyah Mahyudin, Sulistioso Giat Sukaryo,Widowati Siswomihardjo and Hendra Hermawan
Abstract Indonesia is an emerging country with population about 255 million in2015 and 40 % of this population is in their productive age. The country’s nominalGDP for 2015 is about 900 billion USD with 5 % annual growth and generalgovernment debt stays at 26 % of GDP. The government has put healthcare serviceas one of the strategic program in the 2015–2019 National Development Plan alongwith a new effective national healthcare financing scheme. Indonesia is a big marketfor medical products with a market value about 800 million USD in 2015 andestimated to reach 1.2 billion USD in 2019. The government has set policies and aclear roadmap for assuring the availability and distribution of medical devices byfostering local production, improving the quality of local products and tighteningthe surveillance to the pre- and post-market devices. The challenge lies on unifyingthe country’s experts to mutually collaborate under a strong leadership on the sameinterest toward the national independency in producing effective yet low costmedical devices.
Keywords Biomaterials � Indonesian government � Market � Medical devices �Policy � Regulation
F. Mahyudin (&)Airlangga University, Surabaya, Indonesiae-mail: [email protected]
S.G. SukaryoNational Nuclear Energy Agency of Indonesia, Yogyakarta, Indonesiae-mail: [email protected]
W. SiswomihardjoGadjah Mada University, Yogyakarta, Indonesiae-mail: [email protected]
H. Hermawan (&)CHU de Quebec Research Center, Laval University, Quebec City, Canadae-mail: [email protected]
© Springer International Publishing Switzerland 2016F. Mahyudin and H. Hermawan (eds.), Biomaterials and Medical Devices,Advanced Structured Materials 58, DOI 10.1007/978-3-319-14845-8_10
235
1 Indonesia, Facts and Figures
Indonesia is the largest archipelagic country with 17,508 islands spreading over a5,271 km distance from East to West and 2,210 km from North to South with fivebiggest islands namely Sumatra, Java, Kalimantan, Sulawesi and Papua. It islocated over the equator line between Asia and Australia with total land area of1,904,569 km2 or about 5 million km2 total territorial claim including the sea. Thecountry declared its independence on 17 August 1945 after three centuries-longtireless fight against the Dutch colonialization and started their nation building 5years later after winning the heroic post-independence war against the Dutch mil-itary aggression attempting to recolonialize Indonesia (Reid 1974).
Indonesian nominal GDP for 2015 is estimated at 895.677 billion USD with 5 %annual growth or by considering the purchasing power parity the total GDP standsat 2.840 trillion USD or 11,135 USD per capita (IMF 2015). Its economic activityremains significant thanks to a contribution of commodities sector even though thevalue of production and exports has been affected by global recession in recentyears. The declining public debt in Indonesia since the late 1990s has strengthenedthe economy’s resilience, maintaining favorable fiscal and debt positions comparedwith its peers. Indonesian general government debt stays at 26 % of GDP at end2014 and current gross funding needs of around 4 % of GDP a year are much lowerthan the median of other emerging market economies such as Brazil, Malaysia andTurkey (IMF 2015).
The 2011 census reported Indonesian population was 237,424,363 and estimatedto be 255,461,700 in 2015, making Indonesia the 4th country with the largestpopulation in the world (Statistics Indonesia 2015). About 40 % of this populationis in their productive age. Indonesian ethnic composition varies very widely as thecountry has hundreds of ethnic and cultural diversity. However, more than half ofthe population are dominated by two largest ethnics, the Javanese (41 % totalpopulation) and the Sundanese (15 % total population). Both of them are the nativeof Java, the most populated island in Indonesia, home for approximately 60 % ofthe total population of Indonesia. In general the population consists of 50.3 % maleand 49.7 % female with the current life expectancy stands at 72 years old (Ministryof Health et al. 2013).
In 2013, Indonesia has 11 cities with population over 1 million, with Bogor Cityis quickly approaching the 12th. Jakarta, the national capitol, is not just the mostpopulated city in Indonesia, it is also the most populated city in Southeast Asia andthe 13th most populated city on earth. The official metropolitan area, known as“Jabodetabek”, is the second largest in the world, and the metropolis suburbsextend even further. The entire area has a population surpassing 28 million, whichmakes it one of the largest conurbations on earth. It is also one of the fastestgrowing cities on earth, growing faster than Beijing and Bangkok, with populationdensity in the city reaches 15,342 people per square kilometer (Ministry ofHealth et al. 2013).
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All of the above facts, in turn, affect the population health and healthcare servicein Indonesia which at some points touch the aspects in biomaterials and medicaldevices as shown in previous chapters. In recent years, the Indonesian authoritieshave embarked on an initiative towards universal social insurance, including forhealth insurance and old-age security. The initiative began in 2004 with enactmentof the Law on the National Social Security System, followed in 2011 by a lawestablishing a single social insurance administrator for health care, or BPJS Health(Badan Penyelenggara Jaminan Sosial Kesehatan). Under this framework, thegovernment began implementing a universal health insurance system in January2014, consolidating several public health insurance schemes, and is financedthrough contribution payments and aims at covering the entire population by 2019(IMF 2015).
2 Challenge and Opportunity
It has been shown in previous chapters that the large population creates somechallenges in providing basic healthcare services, notably dental care(Chap. “Biomaterials in Dentistry”). In addition, the concentrated population inmain Indonesian cities has created chronic crowd traffics dominated by motorcylesthat in turn contributes to high traffic accidents causing a high incidence of trau-matic bone fractures (Chap. “Biomaterials in Orthopaedics”). These examples showa challenge related to providing adequate quantity of medical products in dentistryand orthopaedics which can be turn into opportunities of producing local, effectiveand low-cost biomaterials and medical devices. At some points, this opportunitycan be also related to utilization of abundant Indonesian natural resources for evenproducing innovative biomaterials with strong local “taste” and self-sustainability(Chaps. “Naturally Derived Biomaterials and Its Processing”, “BiocompatibilityIssues of Biomaterials”, “Biomaterials in Dentistry”, and “Tissue Bank and TissueEngineering”).
Currently, Indonesia is merely a big market for imported medical products with amarket value about 800 million USD in 2015 and estimated to 1.2 trillion USD in2019. This market is dominated by diagnostic imaging, medical consumableproducts and implants. The Indonesian medical device market remains one of thefastest growing, with a compound annual growth rate of 14.6 % to 2019 (BMIResearch 2015). The expansion of the health insurance programme, increasedgovernment spending on healthcare and infrastructure development projects willfurther spearhead growth.
The Government realizes that medical devices are important component in thehealthcare service where their production relies strongly with the technology andeconomic strength of the country. They are considered as one of most valuabletrading commodities with big social impact, therefore with the opening of ASEANfree-trade zone in 2015, the capability of producing medical devices locallybecomes a strategic issue in Indonesia. According to a survey by the Ministry of
Indonesian Perspective on Biomaterials and Medical Devices 237
Health, it is revealed that only 6 % of medical devices are produced locally and therest of 94 % are imported. This number is far below compared to the percentage oflocal products in the neighboring countries such as Malaysia (10 %), Vietnam(13 %), India (18 %) and Thailand (33 %), indicating a high dependence ofIndonesia toward import (Hariyanti 2015).
Locally-owned domestic production mainly consists of the manufacture of basicitems, such as surgical gloves, bandages, orthopaedic aids and hospital furniture,but a few local manufacturer produces orthopaedic implants competing somemedium grade imported products (Chap. “Biomaterials in Orthopaedics”). One ofthe main challenge to local manufacturing of medical devices is the Governmentregulation itself that incurs 15 % taxes to imported raw materials while applies taxholiday to imported ready to use medical products. However, the actual marketprice for imported implants is always more expensive compared to similar productsproduced locally. This could be related to high overhead fee, shipping fee andpromotional fee that at the end must be included in the selling price in Indonesia.Therefore, local products can be more competitive up to 60 % when those threefactors are excluded. However, the next challenge is acquiring the technology ofmedical devices manufacturing and setting up manufacturing plants whereas theinvestment cost is high and increases as the level of technological content (addedvalue) of the devices increases.
Indonesia is not lack of experts in medical devices and its manufacturing. Theyspread in many universities, research institutes and governmental instutions, such asthose who contributed to the writing of this book. The country is not lack ofpotential investors either as there is always a number of rich Indonesians listed inyearly Forbes billionaires list. The total wealth of the 2015 Forbes list of 50Indonesian richest business persons reaches 89.84 billion USD (Forbes 2015). Thechallenge is to unify those experts to mutually collaborate on the same interesttoward the national autonomy (independency) in producing medical devices underan effective leadership. The Government should trigger the investment during theearly research and development phase and when the potential become evidence,private investors will naturally be attracted.
3 Government Policy
3.1 Regulation
Indonesian Government have put healthcare service as one of the strategic programin the 2015–2019 National Development Plan. Along with creating strategic mis-sions such as increasing access to healthcare service for all 255 million population,the authorities developed an effective national healthcare financing scheme thatensures, among all, the avalaibility of drugs and medical devices (Table 1). TheMinistry of Health has set a policy for assuring the availability and distribution ofmedical devices by fostering local production, improving quality of local medical
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products and surveillance to the pre- and post-market medical devices. Anotherpolicy was enacted to strengthen national independency in fulfilling the need forpharmaceutical products and medical devices. One of the policy is the 2009 Law onHealth that sets a strict standard on safety, efficacy and quality of pharmaceuticalproducts and medical devices, pointing out on their affordability (Law 36 2009).A monetary fine up to 100,000 USD can be charged to individual who producesmedical devices that don’t meet the standard or illegally distributes any kind ofmedical product.
3.2 Roadmap for Medical Devices Development
The Government has a strong vision toward national independency on high qualitymedical devices produced based on a rigorous research and development program.Since 2014, serious efforts have been made to fulfill the demand of medical devicesby local industry by facilitating investment in this sector, increasing the variety andquality of local medical devices, giving incentive to local industries and reducingimport. The authorities enforce a regulation in prioritizing the use of local productswhile redefine stringent regulation for import such as the prohibition of using thestate budget to subsidize import. The Indonesian Ministry of Research, Technologyand Higher Education, have launched a multi-years grant scheme to Indonesianresearchers for conducting research and development on biomaterials and medicaldevices utilizing optimum local content, and encourage collaboration with localindustries.
Table 1 Classification of medical devices according to the Indonesian Ministry of Health
Class Consequence of failure ormisuse
Requirement for approval Example
I Will not cause significantmedical problem
Assessment is focused onproduct and its quality
Toothbrush, mask, dentalflos, bandage, icebag,sunglasses (withoutordonance), etc.
IIa Can cause significantmedical problem topatient but not serious(life threatening)
Requires completeassessment but clinical test isunnecessary
AC powereddinamometer, reflexhammer, wheelchair, etc.
IIb Can cause verysignificant medicalproblem to patient but notserious
Requires completeassessment, including riskanalysis and safety proof butwithout clinical test
Contact lenses,ophthalmic laser, etc.
III Can cause seriousmedical problem topatient or operator
Requires completeassessment, including riskanalysis and safety proof andclinical test
Ventricular bypass device,orthopaedic implants,silicon gel filled breast,etc.
Indonesian Perspective on Biomaterials and Medical Devices 239
Finally, the Indonesian Ministry of Health has launched a medium-term (8 years)roadmap for realizing the above vision. This roadmap is divided into three stages asdescribed in Table 2 (Permenkes 86 2013).
One of actual example of national projects conducted under this roadmap is theresearch and development of coronary stents, a small implant used to open coronaryartery occlusion. About 10 % of Indonesian population is elderies having potentialcardiovascular problem and the prevalence of cardiovascular patients in Indonesia wasaround 530,000 in year 2013 (Ministry of Health Information Center 2013). Allcoronary stents used to treat Indonesian patients are imported, soaring the cost of stentimplantation to exceed most of health insurance coverage limit (Tontowi et al. 2013).The IndonesianMinistry of Research, Technology and Higher Education has appointedGadjah Mada University to lead a research and development on coronary stent whichwas started in 2013 under a “Triple Helix” model of university-government-industryinteraction. The team have been conducting an interdisciplinary research coveringmaterials and engineering aspect of stents till in vitro study and planned in vivo andclinical trials (Taufiq et al. 2015; Tontowi et al. 2015).
Apart of this roadmap, examples of other research and development resulting intocommercially produced biomaterials and medical devices have been briefly exposed
Table 2 Indonesian roadmap for medical devices development (2014–2022)
Stage Period Aim
I 2014–2016 Optimizing current medium-low technology of local medical devicesindustry
Increasing number of production facilities for medical devices
Increasing use of local medical devices
Setting up research and development in medical devices technology
Initiating collaboration among industry, university and the Government
II 2017–2019 Developing research-based medium-high technology for medical devices
Increasing number of production facilities with standardization from ISO13485:2003 and good manufacturing practice of medical devices
Increasing research and development activities in medical devicestechnology
Increasing availability of local raw materials
Decreasing number of imported medical devices distribution yetmaximize the use of local products
Increasing export of medical devices
III 2020–2022 Achieving national independency on research-based high technologymedical devices
Increasing number of production facilities with standardization from ISO13485:2003 and good manufacturing practice of medical devices
Increasing investment in medical devices industry
Decreasing number of imported medical devices distribution
Optimizing export of medical devices
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in previous chapters. These include the GAMA-CHA human bone apatite compositefor bone substitution developed at Gadjah Mada University (Chap. “Biocom-patibility Issues of Biomaterials”), Bio-hydrox bovine hydroxyapatite scaffolds andvarious type of stainless steel bone plates developed at Airlangga University incollaboration with the Indonesian Agency for the Assessment and Application ofTechnology (Chap. “Biomaterials in Orthopaedics”).
Finally, we would like to conclude that all favorable factors permitting theachievement of the national vision toward independency on medical devices evi-dently present. The high demand for medical devices has become the Government’sconcern reflected in the new policy of universal public healthcare insurance. Theenthusiastic Indonesian biomaterials scientists find a place in the roadmap ofmedical devices development, where their creativity will continue to transform theactual challenge and opportunity into innovating effective and low-cost medicaldevices.
Acknowledgment We acknowledge the supports from the Ministry of Health and the Ministry ofResearch, Technology and Higher Education.
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