COOS Journal Vol-S lssus-Z, September 2013

ALL CERAMIC SYSTEMS - AN OVERVIEW

Authors: Dr. Sunitha Naveen ShamnurRead~r, Department of ProsthodonticBapuji Dental College & Hospital,

Davangere.Email: sunithans77@yahoo.com

Dr. Santosh DoddamaniIieader, Dept. of Prosthedentles

Cellege of Dental Sciences, Davangere.

Dr. Naveen SharnnurProfesser, Dept. of Orthodontics

College of Dental Sciences,Davangere.

ABSTRACT:In the search for alternative and esthetic restorative materials, many all-ceramic systems have been introduced forthe general practitioner. They are used as veneers, inlays/onlays, crowns, and as enamel/dentin bonded partial ortotal coverage without macroretention. This article describes a classification of the different commercialall-ceramic systems and gives a review of their clinical durability. The primary changes in the field were the prolif-eration of zirconia-based frameworks and computer-aided fabrication of prostheses, as well as, a trend toward moreclinically relevant in vitro test methods. Newer reinforced ceramics showed better durability then the earlier firedceramic reconstructions. This report includes an overview of ceramic fabrication methods, suggestions for criticalassessment of material property data.

KEYWORDAll Ceramic restoration, CAD/CAM, Zirconia, Lithium Disilicate.

INTRODUCTION:All ceramic is the most esthetic choice for full cover-age restorations, If given a choice, a patient willalways select the natural looking restoration over anartificial one. Although the quest for the ideal allceramic material continues, some materials usedtoday approach the esthetics and strength of theenamel- dentin complex in natural dentition.Metal ceramic restorations have been available formore than three decades. 1 This type of restorationhas gained popularity from its predictable perfor-mance and reasonable esthetics." Despite its success,the demand for improved esthetics and the concernsregarding the biocompatibility of the metal has leadto the introduction of all-ceramic restorations.'DISCUSSION:Historical perspectives of ceramics: For nearly1,000 years after its discovery, porcelain was usedprimarily to produce fine dishware and utensils.Itwas also used to create objects of art and jewelry forthose who could afford it. In 1723, Fauchard firstused porcelain to enamel the metal bases of dentures.He is also credited with recognizing the potential ofporcelain enamels and initiating experiments that

would lead to further advances in the use of porce-lainin dentistry. In 1774, Duchateau experimentedwith dentures fabricated with hard porcelain; 20years later,de Chament improved Duchateau'sprocess and secured a patent for "mineral teeth,"which became the first denture teeth." In 1885, Loganintroduced the Richmond Crown, in which porcelainwas fused to a platinum post ; a year later, Landmade the first fused porcelain inlay and crownbacked by platinum foil." The use of porcelain as aviable restorative option in dentistry gained littlefurther momentum until 1949, when the Dentist'sSupply Company of New York invented the vacuumfiring of dense and translucent porcelain teeth. In1958,the first dental porcelain for veneering wasintroduced, which led to the widespread use ofmetal-ceramic restorations in the 1960s and beyond,followed by the invention of the porcelain jacketcrown that was popularizedin the 1960s by McLean 4 1970s saw the advent ofearly experiments in CAD/CAM crown fabrication,followed by an influx of ceramic-based restorativesystems from the 1980s through to the present day.

COOS Journal Vol-5 lssue-Z, September .2013

Indications for all ceramic restorations: Esthetics:ceramics are considered the best in mimicking thenatural tooth appearance.' The optical behavior ofceramic materials differ from system to system andthis should be taken into consideration during theselection of which system to be used."Contraindications of all ceramic restorations:Limited interocclusal distance: in cases of short clini-cal crowns, deep overbite, orwith a super erupted opposing tooth.'Heavy occlusal forces:Due to the brittle nature of thematerial and its abrasive potential, ceramic restora-tions should be avoided in patients with parafunc-tional habits such as bruxism."Inability to maintain a dry field: ceramic restorationsrequire good moisture control at the time of theircementation to ensure positive outcomes.!Deep subgingival preparations:this is not consideredan absolute contraindication, although supragingivalpreparations are desirable to produce a more accuraterecording during impression taking. 8

Advantages: Esthetics: is considered the primaryadvantage."Wear resistance: ceramics are more wear resistantthan direct restorative materials. Precise contourand contacts: indirect fabrication of all ceramic resto-rations provides more precise contour and contactsthan directly placed restorations.Biocompatibility:The allergic reaction by some to

metal alloys is a weak point against metal ceramicrestorations which increased the demand on the morebiocompatible all ceramic restorations. However, thedegree of. cytotoxicity of the metal alloys largelydepends on the type of the dental alloy used in thefabrication of the metal ceramic restoration. 10

Disadvantages: Cost and time: all ceramic restora-tions are fabricated indirectly and require at least twoappointments to be delivered. The additional labora-tory fees make this type of restoration more expen-sive than other direct restorations:'Brittleness of the ceramics:adequate thickness ofceramic should be provided to avoid the fracture ofthe restoration."Wear of apposing dentition and restorations: ceram-ics can cause wear of opposing restorations and/ordentition. This problem has been considered duringthe improvement of ceramic restorations. 1 1

Low repair potential: If fracture occurs, repair is notconsidered a definitive treatment.'

Difficult intraoral polishing : ceramic restorationsare difficult to polish once they are cemented becauseof access problems and lack of proper instruments toperform this task."Simplifying concepts in understanding dentalceramics: 12

Two concepts help in simplifying the understand-ing of dental ceramics.

First, ceramics fall into three main compositioncategories- Predominantly glass

Particle-filled glass- Polycrystalline

Second ,ceramics can be considered as a compos-ite material ,in which the matrix is a glass thatis lightly or heavily filled with crystalline or glassparticles.Predominantly glass: have a high content of glassmaking this type of dental ceramic highly esthetic.This type is the best in mimicking the optical proper-ties of enamel and dentin.Optical effects arecontrolled by manufactures by adding small amountof filler particles.Particle-filled glass: Filler particles are added to theglass matrix to improve the mechanical properties.Fillers can be crystalline particles of high-meltingglasses.

Polycrystalline: This type of ceramic contains noglass. Atoms are packed into regular crystallinearrangement making it tougher and less susceptible tocrack propagation.Similar composition of ceramics could be fabricatedin different ways.'

Classification according to method of fabrication:I. Powder condensation:This is considered the traditional way for fabricationof an all-ceramic restoration. This technique involvesapplying moist porcelain using a specialbrush, thencompactingthe porcelain by removing the excessmoist. The porcelain is then fired under vacuumallowing further compaction.'Ceramics fabricated by this technique have a greatamount of translucency and are highlyesthetic13,and are used mainly as veneering layers.'

Examples of systems utilizingthis technique:"- Duceram LFC(Dentsply)- Finesse low fusing(Dentsply)- IPSe .maxCeram (Ivoclar-Vivadent)- IPSEris (Ivoclar-Vivadent)- Lava Ceram (3MESPE)- VitaD (VitaZahnfabrik)- Vitadur Alpha (VitaZahnfabrik)- VitaN (VitaZahnfabrik)Powder condensation utilizes feldspathic porcelain.Feldspathic porcelain:Potassium and sodium feldspars are naturally occur-ring elements composed mainly of potash (K20) andsoda (Na20),they also contain alumina (AI20) andsoda(Na20).Leucite and a glass phase are formedwhen potassium feldspar is fired to high tempera-tures. This glass phases oftens during firing allowingcoalescence of the porcelain powder particles.Thisprocess is called liquid phase sintering. This processoccurs at a relatively high temperature allowing theformation of a dense solid. Since leucite has a largecoefficient of thermal expansion, it is added to someglasses to control their thermal expansion.2. Slipeastlng:This technique involves forming a mold of thedesired framework geometry and pouring a slip intothe formed mold. Gypsum is usually utilized to formthe mold due to its ability of extracting some of thewater from the slip. The slip then becomes com-pacted against the mold forming a framework. Theframework is then removed from the mold by partialsintering. The resulting ceramic is very weak andporous and must be infiltered with glass or fullysintered before application of the veneeringporcelain.'Materials processed byt his technique tend to havefewer defects from processing ,and exhibit highertoughness than the conventional feldspathicporcelain. 14The use of this technique in dentistry has beenlimited to one of three products.5This limitationmight be due the complicated steps,which makesachieving an accurate fit difficult.P''<"

In-CeramAlumina® (Vita Zahnfabrik)This material was first introduced in 1989, and wasthe first all-ceramic system available for single unitrestorations and 3-unit anterior FPDs.17

A slurryof Al20 is applied on a refractory die andsintered for 10 hours at1120°C.18, 19This produces aporous framework of alumina particles which is infil-trated with lanthum glass during a second firing for 4hours at 11OO°C.This procedure is done to removeporosities, increase strength ,and limit crack propaga-tion sites."Then feldspathic porcelain is used to veneer theproduced coping."In-Ceram Alumina is considered to be a strong mate-rial having a mean biaxial flexure strength of 600MPa.21 The material should not be used in estheticzones because it does not fully allow lighttransmission.2In-Ceram Alumina is recommendedfor anterior and posterior crowns and anterior FPDs.4

In-CeramSpinell ®(Vita Zahnfabrik)In-Ceram Spinell was introduced in 1994 to over-come the opacity of In-Ceram Alumina. The frame-work contains a mixture of magnesia and alumina(MgAI204)to improve the translucency of thematerial+" The basic principles of fabrication are thesame as those for In-Ceram Alumina.It has a flexuralstrength of 250 Mpa which is lower than that forIn-Ceram Alumina.4In Ceram Spinell is indicated foranterior crowns because of its low flexural strength."In-Ceram Zirconia®(VitaZahnfabrik)In Ceram Zirconia is considered a modification ofIn-Ceram Alumina system with the addition of35%of partially stabilized zirconia oxide to the slipto increase the strength of the ceramic.24 Theceramic is fabricated using the traditional slip-castingtechnique.' In-Ceram Zirconia is considered thestrongest of three cores of the slip-casting techniquehaving a flexural strength of700 MPa.4 The materialis considered opaque and has poor translucency limit-ing its use for posterior crowns and posteriorFPDs.24,253. Hotpressing: Molds for pressable dental ceramicsare formed utilizing the lost wax technique.Pressable ceramics are available as glass-ceramicingots which are supplied from manufacturers. Theingots have a similar composition of powder porce-lains, however; they have less porosity and morecrystalline content. The ingots are heated to a hightemperature where they become a highly viscousliquid, and then pressed slowly into the formed mold.The advantage of this techniqueis that it utilizes theexperience that the lab technician already has in lost

_w2x :m.e1;Qod'Yith metaIJlllQys.15,1640

(ODS Journal Vol-5 Issue-2, September 201:3

IPS Empress® andIPS Empress 2® (IvoclarVivadent)are representatives of materials utilizing hot pressingtechnique for fabrication.IPS Empress® (IvoclarVivadent)IPS Empress is aleucite-reinforcedglassceramic(Si02-A1203).26IPSEmpress has a low flexural strength ofl12± 10 MPalimiting its use to single unit complete-coveragerestorations in the anterior region.t-"IPSEmpress 2®(IvoclarVivadent)IPS Empress 2 is a lithium-disilicate glassceramic(Si02-Li20).7IPS Empress 2 has a flexuralstrength of400±40 MPa which is much highert hanthat of IPS EmpressA,26Its increased flexuralstrength makes it suitable for the usage for fabricationof 3-unit FPDs in the anterior region, and can extendto the second premolar.27, 28 Both IPS Empress andIPSEmpress 2 are recommended in situations whereaverage to high translucency is needed.2They areconsidered as monochromatic restorations which canbe surface characterized to the desired shade andproduce comparable esthetics to the layeringtechniques."Another example IS theIPSe.maxPress®(IvoclarVivadent), which wasintroduced in 2005.1t is considered as an enhancedpress-ceramic material when compared toIPSEmpress 2.1t has better physical properties andimproved esthetics."4 Computer aided design/computer aidedmanufacturing:Machinable ceramics are available as prefabricatedglass-ceramic ingots.They are cut by tools that arecontrolled by the computer. After the tooth isprepared, an optical impression is taken for thepreparation by a special scanner. Thei mage is thentransferred to the system's software. Then thesoftware designs the restoration and sends the data tothe computer-Controlled milling machine that grinds the ceramicblock according to the desired shape."

Examples of materials available for the CAD/CAMtechnology:32(a) Silica based ceramics(b) Infiltration ceramics(c) Oxide high performance ceramics.

41

Several CAD/CAM systems offer silica basedceramic blocks for the fabrication of inlays,onlays,veneers, partial crowns and full crowns.Blanks with multicolored layers[VitablocsTriLuxe(Vita), IPSEmpress CAD Multi (IvoclarVivadent)]are available in addition to the monochromaticblocks for the fabrication of posterior crowns.

(b) Infiltration ceramics:Blocks of infiltrated ceramics for CAD/CAMsystems originate from theVitaIn-Ceram system.They have the same composition and clinical indica-tions of the three previously mentioned VitaIn-Ceramproducts.F(c) Oxidehigh performance ceramicsBlocks of aluminum oxideand zirconium oxide arecurrently available for the CAD/CAD technology."Alumina Oxide(A1203)It is considered as a high performance ceramic.lt isground then sintered at a temperature of 1520°C.lt isclinically indicated in cases of crown copings in theanterior and posterior area,and 3-unit FPDs in theanterior region. In-CeramAL Block(Vita) and inCorisAl (Sirona) are examples of aluminum oxide Blocksthat are available in the market."Yittrium stabilized zirconium oxide(Zr02Y- TZP)Zirconium dioxide ceramics have excellent mechani-cal properties. They have high flexural strength(750-> 1000 MPa)when compared to other dentalceramics.32, 37Yttrium-oxide is added to zirconiainorder to stabilizethetetragonal phase at roomtemperature, which asa result can prevent crackpropagationin the ceramic (Transformationstrengtheningj.v'v"Zirconium oxide ceramics are indicated for the fabri-cation of crowns, FPDs and individual implant abut-ments. 32The cores have high radiopacity which isvery useful in evaluation of marginal integrity .Zir-conia has a color similar to teeth but if translucency isneeded then other ceramic materials should beconsidered.Examples of Zirconium oxide blocks."- LavaFrame®(3M ESPE)- CerconSmart Ceramics® (DeduDent)- EverestZSundZH® (KaVo)- inCorisZR® (Sirona)- In-Ceram YZ® (Vita)

Systems availableforceramicblocks:32

themachining

CODS Journal Vol-5 lssue-Z, September 2013~-~---ofthe CONCLUSION:

- DCS Precident®( 1989)Procera®(1993)CEREC inLAB® (2001)Cercon® ( 2001)Everest® ( 2002)Lava ®(2002)CEREC 3D® (2003)TurboDent® (2005)E4D Dentist® (2008)

Marginal integrity ofCAD/CAM restorationsSoftware limitations as well as accuracy of millingdevices may affect the fit of CAD/CAMrestorations.7Most clinicians agreed that marginalgap should not be greater than 100 urn.It has been reported in the literature that restorationsproduced by CAD/CAM systems can have marginalgaps of 1O-50!lmwhich is considered to be within theacceptable range. 15,

Cementation of all-ceramic restorations:The protocol used for cementation of all-ceramicrestorations can be essential for success.9Clinicianscan effectively etch silica-based all-ceramics foradhesive bonding. The clinical lifespan ofsuchall-ceramic restorations significantly increased whenthis protocol is used. Zirconia and alumina-based allceramicmaterials cannot be etched and bonded.Survival of all-ceramic restorations:It is very important to consider the available survivaldata for all-ceramic materials when selecting atreatment strategy. This could be very challengingdue to the numerous all- ceramic systems availableand the definition of failure that varies in theliterature.It has been reported that survival rates ofall-ceramic restorations range from 88to 100% afterservice for 2-5years, and up to 97% after5-15years.7,20,Long-term survival was related to the fabricationmethod of all-ceramic restorations. Restorationsfabricated using the hot pressing technique had thehighest long-term survival. CAD/CAM ceramics hadthe next highest long-term survival. The lowestlong-term survival was for restorations fabricated bypowder condensation.'

42ALL CERAMIC SYSTEMS - AN OVERVIEW

Advances in ceramic science are focusing on thedevelopment of materials that exhibit eathetics andtranslucency with good strength and physical proper-ties. All-ceramic materials and systems will continueto improve. The dental practitioner should be aware ofthis development. The quest for the "Holy grail" ,the perfect all ceramic crown material continues.

•Lr2: )

Inceram ZirconiaVita Inceram

Inceram Zirconia

Machinable Ceramic

Inceram aluminaDicor

COOS Journal Vol-S Issue-2, September 2013REFERENCES:1. Philips' Science of Dental Materials, edl1.Saunders, 20032. Heffernan MJ, Aquilino SA, Diaz-Arnold AM, HaseltonDR, Stanford CM, Vargas MA. Relative translucency of sixallceramic systems. PartII: core and veneer materials. JProsthet Dent 2002;88(1): 10-5.3. FischerH, MarxR. Fracture toughness ofdental ceramics:comparison of bending and indentation method. DentMater2002; 18(1):12-9.4. Kalanta K. A crash course in ceramics. Available :http://www.bethesdamed.navy.mil!careers/postgraduate _denal_ school!comprehensive _dentistrylPearlslPearlsa2.htrn.Accessed on March 19, 20055. Griggs JA. Recentadvances in materialsfor all-ceramicrestorations. DentClin NorthAm 2007;51(3):713-27,viii.6. RaptisNV, MichalakisKX, HirayamaH. Opticalbehaviorofcurrent ceramic systems.Int JPeriodontics Restorative Dent 2006;26(1 ):31-41.7. Conrad HJ, SeongWJ, PesunlJ. Current ceramicmaterialsand systems with clinical recommendations: a systematicreview. JProsthetDent 2007;98(5):389-404.8. Sturdevant'sArt &Scienceof Operative Dentistry, ed4.Mosby20029. Donovan TE. Factorsessentialfor successful all-ceramicrestorations. JAm Dent Assoc2008;139 Suppl:14S-18S.10. Kansu G, Aydin AK. Evaluation of thebiocompatibili-tyofvarious dentalalloys: PartI-- Toxic potentials. EurJPros-thodontRestor Dent 1996;4(3): 129-36.11. Al-Hiyasat AS, Saunders WP, Smith GM. Three-bodywearassociatedwiththree ceramicsand enamel. JPros-thet Dent 1999;82(4):476-81.12. KellyJR. Dental ceramics: what is this stuffanyway?JAm Dent Assoc2008; 139Suppl:4S-7S.13. Craig's Restorative Dental Materials, ed12.Mosby,200614. Antonson SA, AnusaviceKJ. Contrast ratioofveneeringandcoreceramicsas a function of thickness.IntJProsthodont 2001;14(4):316-20.15. SulaimanF, Chai J,JamesonLM, Wozniak WT.Acomparison of themarginal fit ofln- Ceram,IPS Empress,and Proceracrowns.Int JProsthodont 1997;10(5):478-84.16. YeoIS, YangJH,Lee JB.In vitro marginal fit ofthreeall-ceramic crownsystems.J Prosthet Dent2003;90(5):459-64.17. HaseltonDR,Diaz-Arnold AM, Hillis SL. Clinicalassessment ofhigh-strength all- ceramiccrowns. JProsthetDent 2000;83(4):396-401.18. Chai J, Takahashi Y, SulaimanF,ChongK,LautenschlagerEP. Probabilityof fracture ofall-ceramic crowns .IntIProsthodont 2000; 13(5):420-4.

19. Xiao-ping L, Jie-mo T, Yun-long Z,LingW. Strengthand fracture toughness of MgO- modified glassinfi1tratedaluminaforCAD/CAM.Dent Mater2002; 18(3):216-20.20. Bindl A, Mormann WH.An up to 5-yearclinicalevaluation ofposteriorin-ceramCAD/CAM core crowns.Int JProsthodont2002;15(5):451-6.21. Guazzato M, AlbakryM,Swain MV,IronsideJ.Mechanical properties ofln-CeramAlumina andIn-CeramZirconia.IntJProsthodont2002; 15(4):339-46.22. Heffernan MJ, Aquilino SA, Diaz-Arnold AM,Haselton DR, Stanford CM, Vargas MA. Relativetranslucencyofsixall-ceramicsystems.PartI:corematerials.JProsthet Dent2002;88(1 ):4-9.23. Magne P, Belser U. Esthetic improvements and invitrotestingofln-CeramAlumina andSpinell ceramic.IntJProsthodont 1997;10(5):459-66.24. SundhA, Sjogren G. Acomparison of fracture strengthofyttrium-oxide-partially- stabilized zirconia ceramiccrownswith varying corethickness,shapes andveneerceramics. JOral RehabiI2004;31(7):682-8.25. Raigrodski AJ. Contemporarymaterials and technolo-gies for all-ceramicfixed partial dentures: a review oftheliterature. JProsthet Dent 2004;92(6):557-62.26. Fradeani M, RedemagniM. An 11-yearclinical evalua-tion ofleucite-reinforcedglass-ceramiccrowns:aretrospectivestudy.QuintessenceInt2002;33(7):503-10.27. Oh SC, DongJK,LuthyH, Scharer P. Strengthandmicrostructure oflPS Empress 2 glass-ceramic after differ-ent treatrnents.Int JProsthodont 2000;13(6):468-72.28. Esquivel-Upshaw IF, Chai J, Sansano S, ShonbergD.Resistance tostaining, flexural strength,and chemicalsolubilityofcore porcelainsfor all-ceramiccrowns.IntJProsthodont 2001; 14(3):284-8.29. Herrguth M, WichmannM, Reich S. The aesthetics ofall-ceramicveneered and monolithic CAD/CAM crowns.JOral Rehabil2005;32(10):747-52.30. StappertCF, AttW, GerdsT, StrubJR. Fracture resist-ance of differentpartial-coverage ceramic molarrestorations:An in vitro investigation. JAm Dent Assoc2006; 137(4):514-2231. Luthardt RG, Sandkuhl 0, Herold V, Walter MH.Accuracyof mechanicaldigitizingwith a CAD/CAMsystem forfixed restorations.Int JProsthodont2001; 14(2):146-51.32. Edward A. McLaren, DDS, MDC, and Lu Hyo, MDC.Inside Dentistry NovemberlDecember 2006, Volume 2,Issue 9

43

Systems availablefor themachiningceramicblocks:32- DCS Precident®( 1989)- Procera®(1993)- CEREC inLAB® (2001)- Cercon® (2001)- Everest® ( 2002)- Lava ®(2002)- CEREC 3D® (2003)- TurboDent® (2005)- E4D Dentist® (2008)

ofthe

Marginal integrity ofCAD/CAM restorationsSoftware limitations as well as accuracy of millingdevices may affect the fit of CAD/CAMrestorations.7Most clinicians agreed that marginalgap should not be greater than 100 urn.It has been reported in the literature that restorationsproduced by CAD/CAM systems can have marginalgaps of 10-50)lm which is considered to be within theacceptable range. 15,

Cementation of all-ceramic restorations:The protocol used for cementation of all-ceramicrestorations can be essential for success.9Clinicianscan effectively etch silica-based all-ceramics foradhesive bonding. The clinical lifespan ofsuchall-ceramic restorations significantly increased whenthis protocol is used. Zirconia and alumina-based allceramicmaterials cannot be etched and bonded.Survival of all-ceramic restorations:It is very important to consider the available survivaldata for all-ceramic materials when selecting atreatment strategy. This could be very challengingdue to the numerous all- ceramic systems availableand the definition of failure that varies in theliterature.It has been reported that survival rates ofall-ceramic restorations range from 88to 100% afterservice for 2-5years, and up to 97% after5-15years.7,2o,

Long-term survival was related to the fabricationmethod of all-ceramic restorations. Restorationsfabricated using the hot pressing technique had thehighest long-term survival. CAD/CAM ceramics hadthe next highest long-term survival. The lowestlong-term survival was for restorations fabricated bypowder condensation.'

Advances in ceramic science are focusing on thedevelopment of materials that exhibit eathetics andtranslucency with good strength and physical proper-ties. All-ceramic materials and systems will continueto improve. The dental practitioner should be aware ofthis development. The quest for the "Holy grail" ,the perfect all ceramic crown material continues.

•_I. :lC 3)

--_ -----Vita Inceram

Inceram Zirconia

Inceram Zirconia

DieorInceram alumina

42=

(005 Journal Vol-5 Issue-2, Septemb@f 2013RE-F-E~RE-NCES: ~--------~

19. Xiao-ping L, Jie-rno T, Yun-long Z,LingW. Strengthand fracture toughness of MgO- modified glassinfiltratedaluminaforCAD/CAM.Dent Mater2002;18(3):216-20.20. Bindl A, Mormann WH.An up to 5-yearclinicalevaluation ofposteriorin-ceramCAD/CAM core crowns.lnt IProsthodont2002; 15(5):451-6.21. Guazzato M, AlbakryM,Swain MV,IronsideJ.Mechanical properties ofln-CeramAlumina andln-CerarnZirconia.lntIProsthodont2002; 15(4):339-46.22. Heffernan MJ, Aquilino SA, Diaz-Arnold AM,Haselton DR, Stanford CM, Vargas MA. Relativetranslucencyofsixall-ceramicsystems.PartI:corematerials.IProsthet Dent2002;88(1):4-9.23. Magne P, Belser U. Esthetic improvements and invitro .testingofln-CeramAlumina andSpinell ceramic.lntIProsthodont 1997;10(5):459-66.24. Sundh A, Sjogren G. Acomparison of fracture strengthofyttrium-oxide-partially- stabilized zirconia ceramiccrownswith varying corethickness,shapes andveneerceramics. JOral RehabiI2004;31(7):682-8.25. Raigrodski AJ. Contemporarymaterials and technolo-gies for all-ceramicfixed partial dentures: a review oftheliterature. IProsthet Dent 2004;92(6):557-62.26. Fradeani M, RedemagniM. An l l-yearclinical evalua-tion ofleucite-reinforcedglass-ceramiccrowns:aretrospectivestudy.Quintessencelnt2002;33(7):503-10.27. Oh SC, DongJK,LuthyH, Scharer P. Strength andmicrostructure oflPS Empress 2 glass-ceramic after differ-ent treatments.lnt IProsthodont 2000; 13(6):468-72.28. Esquivel-Upshaw IF, Chai J, Sansano S, Shonbergl),Resistance tostaining, flexural strength,and chemicalsolubilityofcore porcelainsfor all-ceramiccrowns.IntlProsthodont 2001; 14(3):284-8.29. Herrguth M, WichmannM, Reich S. The aesthetics ofall-ceramicveneered and monolithic CAD/CAM crowns.JOral RehabiI2005;32(10):747-52.30. StappertCF, AttW, GerdsT, StrubJR. Fracture resist-ance of differentpartial-coverage ceramic molarrestorations:An in vitro investigation. JAm Dent Assoc2006;137(4):514-2231. Luthardt RG, Sandkuhl 0, Herold V, Walter MH.Accuracyof mechanicaldigitizingwith a CAD/CAMsystem forfixed restorations.lnt IProsthodont2001; 14(2):146-51.32. Edward A. McLaren, DDS, MDC, and Lu Hyo, MDC.Inside Dentistry November/December 2006, Volume 2,Issue 9

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