Enamel Acid Etching: A ReviewCE

1

Compendium • January 2007;28(1):662-669662

Aclinician’s ability to bond a res-toration to enamel has influ-enced changes in prosthetic

and cavitary preparations, restorativeapproaches for esthetic corrections,bonding techniques for orthodonticdevices, and the treatment of caries.1-3

Bonding to dentin has been theobjective of several studies over the last2 decades.1-3 In the beginning, the re-search was to find an adhesive systemthat could interact with efficacy indentin, and more recently, the researchhas focused on simplifying the sys-tems.1-3 Because a major part of bond-ing procedures requires simultaneouslytreating enamel and dentin, it is impor-tant to understand that the foundationof enamel bonding strongly influencedthe development of dental adhesivesystems. This article will review somerelevant aspects of bonding to enamelusing the total-etch technique.

Tooth EnamelEnamel is the hardest tissue in the

human body. Its mineral portion is

approximately 96% of its weight,4 therest is organic components and water.The mineral elements include hydrox-yapatite crystals, approximately 0.03µm to 0.2 µm, surrounded by a thinfilm of firmly bound water.4 In pris-matic enamel, which constitutes themain fraction, the crystals are denselygrouped and arranged in 3 directions.With this arrangement, lengthy prisms(a diameter of about 5 µm) from thedentoenamel junction to near the out-ermost surface of enamel are formed(Figure 1). The prisms maintain theirintegrity and support because of theirtransverse arrangement, irregular mor-phology, and overlapping patterns. Atthe moment of enamel instrumenta-tion, the prisms are exposed in severalplanes according to their direction(Figure 2).

In intact enamel, water comprisesup to 4% of the weight (11% in vol-ume),4 either in the hydration layer ofenamel around each crystal of apatiteor in the pores between prisms.4 Aftertooth eruption, there is an enamel

Guilherme Carpena Lopes, DDS,MS, PhDAssistant ProfessorDepartment of Operative DentistryUniversidade Federal de Santa CatarinaSchool of DentistryFlorianópolis, Brazil

Daniela Greenhalgh Thys, DDS, MSResearch AssistantDepartment of Orthodontics Universidade Federal de Santa CatarinaSchool of Dentistry Florianópolis, Brazil

Pricila Klauss, MSResearch AssistantMaterials EngineerUniversidade Federal de Santa CatarinaFlorianópolis, Brazil

Gustavo Mussi, DDSClinical InstructorDepartment of Operative DentistryUniversidade Federal de Santa CatarinaSchool of DentistryFlorianópolis, Brazil

Nicolas Widmer, DDSClinical InstructorDepartment of Operative DentistryUniversidade Federal de Santa CatarinaSchool of DentistryFlorianópolis, Brazil

Abstract

Bonding to enamel has over 50 years of history. Efforts have been made to develop orintroduce a simplified alternative, but enamel acid etching remains the most effectiveprocedure for stable enamel bonding. Although acid etching is considered the mostpopular procedure in dentistry, there are characteristics that deserve special attentionbecause of how crucial they can be in many clinical situations. This article reviewssome of these aspects of enamel bonding using the acid-etching technique.

• discuss aspects of enamel bondingwith the acid-etching technique.

• explain the characteristics of hard tissue.

• describe the current knowledge toovercome saliva contamination dur-ing bonding to enamel.

Learning ObjectivesAfter reading this article, the reader should be able to:

maturation process that makes it more resistant to dem-ineralization. This maturation consists of mineral depo-sition from oral fluids in interprism spaces that were pre-viously filled with water.5 Because all hard tissue is incontinuous ionic change with the environment, it couldbe expected that human enamel will respond to acid con-ditioning differently, depending on age and factors relat-ed mainly to saliva and diet. Further research should be

carried out to verify whether enamel changes over timemight have clinical relevance when acid etched.

Acid-Etching TechniqueDuring the 32nd Annual Meeting of the Interna-

tional Association for Dental Research in 1954,6

Buonocore suggested that using 85% phosphoric acidsolution resulted in an adhesion of acrylic resin to enam-el that lasted 1070 hours to debond when stored inwater.7 Similar to other conceptual and technologic inno-vations, this procedure was introduced in dentistry aheadof its time and only 10 years later the bonding mecha-nism was described,8 Bis-GMA based adhesive systemsand com-posite resins were developed,9 and the first clin-ical application, as a pit-and-fissure sealant, was reportedin the literature.10

Chemical treatment by acid etching enhances thetopography of enamel, changing it from a low-reactivesurface (Figure 3) to a surface that is more susceptible toadhesion (Figure 4 and 5). The demineralization is selec-tive because of the morphological disposition of theprisms. The difference of angulation of the prism crystalscauses the acid to have higher demineralization potentialat certain microregions. After cavitary instrumentation,

Compendium • January 2007;28(1):662-669 663

Figure 1—Scanning electron microscope (SEM) micrograph showing a com-posite-enamel interface. Note the orientation of the enamel prisms. Final mag-nification 150x.

Figure 2—SEM micrograph showing fractured enamel. Final magnification2000x.

Figure 3—SEM micrograph showing the smooth enamel surface. Final mag-nification 1000x.

Figure 4—SEM micrograph showing the enamel etching pattern type I after a32% phosphoric acidc etch applied for 15 seconds. Final magnification 4000x.

Figure 5—SEM micrograph showing the enamel etching pattern type II after a32% phosphoric acidc etch applied for 15 seconds. Final magnification 4000x.

depending on the angulation of the prisms, demineraliza-tion can be greater at the prism head (Figure 4) or at theperiphery (Figure 5). These features are respectivelyknown as type I and type II acid-etching patterns. Thisfeature is important in understanding the fundamentalsof adhesion though it is not clinically relevant.

Acid etching removes appoximately 10 µm of enamelsurface and creates a morphologically porous layer (5 µmto 50 µm deep).11 The surface free energy is doubled,12 andas a result, the low-viscosity fluid resin contacts the surfaceand is attracted to the interior of these microporosities cre-ated by conditioning through capillarity (capillary attrac-tion).13 Therefore, resin tags are formed into microporosi-ties of conditioned enamel (Figure 6) that after adequatepolymerization, provide a resistant, long-lasting bond bymicromechanical interlocking with this tissue.8,14,15

Bonding to Enamel with Hydrophilic PrimersIn most clinical situations, the restoration is bonded to

enamel and dentin. To interact with this intrinsically moisttissue, an adhesive system was needed that could diffuseunder this condition. The introduction of hydrophilicprimers has allowed for adequate bonding to dentin.16 Themodern adhesive systems that use the total-etch techniquecombine the functions of primer and adhesive in 1 bottle,intended for application on moist dentin surfaces.17

For this reason, most adhesive systems that use thetotal-etch technique have in their formulation low-viscosi-ty hydrophilic monomers diluted in organic solvents witha high potential of volatilization (acetone, water, or a mix-ture of both)18,19 to displace the moisture of conditioneddentin. The primer components (eg, hydroxyethyl metha-crylate [HEMA], bis-phenyl dimethacrylate [BPDM], 4-methacryloxyethyl trimellitate anhydride [4-META]) arecalled bipolar because they have 2 functional groups(hydrophilic and hydrophobic). The hydrophilic end hasthe ability to interact even under moist conditions, and thehydrophobic end has chemical affinity with the methacry-

late group of the bonding resin matrix (also called hydro-phobic adhesive) or with the composite resin.20

Regarding bonding to enamel, the rapid volatiliza-tion of the solvent allows for the complete interdiffusionof the adhesive system through the extension of the con-ditioning,21 with a more intimate contact of the compos-ite resin to enamel, which results in high bond strengthsto this tissue18 and adequate marginal sealing,22 even inmoist conditions.19,22

It is not an easy procedure to keep dentin moist anddry only the enamel. It is possible that acetone-andethanol-based solvents, included in mostly 1-bottle adhe-sives, remove residual moisture and promote a superiorflow of the restorative material to acid-etched enamel.19,21,23

Hydrophilic primers become essential when enamel ismoist and work very well when enamel is dry.18,24 However,because the presence of residual moisture and organic sol-vents interferes negatively in the complete polymerizationof monomers, it is important after the application to prop-erly dry with air spray of a triple syringe. Also, it has beentheorized that the stability of bonding to enamel is alsocompromised with time because of the formation of adhe-sive layers similar to semipermeable membranes.25

Isolating the operatory field is important to achievea contaminant-free working area. There is a lack of clin-ical evidence that says that bonding procedures with theuse of rubber dam isolation results in better clinical per-formance than relative isolation, but it has been theauthors’ experience that rubber dam isolation should bepreferred to relative isolation because of the interferenceof patients’ breath moisture. A recent study simulatingthe oral environment compared the bond strength of 2bonding agents (hydrophilic and hydrophobic) to enam-el under temperature and air humidity conditions of theoral cavity (35˚C, 90% to 95% of relative humidity).26 Thesimulated contamination with high levels of air moisturedid not compromise the bonding to enamel, whether itwas accomplished with hydrophilic primer or ahydrophobic adhesive.26

Viscosity of the Adhesive SystemSome adhesives have inorganic filler particles to

increase their film thickness and cohesive strength (fillerloading ranges between 8.5% and 25% weight, dependingon the brand). It seems that an intermediary flexible zoneallows for a better transmission of the interfacial stressesinduced by masticatory forces, differences in modulus ofelasticity, water sorption presented by composite resins,and polymerization shrinkage.27 Filled sealants and flow-able composite resins can bond to conditioned enamelwithout an intermediary adhesive agent.28 However, it hasbeen reported that highly viscous sealants have greater dif-

Compendium • January 2007;28(1):662-669664

Figure 6—SEM micrograph showing the resin-enamel interface after a labo-ratorial demineralization in hydrochloride 6N for 30 seconds. The low-vis-cosity fluid resin wets this high-energy surface by capillary attraction into themicroporosities created by the etching. After polymerization, the tags formedby this extension of resin into the microporosities form a strong micromechan-ical interlocking with the enamel. Final magnification 1500x.

a Dentsply, York, Pa; www.dentsply.comb 3M ESPE, St. Paul, Minn; www.3m.com/espe c Bisco Dental Products, Schaumburg, Ill; www.bisco.comd Coltène/Whaledent Inc., Cuyahoga Falls, Ohio;www.coltenewhaledent.com

ficulty penetrating enamel as much as the conditioningdepth.29 Studies have demonstrated that filled adhesive sys-tems present lower bond strengths to enamel.18,19,30 Thisseems to be related to the high viscosity of these adhe-sives,18,30 which makes it difficult to penetrate in interpris-matic areas as deeply as unfilled adhesives.31 Adhesive sys-tems containing nanofillers have been developed (Prime &Bond NTa, Adper Single Bond 2b). The nanofillers aredesigned to reinforce resin tags and the adhesive layer,32 andit seems that the low molecular weight does not compro-mise the interdiffusion in conditioned enamel.31

Concentration of the ConditionerWhen the acid-etching technique was extended to

dentin (total-etch technique), the manufacturers includedlow concentration acid conditioners in adhesive systemspossibly because of lack of information, knowledge, ormarketing strategy, which supposedly would cause lessaggression to pulpal tissue. In the early 1990s, it was com-mon to find etchants such as 10% phosphoric acid, 10%maleic acid, 10% citric acid, 2.5% oxalic acid, and 2.5%nitric acid. Some of these acids do not result in a dull,frosty-white appearance typical of conditioned enamel,33

but a few studies show that this doesn’t negatively affectimmediate adhesive bonding to instrumented enamel.33,34

However, other research shows a significant decrease of thebond strengths.35 Because of the lack of long-term clinicalevidence on the durability of bonding to enamel usingthese less aggressive conditioners, the previous use of 32%to 40% phosphoric acid conditioner is still the best optionto achieve predictable bonding to enamel.36 Figures 4 and7 compare the 32% phosphoric acidc etch pattern (Figure4) with the 15% phosphoric acidd etch pattern (Figure 7)applied with the same 15-second etching time.

Enamel Acid-Etching TimeWhen enamel etching was introduced in 1955, the

recommended time was 30 seconds for 85% phosphoricacid.7 Then, at the time of its first clinical use (the 1960s),it was extended to 60 seconds.8,10 In the 1980s, it wasreduced to a 30-second application and has remained

today.37-39 Some authors recommend reducing the etchingtime to 15 seconds when a 32% to 40% phosphoric acid isused.40 Most of the manufacturers of adhesive systemshave recommended 15 seconds because it is saves timewithout compromising the adhesive performance.

Reducing times has been suggested because it pre-sents 3 advantages. First, because acid conditioning caus-es superficial tissue loss, it is desirable that minimal toothstructure be dissolved; therefore, minimal acid-applica-tion time should be used.41 The difference between 15-sec-ond and 30-second application time of phosphoric acid onenamel dissolution is very small. The chemical reaction ofthe conditioning occurs quickly and, as mineral compo-nents are lost, the acid potential decreases by buffering.Second, when one is dealing with cavities involving enam-el and dentin, the expansion of the etching technique todentin (also called total-etch technique) is controversialbecause the time should not be longer than 15 seconds indentin, but this is the minimum time required to achievea suitable bonding to enamel.3 As a result, it has been sug-gested that the conditioning time be reduced to 15 sec-onds, which is considered adequate for creating a reten-tive enamel surface with no difference in the enamel etch-ing pattern42 or decrease of the bond strengths to instru-mented enamel.39-41 In vitro studies have demonstratedthat a 15-second conditioning time is also adequate fororthodontic adhesive procedures.43,44 The third advantageis saving chair time.

A 15-second etching time is sufficient when using32% to 40% phosphoric acid to achieve a proper bondstrength when it is applied to instrumented enamel sur-faces or when a cavitary preparation has been accom-plished. However, in the presence of intact enamel, a dif-ferent approach may be preferred, which will be dis-cussed later in the article.

Type of EnamelAn important clinical factor in bonding to enamel is

the tissue to be bonded. The surface instrumentation, thepatient’s age, and environmental factors can lead to subtledifferences in enamel characteristics and influence theability of an acid conditioner to properly demineralize.Several materials have been analyzed in studies on instru-mented enamel surfaces.45 However, it should be taken intoaccount that restorations are commonly extended beyondthe margins of the cavity preparation. Also, a number ofconservative restorative treatments (eg, diasthema closure,tooth recontouring, restoration of fractured teeth, pit-and-fissure sealing, and bonding of orthodontic devices) are allperformed without tissue instrumentation. Because ofhigher inorganic content, the intact enamel surface pres-ents some unique features. First, young patients’ teeth havean aprismatic layer of approximately 30 µm that covers theentire crown.4 This layer is lost with time; however, thehard tissue of the teeth becomes more mineralized whenexposed to the oral environment in patients with equilibri-

Compendium • January 2007;28(1):662-669 665

Figure 7—SEM micrograph showing the enamel etching pattern after a 15%phosphoric acidd etch applied for 15 seconds. Final magnification 3000x.

um in the demineralization process. This causes the sur-face layer of enamel to present hypermineralization fea-tures when compared with the innermost enamel.46 These2 differences can influence the feature of the etching pat-tern and result in less homogeneous etching patterns,40

compromising the quality of bonding. Figure 8 shows cer-vical enamel before and after etching with 35% phosphor-ic acidb for 15 seconds.

The instrumentation of the tissue by a cavity prepa-ration, microetching, or placement of a bevel can changethe response of the tissue to the acid etching. Severalstudies report that the removal of the surface layer ofenamel enhances the etching result, and consequently,the bond strength.47,48 A recent study showed that opti-mal bond strength to aprismatic enamel is achieved byincreasing the time of acid etching suggested by the man-ufacturer from 15 seconds to 30 seconds (with 35%phosphoric acidb).49 It is the authors’ belief that thechemical and morphological characteristics of intactenamel would influence this difference. Further studiesmust be performed to identify the response of enamelwith different mineral features when acid etched.

Cleaning EnamelA relevant factor in bonding to enamel is the clean-

ing of the substrate to be bonded. Some advantages clini-cians attribute to acid etching are bactericidal action andcleansing potential. Phosphoric acid has an antibacterialeffect.50 To potentiate this effect, some acid conditionerswith antibacterial agents (eg, 3% cetypyridinium chlo-ridec) have been made available. Without questioningthe confidence of this fact, this is not the objective of theacid etching when taking into consideration exclusivelybonding to enamel. For a proper etching, the surface ofenamel must be clean. This cleaning must be accom-plished before etching using cotton pellets soaked inagents such as chlorhexidine gluconate and benzalkoni-um chloride. Alternatively, the air/water spray of a triplesyringe is an option in easy access locations. When the

clinician prefers to perform the cleaning after the acidetching, chlorhexidine gluconate (Consepsis Scrube) andbenzalkonium chloride (Tubulicidf) solutions should bepreferred to disinfection pastes, because they do notinfluence the marginal seal.51 Floss and gauze are recom-mended for proximal surfaces. Prophylactic pastes andRobinson brushes are useful on noninstrumented enam-el surfaces. A suitable alternative is a bicarbonate jet.

Bonding to Contaminated EnamelIt has been established that a main reason for debond-

ing is the contamination of the conditioned enamel surfacebefore the application of the adhesive.37 Thus, it is impor-tant to control the oral fluids throughout the adhesive pro-cedures to avoid possible contamination of the operatoryfield. Moisture or contamination with oral fluids impairsbonding of resins to enamel52-62 because the etched enamelsurface is chemically and physically modified.37,56,63

Because rubber dam isolation is impratical in someinstances, there is a risk of surface contamination fromblood or saliva and difficulty keeping the surfaces com-pletely dry. This difficulty can be observed in the surgicalbonding of traction devices to unerupted teeth,64 or seal-ing of occlusal surfaces in erupting teeth. These situa-tions are critical because bonding failure requires a newsurgical intervention or allows for early marginalmicroleakage, respectively.

To achieve suitable clinical results, most of the adhesivesystems require a contamination-free surface.65-67 There arereports that the bond strength is reduced to 50% when theadhesive is applied directly to contaminated enamel com-pared with uncontaminated surfaces.60,61,68 To overcome con-tamination, some manufacturers have intoduced hydro-philic adhesives, suggesting their potential to successfullybond to a contaminated enamel surface. The difficulty ofbonding to contaminated enamel can be minimized if theadhesive is hydrophilic and has the potential to polymerizecompletely, even in the presence of moisture.18,19,23,69,70 A fewstudies have shown that adhesive agents containinghydrophilic monomers can overcome the effect of contami-nants on bond strength to contaminated enamel.68,71,72

Compendium • January 2007;28(1):662-669666

Figure 8—SEM micrograph showing the cervical enamel before (A) and after (B) etched with 35% phosphoric acidb for 15 seconds. Note the presence ofhypermineralized enamel not removed. (A) Final magnification 2000x. (B) Final magnification 3000x.

e Ultradent Products Inc, South Jordan, Utah; www.ultradent.comf Global Dental Products, North Bellmore, NY; www.gdpdental.com

Durability of Bonding to EnamelBonding to enamel is considered a long-lasting pro-

cedure.3,16 When the durability of the adhesion is simu-lated in the laboratory under extensive thermocycling(30,000 cycles), the acid-etching technique in enamelallows for the maintenance of a stable bond strength.Theoretically, an extensive thermocycling (30,000cycles) is comparable (with limitations) to 3 years ofclinical function.73 However, this stability depends on theadhesive system used.74 Some systems could be less sta-ble because of excessive concentration of solvents, andthe presence of hydrophilic monomers that present highwettability potential. Although these monomers allowfor immediate high bond strengths, they are more sus-ceptible to hydrolytic degradation with time when com-pared with hydrophobic monomers. Another significantvariable is the mode of application. The active applica-tion (eg, scrubbing the primer on conditioned enamelwith a disposable applicator) has a negative effect on thebond strength, mainly regarding durability.75

ConclusionBonding to enamel is a simple procedure in the dental

practice; however, some details can influence its durability.High enamel bond strengths are achieved with previousacid etching. This bonding is sufficiently high to compen-sate for the polymerization shrinkage of composite resinsand an effective marginal seal. This is paramount to obtaina suitable clinical performance of composite resin restora-tions, preventing marginal leakage, and allowing for ade-quate retention. Knowing the factors that can influencebonding to enamel is essential when selecting the mostappropriate materials and techniques for each situation.For exampe, it was recently observed that when enamelprisms are exposed perpendicularly, the bond strength isreduced to 50% compared with the parallel exposure of theprisms.76 Therefore, extreme caution is recommended inthe gingival margins of Class II restorations, with thesmoothing of enamel with manual instruments, rubberdam isolation, application of etchant beyond all margins,77

and insertion and polymerization of composite resin insmall increments.78 Taking these details into consideration,more predictable restorations will be obtained.

AcknowledgmentThe first author would like to thank Dr Jorge

Perdigão and Ms Manuela Lopes for the training on scan-ning electron microscopy at the University of NorthCarolina at Chapel Hill from August to September, 1998,and for helping every year to train the Master of Sciencestudents at Universidade Federal de Santa Catarina.

References1. Perdigão J, Lopes M. Dentin bonding—state of the art 1999.

Compend Contin Educ Dent. 1999;20:1151-1162.2. Perdigão J, Lopes M. Dentin bonding—questions for the new

millennium. J Adhes Dent. 1999;1:191-209.

3. Lopes GC, Baratieri LN, de Andrada MA, et al. Dental adhesion:present state of the art and future perspectives. Quintessence Int.2002;33:213-224.

4. Nanci A. Ten Cate’s Oral Histology: Development, Structure andFunction. 2nd edition. St Louis, Mo: Mosby; 1985.

5. Thylstrup A, Fejerskov O. Textbook of Clinical Cariology.Copenhagen: Boston, Mass: Blackwell; 1986.

6. Buonocore MG, Wileman WR, Brudevold F. A simple methodof increasing the adhesion of acrylic filling materials to enam-el surfaces [abstract]. J Dent Res. 1954;33:694. Abstract 4.

7. Buonocore MG. A simple method of increasing the adhesionof acrylic filling materials to enamel surfaces. J Dent Res. 1955;34:849-853.

8. Gwinnett AJ, Buonocore MG. Adhesives and caries preven-tion; a preliminary report. Br Dent J. 1965;119:77-81.

9. Bowen RL. Dental filling material comprising vinyl-silane-treated fused silica and a binder consisting of the reaction prod-uct of bisphenol and glycidyl methacrylate. US patent 3, 006:22-67, 1962.

10. Cueto EI, Bonocore MG. Sealing of pits and fissures with anadhesive resin: its use in caries prevention. J Am Dent Assoc.1967;73:121-128.

11. Gwinnett AJ. Histologic changes in human enamel followingtreatment with acidic adhesive conditioning agents. Arch OralBiol. 1971;16:731-738.

12. Jordan RE, Suzuki M, Davidson DF. Clinical evaluation of auniversal dentin bonding resin: preserving dentition throughnew materials. J Am Dent Assoc. 1989;124:71-76.

13. Van Meerbeek B, Perdigão J, Lambrechts P, et al. Enameldentin adhesion. In: Schwartz RS, Summitt JB, Robbins JW,eds. Fundamentals of Operative Dentistry. A ContemporaryApproach. Chicago, Ill: Quintessence; 1996:141-186.

14. Buonocore MG, Matsui A, Gwinnett AJ. Penetration of resindental materials into enamel surfaces with reference to bond-ing. Arch Oral Biol. 1968;13:61-70.

15. Gwinnett AJ, Matsui A. A study of enamel adhesives. Thephysical relationship between enamel and adhesive. Arch OralBiol. 1967;12:1615-1620.

16. Swift EJ, Perdigão J, Heymann HO. Bonding to enamel anddentin: a brief history of the art. Quintessence Int. 1995;26:95-110.

17. Kanca J 3rd. Resin bonding to wet substrate. 1. Bonding todentin. Quintessence Int. 1992;23:39-41.

18. Swift EJ Jr, Perdigão J, Heymann HO. Enamel bond strengthsof “one-bottle” adhesives. Pediatr Dent. 1998;20:259-262.

19. Swift EJ Jr, Perdigão J, Heymann HO, et al. Shear bond strengthsof one-bottle adhesives to moist enamel. J Esthet Dent.1999;11:103-107.

20. Jacobsen T, Söderholm KJ. Some effects of water on dentinbonding. Dent Mater. 1995;11:132-136.

21. Finger WJ, Fritz U. Laboratory evaluation of one-componentenamel/dentin bonding agents. Am J Dent. 1996;9:206-210.

22. Zanette AC, Lopes GC, Oliveira MT. Microleakage of Class IIcomposite restorations: effect of residual dentin moisture. JDent Res. 2005;84 (CD ROM). Abstract 3001.

23. el-Kalla IH, Garcia-Godoy F. Saliva contamination and bondstrength of single-bottle adhesives to enamel and dentin. Am JDent. 1997;10:83-87.

24. Jain P, Stewart GP. Effect of dentin primer on shear bondstrength of composite resin to moist and dry enamel. Oper Dent.2000;25:51-58.

25. De Munck J, Van Landuyt K, Peumans M, et al. A criticalreview of the durability of adhesion to tooth tissue: methodsand results. J Dent Res. 2005;84:118-132.

26. Mocelin G, Lopes GC, Thys DG, et al. Effect of air humidityon brackets bond strength to enamel. J Dent Res. 2005;84 (CDROM). Abstract 1675.

27. Van Meerbeek B, Dhem A, Goret-Nicaise M, et al. ComparativeSEM and TEM examination of ultrastructure of the resin-dentin interdiffusion zone. J Dent Res. 1993;72:495-501.

28. Frankenberger R, Lopes M, Perdigao J, et al. The use of flowablecomposites as filled adhesives. Dent Mater. 2002;18:227-238.

Compendium • January 2007;28(1):662-669 667

29. Irinoda Y, Matsumura Y, Kito H, et al. Effect of sealant viscos-ity on the penetration of resin into etched human enamel.Oper Dent. 2000;25:274-282.

30. Devaney MW, Swift EJ Jr, Perdigão J. Shear bond strength of one-bottle adhesives to enamel. J Dent Res. 1999;78:154. Abstract 386.

31. Perdigão J, Baratieri LN, Lopes M. Laboratory evaluation andclinical application of a new one-bottle adhesive. J Esthet Dent.1999;11:23-35.

32. Tay FR, Moulding KM, Pashley DH. Distribution of nanofillersfrom a simplified-step adhesive in acid-conditioned dentin. JAdhes Dent. 1999;1:103-117.

33. Uno S, Finger WJ. Effects of acid conditioners on dentin dem-ineralization and dimension of hybrid layers. J Dent. 1996;24:211-216.

34. Perdigão J, Lopes L, Lambrechts P, et al. Effect of self-etchingprimer on enamel shear bond strengths and SEM morphology.Am J Dent. 1997;10:141-146.

35. Swift EJ Jr, Cloe BC. Shear bond strengths of new enameletchants. Am J Dent. 1993;6:162-164.

36. Rosa BT, Perdigão J. Bond strengths of nonrinsing adhesives.Quintessence Int. 2000;31:353-358.

37. Silverstone LM. State of the art on sealant research and prior-ities for further research. J Dent Educ. 1984;48:107-118.

38. Mardaga WJ, Shannon IL. Decreasing the depth of etch fordirect bonding in orthodontics. J Clin Orthod. 1982;16:130-132.

39. Gilpatrick RO, Ross JA, Simonsen RJ. Resin-to-enamel bondstrength with various etching times. Quintessence Int. 1991;22:47-49.

40. Barkmeier WW, Shaffer SE, Gwinnett AJ. Effects of 15 vs 60second enamel acid conditioning on adhesion and morpholo-gy. Oper Dent. 1986;11:111-116.

41. Beech DR, Jalaly T. Bonding of polymers to enamel: influenceof deposits formed during etching, etching time and period ofwater immersion. J Dent Res. 1980;59:1156-1162.

42. Brännström M, Nordenvall KJ. The effect of acid etching onenamel, dentin, and the inner surface of the resin restoration: ascanning electron microscopic investigation. J Dent Res. 1977;56:917-923.

43. Jacobs G, Kuftinec MM, Showfety KJ, et al. Bonding character-istics of impacted versus erupted permanent teeth. Am J Orthod.1986;89:242-245.

44. Wang WN, Lu TC. Bond strength with various etching timeson young permanent teeth. Am J Orthod Dentofacial Orthop.1991;100:72-79.

45. Chigira H, Yukitani W, Hasegawa T, et al. Self-etching dentinprimers containing phenyl-P. J Dent Res. 1994;73:1088-1095.

46. Kanemura N, Sano H, Tagami J. Tensile bond strength to andSEM evaluation of ground and intact enamel surfaces. J Dent.1999;27:523-530.

47. Ripa LW, Gwinnett AJ, Buonocore MG. The “prismless” outerlayer of deciduous and permanent enamel. Arch Oral Biol. 1966;11:41-48.

48. Whittaker DK. Structural variations in the surface zone ofhuman tooth enamel observed by scanning electronmicroscopy. Arch Oral Biol. 1982;27:383-392.

49. Gondo R, Lopes GC, Monteiro JR S, et al. Microtensile bondstrength of resin to enamel: effect of enamel surface preparationand acid etching time. J Dent Res. 2003;82:190. Abstract 1424.

50. Owen BM, Badu JP. Comparison of antimicrobial effects of cav-ity pre-treatment agents. J Dent Res. 2003;82 (CD ROM). Ab-stract 1636.

51. Owens BM, Lim DY, Arheart KL. The effect of antimicrobialpre-treatments on the performance of resin composite restora-tions. Oper Dent. 2003;28:716-722.

52. Buonocore MG. Caries prevention in pits and fissures sealedwith an adhesive resin polymerized by ultraviolet light: a two-year study of a single adhesive application. J Am Dent Assoc.1971;82:1090-1093.

53. Oppenheim MN, Ward GT. The restoration of fractured inci-sors using a pit and fissure sealant resin composite material. JAm Dent Assoc. 1974;89:365-368.

54. Buonocore MG. Sealants: Questions and Answers. In: Thomas

CC, ed. The Use of Adhesives in Dentistry. Chicago, Ill: Mosby;1975:180-197.

55. Reynolds IR. A review of direct orthodontic bonding. Br JOrthod. 1975;2:171-178.

56. Hormati AA, Fuller JL, Denehy GE. Effects of contaminationand mechanical disturbance on the quality of acid-etchedenamel. J Am Dent Assoc. 1980;100:34-38.

57. Thomson JL, Main C, Gillespie FC, et al. The effect of salivarycontamination on fissure sealant-enamel bond strength. J OralRehabil. 1981;8:10-18.

58. Yamamoto T. The effect of contamination on the adhesion ofcomposite resin to etched surface. Jpn J Conserv Dent. 1981;24:93-114.

59. Barghi N, Knight GT, Berry TG. Comparing two methods ofmoisture control in bonding to enamel: a clinical study. OperDent. 1991;16:130-135.

60. Xie J, Powers JM, Mcguckin RS. In vitro bond strength of twoadhesives to enamel and dentin under normal and contami-nated conditions. Dent Mater. 1993;9:295-299.

61. Benderli Y, Gokce K, Buyukgokcesu S. In vitro shear bondstrength of adhesive to normal and fluoridated enamel undervarious contaminated conditions. Quintessence Int. 1999;30:570-575.

62. Rosa BT, Heymann HO, Swift EJ Jr, et al. Shear bond strengthsof one-bottle adhesives to oil-contaminated enamel. J EsthetDent. 2000;12:139-145.

63. Gwinnett AJ. The scientific basis of the sealant procedure. JPrev Dent. 1976;3:15-28.

64. Itoh T, Fukushima T, Inoue Y, et al. Effect of water, saliva andblood contamination on bonding of metal brackets with a 4-META/MMA/TBB resin to etched enamel. Am J Dent. 1999;12:299-304.

65. Brandt S, Servoss JM, Persily KB. Atropine sulphate—an effec-tive antisialogogue. J Clin Orthod. 1981;15:629-634.

66. Powers JM, Finger WJ, Xie J. Bonding of composite resin tocontaminated human enamel and dentin. J Prosthodont. 1995;4:28-32.

67. Woronko GA, St Germain HA Jr, Meiers J. Effect of dentinprimer on the shear bond strength between composite resinand enamel. Oper Dent. 1996;21:116-121.

68. Thys DG, Locks A, Lopes GC, et al. Effect of blood contamina-tion on bonding of metal brackets to enamel with hydrophobicand hydrophilic systems. J Dent Res. 2002;81:A-328. Abstract2618.

69. Fritz UB, Finger WJ, Stean H. Salivary contamination duringbonding procedures with a one-bottle adhesive system.Quintessence Int. 1998;29:567-572.

70. Grandhi RK, Combe EC, Speidel TM. Shear bond strength ofstainless steel orthodontic brackets with a moisture-insensitiveprimer. Am J Orthod Dentofacial Orthop. 2001;119:252-255.

71. Feigal RJ, Hitt J, Splieth C. Retaining sealant on salivary con-taminated enamel. J Am Dent Assoc. 1993;124:88-97.

72. Hitt JC, Feigal RJ. Use of a bonding agent to reduce sealant sen-sitivity to moisture contamination: an in vitro study. PediatrDent. 1992;14:41-46.

73. Gale MS, Darvell BW. Thermal cycling procedures for labora-tory testing of dental restorations. J Dent. 1999;27:89-99.

74. Miyazaki M, Sato M, Onose H. Durability of enamel bond strengthof simplified bonding systems. Oper Dent. 2000;25:75-80.

75. Frankenberger R, Kramer N, Petschelt A. Long-term effect ofdentin primers on enamel bond strength and marginal adapta-tion. Oper Dent. 2000;25:11-19.

76. Carvalho RM, Santiago SL, Fernandes CA, et al. Effects ofprism orientation on tensile strength of enamel. J Adhes Dent.2000;2:251-257.

77. Lopes GC, Vieira LC, Araújo E: Direct composite resin restora-tions: a review of some clinical procedures to achieve pre-dictable results in posterior teeth. J Esthet Restor Dent. 2004;16:19-31.

78. Nikolaenko SA, Lohbauer U, Roggendorf M, et al. Influence ofc-factor and layering technique on microtensile bond strengthto dentin. Dent Mater. 2004;20:579-585.

Compendium • January 2007;28(1):662-669668

Compendium • January 2007;28(1):662-669 669

1. Enamel’s mineral portion is approximately:a. 96% of its weight.b. 16% of its weight.c. 4% of its weight.d. 75% of its weight.

2. Chemical treatment by acid etching does whichof the following, changing it from a low-reac-tive surface into a surface that is more suscep-tible to adhesion? a. enhances the topographyb. lowers the free energyc. minimizes the micromechanical interlocking

with the enameld. increases its free energy

3. Acid etching removes approximately 10 µm ofenamel surface and creates a morphologicallyporous layer with how much depth?a. 0.5 µm to 5 µmb. 0.05 µm to 0.5 µmc. 5 µm to 50 µmd. less than 0.5 µm

4. Most adhesive systems that use the total-etchtechnique have in their formulation:a. water.b. acetone.c. low-viscosity hydrophilic monomers.d. fluoride.

5. In the early 1990s, it was common to findetchants such as:a. 10% maleic acid.b. 10% citric acid.c. 2.5% nitric acid.d. all of the above

6. The use of which concentration of phosphoricacid conditioner is still the best option toachieve predictable bonding to enamel?a. 32% to 40%b. 2.5% to 10%

c. 85% to 100%d. 10% to 15%

7. Cleaning can be accomplished with: a. air/water spray.b. chlorhexidine gluconate.c. benzalkonium chloride.d. all of the above

8. There are reports that the bond strength isreduced to _____ when the adhesive is applieddirectly to contaminated enamel comparedwith uncontaminated surfaces.a. 5%b. 90%c. 50%d. 75%

9. The durability of bonding to enamel depends on:a. the adhesive system used.b. excessive concentration of solvents.c. the mode of application.d. all of the above

10. It was recently observed that when enamelprisms are exposed perpendicularly, the bondstrength is reduced to:a. 50%.b. 10%.c. 80%.d. 75%.

Please see tester form on page 680.

This article provides 1 hour of CE credit from Ascend Dental Media, in association with the University of SouthernCalifornia School of Dentistry and the University of Pennsylvania School of Dental Medicine, representatives of which havereviewed the articles in this issue for acceptance. Record your answers on the enclosed answer sheet or submit them on aseparate sheet of paper. You may also phone your answers in to (888) 596-4605 or fax them to (703) 404-1801. Be sure toinclude your name, address, telephone number, and last 4 digits of your Social Security number.

Quiz1