Ceramic Inlays: A Case Presentation and Lessons Learned from the Literature

Ceramic Inlays: A Case Presentation and LessonsLearned from the Literature

LEE W. BOUSHELL, DMD, MS*

ANDRÉ V. RITTER, DDS, MS†

ABSTRACTCeramic dental restorative materials offer an esthetic alternative to dental amalgam or gold.There is uncertainty relative to the longevity of ceramic inlay restorations. Recently publishedlong-term research studies reveal general clinical performance trends. These trends are discussedwhile presenting a ceramic inlay case. Successful clinical use of ceramic inlay materials is abso-lutely dependent on the creation of an uncompromised adhesive tooth/ceramic interface.Ceramic inlay restorations perform well in terms of long-term retention, color match, and ana-tomic contour stability. These restorations all experience limited margin deterioration that doesnot predispose to marginal discoloration or secondary caries. Patients rarely suffer from post-operative sensitivity secondary to ceramic inlay placement.

Ceramic inlays fail predominantly as a result of crack propagation from material flawsleading to bulk fracture. Some superficial ceramic defects may be repaired with compositeresin. Internal material flaws are minimized by industrial production of indirect pressable glass-ceramic materials or ceramic blocks designed for computer-aided design/computer-assistedmanufacturing (CAD/CAM). External surface flaws are limited by careful polishing techniques.Strategic placement of ceramic inlays in teeth that are not subject to heavy occlusal loading willresult in more predictable long-term performance. Preparation design to prevent flexure ofceramic inlay materials is essential.

CLINICAL SIGNIFICANCEUse of ceramic inlays to restore defects in posterior teeth requires careful attention to detail.Placement of ceramic inlay materials in high-stress areas may result in less predictable long-term performance. Ceramic inlays are advantageous for restoring moderately sized defectswhen optimal control of restoration contours and esthetics is desired.

(J Esthet Restor Dent 21:77–88, 2009)

I N T R O D U C T I O N

The ultimate goal of dentalmedicine is the prevention of

dental disease. When this goal isnot achieved, the focus shiftstoward the correction of dental

disease, which in the case of dentalcaries is achieved with restorativematerials that perform like toothstructure. The introduction oftooth-colored restorations madefrom composite resin or ceramic

has solved many of the estheticconcerns that patients haveexpressed over silver amalgams orgold alloys. These materials dependon an adhesive interface betweenthe restoration and the remaining

*Assistant professor, University of North Carolina School of Dentistry, Chapel Hill, NC, USA†Associate professor, University of North Carolina School of Dentistry, Chapel Hill, NC, USA

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tooth structure, and are thereforesubject to the durability of thatinterface. In addition to depen-dence on an adhesive interface,these restorative materials haveunique characteristics that must beconsidered when restoring stress-bearing areas of the oral cavity.

Enamel, as a substrate, is mini-mally variable from patient topatient and tooth to tooth. Thedurability of the adhesive interfacewith enamel is very predictable.Dentin, however, as a substratevaries greatly within each toothand from patient to patient. Hence,the adhesive attachment to dentinis not as predictable. Tooth-coloredrestorative systems are, therefore,technique sensitive and requiregreater attention to detail thanrestorative systems that do notrequire an adhesive interface. It isincumbent upon the dentist tounderstand this variability andcreate the conditions necessary fora successful adhesive bond to bothenamel and dentin.

Current tooth-colored restorationsmade of composite resin performmuch like amalgams when atten-tion to detail is maintained.1 Lessis known about the clinical perfor-mance of tooth-colored ceramicrestorations. Ceramic restorations,in general, fail from cyclic loading,material flexure, and subsequentpropagation of fractures inherentin the ceramic material and on the

external surface.2,3 Conventionalsintered feldspathic porcelain inlaysare prone to fracture, and methodsto reinforce the porcelain havebeen developed. Industrial produc-tion of ceramic blocks for CAD/CAM helps minimize the inclusionof internal flaws in the ceramic.3

Ceramics that have an increase inthe crystalline phase of the ceramichave greater resistance to fracture.2

One strategy to limit fracturepropagation is to increase theleucite crystal content in the felds-pathic porcelain (IPS Empress andProCAD, Ivoclar Vivadent,Amherst, NY, USA). In these prod-ucts, larger leucite crystals inter-rupt fractures that form in theamorphous phase and resist frac-ture propagation. Another methodis to heat-treat leucite-reinforcedceramic such that the leucite crys-tals begin to convert into the sani-dine crystal polymorph of feldspar(Vita Mark II, Vita Zahnfabrik,Brea, CA, USA). Upon cooling, thesanidine crystals contract morethan the original leucite crystals,resulting in a net compressive forcein the ceramic block with aresultant increased resistance tofracture propagation.4

Research has been undertaken toassess how well dental restorativematerials perform over time. Com-paring the various clinical studiesof these materials has proven to bedifficult because of a lack ofstandardization. The need for

standardization led to the develop-ment of the much-used UnitedStates Public Health Service(USPHS) criteria to allow consis-tent assessment of the various clini-cal parameters that define howthese materials perform over time.A key ingredient to successful stan-dardization is the calibration of theresearcher(s) conducting the study.5

Short-term studies of ceramic inlayperformance have been carefullyevaluated, and a need for improvedstudy design quality was observed.6

This decade has seen the publica-tion of clinical research on ceramicinlay restorative materials withevaluation times ranging from 8 to15+ years. The goal of thesestudies has been to identify thelong-term clinical performance.Modified USPHS criteria have fre-quently been employed in thesevarious long-term clinical researchreports (randomized clinical trials,controlled clinical trials, and casereports).7–12 The type and level ofcalibration of the examiners hasrarely been reported.8,10 Most ofthe published long-term clinicalevaluation of ceramic inlays arecase series studies.7,9,11,12 Studieswith a greater amount of controllack strength because of lowsample size8,10 or uneven samplepopulation (either male/femaleratios or premolar/molar ratios).8–10

In all the published studies evalu-ated in this article, the specificpatient sex (male or female) and

C E R A M I C I N L AY S

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type of restored tooth (premolar ormolar) where the restoration failedare not reported.7–12 Even so, thediligent work of the variousresearchers provides valuable infor-mation to the dental clinician whentreatment planning with ceramicinlays. General performance trendscan be assessed in terms of reten-tion, color match, marginal dis-coloration (interfacial staining),recurrent caries, wear (loss ofanatomical form or contour),marginal adaption (integrity),postoperative sensitivity, or otherfailures. The goal of this casepresentation is to highlight thestrengths and weaknesses ofceramic inlay restorative materialsand discuss how case selectionand preparation design mayincrease predictability.

C A S E R E P O RT

A 26-year-old female patient pre-sented in early 2007 with a moder-ately sized fractured mesio-occluso-lingual (MOL) dental amalgam inan asymptomatic, vital first maxil-lary molar (Figure 1). This molarhad received an occluso-lingual(OL) amalgam in 1991, followedby a mesio-occlusal (MO) amalgamin 1993. The OL amalgam wasfound to be defective in 1998 andwas replaced. Options of anotheramalgam, a composite, or aceramic inlay were discussed interms esthetics and predictable lon-gevity. The patient’s desires were torestore the tooth with a ceramictooth-colored material. Patientdemographics are among the firstcharacteristics to consider whenconsidering use of ceramic inlay

restorative materials. Long-termstudies suggest that ceramic inlaysperform better in females than inmales.7,12 Assessment of tooth vital-ity and an accurate pulp diagnosisare important steps, as one long-term study reported the greatlyreduced survival of ceramic inlaysin nonvital molar teeth.11 Excessiveocclusal wear was not detected.There was no evidence of parafunc-tional habits. Long-term case seriesstudies suggest that the use ofceramic inlays in patients withbruxism or clenching may result ina greatly reduced restoration lifespan.7,9,12 If this had been a mesio-occluso-distal (MOD) amalgam,replacement with an MOD ceramicinlay may not have been the mostpredictable option. Long-termstudies suggest that MOD ceramic

A B

Figure 1. A fractured MOL amalgam in the maxillary right first molar (A). Common esthetic clinical presentation ofthe first maxillary molar restored with amalgam (B).

B O U S H E L L A N D R I T T E R

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inlays in molars do not performas well as other restorationconfigurations.7,10–12 The reasonfor this is unknown.

Evaluation of the current restora-tion and an associated bitewingradiograph revealed fracture devel-opment in the isthmus area wherethe restoration was thin (Figures 1and 2). Ceramic restorations aresubject to fracture propagationduring flexure. Preparation designto allow for the necessary bulk forrigidity becomes essential.7,9,12 It isgenerally accepted that the thick-ness of the ceramic material be~2 mm in stress-bearing areas tolimit flexure under loading.13,14 Inaddition to thickness of ceramic,tooth structure support of theceramic increases resistance to

fracture, especially in interproximalareas where the ceramic materialhas to extend to make adjacenttooth contact.9 In this case, theinterproximal distance between themolar and premolar was normal,and the anticipated support of theceramic marginal ridge wasadequate (Figures 1 and 2).

Creation of an adhesive bond totooth structure requires that thetooth be isolated from saliva, gin-gival crevicular fluid, and bloodwhile preventing dentin dehydra-tion. There has been considerabledebate over whether rubber damisolation provides greater restora-tion predictability than cotton rollisolation. No long-term ceramicinlay study directly compared thetwo isolation methods and

controlled for all other variables.The overall restoration longevityreported in long-term studies doesnot appear to be adversely affectedby the type of isolation tech-nique.7,9,10,12 Not all studiesreported the type of isolationused.8,11 Proper isolation, in anyform, cannot be overemphasized.Rubber dam isolation may wellprovide increased operating fieldcontrol while careful attention isgiven to each procedural step(Figure 3).

Removal of the fractured restora-tion allows evaluation of thecurrent extent of tooth destruction(Figure 3). Removal of the remainsof a pin in the lingual preparationextension was not indicated. In thiscase, avoidance of narrow isthmusareas and thin ceramic requiredincreasing the dimensions of thepreparation (Figure 4). Design ofthe new ceramic restorationallowed for ease of draw duringtry-in and fitting. This limited thelikelihood of binding and inadvert-ent restoration fracture beforecementation. All transitions weregradualized to limit the potentialfor areas of stress concentration.The preparation draw, althoughadequate for fitting, also retainedenough parallelism to provide pro-tection from excessive stress on themicromechanical adhesive bondbetween the restoration and thetooth (Figure 5). Retention ofceramic inlays has rarely been

Figure 2. A bitewing radiograph revealing thin amalgamin the approximate area of fracture. The interproximal boxis likely to retain enamel along the apical cavosurfacemargin. The anticipated interproximal space likely will notrequire excessive unsupported ceramic.



reported as a concern, providedthat appropriate attention is givento isolation and establishment ofthe adhesive interface.15

The preparation design willalso need to be modified to allowfor ceramic bulk at the margins(Figures 4 and 5). Ceramic inlaysdevelop a self-limiting loss ofmarginal integrity at the cavosur-face adhesive interface overtime.7–9,11,12 Long-term studiesreport no increase in cariesas a result of the marginaldeterioration.7–10,12 Three of thesestudies utilized radiographs toassess for caries in interproximalareas that may be difficult todetect clinically.8,10,12

Ease of isolation and greater pre-dictability of enamel bonding dic-tates the placement of ceramicrestoration margins in enamelwhenever possible (Figure 4).It has been unclear whethergingival margins placed in dentinare more prone to recurrentcaries. Long-term studies ofceramic inlays report noassociated increase in carieswhen margins are placed ondentin.7–10,12 The potentialadverse effects of polymerizationshrinkage are minimized becauseof the thin cement layer. Therefore,it may be that the bond to thedentin is relatively more protectedthan it would be if direct compos-ite were used.

A CEREC 3D system (Sirona, TheDental Company, Charlotte, NC,USA) was used to generate theMOL inlay for this individual.Every attempt to ensure a smallmarginal gap was made (Figure 6).It is now possible to consistentlyhave ceramic inlays with marginalgaps less than 100 micrometers(mm). Early CAD/CAM systemscreated marginal gaps of 150 mmor more. Long-term studies withvarious CAD/CAM and pressedglass-ceramic systems report nodetected adverse effects at themarginal interface, even withlarger marginal gaps.7,9–12

The restoration occlusal anatomywas adjusted to recreate appropriate

Figure 3. Isolation with rubber dam and removal of defectiverestoration to assess the size of the cavitation. Narrow isthmusareas that would prevent adequate porcelain thickness wereidentified (a, b, and c).

Figure 4. Divergent walls were created andcavosurface margins adjusted to allowmaximum bulk of ceramic at the interface.Clearance with the adjacent tooth wasestablished to allow interproximal finishing.Margins were maintained in enamel formaximum bond predictability.


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A B

Figure 5. Images (A and B) used during ceramic inlay computer-assisted design (CEREC 3D). Sharp transitions havebeen removed to limit areas of stress concentration. The wall divergence was designed to allow fitting, retention form,and protection of the adhesive interface.

A B

Figure 6. The CAD/CAM unit generated a ceramic inlay with satisfactory fit of a dental stone die (A) as well as fit inthe upper maxillary first molar (B). Slight submargination was present at the lingual margin.



cuspal inclines and marginal ridgeheights. Surface characterizationwas added in the process of glazing(Figure 7A). The Vita Mark II inlaywas etched with 9% hydrofluoricacid and treated with fresh silane. Alight-emitting diode curing light(DEMI, sdsKERR, Orange, CA,USA) was used for all light-curingsteps. The adhesive interface wascreated by closely following themanufacturer’s instructionsincluded with the 3M ESPE Rely-XARC (St. Paul, MN, USA) adhesiveresin cement system (Figure 7B).This system includes the 3M ESPEScotchbond etchant and the AdperSingle Bond Plus Adhesive.GLUMA Desensitizer (HeraeusKulzer, South Bend, IN, USA) wasapplied to the dentin for 30

seconds, between the etch-and-bondsteps, and excess fluid was evapo-rated with a light airstream. Therestoration was completely seatedwith controlled pressure using aball burnisher. Excess cement wasimmediately removed with cautionas to not remove cement from themargin interface. Initial light-curingwas accomplished while maintain-ing controlled seating pressure onthe inlay. Careful compliance withthe manufacturer’s instructions foruse of any particular adhesivesystem cannot be overemphasized.Long-term studies reported the useof various luting systems, but nostrong statements can be made withregard to relative adhesive cementeffectiveness.7–12 The occlusionwas checked and adjusted after

cementation to limit potentialflaw propagation.

Careful attention to the placementof even functional stops on theocclusal surface, which are in addi-tion to natural tooth functionalstops, will limit excessive cyclicloading of the ceramic material.Once the occlusion is perfected,careful attention to surface polish-ing becomes essential (Figure 8).Areas that are adjusted with rotaryinstrumentation are more prone todevelop marginal ridge or bulkfractures.9 Removal of surfacedefects/flaws (which increase thelikelihood of ceramic fracture)cannot be overemphasized.2,9 Thefinal polish is accomplished withrubber instruments, followed by

A B

Figure 7. Staining and glazing of ceramic inlays is optional but can aid in the elimination of surface flaws that maypredispose the inlay to fracture (A). An image of the ceramic inlay immediately after initial seating (B). Predictableclinical performance depends on the establishment of the adhesive interface.


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diamond paste.16 Loss of anatomiccontour from restoration weardoes not appear to be a long-termconcern.7–9,12 None of the long-term studies evaluated wear of theopposing surfaces. The ceramicsurface texture gradually becomesmore rough and pitted over thelong term but rarely becomes aclinical concern.7–10,12

A 1-month follow-up examinationof this individual revealed no post-operative sensitivity associatedwith the new ceramic restoration.Long-term studies report that thevarious amounts of postoperativesensitivity experienced were rarelya substantial patient concern.7,9,10,11

Ceramic inlay materials are veryesthetic and can return the appear-ance of a restored tooth to nearnormal (Figure 9). A 1-yearfollow-up evaluation revealsongoing achievement of esthetics,

good clinical parameters, and noradiographic concerns (Figure 10).Long-term studies report that thecolor mismatch over time graduallybecomes more pronounced, butthis did not present an estheticconcern for the patients.7–10,12

All long-term clinical reports ofceramic inlays find that ceramicfracture is the primary mode offailure.7–12 Many times, the frac-tured area can be repaired withcomposite resin.12 No carefullycontrolled studies have beenaccomplished that allow compari-son of the performance of pressedglass-ceramic inlays with CAD/CAM-produced ceramic inlays.Analysis of the various long-termstudies reveals that, in general,ceramic inlays have greater longev-ity in premolars than inmolars.7,8,11,12 Careful thoughtshould be given to the level of

anticipated cyclic loading beforechoosing a ceramic inlay to restoreany particular tooth. Clinical detec-tion of bulk fracture is not alwayspossible, and this may have inflatedthe survival probabilities reportedin the various long-term studies.17

Identification and interpretation ofthe relative severity of ceramic frac-ture and need for intervention maybe highly subjective.11 Within thelimitations of these studies,reported survival probabilities thatrange between 75 and 92% at 15+years indicate that ceramic inlayrestorations are fairly predictablewhen used as indicated.11,12

Treatment planning discussionsmust inform patients of thestrengths and weaknesses of thisparticular restorative material.Specific attention to indicationsand relative contraindications,along with sensitivity to the techni-cal demands of creating an adhe-sive interface, will increase thelikelihood of providing a highlyesthetic and predictable ceramicinlay restoration (Table 1).

C O N C L U S I O N S

Ceramic inlays are a highly estheticrestorative option. Their use shouldbe limited to vital teeth that arenot under heavy occlusal loading.Attention to detail in every step is aprerequisite to long-term success.Establishment of an excellent adhe-sive interface, an adequate ceramicthickness, and a highly polished

Figure 8. The adjustment of the occlusal contacts allowsshared, even loading of the natural tooth and the ceramicinlay.



A B

Figure 9. One-month follow-up images (A and B) revealing optimal esthetic and functional clinical performance of theceramic inlay restoration.

A B

Figure 10. One-year follow-up image revealing optimal clinical performance (A). One-year follow-up bitewingradiograph with normal radiographic appearance (B).


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restoration surface helps to preventfracture propagation and failure.When used in the correct circum-stances, ceramic inlays may offer anattractive alternative to nontooth-colored restorative materials.

D I S C L O S U R E

The authors do not have anyfinancial interest in the companies

whose materials are included inthis article.

R E F E R E N C E S

1. Opdam N, Bronkhorst E, Roeters J,Loomans B. A retrospective clinical studyon longevity of posterior composite andamalgam restorations. Dent Mater2007;23:2–8.

2. Seghi RR, Denry IL, Rosensteil SF. Rela-tive fracture toughness and hardness of

new dental ceramics. J Prosthet Dent1995;74:145–50.

3. Thompson JY, Bayne SC, Heymann HO.Mechanical properties of a new mica-based machinable glass ceramic for CAD/CAM restorations. J Prosthet Dent1996;76:619–23.

4. Mackert JR, Twiggs SW, Williams AL.High-temperature x-ray diffraction mea-surement of sanidine thermal expansion.J Dent Res 2000;79:1590–5.

5. Bayne SC, Schmalz G. Reprinting theclassic article on USPHS evaluationmethods for measuring the clinicalresearch performance of restorative mate-rials. Clin Oral Investig 2005;9:209–14.

6. Hayashi M, Wilson NHF, Yeung CA,Worthington HV. Systematic review ofceramic inlays. Clin Oral Investig2003;7:8–19.

7. Otto T, De Nisco S. Computer-aideddirect ceramic restorations: a 10-yearprospective clinical study of CERECCAD/CAM inlays and onlays. Int J Pros-thodont 2002;15:122–8.

8. Sjogren G, Molin M, van Dijken JWV. A10-year prospective evaluation of CAD/CAM-manufactured (CEREC) ceramicinlays cemented with a chemically curedor dual-cured resin composite. Int J Pros-thodont 2002;17:241–6.

9. Kramer N, Frankenberger R. Clinical per-formance of bonded leucite-reinforcedglass ceramic inlays and onlays after eightyears. Dent Mater 2005;21:262–71.

10. Thordrup M, Isidor F, Horsted-BindslevP. A prospective clinical study of indirectand direct composite and ceramic inlays:ten-year results. Quintessence Int2006;37:139–44.

11. Reiss B. Clinical results of CEREC inlaysin a dental practice over a period of 18years. Int J Comput Dent 2006;9:11–22.

12. Otto T, Schneider D. Long-term clinicalresults of chairside CEREC CAD/CAMinlays and onlays: a case series. Int JProsthodont 2008;21:53–9.

13. Prakki A, Cilli R, Da Costa AU, et al.Effect of resin luting film thickness onfracture resistance of a ceramic cementedto dentin. J Prosthodont 2007;16:172–8.

TA B L E 1 . S E V E N T E E N L E S S O N S O N C E R A M I C I N L AY U S E .

1. Ceramic inlays perform better in females than in males over time.7,12

2. Ceramic inlays do not survive well in nonvital molar teeth.11

3. Ceramic inlays do not survive well in patients with bruxism orclenching.7,9,12

4. MOD ceramic inlays in molars do not perform as well as otherrestoration configurations.7,10–12

5. Preparation design for ceramic inlay restorations must allow ~2-mmmaterial thickness in stress-bearing areas to limit flexure underloading.2, 3,7,9,12–14

6. Overcontour of ceramic to close large interproximal areas maypredispose to early failure.9

7. Absolute isolation is essential. Use whatever method works best.7,9,10,12

8. Careful attention to adhesive technique and preparation design will helpinsure predictable retention of ceramic inlays.7–12,15

9. Ceramic inlays develop a self-limiting loss of marginal integrity at thecavosurface adhesive interface over time.7–9,11,12

10. Ceramic inlay marginal deterioration does not appear to increaselikelihood of caries.7–10,12

11. Subgingival ceramic inlay margins has not been associated with anincrease in recurrent caries.7–10,12

12. The size of the marginal gap of ceramic inlays fabricated using variousCAD/CAM and pressed glass-ceramic systems has not been reported tohave an adverse effect on restoration longevity.7,9–12

13. Surface flaws of ceramic inlays must be carefully removed (by polishing)to avoid crack propagation that may lead to marginal ridge or bulkfractures.9

14. Ceramic inlays maintain anatomic contour over time.7–9,12

15. Ceramic inlays gradually develop rough and pitted surface texture overtime.7–10,12

16. Fracture is the primary mode of failure of ceramic inlays.7–12

17. Premolar ceramic inlays have more longevity than molar ceramicinlays.7,8,10,12



14. Federlin M, Krifka S, Herpich M, et al.Partial ceramic crowns: influence ofceramic thickness, preparation designand luting material on fractureresistance and marginal integrityin vitro. Oper Dent2007;32:251–60.

15. Molin MK, Karlsson SLA. Randomized5-year clinical evaluation of 3 ceramic

inlay systems. Int J Prosthodont2000;13:194–200.

16. Sasahara RM, Ribeiro Fda C, Cesar PF,Yoshimura HN. Oper Dent2006;31(5):577–83.

17. Clinical Research Associates. CEREC20th anniversary—is it time to buyin-office CAD-CAM? CRA FoundationNewsletter 2006;30:1–4.

Reprint requests: Lee W. Boushell, DMD,MS, University of North Carolina School ofDentistry, 448 Brauer Hall, University ofNorth Carolina at Chapel Hill, Chapel Hill,NC, 27599. Tel.: 919-966-2776; e-mail:[email protected]


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Ceramic Inlays: A Case Presentation and Lessons Learned from the Literature