Quality of dental restorations. FDI Commission Pro... - ResearchGate

123that continues over time in an individualavoiding fluoride result insecondary caries. However, fromclinical experience we know thatan incident of interest, such as theexample here using secondarycaries, can often be caused by morethan one set of sufficient causes.Thus, different causal pathwaysmay exist in different situations.Causal pathways (alternativelytermed causal web or cause-andeffectrelationships) involve theactions of risk factors acting individually,in sequence, or togetherthat result in an incidence of interest.These pathways may varywith different sets of risk factors.Understanding these pathways isnecessary to devise preventivecountermeasures or interventions toavoid a specified outcome, and thecountermeasure may be unique tothe pathway.Causal relationship can be determinedusing various levels ofevidence. In theory, all informationregarding a hypothetical causalrelationship can be labelled evidenceand must therefore be appraised.However, formal requirements areneeded to address validity ofevidence, and this is applied onscientific data. Inferences of causalrelationship are directly associatedwith study design. For many clinicalquestions, randomised controlledtrials (RCTs) are regarded asthe strongest evidence for causalrelationship. However, many determinantsof aetiology, diagnosis andprognosis can for various reasonsonly be estimated indirectly usingcross-sectional, cohort or casecontrolstudy designs. In thesesituations, inference must beassumed on the basis of how findingssatisfy different criteria ofcausation.Statistical issuesClinical studies may be classified asexperimental or observational.Only studies with experimentaldesigns can be considered inductive,that is, can give an indicationof a cause-effect relationshipbetween different factors or variableswith a certain degree ofuncertainty. All other methodsinvolve limitations through bias orconfounding. However, data fromobservational studies should notbe regarded as unimportant orincorrect. Hypotheses are oftengenerated first on the basis ofobservational studies, and are thentested for validity under morerigorous experimentally designedconditions.Certain requirements must befulfilled to qualify as an experimentalstudy. These are the presence ofcontrol groups, predefined allocationof variables, and standardisedevaluation procedures and criteriafor the evaluation of outcomes. Theallocation of variables is randomisedif possible, in order to make evenstronger statistical inferences, i.e. arandomised controlled trial. Thespecific aim of the study and theformulation of a hypothesis shouldbe documented. When these criteriaare not met, or when observationsare made of phenomena that arenot manipulated by the investigator,a clinical study is classified asobservational.Relatively few clinical studies inrestorative dentistry fulfil the criteriaof an experimental design 5,16,17,63 .The majority of clinical studieswhere an association has beenreported between clinical variablesand restoration performance havebeen observational studies. Thisis because although the studieswere experimentally designed toobtain information on differencesbetween, for example materials orcommercial products, the observationsand descriptions of theinfluence of other factors were notobtained by the manipulation ofthese factors.Many clinical studies are carriedout according to recommendationsoutlined by various national orinternational acceptances programmeguidelines, for example FDI 64 ,NIH 65 and ADA 66–68 . These guidelinesare designed to address ‘safety’and ‘efficacy’, that is attempts toscore performance as passing orfailing and not to rank clinicalperformance. This is why many ofthe criteria are based on a passinglevel of, for example 85–90 percent alpha scores according to theUSPUS criteria after one to threeyears, and only distinguish betweenunacceptable and acceptable performance.For different reasons theseguidelines do not require controls,do not test for placebo effects anddo not have statistical powers greatenough to answer anything otherthan simple experimental questions.The most commonly tested hypothesisis whether a new material orproduct has been comparable to aspecific traditional material.Many of these trials are carriedout in research environments, asopposed to general practitioners’practices. The operators are oftenselected and trained to ensure optimalhandling. Furthermore, thepatients are often dental students,dental school staff or dentists withabove average oral hygiene 12,13,16,17,69 .Controlling operators and theirworking environment, patients, andsize and intra-oral location of therestorations reduces confounding,when comparing different materialsor products. However, datafrom such studies do not reflectthe situation in ‘real-world’ dentalpractice 70 . This is especially apparentwhen technique-sensitivematerials are involved 1 . In generalpractice, treatment times areconstrained, the diagnostic thresholdsfor replacement may vary withthe patient load, and there are noeconomic incentives to producehigher clinical standards aboveacceptable 61 . In general, there ispublic concern that there is lack ofdata on clinical performance ofrestorative materials and on thequality of service provided bydentists in general practice, andespecially on the interaction betweenclinical performance of restorationsand quality of service 71 .It is evident from the literaturethat there are disagreements concer-FDI Commission, Jokstad et al.: Quality of dental restorations

124ning the material, operator andpatient effects on restoration quality.One of the major issuesappears to be the statistical treatmentof data. It is difficult toconduct clinical studies, with theaim of establishing a numericalrelationship between one specificrisk factor and the technical excellence,restoration service period orreplacement reasons. The mainreason is that the clinical performanceof a restoration is dependenton many known and unknownclinical variables that are difficultto control or record. It is alsodifficult, if not impossible, toassure independence among manyclinical variables that affect restorationclinical performance. Currently,there do not appear to be anygenerally acceptable, valid statisticaltechniques for isolating theinfluence of a single variable;indeed, many of the variables maynot be independent. In full knowledgeof this situation, clinicalresearchers employ various strategieswhen designing trials aimingto clarify parameters of restorationquality (Figure 3).Restoration quality has beenaddressed in both prospective andretrospective longitudinal studies aswell as in cross-sectional studies.Data from prospective and retrospectivelongitudinal studies can beused for constructing survivalcurves, proportions of restorationswith varying technical excellence asa function of time and reasons forreplacement.Current restorative materialshave excellent physical and mechanicalproperties. Prospective clinicalstudies therefore need to beextended for many years and/orinclude large numbers of restorationsbefore any strong statisticalinferences can be made. Longobservation periods are associatedwith problems such as patient dropouts,patient representativity andchanges in the clinician’s diagnosticabilities or understanding of replacementcriteria. Finally, also ethicalreasons may occasionally restrict theFigure 3. Parameters of the quality of dental restorations. The horizontal axis representstime, while the vertical axis is the proportion of restorations remaining over time. The boldline represents the proportion of restorations remaining in situ (that is ‘survival’), and theseare in the category ‘excellent’ (for example ‘alpha’), ‘acceptable’ (‘beta’) or ‘defective’(‘charlie’). Replacements may be ‘true’ reasons, that is bulk fractures, secondary caries,marginal deficiencies, discolouration, etc, or because of faulty diagnosis, inclusion intolarger restorations, primary caries on other surfaces, etc. Arbitrarily lines depict theproportion of restorations/replacements that fall into the carious categories. The horizontalline at 50% marks the median survival time. The intersections between this line and the otherlines represent from left to right when 50% of the remaining restorations are: excellent,acceptable and remaining in situ.possibility of conducting prospectiveclinical studies.Retrospective studies are basedon analysing patient records or acombination of patient records andquality evaluation of restorations.A frequent problem with manyretrospective studies is that little orno information is available onpossible reasons for replacement.Several studies have revealed thatreplacements are not alwaysexplained by restoration failure 1 ,and even if they are, retrospectivedata give no indication regardingwhether the failures are relateddirectly to the restoration, to therestorative process or to externalfactors 72 .Cross-sectional clinical studieshave either been presented asreplacement studies or recordingsof data from patients’ records.Other data have been derived fromassessment of technical excellenceof restorations in situ or inextracted teeth, or from detailedstudies of failed restorations.Cross-sectional studies that focuson mean age of failed restorationsidentify the ‘geometric centre’ ofthe area above the survival curve inFigure 3, while studies that focuson the age of remaining restorationsidentify the centre below thiscurve.In replacement studies, theprevious history and age of therestorations is often unknown.Although the type of materialusually is recognised, specific tradenames or batch numbers areseldom recorded. A characteristicof the study method is that theevaluation criteria are not explicit,which leaves the diagnoses to theoperators involved in the study. Theresults do not indicate any causalrelationships, and they are probablyinfluenced by factors such associoeconomy, patient demographyand the dentist:patient ratio. Thesame arguments are applicablewhen interpreting results fromcross sectional studies. Although theevaluation criteria may often beaccurately described, the history andclinical parameters at the time ofrestoration placement remainsunknown.International Dental Journal (2001) Vol. 51/No.3

128cement, composite resin/resinmodifiedglass-ionomer cementand resin-modified glass-ionomercement/glass-ionomer cement.Several studies have reportedcomparisons between ‘sandwich’versus homogeneous restorations,but the conclusions are conflicting.Patient factorsEmpirical observations indicate thatnot only surface, but also bulk andmarginal discolouration vary amongpatients. However, very few studieshave identified specific patientfactors that may influence the opticalcharacteristics of restorations.Marginal discolouration alongveneers made from compositeresin on 87 maxillary anteriorteeth in 23 young patients wasmore common among smokerscompared to non-smokers in alongitudinal study over five years 102 .In a study of 52 pairs of ClassIII microfilled composite resinrestorations after eleven years,surface discolouration was mostoften recorded among smokers,and significant correlations werefound between the patients’consumption of alcoholic beveragesand body and surfacediscolouration 88 .AdaptationTraditionally, the terms used todescribe adaptation have variedwith the examination method, thetype of restoration and the natureof the restorative material. Horizontaldiscrepancies on smooth andapproximal surfaces have oftenbeen termed ‘overhangs’, while theterm ‘marginal ditching’ has beenused to describe defects alongmargins on the occlusal surfaces ofteeth containing mainly amalgamrestorations. The terms over- andunder-extension, with additionaldescriptors of the cement marginmorphology, for example ‘marginalwear’ and ‘cement excess’, haveusually described the adaptation ofindirect restorations. Finally, theterm ‘gap’ has also been used formany years to infer a lack of adaptationbetween the materials andtooth tissues. However, this term israther ill defined and non-specific.Discrepancies measured alonga horizontal or a vertical axistangential to the interface haveoccasionally been interpreted assynonymous to marginal adaptation.Such discrepancies can beassessed clinically, but will necessarilyonly express the adaptationalong the margin on the toothsurfaces. Several methods havebeen used to assess adaptation ofthe entire restoration-tooth interface,but all these methods aredestructive 103 .The clinical evaluation of marginaldiscrepancies is questionable,explained by a lack of reliablediagnostic skills of clinicians. It hastherefore been argued that thescientific community must acceptthat dental restorative materials willbe misjudged during the processof evaluating the marginal qualitiesof restorations 104 .Material factorsThe dental literature containsnumerous papers in whichmarginal degradation has beenevaluated as a function of materialcomposition. The prevailing materialin these studies has been amalgam,and there is consensus that highcopperalloys are clinically superiorto low-copper alloys 105 .Inter-group differences in respectof the marginal degradation ofamalgam restorations often appearafter a short time, and remainconstant 29,69,106–109 . This signifies thatat least one process that results inmarginal fractures occurs duringthe first year after placement ofthe restoration. This hypothesis,however, does not identify orexclude other aetiological factorsthat may be associated withmarginal fractures, including creep,mercuroscopic expansion, biomechanicalrelationships, bulk andcrevice corrosion or fatigue rupture.There may also be differencesbetween composite resins, Bryantet al. 110 having reported thatparticular types of marginal defectsare commonly associated withspecific types of composite resins.In general, restorations of microfilledcomposite resins show moremarginal degradation compared torestorations of other types ofcomposite resins.Operator factorsJokstad 29 reported an influence ofthe operator on the performanceof 468 amalgam restorations offive alloys placed in 210 patientsafter five years. The five dentistswere all able to obtain superiormarginal adaptation with the bestalloys, and contrary to the findingsof Mahler and Marantz 21 , all fivealloys performed equally well forthe five operators. Further, it wasevident that one operator alsoobtained satisfactory marginaladaptation with a low-copperalloy. It was concluded that themain operator variables influencingthe marginal adaptation werethe final condensation of the amalgamand the treatment of thesurface and margins.Mahler and Marantz 21 reportedon restorations of four amalgamalloys placed by four operators.The amalgams were chosen on thebasis of their marginal fracturebehaviour as found in an earlierstudy, ranging from little to extensivefracture. Following placementof the restorations, three-yearevaluation of marginal fracture wasundertaken using a linear ratingscale. It was found that the operatorinfluenced the marginal fractureindex, but in different waysdepending on the alloy. For thealloys with the most and leastmarginal fracture, there was nooperator difference. However, forthe two intermediate alloys, therewere large differences among theoperators. Overall, the associationwith alloy was stronger than withoperator, and it was thereforeInternational Dental Journal (2001) Vol. 51/No.3

129recommended that non-gamma-2amalgams should be used.Cavity designStratis and Bryant 111 carried out atwo-year study of 111 Class I andII amalgam restorations placed byone operator, and reported that acombination of modification of theocclusal cavo-surface angle andfinishing of the restoration had aninfluence on the marginal fractureat two years.Kreulen et al. 112 reported a photographicevaluation of the marginsof 245 Class II amalgam restorationsplaced by three dentists. Theprinciple variable influencingmarginal adaptation was the dentist.In addition, improvement of themarginal adaptation by an occlusalbevel was discussed compared withnon-bevelled margins.Investigations published before1992 on the possible relationshipbetween marginal fracture andClass I and Class II cavity preparationsfor amalgam has beenreported in a previous paper, andwill not be discussed further 113 .Fukushima et al. 114 reported astudy on the early marginal breakdownof 432 posterior compositeresin restorations. It was determinedthat smaller cavities, greaterbulk of material at the margin(especially in functional cusp areas),and well-finished margins withoutoverfilling seem to reduce theoccurrence of marginal fracture.Material handling and proceduresSuccessful bonding is associatedwith several technique-relatedfactors. The use of adhesives istechnique sensitive because ofcomplex multi-step applicationtechniques 38,115 . Careful managementof the status of the collagenmeshwork is important to preventit from disintegration or collapseand thereby ensuring optimal resinpenetration 116 .A clinical technique, commonlyreferred to as ‘wet bonding’, hasbeen recommended especially foradhesive systems that utilise waterfree,acetone-containing primers.However, recent research hasrevealed that bonding systems thatutilise water-based primers appearto bond with equal effectiveness todry and wet dentine 117 . Adhesivesystems using acetone-based primersrevealed a higher techniquesensitivity 118 , whereas adhesivesystems containing water-basedprimers appear to be less techniquesensitive,as far as the remainingwetness of the acid-etched dentinesurface is concerned 119 .Clinically, the exact timing ofthe different stages of bonding asrecommended by the manufactureris often very difficult. For example,parts of the dentine may beetched for the same amount oftime as the enamel because theprecise differentiation between thetwo substrates is not always possible.Excessive etching may result indemineralisation depths that aregreater than monomers can effectivelypenetrate 115,119 , and causesevere collapse of the collagenmeshwork 119 . The depth of demineralisationis dependent on etchingtime and phosphoric acid concentration120 , while the thickness of themonomer penetration, or ‘hybrid’,layer is a function of conditioningtime 121 . However, the implicationsof these variables on long-termclinical outcomes remain uncertain.IsolationDesiccation of the demineraliseddentine causes collapse of thecollagen meshwork, which impedesthe proper infiltration of theprimer 121 . Therefore, a wet bondingtechnique is recommended 122,123 .However, there is a wide range ofinterpretations of ‘wet’ 124,125 , withno clear guidelines in manufacturers’directions for use. While thenegative consequences of excessiveair-drying are well documented foracetone-based systems 122,123 , theresults for water-based systems arevariable 125 .Contamination of the etchedenamel surface with saliva prior tothe placement of a resin-basedmaterial significantly reduces thebond strength to enamel. Studieson the influence of saliva contaminationon dentine bonding arevariable. Although the tolerance ofmodern adhesives to saliva contaminationhas improved, reductionsin bond strengths may be anticipatedafter saliva contamination. Itis therefore important to preventsaliva contamination after applicationof the primer 126 .The effect of using rubber damremains uncertain. In an experimentalstudy comparing shear bondstrength of 36 composite resinrestorations placed either withcotton rolls or under rubber dam,no significant differences werenoted between the two groups 127 .In another study using the sameprotocol, microleakage was assessed.This study concluded that the useof rubber dam isolation resulted inless microleakage at the enamelresininterface 128 .Patient factorsIntraoral locationAs for wear, bite force is probablya significant aetiological factorregarding the extent of materialdeterioration. As a result of relativelyhigh bite forces in the firstmolar region, it can be assumedthat more marginal fractures willoccur in this location.In a study of 88 composite resinrestorations placed by nine dentalstudents, it was observed after twoand three years that marginal integritywas significantly better inpremolars compared to that inmolars 100,101 .Berg and Derand 129 reporteddata on 51 out of originally 115porcelain inlays made with theCerec technique after five years in46 patients. No significant differencesin marginal ditching weredetected between molars andpremolars.Jokstad 29 did not find any strongrelationship between marginaldegradation and intraoral locationafter five years observation of ClassII amalgam restorations. Only thelower premolars showed lessFDI Commission, Jokstad et al.: Quality of dental restorations

130marginal degradation compared tothe other tooth groups. Osborneand Gale 130 reported that themarginal fracture of high-copperamalgam restorations could not berelated to the intraoral locationafter fourteen years service. Interactionsbetween tooth position andwidth indicated that lowerpremolars with conservative restorationsexhibited the least fractureat the margins, and upperpremolars with a wide preparationexhibited the most. Osborne andGale 131 reported that the marginaldegradation of 429 Class II amalgamsafter two years was less inlower premolars than in the otherposterior teeth.Goldberg et al. 132 studied 475restorations over 1.5 years. UsingANOVA analyses, these investigatorscompared marginal fracturescores among different subgroups,categorised by intraoral location andfound more fractures in molars thanin premolars.Oral environmentDerand 133 assessed restorations offour amalgam alloys in 163 teethafter 2.5 years. The patients weredivided into three levels of bitingforce. It was found that marginalfractures increased with increasingbite force for the conventionalalloys, but that the relationship wasnot significant for the three nongamma-2alloys.Restoration failure andclinical factorsTechnical excellence of restorationsdeteriorates in clinical service andmay or may not be linked to restorationfailure. Certain investigators,including those of Harris 134 andOwens 135 , reflect a common opinionthat materials themselves areoften the least of the problems andthat most restoration failures canbe attributed to poor attention todetail in cavity preparation andmaterial handling. However, thisview can at best be regarded asexpert opinion, and is linked to thefailure criteria. In a survey of 571International Dental Journal (2001) Vol. 51/No.3dentists, perceived causes of restorationfailure were ranked bypatient-related factors (45 per cent),dentist-related (35 per cent) andmaterial choices (20 per cent) 136 . Anamusing secondary finding was thatthese estimates were for restorationsin general, while the percentageswere 48, 26 and 26 per centrespectively when dentists addressedthe causes of failure of the restorationsthey had made themselves.The following sections presentthe effects of the numerousdependent and independent variablesinfluencing the quality ofrestorations, notably the operator;the operative techniques and instrumentused; the material; the location;type; size; initial and short-termtechnical excellence of the restorationand patient factors.General performanceMaterial factorsDifferences in composition andphysical propertiesSubtle differences in physical propertieswithin specific materialgroups may be considered to havea small effect on clinical performancein general practice settings. Aparticular exception is perhaps compositeresin cements for indirectrestorations, where the microfilledcements seem to be superior tocements with larger fillers 14,136 ,although conflicting results havebeen reported 138 . Two longitudinalmulticentre studies involving 24dentists in seven clinics revealed onlyminor differences amongst sixcomposite resins after three andfive years 139,140 . Dunne and Millar 141reported the evaluation of 315porcelain labial veneers in 96patients, fitted up to five yearspreviously in two teaching hospitals.Increased problems and failurerates were associated with veneerswhere inappropriate luting agentswere employed, that is, lutingcements not dedicated to veneercementation. In studying over 1,544amalgam restorations, 1,213 restorationsremained after 15 fifteenyears. The conclusions from thisstudy was that the type of amalgamalloy used had no associationwith restoration survival 108,109 . VanNoort and Davis 142 observed in afive-year prospective study thesurvival of 2,399 Class III and 1,093Class V chemically-activated anteriorcomposite resin restorations in26 general dental practices, that thedifferences in clinical performancesbetween six materials was small. Ina cross-sectional study, 75 privatepractitioners evaluated 1,147 twoto-fouryears old anterior restorationsof 25 different materialsaccording to the CDA system. Withthe exception of one compositeresin, no obvious differences in thequality of dental restorations wereobserved 33 .Operator factorsAmong various clinical factorsaffecting restoration performance,an operator association is frequentlydetected in multicentre and crosssectionalstudies (Table 1). Controlledclinical studies are usually designedto avoid such operator effects, anddifferent research groups haveemployed various strategies (seesection on statistical issues) tocontrol these effects.Most of the relevant papersoffer no explanation of theobserved variation in operatoreffect, although some authors stressthe necessity of specific training fordental personnel using new materials.It is also possible that anindirect patient association may haveinfluenced an apparent operatorassociation. Whether the experienceof the operator can be associatedwith technical excellence is uncertain.For example, Hawthorne andSmales 150 reported that the survivalfor composite resin restorationswas best for the most recent graduates.By contrast, Shaini et al. 151commented that the poorestresults were seen in relation to theinexperienced operators. Of course,appropriate clinical training andexperience are necessary prerequisitesfor favourable clinical outcomes.

132I inlays was lower than that for theother types of inlays, that is two-,three- and four-surface inlays.In study of over 1,544 amalgamrestorations, 1,213 restorationsremained after fifteen years. Itappeared as if the three-surfacerestorations had less favourableclinical outcomes compared totwo-surface restorations after 15years. Also, the provision of a 90 ocavosurface angle combined witha cavity wall finish reduced the riskof failure of amalgam restorations,compared to larger cavosurfaceangles 108,109 .Prati et al. 161 reported three-yeardata on 116 Class III and V polyacid-modifiedcomposite resin(‘compomer’) restorations. Theyfound no statistical differences withrespect to the USPHS criteriabetween the Class III and V restorations.In a cross-sectional appraisal of520 cast restorations in 56 patientsmade between one to 40 yearspreviously, the restorations includingmore than two surfaces wereassociated with less favourableoutcomes of quality and survival 162 .The outcome after three yearsof 446 restorations placed byone dentist and two dental nursesin 282 patients using the ARTtechnique was reported byPhantumvanit et al. 148 . The survivalwas lower for occlusal surfacerestorations compared to those inother surfaces.Friedl et al. 163,164 carried out across-sectional study in which 102dentists provided informationabout 3,375 composite resin and5,240 amalgam restorations. Thefailed restorations with foursurfaces had a lower median agecompared to the other types ofrestorations.Jokstad et al. 165 reported on across-sectional study of 8,310restorations a marked associationbetween the age of the restorationsand both the types and the size ofthe restorations.Data from a five-year prospectivestudy of the of 2,399 Class IIIand 1,093 Class V chemically-activatedanterior composite resinrestorations assembled from 26general dental practices indicatedthat the overall probability ofsurvival at five years was 10 percent higher for Class V restorationsthan for Class III restorations 142 .Smales and Gerke 166 evaluated700 anterior composite resinrestorations over four years. Significantlymore failures occurred inClass IV and V preparations. Ofall failures, 81 per cent were fromClass V preparations, which mayreflect undue reliance on dentinebondingsystems for restorationretention in premolar non-cariouscervical lesions.Fritz et al. 167 reported the longtermoutcome of 2,717 castrestorations provided for 548patients during 1960–1989. Relativelyminor differences in the 15year survival were noted for foursizes of casts: single surface (65 percent), two-surface (60 per cent),three-surface (68 per cent) andinlays and onlays (70 per cent).Investigations published before1992 on the association betweenClass I and Class II cavity preparationsfor amalgam and restorationsurvival has been reported in aprevious paper and will not bediscussed further 113 .Wilson and Norman 147 reportedfive-year findings of an 11-centretrial of a posterior composite resin.The findings were based on datacollected from 649 (68 per cent)of the 958 restorations originallyplaced. Chi-square analyses indicatedthat of the independentvariables investigated, size ofrestoration had the greatest associationwith clinical performance.In a study of 950 anteriorcomposite resin restorations oversixteen years there were significantlymore failures with the Class IVcompared to the Class III restorations153 .Bentley and Drake 168 reported astudy of 1,207 restorations placedby students in 70 patients. Singlesurfacerestorations lasted longerthan multi-surface restorations.Moreover, multisurface restorationsincluding the occlusal surfacesurvived significantly longer thandid those including the facial orlingual surface.Material handling andproceduresFactors associated with materialhandling and procedures that mayaffect the incidence of margin failuresof amalgam restorationsinclude trituration time 106 , use ofrubber dam 169,170 , condensationtechniques 171 , and the carving,burnishing and polishing techniques172 . The effect of burnishingamalgam restoration margins isdifficult to estimate, and nearlyimpossible to quantify since the‘surface treatment’ is influenced byfactors such as burnishing load,direction of the strokes, numberof strokes, beginning time aftertrituration and the size of theburnisher 172 .To what extent cavity varnishesand their thicknesses promotemarginal failures is unknown. It isconceivable that some varnishesmay be incorporated into the amalgamalong the margin, and therebyreduce the strength in these areas.Thus, there is a theoretical possibilitythat the type or amount ofvarnish may be related to marginfracture. However, clinical data onsuch a relationship is sparse, andexisting data are not conclusive. Inone longitudinal study it wasrevealed that application of avarnish or silver suspension did notinfluence the risk of long-termrestoration failure 107–109 .Letzel et al. 171 assessed the typeof condensation instrument, togetherwith patient and operator on theperformance of a single amalgamalloy over 2.5 years. The authorsreported an association betweenfailure and the patient and theoperator, but there were too fewfailures to establish an associationwith condensation instrument.However, the authors did not indicatehow ‘failure’ was assessed.International Dental Journal (2001) Vol. 51/No.3

133IsolationThe debate about the necessity ofusing rubber dam in operativedentistry has been ongoing withvariable intensity for many decades.In this context it should perhaps beemphasised that working withoutrubber dam does not necessarilyallow saliva contamination duringoperative procedures.Raskin et al. 157 reported a tenyearlongitudinal study of 100Class I and II composite resinrestorations in a group of selected,predominantly young patientsunder highly controlled conditions.The method of isolation was notfound to significantly influence clinicalperformance and survival.Dunne and Millar 141 reportedthe evaluation of 315 porcelainlabial veneers in 96 patients, fittedup to 63 months previously in twoteaching hospitals. The use of rubberdam could not be associatedwith survival.The consequence of using eitherrubber dam or cotton roll isolationon clinical deterioration wasreported by Smales 169,170 . In onestudy, 546 polished amalgam and148 anterior enamel-bonded compositeresin restorations were evaluatedover periods of up to 15 years. Heconcluded that although a statisticallysignificant difference wasfound between the two isolationmethods for marginal fracture ofthe composite resins, the clinicalrelevance of this difference wasquestionable. In the second paperthe survival of the restorations wasrelated to the possible influence ofsix other clinical parameters. Therewere no clinically significant differencespresent in the initial highquality of the restorations, or intheir later survivals, which could bedirectly related to the use ofrubber dam.In a survey where the clinicalhandling properties of glassionomercements were addressed,Knibbs and Plant 173 attributed themain cause of unsatisfactory restorationsin deciduous teeth made by17 general dental practitioners topoor handling of the material, principallyby moisture contamination.Van Dijken and Horstedt 174assessed 35 patients who receivedone hybrid and one microfilledcomposite resin restoration placedin anterior teeth with and withoutrubber dam. After one year themarginal adaptation was investi-Table 2Clinical studies reporting a relationship between restoration performance and intraoral locationReference Restorations/ Restoration types Obs. period General performancepatients (years)LongitudinalKöhler et al., 2000 87 63/45 Posterior composite 5 No statistically significant difference betweenpremolars and molars, and between maxillary andmandibular teethLundin and Koch 2000 155 117/65 Posterior composite 10 Restorations in premolars had a higher failurerate than in molarsPyk and Mejare, 1999 158 242/142 Glass cermets – tunnel 3.5 Failure occurred about five times as often inmolars as in premolarsRaskin et al., 1999 157 100/ Posterior composite 10 Location not found to influence survivalDonly et al., 1999 176 72/18 Gold cast and composite 7 The acceptable restorations were located mainlyinlayin the premolarsPrati et al., 1998 161 116/ Class III and V polyacid- 3 No association with respect to the USPHS criteriamod. compositeand intra-oral locationGeurtsen and Schoeler, 1209/ Class I and II composite 1–4.5 More restorations with rating Alpha in premolar1997 177 teeth compared to molar teethGruythuysen et al., 1213/ Class I and II amalgam 15 The type of tooth had no association with1996 108 survivalSmales and Gerke, 700/ Class III and V composite 4 More failures occurred in premolar teeth com-1992 166 pared to other locationsJokstad, 1992 29 468/ Class II amalgam 10 No effects of intraoral location detectedRetrospectivePelka et al., 1996 162 520/56 Cast 1–40 Molars had less favourable outcomes of qualityand survival compared to premolarsDrake et al., 1990 61 1207/70 All types 1–20 No statistically significant differences wereBentley and Drake,observed. Mandibular incisive restorations lasted1986 168 longer than maxillaryCross-sectionalMcDaniel et al., 2000 178 706/ Class I and II amalgam ns Mandibular first (36%) and second (20%) molarsaccounted for most fractures among cuspalcoveragerestorationsJokstad et al., 1994 165 10091/575 All types >10 The restoration age is possibly influenced byintra-oral locationKerschbaum et al., /1841 Fixed prostheses 1–15 An anterior placement and the lower jaw associ-1991 179 ated with a lower survivalFDI Commission, Jokstad et al.: Quality of dental restorations

134Table 3Clinical studies reporting a relationship between restoration performance and gender and age.Reference Restorations/ Restoration types Obs. period General performancepatients (application) (years)LongitudinalPyk and Mejare, 1999 158 242/142 Glass cermet (tunnel) 3.5 Success rate was not related to patient agePlasmans et al., 1998 145 300/ Amalgam (complex) 8.5 Restorations more prone to failure in patients >30yrs old than in younger onesPrati et al., 1998 161 116/ Class III/V polyacid – 3 No association between USPHS criteria andmodified compositepatient age and genderPhantumvanit et al., 1996 148 446/282 Glass-ionomer (ART) 3 No differences between ART restorations inchildren and adultsGruythuysen et al., 1996 108 1213/ Class I and II amalgam 15 20% of the study restorations were replaced inmales, 16% in femalesJokstad, 1992 29 468/ Class II amalgam 10 Survival associated with patient age, but sampleincluded caries-susceptible childrenSmales and Gerke, 1992 166 700/ Class III and V composite 4 Significantly more failures occurred among theelderly patientsRetrospectiveHawthorne and Smales, /100 Amalgam and composite 1–40 Lowest survival rates in the 0–20 and 61+ year1997 150 age groupsPelka et al., 1996 162 520/56 Cast 1–40 No association between patient age and outcomesof quality and survivalMahmood and Smales, /1588 All types 1–15 Restoration survival was superior in female1994 152 patientsDunne and Millar, 1993 141 315/ Porcelain (veneer) 5 Patient age and gender could not be associatedwith failureBentley and Drake, 1986 168 1207/70 All types 1–20 Survival less favourable for patients >60 yrs oldcompared to the younger patients. No differencesbetween males and femalesCross-sectionalMjör et al., 2000 36 6761/ Amalgam and composite 1–30 Minor differences noted in longevity betweenmale and female patientsGlantz et al., 1993 180 /77 Fixed prosthesis 1–15 No differences regarding fracture, loss ofretention and/or dental caries between agesubgroupsDawson and Smales, 1992 181 1918/100 Amalgam and composite 1–16 Survival lower in the oldest of three age groups.A small gender difference also notedSmales, 1991 153 950/ Anterior composite 1–16 Median survival 7 yrs in age group 60 yrs, 12 yrs in group 21–60 yrs. More failuresseen in the oldest groupSmales, 1991 154 1476/ Amalgam 10 Patient age had a significant association for oneof five alloysKerschbaum et al., 1991 179 /1841 Fixed prosthesis 1–15 A lower survival of fixed prostheses wasassociated with higher age group (especially ifthe patient was older than 70 yrs)Kroeze et al., 1990 182 /600 All types ns The prevalence of unsatisfactory restorationstended to be higher with increasing agegated and no differences wereobserved.International Dental Journal (2001) Vol. 51/No.3Patient factorsCollins et al. 175 concluded, after aneight-year longitudinal study ofposterior composite resin restorations,that there was evidence toconfirm the importance of theinfluence of the patient, since manyof the observed failures occurredamong few patients. However, nodetails were reported that characterisedthese patients.The findings related to anassociation between restorationperformance and patient factors aresummarised in Tables 2 and 3.The majority of the studiesdescribe a minor difference. However,as for many of the otheralleged associations to clinical factorsone must be aware of publicationbias. Moreover, most clinical studieswere designed to address specificclinical problems. Issues such asinfluence of operator, patient factorsand intraoral location were usuallycarried out as secondary analyses.It is impossible to know if no suchrelationships are reported becauseno secondary analyses have beencarried out, or if the relationshipswere negative and thus omitted inthe text (Figures 4).Oral environmentReduced salivation and xerostomiaare associated with older patients,side effects of drug therapy andcancer treatment. Consequently,

135abcdeFigure 4 (a–e). Old composite resin restorations remaining in situ due to patient satisfaction. Other patients, as well as clinicians, might wellconsider the restorations ‘unacceptable’.caries risk increases significantly.Wood et al. 183 studied 54 pairs ofClass V amalgam and glassionomercement restorations overtwo years in 36 xerostomic cancerpatients. Survival times were veryshort (8.5 months) for all restorations.Among the individuals usingfluoride, 8 per cent of the glassionomercement and 100 per centof the amalgam restorationssurvived after six months. For thesubgroup of eight non-fluorideusers survivals were approximately100 per cent and 24 per cent. Thus,the degree of fluoride use wasassociated with the rate of restorationfailure.Caries activity might be expectedto affect the performance ofrestorations; however, there are fewdata on this aspect. In a longitudinalstudy of 242 tunnel restorationsin 142 individuals, the cumulativeproportion of successful restorationswas 81 per cent after twoyears and 64 per cent after 3.5 years.FDI Commission, Jokstad et al.: Quality of dental restorations

136Secondary caries caused replacementof 50 per cent of the restorations,but statistical analyses revealed noassociation between caries activityand replacement 158 .Strand et al. 159 observed in a threeyearstudy of 161 glass-ionomercermet cement tunnel restorationsthat there were significantly morefailures among patients with a highcaries activity.Restoration survival was stronglyinfluenced by caries activity in aten-year longitudinal study of ClassII amalgam restorations 29 . The 210patients in the study were dividedinto high, medium and low cariesactivity, depending on the incidenceof primary and secondary carieslesions during the first eight yearsof a 10 year study of amalgamrestorations. However, some cautionwas expressed in interpreting thesedata, as the study sample includeda group of caries-susceptiblechildren.Bentley and Drake 168 reportedon a study of 1,207 restorationsplaced by students in 70 patients. Asubset of the population (19 percent) with a disproportionatelyhigher failure rate accounted for56 per cent of all failed restorations.The authors speculated thatit may have been a reflection ofhigher caries activity, but theprecise nature of this groupremained uncertain. A subsequentanalysis of the study material identifiedonly minor differences ofsalivary risk markers for cariesbetween patients in the high- andlow-failure groups 184 .Patient attendanceHawthorne and Smales 150 relatedsurvival for amalgam and compositeresin restorations with patientattendance in a retrospective studyof five types of restorations placedby 20 male dentists in 100 adultpatients. There were no significanteffects on restoration survival fromchange of dentist, and generally onlyone or two types of restorationshad their survivals influencedsignificantly by frequency ofpatient attendance or experience ofdentist. Restoration survival was notinfluenced significantly by whether,or not, any replacements weremade by the dentist who placedthe initial restorations.Regularly attending patients areprobably more dental healthconscious than irregular attenders.Furthermore, at recalls, dentistscorrect minor discrepancies that arebelieved to put the prognosis of arestoration at risk. Therefore,improved restoration longevity ismore likely in regular attenders.However, Jokstad et al. 165 did notdetect this difference in a crosssectionalstudy of 8,310 restorations,where similar restoration ages wererecorded for the regular andirregular attenders.Mahmood and Smales 152 comparedlongevity of dental restorationsin selected patients fromdifferent practice environments intwo countries, private practices inPakistan and a dental hospital inAustralia. In both countries, restorationsurvival was significantlyimproved when patients attendedinfrequently for treatment, andwhen the patient routinely changeddentist.In an examination of the survivalof 1,918 restorations in an Australianmilitary population, no differencesin survival as a function of frequencyof attendance or frequency ofchange of dentists were reported 181 .Kroeze et al. 182 examined, in anational epidemiological survey, therestoration quality of 600 dentateadults. The authors reported thatthe restoration quality could berelated to the frequency of visits toa dentist.A re-examination of 720 dentateScottish residents who had takenpart in a dental health survey fiveyears previously suggested superiorrestoration longevity among thepatients who had not changeddentist frequently 185 .Does technical excellencepredict failure?In several longitudinal studies ingeneral practice settings, it has beenobserved that dentists do notnecessarily replace restorations evenwhen one or more features havebeen graded as unacceptableaccording to the USPHS/CDAcriteria 140,186–190 . Thus many dentistspractice a treatment philosophywhere the discrepancy is observedrather than effecting an immediateoperative intervention. Interestingly,the same longitudinal studies alsoreveal that restorations will performsatisfactorily for many years in spiteof ‘unacceptable’ USPHS/CDAscorings.One main conclusion from afifteen-year longitudinal study of1,213 Class II amalgam restorationswas that the short-termmarginal performance was not anindication of long-term survival, andthat there was a lack of a validpredictive parameter 107–109 .In a longitudinal study of ClassV composite resins, the authorsreported that it was apparent thatthe results after two years ofobservation could not be used topredict the three-year results 191 .Smales and Webster 188 attemptedto determine the relationshipbetween the deterioration and thelater failure of a very large numberof amalgam and anterior compositeresin restorations examined overperiods of up to sixteen years.Assessments were made of thedeterioration in various characteristicsof restorations that werethought to predict later failure. Foramalgam, there was a significantassociation found between surfacetarnishing and failure. Marginal fractureand marginal staining were notsignificantly associated with any ofthe three failure modes. For thecomposite resins there were significantassociations between thesurface roughness, marginal fractureand colour mismatch. However,surface and marginal staining werenot associated with any of the threefailure modes. Many restorationsassessed as being unsatisfactorycontinued to function on averagefor a further two to three yearsInternational Dental Journal (2001) Vol. 51/No.3

137before being replaced, often forunrelated reasons.The median function period ofrestorations can possibly bepredicted by a Weibull distributionfunction. However, Smales et al. 192reported, after applying such atheoretical model on three restorativematerials, that this is problematicif the model includes slowlydeteriorating restoration features.Specific replacementreasonsAllergyGiven the enormous number ofdental restorations placed worldwide, the incidence of adversereactions seems exceedingly small.Researchers have tried to estimatethe population risk of adversereactions to materials used indentistry 193 , but the accurateness ofsuch estimates of risk remainsuncertain. However, there are in allpopulations a minority of individualsthat responds negatively to variousextrinsic and intrinsic substances,including biomaterials found to beof acceptable biocompatibilityaccording to International Organisationfor Standardisation (ISO)standards. All dental restorativeshave the potential to cause adverseeffects, even when used correctly.Higher risks of adverse reactionsare present if the material is notproperly stored or handled, forexample, incorrect proportioning,contamination, inadequate polymerisation,date expiration, incorrectstorage temperature and/or humidity.Several comprehensive reviewarticles 194,195 proceedings and consensusstatements on the subject ofbiocompatibility of materials canbe found in the dental literature.Endodontic complicationsPostoperative sensitivity is anoutcome that is a complex combinationof the effect of the extentand depth of the initial carieslesion, cavity preparation depth,period of dentine exposure tosaliva and caries, material-to-cavityadaptation, quality and quantityof exogenous bacterial products,restoration sealing and variablepatient pain thresholds 196,197 .Post-operative sensitivity aftercementation may be associated witha deformation of the abutmentfollowing high pressure or misalignmentof the casting during cementation.The hypersensitivity resultsfrom fluid movement within thedentinal tubules 198 .Material factorsThe previous belief that pulpcomplications following restorativetreatment were either the consequenceof insufficient removal ofbacteria in the dentine or to toxiceffects from the material was challengedapproximately 10 years ago.In a consensus report from 1992,it was stated that much of theprevious work on pulpal reactionsto restorative procedures andmaterials had up to then beenflawed because of leakage ofbacteria and their products aroundfilling materials 199 . The general viewtoday is that most restorativematerials do not per se cause pulpdamage as long as they are properlyhandled, but problems willdevelop if the handling proceduresare not followed to ensure optimaladaptation to the cavity walls 200 . Anexception is perhaps glass-ionomercements when applied in a veryclose proximity with the pulp 195 .Poor adaptation between arestoration and remaining toothtissues increases the risk for endodonticcomplications given thepotential leakage of detrimentalsubstances. A number of highlysophisticated laboratory techniqueshas been developed to measureadaptation, but the association withclinical significance remains uncertain.Thus, quantitative data fromlaboratory leakage studies do notgive sufficient information topredict clinical performance. Theenvironmental conditions in themicrospace between restoration andcavity walls remains unknown, aswell as the interaction mechanismbetween the potentially detrimentalsubstances in the space and thetooth tissues. Even the characteristicsof the bacteria in, or adjacentto, the gap have not been firmlyestablished. It is clear that thesurface chemistry of the materialsignificantly influences the microecologicalenvironment 201 . However,it is unclear if this is due to a localtoxic effect of possible componentsreleased from the restorativematerial, or if it is indirectly due toan effect on the initial biofilmcomposition that is formed on therestoration surface.Anecdotal sources have reportedthat in some practices, alarmingnumbers of endodontic procedureshave become necessary because ofpulp damage after prosthesis cementation202 . Third-party paymentcompanies report that many teethreceiving crowns require endodontictherapy within five years. It isuncertain if this can be related to agradual shift of use from conventionalzinc phosphate cements toalternative cements and/or cementationtechniques.Operator factorsCavity designThe remaining dentine thickness isa critical factor in the developmentof pulp damage given the largesurface area of open dentinetubules close to the pulp. Dentinetubules may provide diffusionchannels for noxious substances,which diffuse toward the pulpwhere they can activate the immunesystem, provide chemotacticstimuli, cytokine production, andelicit pulpal inflammation 116 . Postoperativehypersensitivity, on theother hand, seems to occur in someindividuals regardless of the depthof the prepared cavity 203 .The incidence of pulpal complicationsfollowing crown and bridgework was discussed by Valderhauget al. 190 in a report describing theresults of a longitudinal clinicalFDI Commission, Jokstad et al.: Quality of dental restorations

138study of initially 158 fixed prosthesesmade by senior dental students25 years previously. The resultsindicated that the frequency of pulpdeterioration in association withbridges tends to be related to thesize of the prosthesis. It can bespeculated that this can be theeffect of biomechanical complexity,including factors such as acomplex alignment of preparationswith possible iatrogenic tissueremoval and overtapered abutments;lack of acceptable fit in partsof the casting; tendency to acceptsmall discrepancies in large, fixedprostheses compared to singlecrowns, and the complications oforal hygiene procedures.Periapical complications andvertical root fractures following theplacement of restorations orcrowns with pulpal or parapulpalposts may be considered as iatrogenic.Cross-sectional studies indicatethat this is perhaps morecommon than is acceptable. Grieveand McAndrew 204 examined radiographically327 post-retained crownsfor length of post, length ofremaining root filling, periapicalcondition, fit and angulation ofthe post and quality of root filling.Most root fillings were judged tobe unsatisfactory, and there wasno radiographic evidence of anyroot filling in nearly 10 per cent ofcases.Investigations published before1992 on the possible relationshipbetween Class I and Class II cavitypreparations for amalgam andadverse effects on the pulp hasbeen reported in a previous paper,and will not be discussed further 113 .Material handling andproceduresThe principles for prevention ofpulpal damage during preparationwith rotating instruments wereoutlined many years ago, and arestill valid today. Key factors arefrictional heat and adequate cooling,excessive dehydration and airblast, and vibration and highspeed 46 .Concerns over possiblemicroleakage and postoperativesensitivity with amalgam restorationshave led many practitionersto use various varnishes and resincontaininglining, or ‘adhesive’materials. However, others havequestioned the merit of amalgambonding, and the results areconflicting 205 .Cases of persistent post-operativesensitivity with composite resinrestorations following total etchingand application of some dentineadhesives have been reported. Thisclinical phenomenon can occurdespite careful isolation prior todirect restorative procedures andthe use of an incremental build uptechnique, as well as after cementationof indirect restorations inconjunction with using a compositeresin cement. Problems regardingpost-operative sensitivity are hypothesisedto be related to a deficientlight-curing source, or incompleteevaporation of the primer solventsprior to application of the bondingagent. Alternative suggestions aregaps, cracks in enamel related topolymerisation stresses, fracture oftooth substance at the restorationcavity interface and polymerisationshrinkage followed by hydraulicforces induced during masticationon the dentinal tubule fluid followingflexure of the restoration 195,206 .Patient factorsIntraoral locationIn a study of 88 composite resinrestorations over two years it wasobserved that the postoperativesymptoms were significantly lowerin premolars compared to molars 101 .Borgmeijer et al. 196 reported postoperativesensitivity after placing244 Class II restorations ofcomposite resin and amalgam. Postoperativesensitivity occurred moreoften in the molars than in thepremolars although the differencewas not statistically significant. Theresearch group reported that thisfinding had also been observed inanother study of 240 indirect ClassII composite resin inlays and amalgamrestorations 207 .Age and genderDuring function, secondary andreparative dentine is deposited inthe pulp. At age 55 years, thevolume of the pulp is about 20 percent of that at age 25, and containsonly 20 per cent of the bloodsupply 208 . This suggests that thepulp’s capacity of recovery decreaseswith age. However, there are nodata in the literature reporting theincidence of endodontic complicationsas a function of patient agefollowing restorative therapy.Oral environmentAnecdotal observations suggest thatbruxism may be associated with anincreased risk of pulpal complicationsfollowing flexing of therestorations and gap formation.The clinical evidence for this is poor.In one early in vitro study it wasdemonstrated that composite resinrestorations placed in third molarsexhibited increased microleakagewhen an antagonist was presentcompared to none 209 . The authorconcluded that bacterial leakagearound restorations in cavitiessurrounded by enamel would mostoften be the result of stress in therestored tooth during occlusion andarticulation. The study has not beenduplicated using modern dentinebonding systems, so it is uncertainto what extent the conclusion isapplicable to newer composite resinmaterials.Does technical excellencepredict failure?A clear relationship between endodonticcomplications and criteriafor technical excellence of dentalrestorations has not been demonstrated.Several review papers havesuggested that such a relationshipexists, but this is substantiatedmostly with laboratory andmicroleakage studies 210 . In one clinicalstudy the radiographic qualityof the root filling and the appearanceof the apical one-third ofInternational Dental Journal (2001) Vol. 51/No.3

1391,010 endodontically treated teethwas scored 211 . This was related tothe presence of open margins,recurrent decay or overhangsdetected in radiographs. By calculatingthe odds ratios of periapicalinflammation as a function of theroot-filling and restoration qualities,the authors concluded thatrestoration qualities are moreimportant than root-filling quality.Although this finding may give riseto concerns there are many methodologicalissues that can be raised,and scientifically sound researchdesigns are needed to substantiatethe hypothesis. Indeed, a recentidentical study resulted in contradictoryresults 212 .Periodontal problemsThe research focused on dentalrestorations and periodontal diseaseis a good example of how thecriteria for causation as establishedby Hill have been applied successivelyto clarify the relationshipbetween the two factors 213 . Thereis consistent association for severalepidemiological studies betweenrestorations with and withoutdiscrepancies and indicators of periodontaldisease 214,215 . Strength ofassociation and degree of exposurehas also been demonstrated.For example, Lang et al. 215 observeda close relationship between aninflammatory response to poormargins and increasing sizes of overhangs.Hill’s criteria of temporalityhas been verified in numerous studies,showing that the periodontaltissues around restored teeth havemore gingival inflammation thanthe periodontal tissues around intactteeth in intra- and inter-patientcomparisons. The criteria for interventioneffect was demonstratedin a study by Coxhead 216 , whoreported that following removalof restoration overhangs on 50patients, the conditions of the periodontaltissues improved significantly.A biological plausibility andcoherence of results has beenestablished in experimental studieswhere significant changes in themicrobial ecosystem followingintroduction of unfavourable characteristicsof the restorations wereobserved 217 . Finally, experimentalevidence of a causal relationshiphas been confirmed in numerousanimal studies.Material factorsMultiple studies have compared theperiodontal response to differentdental materials, but only smalldifferences have been detectedprovided that the restoration surfaceis smooth 218,219 . No studies havebeen located in the literature linkingperiodontal problems to specificphysical properties of materials.A speculative suggestion is thatrestorations made from materialswith high creep values will extrudeout of the cavity as a result ofocclusal stress, and thus cause plaqueretention with periodontal diseaseas a consequence. However, noclinical data substantiate thisconcept.Operator factorsCavity designIn general, the proportion of restorationswith poor margins gingivally,correlates with the gingivoaxiallocation, and thus contributes moreto periodontal disease than restorationsplaced away from thegingival sulcus 215,216 . In one clinicalstudy, no improvement in gingivalstatus was noted following theremoval of overhangs. It washypothesised that this was due to acorrelation between, on one side,the axial location of the restorationmargin, and, on the other side, thedimensions of the overhangs andgaps 220 .Investigations published before1992 on the possible relationshipbetween Class I and Class II cavitypreparations for amalgam andadverse effects on the periodontiumhave been reported in aprevious paper, and will not bediscussed further 113 .Material handling andproceduresIndirect restorations may beovercontoured or overextended ifthe impression of the preparationis deficient. One paper reportedthat there was little evidence thatestablished guidelines for thepreparation of teeth for porcelainlaminate veneers were beingapplied in full in general dental practices221 . Other papers conclude thatthe general quality of impressionsfor crowns received at commercialdental laboratories may be a causefor concern 222,223 . Johnson et al. 224reported a wide variation of qualitybetween three-unit bridges madefrom different commercial dentallaboratories. Lack of a satisfactoryprescription, representative ofwhich may be used by clinicians,was singled out as an importantexplanatory factor.Patient factorsThe most important aetiologicalfactor in periodontal disease is thepresence of microbial plaque.Unless the patient can establishplaque control the risk of developingperiodontal disease is high,regardless of the technical excellenceof a restoration. The fact thatoral health maintenance is a majorsignificant factor in avoiding periodontitisand caries has beenestablished repeatedly since themid-1970s 225 . Grasso et al. 214concluded after a cross-sectionalstudy including 291 patients thatplaque control measures were probablymore important in reducingperiodontal disease than improvingthe technical excellence of therestorations.No studies have been identifiedin the literature linking periodontalproblems to restoration propertiesas indirectly influenced by specificpatient factors.Does technical excellencepredict failure?It is difficult to separate the effectsFDI Commission, Jokstad et al.: Quality of dental restorations

140of various local aetiological factors,when assessing the associationbetween periodontal disease andrestorations. Reported restorationparameters include the axiogingivallocation of the restoration margin,the location of the contact area andthe axial contour of the restoration.Other factors are the plaqueretentive ability, chemical state androughness of the restorative material,the occurrence and size ofoverhangs and crevices, and thepossible contributing effects of arestoration on an adjacent tooth.Adverse effects on the softtissues have been attributed either toimproper contact areas with foodimpaction 226 or to details such assurface roughness, contour gaps andoverhangs. Within limits, it appearsthat surface roughness does notlead to gingival changes 218,219,227 .There is general consensus thatall factors that enhance theaccumulation of plaque promoteperiodontal disease. Therefore,cavity designs that increase theprevalence of restoration discrepanciesindirectly cause supportivetissue breakdown. The prevalenceof gingival restoration margindiscrepancies varies among differentreports. One major reason is the lackof common assessment techniquesand a common terminology.AestheticsThe topic of aesthetics includesboth the qualities of shape andappearance 228 . Shape depends on theoperator’s ability to contour andfinish the surface, as well as thematerial’s wear resistance. Appearancedepends primarily on materialoptical properties of colour andtranslucency. Metamerism, (a differencein colour appearance that varieswith the light source) is also acommon concern in aesthetic dentistry.The same concern exists forfluorescence of materials and teeth.Many would argue that a highlypolished, anatomically correct castingor amalgam restoration isaesthetically pleasing. When patientsare asked their opinion of aesthetics,it comes as little surprise, that toothcolouredrestorations are preferred.Numerous clinical studies haveconfirmed strong patient acceptanceof tooth-coloured inlays. Rimmerand Mellor 229 evaluated patients’perceptions of different types offixed anterior restorations. Respondentsthought that crowns and fixedprostheses with normal marginswere of a higher technical standard,and those restorations were preferableto crowns with metalmargins. The shade and colour ofthe restorations were the mostimportant factors in the participants’assessments.Abrams et al. 230 compared theassessment of quality by 117 patientsafter two dentists had assessed theirrestorations. The authors observedthat when the patients and dentists’perceptions of the quality of thedental restorations were compared,no relationship existed. It wasconcluded that patients anddentists employ different criteriaand priorities when judging qualityof dental care. The logical view ofaesthetics of dental restorations isrelated to the patient perspective,notably to what extent do dentalrestorations deviate from the appearanceof sound teeth? (Figure 5)Material factorsSeveral tests have been devised toscreen materials at risk for bulkdiscolouration. These tests employhigh intensity light sources and/orliquids with high chromaticity toevaluate colour stability. No testsexist that correlate laboratory findingswith clinical observations ofdiscolouration. The complex eventsproducing restoration discolourationin the oral environment arepoorly understood. Bulk andmarginal discolouration variesconsiderably among different typesof dental materials, and withindental material groups such ascomposite resins 189,231,232 and glassionomercements 233 .In general, there is consensusthat amongst the direct restorativematerials, the composite resins havethe best long term clinical performanceregarding aesthetics 234–236 . Somedifferences among the compositeresins have also been reported:• Among conventional chemicallycured composite resins, restorationswith macrofillers discolourmore over time comparedto the same composite resincontaining microfillers 189 .• Chemically cured composite resinsdiscolour more than light-curedover time, probably because ofdifferent polymerisation initiators232 .• Most restorative materials increaseopacity and lightness after aperiod intraorally followingwater absorption, but this variesconsiderably between variousproducts 237 .Operator factorsMaterial handling andproceduresThe aesthetic limits of restorationsin anterior teeth are determinedmainly by :• The size and nature of the lesion• The characteristics of the fillingmaterials• The technique of application• The age of the filling• The oral environment 231 .It is self-evident that an optimalmaterial handling and restorationprocess should be followed toensure a satisfactorily aesthetic result.Numerous papers have detailedtechniques necessary to create aestheticallysatisfactorily restorationsfocusing on variables such as longbevels, polishing, anatomic andsurface sharpening, multi-layeringtechniques, sufficient veneering andapplication of subsurface tints. Noclinical studies, however, have testedthe relative importance of these variousprocedures on the aesthetic outcomesin a long-term perspective.Patient factorsOral environmentIn a clinical study over 18 monthsInternational Dental Journal (2001) Vol. 51/No.3

141abcdeFigure 5 (a–e). ‘Quality’ has a different meaning for different individuals, patients and dentists alike.of composite veneers and artificialresin teeth the effects of consumptionbehaviour, such as coffee, teaand smoking, and cleaning habitson discolouration was evaluated.No significant influence on discolourationcould be detected 238 .Qvist and Strom 88 observed 52pairs of Class III composite resinsover 11 years. Surface discolourationwas most often recordedamong smokers. Significant correlationswere also found betweenthe patients’ consumption of alcoholicbeverages and bulk andsurface discolouration of the restorations.On the basis of a clinical studyit has been suggested that local oralhygiene may play a role in theextent of surface staining 239 .Does technical excellencepredict failure?Although the initial aesthetics ofrestorations of tooth-colouredmaterials can be outstanding, a lastingoutcome requires a material thathas a high proportion of polymer-FDI Commission, Jokstad et al.: Quality of dental restorations

142ised matrix. Restorations with aninsufficiently polymerised matrixwill discolour faster than those witha well-polymerised matrix, and forlight-cured materials this depends,among other things, on an acceptablelight intensity. There are a largenumber of variables (instrumentation,manipulative, restorative) thatalso influence the degree of conversionof monomer to polymer.Rarely are restorations well cured,which is partly because manydentists use light-curing units withlow light intensities 240 . The intensityoutput from a lamp in a lightcuringunit deteriorates over time,and the minimum acceptable lightintensity level is 300mW/cm 2 .Unfortunately, there seems to be alow awareness among dentists ofthe need for maintenance and regularchecking of light intensity aspart of a quality managementprogramme 241 .Material deteriorationMaterial deterioration includes bulkand marginal fracture, as well asexcessive wear or dissolution ofthe material. Excessive dissolutionis seldom seen when materialswhich comply with ADA or ISOstandards are correctly used. Inparticular, the presence of salivaduring material placement may havea strong negative effect on theresistance to deterioration, forexample glass-ionomer cement 242 .Excessive wear of luting cementsmay occur if the cement margin iswide. Modern composite resincements seem to resist wear betterthan conventional cements 243 . Cementsmay also begin to disintegrateunder luted restorations duringdeformation of the restoration,initiating and propagating cracksleading to cement fracture.Bulk fracture is a common reasonfor restoration replacement, and itis often associated with caries.Caries may either have precededthe fracture, or have developedrapidly after fracture if a remnantof a broken restoration remains inthe cavity 244 . No reference in theliterature has been found as to estimatesof the incidence of the twooccurrences.Material factorsMjör 245 compared reasons for replacementof restorations with thosefrom another study recorded 16years previously. The proportionof replacements of amalgam restorationsdue to bulk fracture hadremained much the same over theperiod, which suggest little effectof the improvements in amalgamalloy compositions. On the otherhand, a significant relationshipbetween the zinc and coppercontents of amalgam alloys andbulk fractures was reported byLetzel et al. 69 on the basis of alongitudinal study over 15 years.The authors attributed this to thesuperior corrosion resistance of thenon-gamma-2 (high-copper) amalgamscompared to conventionalalloy compositions.For composite resin restorationsthere has been a notable decreasein the relative frequency of replacementsas a result of degradationand wear, and an increase in thereplacements following bulk andmarginal fractures, which is attributedto changes of materialcomposition 245 .Tyas 246 reported three-year observationsof 102 Class IV restorationsof four composite resins.Significant correlations (P < 0.01)were found between surface chipping/bulkfracture and fracturetoughness, elastic modulus andtensile strength. Moreover, therewas a trend towards an associationbetween incisal wear and both elasticmodulus and inherent flaw size.Operator factorsIt is difficult to assess the influenceof important operator factors suchas poor cavity adaptation, extentof porosities and extent of contaminationof the material duringhandling on the restoration. It canbe assumed this occurs at leastoccasionally with a possible detrimentaleffect on restoration strength.To what extent this acceleratesmaterial deterioration remainsunknown.Of the 15 studies inclu-ded ina systematic review of CERECrestorations, comparable results interms of fracture rates were seen instudies undertaken in general practiceand university environments 15 .Malament and Socransky 247observed 1,444 restorations madefrom Dicor glass-ceramic over 14years, and found no significantdifference between the bulk fractureof inlay and onlay restorations.The fracture incidence improvedsignificantly when restorations wereacid-etched before luting. Therewas no significant differencebetween acid-etched Dicor restorationsthat were placed onshoulder or chamfer preparations,nor did the thickness of the restorationmeasured at the mid-axialpoint of each surface relate to fractureincidence.Letzel et al. 69 reported a significantassociation between amalgamalloys and bulk fractures over anobservation period of five to 15years. Although not much wascommented on in their report, atable showed a marked associationbetween operator and incidence ofbulk fracture.Lemmens et al. 248 reported ananalysis of 176 fractured amalgamrestorations and concluded thatthere was a statistically significantinfluence of the dentist on the incidenceof bulk fracture.Cavity designWilson et al. 146 reported on a fivecentrestudy for the five-yearoutcome of 232 restorations. Largerestorations consistently deterioratedmore than moderate-sizedones, with respect to class ofrestoration or type of toothrestored. In a cross-sectional studyof approximately 2,500 amalgamrestorations bulk fractures wereInternational Dental Journal (2001) Vol. 51/No.3

143most prevalent in fillings with threeor four surfaces 163 .In a three-year study of 438Class I restorations of glassionomercement, composite resinand amalgam, loss of materialand surface cracking or crazingappeared to a greater extent in largeconventional preparations, andespecially among glass-ionomercement restorations 249 .The possible relationship betweenbulk fracture risk and Class I andClass II cavity preparations foramalgam has been reported in aprevious paper, and will not bediscussed further 113 .Patient factorsIntraoral locationMalament and Socransky 245 foundfewer fractures of Dicor restorationsin female than in malepatients. The highest fracture levelwas observed in second molars.Mjör and Jokstad 187 examinedthe clinical performance of 274amalgam, glass-ionomer cermetcement and composite resin restorationsover five years in small ClassII cavities. The majority of the bulkfractures, which were mostly inglass-ionomer cermet cementrestorations, were located in theupper molars.In a 10 year longitudinal studyof 468 amalgam restorations,Jokstad 29 reported findings thatcontrasted with the results byLemmens et al. 243 . Only one of 27fractured restorations was locatedin lower premolars. No effect ofthe intra-oral location on bulkfracture was observed.On the basis of longitudinalstudies over seven years, including176 fractured amalgam restorations,it was suggested that restorationsin the mandibular teeth and especiallyin the premolars were verysusceptible to bulk fracture 248 .Oral environmentWilson et al. 146 reported that thepresence of occlusal contacts had asignificant effect on deteriorationof occlusal marginal adaptationover five years. This appearedgreatest in the large Class I andboth small and large Class II amalgamrestorations in molars. Thisfinding led the authors to suggestthat future longitudinal studiesshould include assessment ofocclusal function, diet and chewingpatterns.In a longitudinal clinical studyof ceramic inlays over three yearsÅberg et al. 251 reported that ofthe fractured inlays, two-thirdsoccurred in patients with signs ofbruxism.In a retrospective study after10–15 years on the quality of 793restorations, bulk fractures in amalgamrestorations were recordedprimarily in patients with severebruxism 170 . The levels of oral healthand smoking were also included inthe analyses, but no influence ofeither was found.Klausner et al. 252 recorded thereasons for replacements of restorations.For bulk fracture, 43 percent of restorations were 10 yearsof age or older, while 80 per centwere older than four years. Theauthors commented that if faultyocclusion or thin pulpal-occlusalsections of amalgam were the principalreasons for isthmus fracture,then these fractures should havebecome evident at an earlier time.Does technical excellencepredict failure?Few clinical studies have addressedthe correlation between materialdeterioration and duration ofclinical service. Early occlusalmarginal fractures, may 69,106,248 ormay not 188,253,254 correlate withfurther material deterioration.Jokstad 29 observed 468 amalgamrestorations of five alloys placed in210 patients for 10 years. Marginalfractures after relatively short clinicalservice were associated with laterbulk fracture.Wear is not linear over time. Ithas therefore been suggested thatit is misleading to calculate anddescribe wear levels in terms ofmicrometre/year 255 . It is probablethat wear decreases over time,because the more wear-resistantadjacent enamel surface protects theremaining material surface to anincreasing extent 256 .CariesThere is no reason to considersecondary caries as any differentfrom primary caries 257 . It is a localiseddisease caused by a localaccumulation of mechanicallyundisturbed bacterial biomass.Several facts should be examinedin this regard. First, even whenthere is a very close adaptationbetween a restoration and tooth,there is still more than enough spacefor bacterial ingrowth. Second, thereis little evidence of ‘undetectablemicroleakage’ causing secondarycaries. Third, most papers havereported only weak evidence of arelationship between marginaldiscrepancies and secondary caries.Fourth, in spite of hundreds oflaboratory microleakage studies, nocorrelation with secondary carieshas been established. Fifth, groundsections of restored teeth withsecondary caries often revealsubsurface lesions unrelated to thecavity wall. Finally, some clinicaldata suggest that the occurrence ofsecondary caries is a localisedphenomenon related to the conditionsfor evolution of cariogenicplaque, rather than a universalattack along the entire interfacebetween tooth and restoration 257 .Thus, secondary caries maydevelop in the presence of cariogenicplaque, but will neverdevelop if cariogenic plaque isabsent regardless of the technicalexcellence of the restoration. Adiscussion of which restorationdetail constitutes a major or aminor ‘focus’ of plaque retentionappears from this aspect to be anacademic discussion. It is thepatient’s oral hygiene habits that willdetermine if caries develops, notFDI Commission, Jokstad et al.: Quality of dental restorations

144whether the restoration can beconsidered as ‘excellent’, ‘adequate’or ‘deteriorated’.Material factorsThe increased popularity of restorativematerials that release fluorideis in part explained by the beliefthat secondary caries can somehowbe prevented by incorporating thiscomponent. The anticariogenicproperties of glass-ionomer cementrestorations are not strongly substantiatedby clinical investigations 13 .On the other hand, the lack ofstrong evidence of an anticariogenicpotential may stem fromclinical studies conducted in academicenvironments on selected patientswith minimal caries risk instead ofin ‘real-life’ general practices.In a longitudinal study of 274large Class II open-sandwich resinmodifiedglass-ionomer cementrestorations over three years, nosecondary caries was noted, despitea large number of participatingpatients with high caries risk 258 . Inthese patients, a far higher cariesfrequency around the other restorativeswas recorded, leading theauthors to suggest a possibleanticariogenic effect of this material.Operator factorsSeveral textbooks advise thatbecause of polymerisation shrinkage,the location of the gingivalmargin for posterior compositeresin restorations should be placedat least one millimetre, when possible,from the enamel-cementmargin. Several cross-sectionalstudies imply that this rule is notfollowed by general practitioners.However, it has not been possibleto identify in the literature any clinicalstudies that have associated thischaracteristic of the cavity designwith the development of secondarycaries.The possible relationship betweensecondary caries risk and Class Iand Class II cavity preparations foramalgam has been reported in aInternational Dental Journal (2001) Vol. 51/No.3previous paper, and will not bediscussed further 113 .Patient factorsIn a clinical evaluation of 63 ClassII composite resin restorations overfive years, 8 of the 11 patients withrestorations that failed because ofcaries and marginal defects hadhigher counts of mutans streptococciat baseline compared to theremaining patients. This led theauthors to suggest that the cariesactivity should be managed to avoidfuture secondary caries 87 .In a study of 4,294 childrenobserved over three years, the incidenceof secondary caries be associatedwith some oral hygieneparameters 259 . Water rinsing afterbrushing and the use of a beakerfor rinsing was associated withsecondary caries. Also, subjects whobrushed less often than twice a daydeveloped more secondary cariesthan the others did.Clarkson and Worthington 260reported that in a group of 270adults an association was seenbetween caries, most commonlysecondary caries, and attendance.The irregular attenders experiencedmore caries than did the regularattenders.van Dijken 261 has carried outseveral longitudinal clinical studieswhere part of the study design hasbeen to classify the patient accordingto few or many caries riskfactors, based on the net effect ofmicrobial counts, oral hygiene, salivaryflow levels, buffer values, andfermentable carbohydrate intake 32 .However, the difference betweenthese two groups has only beenreported in two studies. In a sixyear longitudinal study of 150tooth-coloured restorations, allrestorations which subsequentlydeveloped secondary caries (n=7),except for one, were from the highcaries-riskgroup 261 . In another sixyear study of seven anteriorcomposite resins, a markedly higherincrement of caries was recordedamong the patients with manycaries risk factors 32 .In a 10 year longitudinal studyof 468 amalgam restorations, themost important factor that couldbe associated with the developmentof secondary caries was thepatient’s yearly DFT increment 29 .Does technical excellencepredict failure?Roulet 104 stated categorically thatmarginal integrity is an importantparameter for restoration longevity,since recurrent caries and pulpaldisease is associated with marginalgaps. However, the gap size per semay not play any role in secondarycaries initiation. What is of importanceis whether it promotesformation of cariogenic plaque,which encompasses additional variablesbesides just gap size. It istheoretically possible that the quantityand quality of the plaqueformation around restorations maybe a better prognostic marker ofrestoration longevity than variouscriteria of technical excellence 201 .The alleged correlation betweenmarginal fractures and recurrentcaries is controversial. Two factorsshould be considered in this context.What is the association between thelocation of the defect and locationof secondary caries? What is therelationship between the size of thedefects and secondary caries? Noreports have been identified thatdemonstrate a correlation betweenocclusal discrepancies and marginaladaptation on the approximalsurfaces, which are the areas wheresecondary caries lesions prevail.Therefore, it is difficult to understandhow marginal fractures onthe occlusal surface can be relatedto a higher risk of secondary caries.While some authors reportassociations between marginal fractureand secondary caries 262 , othersdo not 263,264 . Other laboratoryexperiments suggest that a correlationdoes not seem to exist betweenthe size of the crevice and secondarycaries 265 , or describe only acorrelation in extremely cariogenicenvironments 266 .

145Staining around both amalgam 267and tooth-coloured restorations 268is considered unreliable in the diagnosisof active recurrent caries.Hewlett et al. 269 reported that 86per cent of 822 restorations withmarginal defects revealed nosecondary caries on radiographs.This led the author to suggest thatthe replacement of all restorationswith defects related to a perceivedrisk of secondary caries wouldconstitute overtreatment.After observing 468 amalgamrestorations of five alloys placed in210 patients for ten years, Jokstad 29reported that those restorationswith early marginal fractures couldnot be correlated with later developmentof secondary caries.In an observational longitudinalstudy, an increased prevalence ofsecondary caries was recorded inthe restorations with the poorestmargin fracture scores 270 .A longitudinal clinical study over10 years demonstrated no differencesin secondary caries levelsbetween a spherical amalgam alloyand a non-gamma-2 alloy, despitedifferences in marginal deteriorationduring the first years 271 .Goldberg et al. 272 examined1,556 restorations in 87 patients ina cross-sectional study. The prevalenceof secondary caries wascorrelated with the marginal fracturescores and indices of thepatients’ oral health. Using loglinearanalyses, the investigatorssuggested that there was a significantrelationship between thesethree factors.Tooth fractureTooth fractures include cusp fractures,dentine cracks, incompletedentine fractures, crack lines, andcracked tooth syndrome. Some usethe term ‘infraction’ when the crackline is limited only to the enamel.There is general consensus that arestored tooth is stronger than anon-restored tooth with caries, butthat a tooth with an intracoronalrestoration is weaker than an intacttooth regardless of material. Theprocesses involved regarding theway in which tooth strength isassociated with choice of restorativematerial, adaptation and themicrostructural relationship at thetooth-material interface are controversial.This can be explained bythe fact that the incidence of toothfractures is relatively low, whichimpedes the execution of clinicalstudies. Our understanding of therelationship between clinical factorsand tooth fractures is therefore toa large extent based on extrapolationof case descriptions andlaboratory findings 273–275 .Material factorsThermal dimensional stability, hygroscopicexpansion and setting/polymerisation shrinkage of restorativematerials, as well as excessiveloading, have been related tostress build-up in tooth tissues 1,65,73 .The stress will be best tolerated bydentine due to its elasticity, whileinfractions may develop in theenamel. The material-caused stressapplies to restorative materials thatdo not exceed the limits accordingto the existing material test standards.An in vitro investigation hasdemonstrated fractures of ceramiccrowns with cores made fromresin-modified glass-ionomer cementmaterials. It was hypothesised thatthe fractures were caused by hygroscopicexpansion 276 . Several manufacturersdo not recommend thisclass of material for core builds oras a luting cement for full-ceramicrestorations.Several papers postulate thatinfractions in enamel and cuspfractures in teeth restored withamalgam are caused by an expansionassociated with heat or withchemical reactions in the alloy, orcorrosion of the amalgam. However,there is no clinical documentationof such relationship.Furthermore, no standardisationtests have been devised to screenmaterials for this alleged expansion.Operator factorsCast restorations, especially inlaysor dowels with improper fit, causestress that increases the risk of toothfracture. Strain can also be introducedif high pressure is used ormisalignment of the casting occursduring cementation. Also, it hasbeen suggested that tooth preparationusing eccentric or worn bursincrease the risk of crack propagationin the tooth.The possible relationships betweentooth fracture risk and Class I andClass II cavity preparations foramalgam have been reported in aprevious paper, and will not bediscussed further 113 .Patient factorsMost tooth fractures originate inthe 30–50 year age group and inteeth with large intracoronal restorationsor caries. Fractures ofcontralateral teeth are common 275 .All factors that cause high strain ontooth tissue increase the risk ofcrack-line development and cuspfractures. Examples are bruxism,lack of occlusal support followingloss of teeth, malocclusion, supracontactsor frequent intake ofcoarse foods. Cusp fractures andcrack lines in the posterior teethare most frequently observed onbalancing cusps, which are subjectedto lateral chewing forces (thatis, the lingual cusps in the mandibleand buccal cusps in the maxilla).Ellis et al. 274 reported a metaanalysisof the influence of patientage on tooth fracture and concludedthat incomplete tooth fracturesare uncommon in students attendingan emergency clinic. It wasnoted that complete fractures mightoccur at any age, while it appearsthat incomplete fractures are associatedwith older age groups.Does technical excellencepredict failure?No papers were found that reportany association between clinicalobservations of technical excellenceFDI Commission, Jokstad et al.: Quality of dental restorations

146of restorations versus the incidenceof later tooth fractures.Loss of restorationLoss of entire restoration is limitedmostly to Class V restorations,especially when placed withoutcavity preparation. Loss of othertypes of restorations would onlyoccur due to inappropriate selectionof material, improper preparationof the tooth before restoration,violation of biomechanical principlesfor designing the restoration,mishandling the material, or acombination of these factors.Material factorsDeviations from the manufacturer’sdirection for use may lead todecreased clinical performance. Thishas been reported in a three-yearstudy of resin-modified glassionomercements placed in cervicalcavities, where retention wasassociated with surface wettingfollowing variations in the powder/liquid ratio at the time of placement277 .Much discussion has taken placeon the importance of the modulusof elasticity of polymeric materials278 . There are diverging views onits relevance, and this confusion typifiesour poor understanding oftooth biomechanics. There is alsoan ongoing discussion about whichmaterial is most appropriate fornon-carious cervical lesions. Iscomposite resin, glass-ionomercement, polyacid-modified compositeor resin-modified glass-ionomercement the optimal material ofchoice 279,280 ?Operator factorsAlthough presented as anecdotalevidence, Friedman 281 recounts hisclinical experiences after placing asubstantial number of porcelainveneers (n=3,500) over 15 years.The author attributes the three mainfailure reasons (debonding, marginaldiscolouration and adhesive fractures)to poor bonding, which isan indirect indication of impropertooth preparation or materialhandling. It has been suggested thatthe effectiveness of dentine bonding,and thus the retention ofrestorations, is influenced byoperator factors such as cavitypreparation relative to the activecaries process, technique for materialapplication, and procedures forpolishing 282 .Cavity designVital dentine is continuously remodellingits microstructure to respondto physiological and pathologicalchanges. Therefore, bonding mayencounter differences such assclerotic dentine, hypersensitivedentine (with open tubules), cariesaffectedareas, superficial dentinewith few tubules, or deep dentinelayers close to the pulp 283 .IsolationCervical composite resin restorationsplaced with isolation eitherwith rubber dam or with cottonrolls suggested no statisticallysignificant differences in retentionafter two years of service. Thus,loss of retention was not differentwhen a careful cotton roll techniquewas used as a moisturecontrol method, as long as salivacontamination was avoided 174 .Patient factorsGender and ageIt has been suggested that bondingto sclerotic dentine is less reliablethan to young dentine, at least witholder restorative materials 284 . Tworecent clinical studies have refutedthe hypothesis 285,286 . In these studies,lower failure frequencies wereseen in the oldest age groups andthe restorations placed in scleroticdentine had an almost equal failurerate compared to the ones placedin non-sclerotic lesions.McCoy et al. 191 suggested, aftera three-year longitudinal study ofClass V composite resin restorations,that a high proportion of oldpatients in the study contributed torelatively high proportion of loss,as a result of changes in the characterof the dentinal surface.Heymann et al. 287 reported onthe determinants of failure of bondedcomposite resin restorations in noncariouscervical lesions. A strongassociation between patient age andrestoration loss was identified,which was attributed to the greatertooth flexure in older patients, andthe smooth, sclerotic nature of ‘old’dentine.Oral environmentIn a recount of a clinical experienceafter placing 3,500 porcelainveneers over 15 years, Friedman 281distinguishes between three fracturetypes, and suggests the aetiologicalmechanism for each type. Theauthor ascribed static fracture linesand cohesive fractures to excessiveloading.McCoy et al. 191 noted in a threeyearlongitudinal study of Class Vcomposite resin restorations thatsome restorations were lost fromteeth with marked signs of occlusalwear, supporting earlier reports ofhigher loss of restorations amongbruxers compared to non-bruxers 288 .Does technical excellencepredict failure?There are no known papers thathave reported any associationbetween clinical observations oftechnical excellence of restorationsversus later loss of restorations.Orthodontic changes andtemporomandibular jointproblemsComposite resins placed during1970–1980 had relatively poorresistance to wear when used in theposterior occlusal segments. In spiteof this, products were sold in largequantities and used for thispurpose by many general practitioners.Annual wear of 30–60mmwas reported, raising concerns forpossible hypereruption of opposingteeth and mesial migration ofteeth distal to those undergoing lossInternational Dental Journal (2001) Vol. 51/No.3

147of approximal contact 289 . Despiteconcerns that composite resins wereunsuitable for surfaces exposed toheavy masticatory forces, therewere no reports that extensive useled to tooth misalignments ortemporomandibular joint problemscaused by occlusal changes.The resistance to wear ofcorrectly handled modern materialshas now been markedlyimproved. Thus, the risk of largegeneralised wear and potentialpathological joint changes andtemporomandibular problems areminor. However, the potentialexists if materials are handledincorrectly, following eating disordersor harmful occupationalenvironments, or if new restorativematerials are applied that havenot been adequately tested forclinical wear.Treatment decisions andtechnical excellenceThe planning of restorative treatmentconsists of a series of interactiveexchanges of information betweenthe dentist and the patient. Lack ofawareness of a patient’s complaintsand expectations can lead tounnecessary conflicts, a situationcherished by sensational newsmedia. A common principle inmarketing is ‘do/say the right thingto the right people at the righttime’. This quotation can beimproved for our purposes byrefining the words into the dentalstrategy. Optimal dental treatmentof patients consists of: (1) At theright time, (2) offer the right treatment,(3) to the right patient, (4) inthe right way, (5) with the rightresults.The interpretation into dentalterms is (1) make the correct diagnosisat the outset, (2) explain tothe patient the options and suggestthe best alternative, (3) take intoconsideration the patient’s prioritiesand preferences, (4) carry outthe restorative intervention accordingto correct procedures andmaterial handling to ensure thehighest possible technical excellence,and (5) aim to accomplishthe pre-set objectives that you as adentist and patient have agreed on.The most relevant issue is the evaluationof the technical excellenceof dental restorations as part ofthe first step: making a correctdiagnosis. Main objectives are torecognise a pathological condition,understand the patient’s problemand identify risk markers ofprogressive oral disease. The technicalexcellence of restorations is,at this stage, of secondary importance.Patient dissatisfactionPatient dissatisfaction with a particularrestoration is easy to detect. Itincludes complaints about pain,aesthetics, surface roughness, contour,detectable margins, supraocclusionor food retention. As long as thecontributing factor is identified andcorrected, there is no problem.However, if the patient’s dissatisfactionis with a restoration thatmeets all criteria for technicalexcellence the situation is morecomplicated. Then patient informationand ethical considerationsmust prevail, tempered by existinglocal or national legislative precedentsor regulations. The patientmust always be advised of thepotentially iatrogenic damage associatedwith restoration replacement,such as risk of pulp deteriorationand increased cavity dimensions,as well as the possibility of noimprovement in spite of restorationreplacement.Some studies have attempted tocategorise or distinguish patientcharacteristics versus expectationsof dental treatment. Several taxonomieshave been presented. Håkestamet al. 290 suggests there are threegroups: the aesthetic, the costconscious and the longevityfocussed.Lutz and Krejci 291categorised the patients as in orally‘functional’, ‘presentable’, ‘healthy’,‘beautiful’ and ‘metal-free’ groups.Other studies have applied furtherpatient classifications. Althoughsuch systems tend to appear simplistic,they highlight the fact thatpatients’ personalities, values andpriorities differ considerably. Modernhealth care places great emphasison patient satisfaction as a criterionfor quality. However, thetheoretical principles of patient satisfactionare complex and correlatepoorly with criteria for technicalexcellence commonly used bydentists 292 .Estimating risk for oraldiseaseAssessment of risk markers of oraldisease is detailed in at least oneexcellent textbook on risk and oraldiseases 293 , and within textbookson cariology 46,267,294,295 and periodontology296,297 . Briefly, risk assessmentassociated with susceptibility to oraldisease consists of determiningfactors related to the patient’ssocial and medical history, plaquecontrol, saliva and clinical signs ofdisease. Estimating the risk for oraldisease progression can be assessedat the patient, tooth and site levels.At the patient level, the key oraldisease risk markers are the presenceof a systemic disease, irregulardental attendance, prior carieshistory, periodontal problems, plaqueand/or bleeding scores, medicationside effects and saliva quantityand quality. Other risk markers mayrefine decisions about interventions.For example, information on socialdeprivation, active oral disease insiblings or low dental IQ andhistory of repeated interventionsmay be relevant factors.For periodontal disease, presenceof residual pockets and cigarettesmoking are additional factors tobe considered when assessing riskwhile additional factors for addressingrisk for future caries are dietaryhabits, frequency of sugar intake,availability of snacks and use offluorides.At the tooth and site levels, riskfactors include residual periodontalsupport, inflammatory parametersFDI Commission, Jokstad et al.: Quality of dental restorations

148Table 4 Intervention strategies based on combining a risk assessment for oral disease and the technical excellence ofthe patient’s restorations. The codes used in the CDA evaluation system criteria 31 are included to enhance the interpretationof the table (see Table 5 for abbreviations)1. Consider consequences of monitoring, correcting, removing or replacing restoration in case of:CariesCaries along restoration margin (VCAR)Radiographic evidence of caries/voidsMarginRetained excess cement (TCEM)Restoration overhang/surplus (TOV)OtherTooth structure is fractured (VTF)Mobile restoration (VMO)Superficial or penetrating fracture line (VFR)Restoration is partially or in toto missing (VMIS)Evoked pain during clinical examination2a. If markers of high-risk caries present: 2b. If markers of high-risk periodontitis present:1. Assess if these criteria possibly are associated with 1. assess if these criteria possibly are associated withor can contribute to diseaseor can contribute to disease2. Consider consequences of monitoring, correcting or 2. Consider consequences of monitoring, correcting orreplacing restorationreplacing restorationSurfaceSurfaceFractured, rough or pitted or irregular, flaking or hasFractured, rough or pitted or irregular, flaking or hasgross porositiesgross porosities(SRO)(TGI)(TPIT)(VSF)(VFK)(VGP)(SRO)(TGI)(TPIT)(VSF)(VFK)(VGP)ContourContourExposed dentine or base (TDE)(TBA)Contact slightly open or faulty (SCO)(TCO)Undercontoured cervical area approximally (SPX)(TPX)Undercontoured cervical area approximally (SPX)(TPX)MarginMarginDitch or gap along the margin (SCR)(TMD)Ditch or gap along the margin (SCR)(TMD)Discoloured margin (SDIS)(TPEN)OtherTraumatic occlusion (VTO)3. Limit intervention to monitoring – unless the patient is dissatisfied.ContourUndercontoured or overcontoured restoration (SUCO)(TUCO)(SOCO)(SOC)(TOCO)(VUO)The occlusion is affected (SOH)(TET)(TOC)Under-contoured marginal ridges (SMR)Flattening present facially or lingually (SFA)(SLG)and their persistence, presence ofecological niches with difficult toaccess sites such as furcations, andthe presence of iatrogenic factorssuch as restoration discrepancies.Information gathered by clinicalmonitoring and continued multilevelrisk assessment produces anestimate of the oral health status ofan individual, and risk of oraldisease progression at a particulartooth or site. It is not until thisstage that concern about the technicalexcellence of one or moreparticular restorations should beaddressed. Thus, the risk level fororal diseases must in a systematicway first be recognised, and thencoupled with treatment optionsthat are consistent with the potentialfuture caries increment orperiodontal disease. It has beensuggested that a decision-treeInternational Dental Journal (2001) Vol. 51/No.3approach and/or treatment-indexconcept should be applied tospecific clinical conditions andpreventive-restorative options toestimate the probable outcomes 298 .In the introduction, a definitionof the quality of restorationsemphasised the risk of jeopardisingthe integrity of remainingdental-related tissues. Patients withindications of severe caries or periodontaldisease require moreattention to possible detrimentalcharacteristics of restorationscompared to patients with no signsof disease. The concept of such anapproach is consistent with thetreatment decision philosophypractised by many clinicians. Theclinician always has three options indeciding on a strategy for intervention.Either to ignore the currentstatus, to adjust or repair, or restorationreplacement.Table 4 suggests how the technicalexcellence of restorations shouldbe appraised clinically in light ofrisks of oral disease. The wordingof the criteria parallels descriptionsused in the CDA evaluationsystem 31 and textbooks cited at thestart of this section. Table 5 showsthe CDA quality evaluation ratingsystem and USPHS criteria forevaluation.It must be emphasised that theconsiderations of the consequencesof monitoring, correcting, removingor replacing an existing restorationmust be but one component of themanagement of oral disease. Furtherrequirements to justify operativeintervention should include patientunderstanding of risks and prognosis,assessment of aetiology andthe instruction of preventive proce-

149Table 5 Relationship between the CDA and the USPHS criteria for evaluation of dental restoration systems 30,31 .Surface and color Anatomic form Margin IntegrityR: Range of excellenceRestoration is of satisfactory quality and is expected to protect tooth and surrounding tissueCDA USPHS CDA USPHS CDA USPHSSurface of restoration is The restoration appears to Restoration contour is in The restoration is a No visible evidence of There is no visual evidence of dark,smooth match the shade and functional harmony with continuation of existing crevice on margin into deep discoloration adjacent to theNo irritation of adjacent translucency of adjacent adjacent teeth and soft anatomic form or is slightly which explorer will penetrate. restorationtissue is occurring tooth tissues tissues with good individual flattened. It may be over- Satisfies principles of marginThere is no mismatch in anatomic form contoured. When the side of placement wherever possible. The explorer does not catch whencolor or translucency (The restoration must be the explorer is placed No discoloration on margin drawn across the surface of thebetween restorations and examined without using a tangentially across the between restoration and restoration toward the tooth, or, if theadjacent teeth* mouth mirror) restoration, it does not touch tooth structure* explorer does catch there is no visibletwo opposing cavosurface crevice along the periphery of theline angles at the same time restorationThere is no visual evidence ofmarginal discoloration difference fromthe color of the restorative materialand from the color of the adjacenttooth structureS: Range of acceptabilityRestoration is of acceptable quality but exhibits one or more features that deviate from idealCDA USPHS CDA USPHS CDA USPHSSRO Surface of restoration The restoration does not SOCO Restoration over- A surface concavity is SCR Visible evidence of There is visual evidence of marginalis slightly rough or pitted; match the shade and contoured slightly (but evident. When the side of an slight marginal discrepancy discoloration at the junction of thecan be polished translucency of adjacent excess material can be explorer is placed tangentially with no evidence of decay; tooth structure and the restoration, butSMM Slight mismatch tooth tissues, but the removed) across the restoration, the repair can be made or is the discoloration has not penetratedbetween shade of mismatch is within the normal SUCO Restoration slightly explorer touches two unnecessary (visible ditching along the restoration in a pulpalrestoration(s) and adjacent range of tooth shades undercontoured opposing cavosurface line along the margin not directiontooth or teeth* SOH Occlusion is not totally angles at the save time, but extending to the DE junction)(… and tooth structure within functional (or height reduced the dentin or base is not The explorer catches and there isthe normal range of tooth locally(not in toto)) exposed SDIS Discoloration on margin visible evidence of a crevice, into whichcolor, shade and/or SMR Marginal ridges slightly between restoration and the explorer penetrates, indicating thattranslucency) undercontoured tooth structure* the edge of the restoration does notSCO Contact slightly open adapt closely to the tooth structure.SFA Facial flattening present The dentin and/or the base is notSLG Lingual flattening present exposed, and the restoration is notSAF Anatomic form of pontic mobilemay cause food retention; noirritation of soft tissueSOC Occlusal contour notcontinous with that of cuspsand planesSPX Interproximal cervicalarea slightly undercontouredFDI Commission, Jokstad et al.: Quality of dental restorations

150T: Replace or correct for preventionRestoration is not of acceptable quality. Future damage to tooth or surrounding tissue is likely to occurCDA USPHS CDA USPHS CDA USPHSTGI Surface grossly irregular, The restoration does not TUC0 Restorations grossly There is a loss of restorative TFAM Faulty margins that There is visual evidence of dark, deepnot related to anatomy and match the shade and undercontoured substance so that a surface cannot be properly repaired discoloration adjacent to the restorationnot subject to correction translucency of the adjacent TOCO Restorations grossly concavity is evident and the TPEN Penetrating discoloration (but not directly associated withTMM Mismatch between tooth structure, and the overcontoured base and/or dentin is along margin of restoration in cavosurface margins)restoration(s) and adjacent mismatch is outside the TET Occlusion affected exposed pulpal direction*tooth or teeth outside normal normal range of tooth shades TCO Contact is faulty TCEM Retained excess The explorer penetrates a crevicerange of color, shade, or and translucency TOV There is marginal cement defect that extends to the dentoenameltranslucency* overhang junctionTAF Anatomic form of pontic TMD visible ditching alongTPIT Surface deeply pitted, likely to result in food the margin extending to the There is visual evidence of marginalirregular grooves (not related retention, causing irritation to DE junction discoloration at the junction of the toothto anatomy) cannot be soft tissue or caries in TMB ditching along the structure and the restoration that hasrefinished abutments margin extending to the penetrated along the restoration in acenter base pulpal directionTDE Dention is exposedTBA base is exposedTOC A occlusion is affectedTPX contact is faulty –self-correction unlikelyV: Replace statimRestoration is not of acceptable quality. Damage to tooth or its surrounding tissues is now occurringCDA USPHS CDA USPHS CDA USPHSVSF Surface is fractured VTO Traumatic occlusion VMO Mobile restorationVGP There are gross VUO Gross underocclusion or VFR Fractured restorationporosities in crown material restoration VCAR Caries continuous withVSD Shade in gross VPN Restoration causes margin of restorationdisharmony with adjacent unremitting pain in tooth or VTF Tooth structure isteeth* adjacent tissue fracturedVDM Damage is now occurringVFK surface is flaking to tooth, soft tissue, orVUN Esthetically displeasing supporting bonecolor, shade and/ortranslucency VMIS restoration is missing*Criteria apply only to anterior teethInternational Dental Journal (2001) Vol. 51/No.3

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