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

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