International Dental Journal (2001) 51, 117–158

Quality of dental restorations FDI Commission Project 2-95*

Asbjorn Jokstad Oslo, Norway Stephen Bayne Chapel Hill, USA Uwe Blunck Berlin, Germany Martin Tyas Melbourne, Australia Nairn Wilson Manchester, UK

*Project initiated and report approved by FDI Commission A major undertaking for general practitioners is the provision and assessment of dental restorations. High quality restorative therapy encompasses several key elements that fulfil specific criteria. Enhanced knowledge of these elements is a significant step toward improve- ment of the quality of restorative dental care1. Several studies have demon- strated that a major component of a dentist’s work is re-restoration of previously restored teeth. Collec- tively this represents a worldwide billion-dollar industry2. Estimates of annual expenditures for ‘replace- ment dentistry’ are US$5000m (USA, 1984)3, NLG600m (Nether- lands, 1988)4, and GB£100m in the public sector alone in UK in 19915. Quality of dental restorations encompasses wide-ranging clinical considerations, which are reflected by many strategies used to explore the issue. Such strategies include appraisals of criteria for quality or causes of failures of restorations6,7, health gains through improvement of clinical practice8, standards of dental care and practice9–11, and Correspondence to: Dr. Asbjorn Jokstad, Institute of Clinical Dentistry, Dental Faculty, methods for evaluating restoration University of Oslo, PO Box 1109 Blindern, N-0317 Oslo, Norway. E-Mail: 12 [email protected] performance .

© 2001 FDI/World Dental Press 0020-6539/01/03117-42 118

Longevity of restorations has viduals’ use and interpretation of custom-made in a wide range of frequently been reviewed. Recent the term ‘quality’ depend on socio- clinical situations and using differ- reports address longevity of resto- economic and cultural backgrounds. ent restorative materials. It is used rations of glass-ionomer cements13, Moreover, the term invokes differ- for any alloplast put in or on a inlays14 and CEREC ceramic inlays15. ent interpretations depending on the tooth, regardless of size, location A systematic review of 652 context in which it is used, for or reasons for placement. The relevant papers on directly placed example, in English. In the dental validity of this practice can be ques- materials commissioned by UK literature it seems that restoration tioned. Consider, as examples, National Health Services has also ‘quality’ is regarded as synonymous bonding thin ceramic laminates on been published5,16. In addition, to ‘technical excellence’. However, worn cuspids in a 60 year old another group of investigators has technical excellence is but one factor patient, applying ‘preventive resin reported a detailed appraisal of the among others that constitute restoration’ in the fissures of the scientific validity of clinical stud- quality. first permanent molar in a 7 year ies17. The reviews highlight that In industrial production systems old, and placing a large MODBL clinical studies have generally been quality is described as: ‘The quality amalgam filling in a lower second carried out under optimal condi- of a product is measured against molar caused by gross caries in an tions, and suggest that reported some objective standard, which 18-year old patient. What do these longevity is unlikely to be achieved includes appearance, performance different variants of ‘restoration’ in routine general dental practice. characteristics, durability, service- have in common besides a name? It is more likely that in routine prac- ability, and other physical charac- They are all being made to tice subjective factors have a greater teristics; timeliness of delivery; cost; improve or restore morphology impact on longevity than objective appropriateness of documentation and/or function with a technical factors such as the physical prop- and supporting materials; and so solution designed to last indefinitely. erties and biocompatibility of the on’18. When the question of quality is of restorative material. It is not complicated to assess a concern, restoration characteristics The aim of the present report is single restoration relative to timeli- should not be of primary interest. to thoroughly review all factors that ness of delivery and cost. Nor is it Rather, focus should be on the may affect the quality of a dental difficult to grade appearance and extent to which the objectives for restoration and to review studies physical characteristics of a resto- placement have been achieved and that have investigated those issues. ration versus a natural tooth. Data maintained. This analysis will consider: on durability and serviceability of It follows that there are funda- • Specific definitions of quality restorations can be aggregated for mental differences between labora- • Variations among clinicians the operator, clinic or even for tory and clinical research outcomes • Analysis of longevity national levels to give some indica- regarding assessment of restoration • Material, operator, and patient- tion of the ‘standard’ of quality. quality. Laboratory research can, at factors affecting initial technical However, measuring quality of a best, only provide indications of excellence dental restoration in this manner is probable or possible technical • Material, operator, and patient untenable for several reasons. The excellence. Clinical studies can, factors contributing to clinical most fundamental reason is that under controlled conditions, provide failure the primary aim in restorative indications of potential restoration • Treatment decisions. therapy is not ‘production’ of quality. Clinical performance needs restorations. Dental restorations to be appraised in general practice must be evaluated in terms of settings. What is quality? pre-set aims such as preserving Most restorative therapy is asso- Definition of quality remaining tooth tissues or improv- ciated with managing damage The literature abounds with papers ing appearance. Of course, this caused by dental caries. Other focused on quality aspects in should not deter dentists from reasons include managing effects restorative dentistry. It becomes striving to consistently place resto- of trauma, wear or erosion with a apparent when reading these papers rations of the highest technical common goal being prevention or that there is little consistency in the excellence. avoidance of further damage. use of the term ‘quality’. This is Alternative indications are aesthetic probably because the term has and functional considerations. multiple interpretations, as the origi- Dental restorations and Although the outcome, that is a nally Latin term ‘qualitas’ has quality restoration, is similar, it would seem varied in different languages The term, dental restoration, is used illogical to prescribe different qual- throughout history. Furthermore, to describe three-dimensional ity criteria for restorations placed it is reasonable to assume that indi- inserts and additions to teeth, following caries versus placement

International Dental Journal (2001) Vol. 51/No.3 119

by tooth prognosis and not by level training of the evaluators varies or of technical excellence. Conse- the procedures for evaluation are quently, evaluations of restoration not detailed. Moreover, evaluation quality are only valid when done procedures and use of supplemen- clinically by a trained clinician with tal aids (for example radiographs knowledge of the patient’s past and and colour photographs) varies. All present oral disease history. The such factors significantly affect the patient’s opinion of a restoration, validity of clinical findings. Two which includes satisfaction with clinical systems for evaluating Figure 1. Risk considerations of three aesthetics, tooth sensitivity, surface restorations are widely used. The restorations. 1. Is the remaining tooth texture and contour is an important original system was developed by integrity intact on both laterals? 2. Are the periodontal tissues damaged? 3. Are determinant of quality. However, the Cvar and Ryge in 1971 and intro- remaining tooth tissues jeopardised by the possibility of inducing an increased duced as ‘Criteria for the clinical discrepancies in the restorations? 4. Will risk of adverse biological effects evaluation of dental restorative any of the restorations wear or degrade to following an operative intervention materials’ for use by United States an unacceptable level before the next 30 appointment? (or lack of it) versus a patient Public Health Service . These demand must always be considered. criteria are also often termed ‘Ryge’ Restorations should not be or ‘USPHS’ criteria. The second due to other reasons. With these presumed to be ‘permanent’. Certain system is a variation of the USPHS points in mind, quality of a dental restorations, for example tooth- system and titled ‘Standards of restoration can be described in coloured restorations in non-carious quality of dental care’ used by the terms of: cervical lesions, may be placed in California Dental Association • Risk to the integrity of dental the knowledge that longevity may (CDA)31. Both systems evaluate and oral tissues be limited. However they may still colour, anatomic form and marginal • Extent of imitation of natural be considered to have excellent characteristics (adaptation, discol- form, function and properties qualities because of reduced future ouration, and caries); both are of the tooth risk of adverse biological effects based on an ordinal scale and on • Patient satisfaction, over time. as a result of iatrogenic tooth ‘an operationally defined threshold’, Several comments are pertinent substance loss. Finally, there are cost that is acceptable or not accept- to this definition. A prime concern implications of differences in able. Several authors have described of any therapeutic intervention is dentists’ restorative treatment deci- ‘modified criteria’ to complement to cause no harm. Thus, any other sions that need to be considered the basic USPHS and CDA criteria for assessment of quality when discussing restoration quality systems for scoring different types must be secondary to this aspect. versus replacements19. of characteristics of direct and The risk of adverse biological indirect restorations32,33. The argu- effects is always possible when a ment against using the USPHS and foreign material is introduced into Clinical evaluation systems CDA systems as a basis for resto- the oral cavity (Figure 1). Restora- Direct and indirect methods for ration replacement is that they tion quality and technical excellence assessing technical excellence of describe only degrees of deviation are related, but not synonymous. dental restorations12 focus on from an ‘ideal’ state. As such, only The operational consequences of specific restoration features rather degree of technical excellence is lack of technical excellence must than general state of the restora- addressed, with operational conse- be considered in the context of the tion. Criteria have been developed quences that cannot be applied with oral environment. The conse- to assess occlusal margins20–24, validity in different patients, with quences of a particular defect in a approximal margins25, surface for example, high versus no caries restoration may be completely dif- wear26,27, and surface roughness28. activity. An attempt to apply the ferent between individuals. In some Indirect evaluation methods further CDA criteria as a component in a patients, less than ideal restorations obscure any global assessment of treatment decision process is may be considered acceptable, yet restoration quality. Clinical assess- presented in the last section of this in need of replacement in other ment should be preferred, whether report. patients. By way of an example, or not it is subjective or objective An entirely different concept for loss of approximal surface integ- according to precisely specified addressing quality of restorative care rity in a patient with rampant caries criteria29. was proposed by Lutz et al.34. The may have greater effects than in a Evaluation systems differ in authors describe three standards, patient with no caries incidence number of criteria used, extent of whereby various goals are pursued: during the previous ten years. rating options, and completeness preservation as the lowest aim, Quality assessment is influenced of descriptive criteria. Quite often, through function, to the highest

FDI Commission, Jokstad et al.: Quality of dental restorations 120 level of ‘imperceptible restitution by salaried dentists was significantly there is a potential that restorations of teeth’. The authors advanced lower than that by private practi- may be made from a material with suggestions for applying specific tioners. Finally, the age of the less-than-optimal physical proper- USPHS criteria to satisfy the three restorations was shortest for the ties if improperly handled by the standards. In order to classify group of clinicians with least clini- operator. technical quality of restorations in cal experience, and highest for those Interestingly, variability in mate- children, Carpay et al.35 reported a that graduated more than thirty rial handling is also a major problem combined quality assessment- years earlier36. in institutions where standards test- dental treatment index with six In a study comparing students ing is carried out. Dermann43 repor- criteria. Quality was analysed in and dentists’ abilities to handle ted variations in amalgam specimen relation to the child’s age and adhesives, Sano et al.37 concluded strengths, and attributed this to vari- region of residence, type of dental that clinical experience is not able condensation pressure when professional regularly visited, size necessarily predictive of satisfac- preparing the specimens. McCabe of the restoration, and whether or tory material handling. Ciucchi et et al.44 reported variability among not the restoration was polished. al.38 evaluated adhesive bonds three test centres, and speculated Unfortunately, the index has not produced by 92 dentists attending that this could be explained by been validated in any longitudinal clinical courses using nine different subtle differences in material clinical studies. adhesive systems. After an intro- handling, or in the surface finish of ductory hands-on course, a total the specimen moulds. Ferracane of 2,508 composite cylinders were and Mitchem45 commented in a Variations amongst clinicians bonded to prepared bovine study of composite resin testing Several studies have explored vari- dentine. The measurement of bond among seven centres, that the ations in clinical, perceptual and strengths demonstrated a large production of specimens occurred judgmental abilities of dentists and variation in results and a significant in a non-uniform manner, despite related this to education, clinical effect in respect of the handling. a similar protocol being used by all training, practice experience and The variation in results among participants. They suggested that the commitment to continuing dental the practitioners was larger than reason was difference in experi- education. that among nine tested adhesive ence of the personnel, which systems. significantly influenced the results. The condensation pressure used It seems difficult to avoid such Clinical variation during the placement of amalgam inter-individual variations in dental Variations in material handling varies greatly. In a study among 44 clinics, when similar problems are among practitioners and auxiliary practitioners it was reported that experienced even amongst highly personnel have been reported. lower condensation pressure was trained investigators working in Usually, this will compromise the used than that recommended in the laboratory environments. physical properties of the material. manufacturers’ directions for use39. However, most of these studies Wasson and Nicholson40 reported have been carried out as process that, in general, the ability to evaluate Perceptual variation studies without any assessment of correct material consistency among The clinical examination of resto- the clinical consequences of the inexperienced operators was poor. rations requires a clean, dry and variations. It is therefore uncertain Thus, lower values for physical well-lit field. For approximal resto- to what extent such variations properties for glass-ionomer cements rations, additional prerequisites are influence the long-term clinical were obtained, compared to semi- dental floss and high quality radio- performance of restorations. skilled or skilled operators. graphs46. The lack of adherence to In a cross-sectional study of A report on handling of these requirements partly explains 6,761 restorations replaced in glass-ionomer cements by general reports of large variations in clini- permanent teeth, some interesting practitioners suggested that these cal treatment decisions among links were observed between were often mixed in a much lower clinicians. The importance of replacement and characteristics of powder:liquid ratio than recom- conducting a comprehensive clini- the 243 operators who participated. mended41. Gjerdet and Hegdahl42 cal evaluation to appraise the true The result revealed that the median reported substantial variations in condition of restorations has been age of amalgam and composite resin strength properties of amalgam highlighted by Poorterman et al.47. restorations replaced by male clini- restorations placed by 59 dentists The authors reported on the basis cians was higher than that for although the study was carried out of a clinical epidemiological study female clinicians irrespective of in the laboratory, so it is difficult to of 621 participants that the preva- clinical setting. Moreover, the interpret its clinical significance. lence of approximal caries and median age of restorations replaced However, the findings suggest that defective restorations was highly

International Dental Journal (2001) Vol. 51/No.3 121 underestimated. Of the total number of recorded decayed or defective restoration surfaces, only 10–15 per cent were found clini- cally. Added to this are problems of inter- and intra-examiner varia- tions of interpretation and differ- ent diagnostic abilities. Tobi et al.48 examined observer variation in assessing marginal adaptation of composite inlays and amalgam restorations. The authors concluded that the observers’ agree- ment depended on the clinical performance of the material. Consequently, they advocated a log-linear modelling approach for evaluating materials that simultane- ously takes into account observer agreement and material performance. Finishing and polishing may influence the decision to replace amalgam restorations. In a study including 60 practitioners and students ‘appearance’ or anatomic shape was the most frequently cited reason for replacement before finishing and polishing, followed by marginal defects and secondary caries. Subsequent finishing and polishing significantly reduced the number of replacement decisions for all practitioners49. Dental students have large vari- ations in visual ability to accurately judge size, depth and angle50. Interestingly, ability to improve Figure 2. Reasons for replacement of restorations (Table copied from: NHS Centre for 5 visual perception by training seems Reviews and Dissemination, 1999 ; with permission). to be limited. The author advo- cated use of standardised objects dentists’ assessment of dental restor- treatment decisions and recommen- to allow size or angle judgement ations are perhaps not surprising. dations are not well documented. by direct comparison. A logical Substantial variations have also been This is unfortunate, since it is deduction of this finding is that it is documented in dentists’ abilities to important to determine normative probable that many dentists daily diagnose, for example, occlusal treatment needs, to evaluate inter- make inaccurate and variable judge- caries clinically52, dentine caries on ventions designed to reduce the ments caused by poor visual radiographs53, approximal caries and frequency of inappropriate treat- perception. deficient restorations on radio- ment, and for developing valid Dunninger et al.51 observed that graphs47 and perception of tooth practice parameters. In a system- agreement between investigators colour54. Much can be summed up atic review of 652 reports on assessing restorations ranged from by the statement ‘operators detect clinical studies of dental restora- 56 per cent to 88 per cent, depen- what they are trained to see’. tions, several factors influencing ding on the criteria used. The more Research is needed to assess the clinicians’ decisions to replace resto- positive the results of the assess- effectiveness of different strategies rations were identified5 (Figure 2). ment and the more objective the to improve clinical diagnostic abilities. Kay and Blinkhorn55 have sug- criteria, the higher the level of gested, following in-depth inter- agreement. Judgmental variation views with 20 randomly selected The reports on variations in Factors associated with operator’s general dentists, that an understand-

FDI Commission, Jokstad et al.: Quality of dental restorations 122 ing of disease processes and of included dentists’ gender, year of understand diseases, but they are available treatment options may graduation and type of practice58. also applicable to the clinical be an insufficient basis for treat- Bader and Shugars59 reported performance of dental restorations. ment decision-making. The authors agreement of treatment recommen- By example, the risk of occurrence uncovered many considerations dations made by 51 dentists on of a specified outcome or incident outside straightforward concepts 1,187 teeth in 43 patients. The reli- of interest, such as secondary of oral health that influenced the ability of inter-examiner agreement caries, bulk fracture or degradation. choice of clinical treatment deci- for restorative treatment was An association exists if two vari- sions. lowest for recommendations concer- ables appear to be related by a Hawthorne and Smales56 inves- ning previously restored teeth. It mathematical relationship. Thus, a tigated the amount of treatment was concluded that much of the change of one appears to be provided for 100 adult patients variation in dentists’ practice related to the change in the other. treated by 20 male dentists over profiles was explained by basic Association is necessary for a causal approximately 25 years in three differences in decisions to recom- relationship to exist, but associa- selected private practices. Particu- mend treatment for individual teeth tion alone does not prove that a lar types of restorative treatments with specific conditions. The pres- causal relationship exists. By exam- were significantly related to patient ence of previous restorations ple, surface discolouration and age, gender and frequency of seemed to magnify these differ- wear are often associated, but there attendance, to practice location, ences. The same authors had in an is no causal relationship. A risk is change of dentist and number of earlier paper also suggested that a the likelihood that a specified out- changes of dentist, and to the lack of knowledge about relative come will develop in a defined time experience or time since gradua- effectiveness of treatment options period. By example, risk of bulk tion of the dentist. These factors might be an important cause of fracture within five or ten years of were of special significance for the dentists’ variations in treatment a ceramic inlay. A risk factor (some- number of crowns provided, of planning60. times also termed ‘condition deter- which the majority were placed in Drake et al.61 compared three minant’ or ‘predisposing factor’) is older patients by the most-experi- dentists who replaced restorations an attribute (intrinsic characteristic) enced dentists. However, there was using various failure criteria. The or exposure (external environment) no evidence of increased numbers authors attributed differences to that is positively or negatively asso- of direct placement restorations individual practice philosophies, ciated with the occurrence of a being received by patients who demonstrating that clinical informa- specified outcome. By example, attended frequently or who changed tion was not the sole determining inadequate thickness of inlay their dentists often. factor as to the type of replacement (intrinsic characteristic) placed in the Paterson et al.57 attempted to restorations that patients received. second molar of a patient showing develop policy statements on marked signs of heavy bruxing maintenance and replacement of (external environment) are risk amalgam restorations. A Delphi Risk evaluation factors related to inlay bulk frac- technique commonly used in social Probably the most important factor ture. Cause is a combination of sciences was used to produce a explaining variation in treatment necessary and sufficient factors, the consensus view on 17 statements. decisions is the difference of esti- presence of which, alone or in Agreement was rapidly reached that mation of risk as well as attitude combination, at some time inevita- ‘ditching’ of amalgam restoration towards risk among dentists. bly result in an incidence of interest. margins did not justify their Worthington et al.62 surveyed 24 A necessary factor/cause is a risk replacement, and that repair was general dental practitioners with factor that must be, or have been, preferable to total replacement. respect to general treatment or present for a specified outcome to However, some difficulty was treatment related to caries on 2,553 occur. By example, plaque remain- experienced in arriving at a consen- patients. The authors concluded that ing close to a restoration margin sus view on the correct management common assumptions used by can lead to secondary caries, but of ‘white spot’ lesions at restora- practitioners to estimate their although plaque is required it is not tion margins and dentinal staining patient’s risk for future treatment inevitable that caries develops. A adjacent to amalgam restorations. varied, as well as the practitioners’ sufficient factor/cause is the mini- In a study of restorative deci- attitudes towards risk. Dentists mal or combination of risk factors sion making among dentists, should have a basic understanding that inevitably results in a specified significant relationships were noted of the terms association, risk and outcome. By example, plaque between replacement rates and causality. These terms are funda- remaining close to a restoration several dentists’ practice and mental in causal theory. In epide- margin combined with frequent demographic characteristics. These miology, the terms are applied to intake of carbohydrate-rich foods

International Dental Journal (2001) Vol. 51/No.3 123 that continues over time in an indi- of a cause-effect relationship and ‘efficacy’, that is attempts to vidual avoiding fluoride result in between different factors or vari- score performance as passing or secondary caries. However, from ables with a certain degree of failing and not to rank clinical clinical experience we know that uncertainty. All other methods performance. This is why many of an incident of interest, such as the involve limitations through bias or the criteria are based on a passing example here using secondary confounding. However, data from level of, for example 85–90 per caries, can often be caused by more observational studies should not cent alpha scores according to the than one set of sufficient causes. be regarded as unimportant or USPUS criteria after one to three Thus, different causal pathways incorrect. Hypotheses are often years, and only distinguish between may exist in different situations. generated first on the basis of unacceptable and acceptable perfor- Causal pathways (alternatively observational studies, and are then mance. For different reasons these termed causal web or cause-and- tested for validity under more guidelines do not require controls, effect relationships) involve the rigorous experimentally designed do not test for placebo effects and actions of risk factors acting indi- conditions. do not have statistical powers great vidually, in sequence, or together Certain requirements must be enough to answer anything other that result in an incidence of inter- fulfilled to qualify as an experimen- than simple experimental questions. est. These pathways may vary tal study. These are the presence of The most commonly tested hypoth- with different sets of risk factors. control groups, predefined alloca- esis is whether a new material or Understanding these pathways is tion of variables, and standardised product has been comparable to a necessary to devise preventive evaluation procedures and criteria specific traditional material. countermeasures or interventions to for the evaluation of outcomes. The Many of these trials are carried avoid a specified outcome, and the allocation of variables is randomised out in research environments, as countermeasure may be unique to if possible, in order to make even opposed to general practitioners’ the pathway. stronger statistical inferences, i.e. a practices. The operators are often Causal relationship can be deter- randomised controlled trial. The selected and trained to ensure opti- mined using various levels of specific aim of the study and the mal handling. Furthermore, the evidence. In theory, all information formulation of a hypothesis should patients are often dental students, regarding a hypothetical causal be documented. When these criteria dental school staff or dentists with relationship can be labelled evidence are not met, or when observations above average oral hygiene12,13,16,17,69. and must therefore be appraised. are made of phenomena that are Controlling operators and their However, formal requirements are not manipulated by the investiga- working environment, patients, and needed to address validity of tor, a clinical study is classified as size and intra-oral location of the evidence, and this is applied on observational. restorations reduces confounding, scientific data. Inferences of causal Relatively few clinical studies in when comparing different materi- relationship are directly associated restorative dentistry fulfil the crite- als or products. However, data with study design. For many clini- ria of an experimental design5,16,17,63. from such studies do not reflect cal questions, randomised control- The majority of clinical studies the situation in ‘real-world’ dental led trials (RCTs) are regarded as where an association has been practice70. This is especially appar- the strongest evidence for causal reported between clinical variables ent when technique-sensitive relationship. However, many deter- and restoration performance have materials are involved1. In general minants of aetiology, diagnosis and been observational studies. This practice, treatment times are prognosis can for various reasons is because although the studies constrained, the diagnostic thresh- only be estimated indirectly using were experimentally designed to olds for replacement may vary with cross-sectional, cohort or case- obtain information on differences the patient load, and there are no control study designs. In these between, for example materials or economic incentives to produce situations, inference must be commercial products, the obser- higher clinical standards above assumed on the basis of how find- vations and descriptions of the acceptable61. In general, there is ings satisfy different criteria of influence of other factors were not public concern that there is lack of causation. obtained by the manipulation of data on clinical performance of these factors. restorative materials and on the Many clinical studies are carried quality of service provided by Statistical issues out according to recommendations dentists in general practice, and Clinical studies may be classified as outlined by various national or especially on the interaction between experimental or observational. international acceptances programme clinical performance of restorations Only studies with experimental guidelines, for example FDI64, and quality of service71. designs can be considered induc- NIH65 and ADA66–68. These guide- It is evident from the literature tive, that is, can give an indication lines are designed to address ‘safety’ that there are disagreements concer-

FDI Commission, Jokstad et al.: Quality of dental restorations 124 ning the material, operator and patient effects on restoration qual- ity. One of the major issues appears to be the statistical treat- ment of data. It is difficult to conduct clinical studies, with the aim of establishing a numerical relationship between one specific risk factor and the technical excel- lence, restoration service period or replacement reasons. The main reason is that the clinical perform- ance of a restoration is dependent on many known and unknown clinical variables that are difficult to control or record. It is also difficult, if not impossible, to Figure 3. Parameters of the quality of dental restorations. The horizontal axis represents assure independence among many time, while the vertical axis is the proportion of restorations remaining over time. The bold clinical variables that affect restora- line represents the proportion of restorations remaining in situ (that is ‘survival’), and these tion clinical performance. Currently, are in the category ‘excellent’ (for example ‘alpha’), ‘acceptable’ (‘beta’) or ‘defective’ (‘charlie’). Replacements may be ‘true’ reasons, that is bulk fractures, secondary caries, there do not appear to be any marginal deficiencies, discolouration, etc, or because of faulty diagnosis, inclusion into generally acceptable, valid statisti- larger restorations, primary caries on other surfaces, etc. Arbitrarily lines depict the cal techniques for isolating the proportion of restorations/replacements that fall into the carious categories. The horizontal influence of a single variable; line at 50% marks the median survival time. The intersections between this line and the other lines represent from left to right when 50% of the remaining restorations are: excellent, indeed, many of the variables may acceptable and remaining in situ. not be independent. In full knowl- edge of this situation, clinical researchers employ various strate- possibility of conducting prospec- identify the ‘geometric centre’ of gies when designing trials aiming tive clinical studies. the area above the survival curve in to clarify parameters of restoration Retrospective studies are based Figure 3, while studies that focus quality (Figure 3). on analysing patient records or a on the age of remaining restora- Restoration quality has been combination of patient records and tions identify the centre below this addressed in both prospective and quality evaluation of restorations. curve. retrospective longitudinal studies as A frequent problem with many In replacement studies, the well as in cross-sectional studies. retrospective studies is that little or previous history and age of the Data from prospective and retro- no information is available on restorations is often unknown. spective longitudinal studies can be possible reasons for replacement. Although the type of material used for constructing survival Several studies have revealed that usually is recognised, specific trade curves, proportions of restorations replacements are not always names or batch numbers are with varying technical excellence as explained by restoration failure1, seldom recorded. A characteristic a function of time and reasons for and even if they are, retrospective of the study method is that the replacement. data give no indication regarding evaluation criteria are not explicit, Current restorative materials whether the failures are related which leaves the diagnoses to the have excellent physical and mecha- directly to the restoration, to the operators involved in the study. The nical properties. Prospective clinical restorative process or to external results do not indicate any causal studies therefore need to be factors72. relationships, and they are prob- extended for many years and/or Cross-sectional clinical studies ably influenced by factors such as include large numbers of restora- have either been presented as socioeconomy, patient demography tions before any strong statistical replacement studies or recordings and the dentist:patient ratio. The inferences can be made. Long of data from patients’ records. same arguments are applicable observation periods are associated Other data have been derived from when interpreting results from with problems such as patient drop- assessment of technical excellence cross sectional studies. Although the outs, patient representativity and of restorations in situ or in evaluation criteria may often be changes in the clinician’s diagnostic extracted teeth, or from detailed accurately described, the history and abilities or understanding of replace- studies of failed restorations. clinical parameters at the time of ment criteria. Finally, also ethical Cross-sectional studies that focus restoration placement remains reasons may occasionally restrict the on mean age of failed restorations unknown.

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Most clinical studies have been Laboratory screening tests Clinical studies conducted with the aim of enhanc- The present body of knowledge The following sections present data ing the performance of restorative on clinical performance of materi- from studies that have reported materials. In this context, rigorous als indicates that there is a poor an association between technical adherence to the study protocol is correlation between laboratory and excellence and material, operator required to minimise any confound- clinical findings70,73. There is also and patient factors. The references ing factors. However, this is quite the factor of ‘clinical time’. One are limited to clinical studies different from ‘real-life’ dentistry. might say that on average, low- including adult or adolescent Although there is much literature copper dental amalgam restorations patients and which have been on clinical performance of restora- fail by penetrating corrosion, published since 1980, although it is tive materials, the strict protocol and which is reflected by continually possible that the authors have failed controlled environment of these worsening occlusal margins. The to mention the work of some studies does not permit generalisa- actual failure is secondary caries, investigators. Such omissions do tions to the environment of general not the poor margins, but the not necessarily reflect the impor- practice. Only rarely have pragmatic observation does correlate with the tance of such studies, but the studies been conducted that are problem. Furthermore, one would inability in identifying or gaining aimed at assessing how materials say that typically, high-copper access to this material behave in the hands of general prac- dental amalgam restorations fail A vast number of controlled titioners. There are various reasons by secondary caries and then later clinical studies have compared the for this situation. Medical research by bulk fracture if they survive a performance of an array of differ- funding is very competitive, and long time. This is clearly a different ent dental materials. Obviously, the performance of dental restora- set of processes than for low- there are large differences in clini- tions in the general population does copper dental amalgam, and the cal performance among the many not have high priority. The indus- processes are dependent on intra- dental restorative materials, both in try is not responsible for assessing oral conditions of the patient and general as well as relative to how restorative materials behave linked to age, caries risk and resto- intraoral location and cavity class. when used by the ‘average’ dentist, ration survival time. What labora- Because of the sheer number of since quality assurance of dental care tory test should be used to screen publications, little emphasis is given in society is the responsibility of high-copper amalgams? Creep to these differences. Rather, data local health authorities. Thus, the predicts corrosion level but does reported under ‘material factors’ industry sponsor mandatory clini- not predict approximal caries or are limited to variations in compo- cal studies to satisfy criteria set by bulk fracture, and static mechanical sition and physical characteristics various acceptance programmes64–68 tests predict bulk fracture. Infor- within one specific type of material while pragmatic studies are limited mation on fatigue is sparse or not that may seem to have a potential to field testing of various handling available or done only on simple effect on the clinical performance properties for subsequent market- geometries that do not mimic of restorations. ing purposes. actual clinical restoration shapes. Several publications have exam- Tests are run with stand-alone ined the influence of the operator Technical excellence samples and not with those that and/or patient on the perform- The ultimate aim when restoring are interfaced to tooth structure, ance of restorations. Those factors or improving the integrity of teeth wet at 37°C, and after long peri- that collectively describe the is to simulate tooth tissues both ods of time. Some investigators operator factors are the dentist’s initially and over time. A restora- use, for example, 500 cycles while clinical experience, cavity design and tive material should ideally possess others use 5,000 cycles, and some size variables, material handling and similar mechanical and optical even include other parameters of procedures, isolation of the work- properties to tooth tissues, which questionable value in laboratory ing field and finishing. In clinical at present no material fulfils. tests, for example thermocycling. trials, good operators are often Furthermore, the outcome regard- Others argue that no significant selected to participate, and the ing the restoration adaptation, form heat transfer occurs during short- operator influence is usually exam- and function depends very much term thermal cycling and so this is ined secondarily. Therefore, only on the operator’s clinical skills. a worthless exercise. In a similar small differences between good Besides the material and operator vein, some solubility tests of dental operators are usually distinguished. factors, patient factors have a cements have been determined to There is also a tendency to try to significant influence on the deterio- be of little scientific value, even distinguish differences without ration of the restoration’s technical though they are still used as screen- analysing the reasons for differences, excellence. ing tests for materials. such as perceptual differences,

FDI Commission, Jokstad et al.: Quality of dental restorations 126 treatment philosophies, decision- which is often the case in two- for example, to manage abnormal making and technical skill. The body contacts. Erosive wear occurs wear. patient factors include gender, age, if hard particles are present in a It has been suggested that the frequency of attendance and oral medium between two moving overall wear of a composite resin environment factors such as bite objects, in particular in acidic envi- restoration is more dependent on force, caries activity and microflora. ronments. Fatigue wear occurs the material properties than on other Dentists should be aware of the when the surface is overloaded clinical variables such as cavity class concept of power in relation to beyond its elastic limit. Adhesive and tooth type77. However, data to hypothesis testing, that is the prob- wear happens when two opposing support this statement are weak. ability that a study of a given size surfaces touch each other resulting will detect as statistically significant in extremely high pressure at a real difference of a given magni- isolated points, causing parts of the Operator factors tude. Terms in this context are type weaker material to adhere to the Cavity design 1 and type 2, or alpha and beta, other if relative movement occurs. Wilson et al.78 reported on a longi- 74 errors . Many of the papers being This is most likely to occur for tudinal study of a posterior cited in this review conclude that metals. Finally, corrosive wear takes composite material over five years. there are no or minor differences place when the surface is attacked The greatest amount of generalised between variables. The real truth is, chemically. A major problem with occlusal wear tended to be seen in however, that the great majority of the early composite resins (and with large-sized Class II restorations in clinical studies do not have suffi- silicate cements and old style molar teeth, the main factor influ- cient sample sizes to have enough copper amalgams) was poor encing wear being the type of statistical power to distinguish such resistance towards chemical degra- restoration (Class I or Class II). differences. Thus, very few studies dation, that is, corrosive wear. The occlusal wear after five years supply good evidence of making Any of the five wear mecha- did not differ between occlusal butt strong statistical inferences of rela- nisms can occur in isolation, or joint and bevel-edged preparations. tionship between quality and interact with each other. Dental Wear in the occlusal contact area 74 clinical variables . restorative materials vary in resist- was higher in two MOD cavity ance to the various wear mechanisms. types by a factor of 1.5 and 2.5 for Restorative materials may therefore amalgam, and 2.5 and 4.5 for Form (contours, texture and show extensive wear in some composite resins in a clinical study wear) patients with a particular oral over one year79. The wear of Surface wear is a complex phenom- environment, while they can be composite resin restorations was enon that depends on several completely absent in other patients. approximately 2.5 to 9 times higher known and unknown factors, both in contact areas compared to extrinsic and intrinsic. Thus, the Material factors contact-free areas. The authors multifactorial aspects of the wear stated that for composite resins, process explain the wide variations Comprehensive reviews of dental wear data from Class I restora- in observed wear, and are exem- material performance and wear tions could not be extrapolated to 14,76 plified by large standard deviations have been published . In general, MOD restorations79. in clinical wear measurements. For the wear resistance is in the order the same reasons, laboratory- gold > ceramics > amalgam > Finishing testing protocols that predict composite resins > glass-ionomer In a longitudinal study of 600 clinical wear remain to be developed. cements. However, large variations posterior composite resin restora- Consequently, it is inappropriate to in wear resistance have been tions over three years, extensive generalise laboratory findings to the observed within ceramics and wear developed in the restorations clinical situation. The terminology composite resins. This is presum- placed by one of three clinicians80. used to describe wear in dentistry ably related to differences in It was suggested that the cause was is also variable, but there is gradual physical properties as well as varia- variations in the surface contouring understanding in the dental profes- tions in material handling. process. Neither was use of a sion that the most appropriate terms Should restorative materials wear rubber dam identified as a signifi- should be those used by tribologists, at the same level and in a similar cant factor for wear. that is scientists who study lubrica- manner to natural tooth tissues? If Surface finishing with carbide tion, friction, and wear75. the answer is yes, then restorative finishing burs compared to white Surface wear results from a materials such as gold fail in this stones was associated with a higher combination of several mecha- regard and, as a consequence, amount of occlusal wear in poste- nisms. Abrasive wear occurs when should have limited applications to rior composite resin restorations a hard body ploughs grooves, situations where the clinician wishes, observed over one year81.

International Dental Journal (2001) Vol. 51/No.3 127

Patient factors Oral environment correctly interfacial, discolouration Bite forces are probably a signifi- In a multicentre study on Class II is the result of percolation of cant aetiological factor with respect composite resin restorations a chromatic substances along the to changes in surface texture and significantly higher wear level was restoration-tooth interface. Both wear. Several papers conclude that recorded after three years in this phenomenon and ‘micro- the highest bite force occurs in the patients with a high level of salivary leakage’ have received much 5 first molar region, and it is there- lactobacilli (> 10 colony-forming attention in the literature, since it is fore to be expected that the units/ml at base line) compared assumed they may lead to second- greatest changes in form will occur with those with lower levels. The ary caries and pulpal complications. in this region. An additional authors suggested that an acid However, the alleged relationship confounding element when environment might enhance the has not been adequately verified in appraising the relationship between wear level of composite resin long term clinical studies. In a 86 form changes and effects of restorations . However, the asso- recent review it was concluded that different patient factors is that males ciation between wear level and high ‘microleakage’ was unrelated to the 91 have on average higher bite forces levels of salivary lactobacilli at base- development of secondary caries . than females, and that large varia- line compared with those with low tions occur in bite forces in both levels observed after three years genders. did not reach significance at the Operator factors five-year recall87. Composite resins shrink during Intraoral location Significant correlations were polymerisation, and numerous Restorations in permanent molar found between patients’ consump- papers have detailed often elabo- teeth show more wear than in tion of alcoholic beverages and rate clinical procedures to minimise premolars. One estimate is that if surface wear in an investigation of shrinkage. Special cavity prepara- restorations in the first mandibular 52 pairs of Class III microfilled tions have been employed92,93, premolar wear at 1x, the wear in composite resin restorations after together with techniques for the the first maxillary premolar is 3x, eleven years88. use of light-reflecting wedges94, in the second maxillary and incremental placement of materials95, mandibular premolars 4x, in the various devices and procedures for maxillary molars 5x and in the Optical properties light curing96, and different proce- 26 mandibular molars 6x . Lambrechts Optical characteristics include both dures for polishing97. On the other 82 83 et al. and Johnson et al. have in the match of colour and translu- hand, it has been suggested that part supported these ratios. In cency with the remaining tooth current adhesives appear to be less 77 contrast, Freilich et al. report that tissues, and lack of discolouration sensitive to substrate and other cavity class and tooth type had no along the restoration-tooth inter- clinical variables than earlier prod- association with the occlusal wear face. Surface tarnish of metallic ucts98. It has also been suggested of restorations in an investigation restorations was previously consid- that marginal gaps resulting from of three composite resins. ered by many as an important polymerisation shrinkage eventually Approximal wear was observed ‘aesthetic parameter’ when differ- disappear following water sorption by using indexed transfer copings ent metallic products were and expansion that re-establishes on 70 direct and indirect compos- compared. Today, the promotion the composite resin volume. ite resin restorations over two years. of restorative materials focuses on However, the initial adhesion is not No differences in wear, as a func- how closely the material imitates restored and remains damaged99. tion of tooth position in the arch, the optical properties of tooth In a study of 88 composite resin 84 were detected . tissues. restorations over three years it was Gender and age observed that the marginal Wendell and Vann85 compared the discolouration was significantly wear of 190 composite resin Material factors lower in the two-surface cavities restorations in primary versus Microfilled composite resins are compared to the three-surface permanent molar teeth after two considered to have the best optical cavity restoration100. This was not years. They concluded that there properties among the tooth- apparent at the two-year observa- were no significant differences coloured materials. In general, tion101. between the wear level of restora- composite resins have superior Elimination or minimising tions in primary teeth and perma- optical properties to resin-modi- possible microleakage is the aim of nent teeth at any recall. They claimed fied glass-ionomer cements, which the use of material laminate also that this finding was in are superior to the glass-ionomer combinations in approximal and contrast to previous findings of less cements89,90. cervical restorations, for example, wear in primary molars. Marginal, or perhaps more composite resin/glass-ionomer

FDI Commission, Jokstad et al.: Quality of dental restorations 128 cement, composite resin/resin- term ‘gap’ has also been used for There may also be differences modified glass-ionomer cement many years to infer a lack of adap- between composite resins, Bryant and resin-modified glass-ionomer tation between the materials and et al.110 having reported that cement/glass-ionomer cement. tooth tissues. However, this term is particular types of marginal defects Several studies have reported rather ill defined and non-specific. are commonly associated with comparisons between ‘sandwich’ Discrepancies measured along specific types of composite resins. versus homogeneous restorations, a horizontal or a vertical axis In general, restorations of micro- but the conclusions are conflicting. tangential to the interface have filled composite resins show more occasionally been interpreted as marginal degradation compared to synonymous to marginal adapta- restorations of other types of Patient factors tion. Such discrepancies can be composite resins. Empirical observations indicate that assessed clinically, but will neces- not only surface, but also bulk and sarily only express the adaptation marginal discolouration vary among along the margin on the tooth Operator factors patients. However, very few stud- surfaces. Several methods have Jokstad29 reported an influence of ies have identified specific patient been used to assess adaptation of the operator on the performance factors that may influence the opti- the entire restoration-tooth inter- of 468 amalgam restorations of cal characteristics of restorations. face, but all these methods are five alloys placed in 210 patients Marginal discolouration along destructive103. after five years. The five dentists veneers made from composite The clinical evaluation of margi- were all able to obtain superior resin on 87 maxillary anterior nal discrepancies is questionable, marginal adaptation with the best teeth in 23 young patients was explained by a lack of reliable alloys, and contrary to the findings more common among smokers diagnostic skills of clinicians. It has of Mahler and Marantz21, all five compared to non-smokers in a therefore been argued that the alloys performed equally well for longitudinal study over five years102. scientific community must accept the five operators. Further, it was In a study of 52 pairs of Class that dental restorative materials will evident that one operator also III microfilled composite resin be misjudged during the process obtained satisfactory marginal restorations after eleven years, of evaluating the marginal qualities adaptation with a low-copper surface discolouration was most of restorations104. alloy. It was concluded that the often recorded among smokers, main operator variables influenc- and significant correlations were ing the marginal adaptation were found between the patients’ Material factors the final condensation of the amal- consumption of alcoholic bever- The dental literature contains gam and the treatment of the ages and body and surface numerous papers in which surface and margins. discolouration88. marginal degradation has been Mahler and Marantz21 reported evaluated as a function of material on restorations of four amalgam composition. The prevailing material alloys placed by four operators. Adaptation in these studies has been amalgam, The amalgams were chosen on the Traditionally, the terms used to and there is consensus that high- basis of their marginal fracture describe adaptation have varied copper alloys are clinically superior behaviour as found in an earlier with the examination method, the to low-copper alloys105. study, ranging from little to exten- type of restoration and the nature Inter-group differences in respect sive fracture. Following placement of the restorative material. Hori- of the marginal degradation of of the restorations, three-year zontal discrepancies on smooth and amalgam restorations often appear evaluation of marginal fracture was approximal surfaces have often after a short time, and remain undertaken using a linear rating been termed ‘overhangs’, while the constant29,69,106–109. This signifies that scale. It was found that the opera- term ‘marginal ditching’ has been at least one process that results in tor influenced the marginal fracture used to describe defects along marginal fractures occurs during index, but in different ways margins on the occlusal surfaces of the first year after placement of depending on the alloy. For the teeth containing mainly amalgam the restoration. This hypothesis, alloys with the most and least restorations. The terms over- and however, does not identify or marginal fracture, there was no under-extension, with additional exclude other aetiological factors operator difference. However, for descriptors of the cement margin that may be associated with the two intermediate alloys, there morphology, for example ‘marginal marginal fractures, including creep, were large differences among the wear’ and ‘cement excess’, have mercuroscopic expansion, biome- operators. Overall, the association usually described the adaptation of chanical relationships, bulk and with alloy was stronger than with indirect restorations. Finally, the crevice corrosion or fatigue rupture. operator, and it was therefore

International Dental Journal (2001) Vol. 51/No.3 129 recommended that non-gamma-2 free, acetone-containing primers. bond strength to enamel. Studies amalgams should be used. However, recent research has on the influence of saliva contami- revealed that bonding systems that nation on dentine bonding are Cavity design utilise water-based primers appear variable. Although the tolerance of Stratis and Bryant111 carried out a to bond with equal effectiveness to modern adhesives to saliva contam- two-year study of 111 Class I and dry and wet dentine117. Adhesive ination has improved, reductions II amalgam restorations placed by systems using acetone-based prim- in bond strengths may be antici- one operator, and reported that a ers revealed a higher technique pated after saliva contamination. It combination of modification of the sensitivity118, whereas adhesive is therefore important to prevent occlusal cavo-surface angle and systems containing water-based saliva contamination after applica- finishing of the restoration had an primers appear to be less technique- tion of the primer126. influence on the marginal fracture sensitive, as far as the remaining The effect of using rubber dam at two years. wetness of the acid-etched dentine remains uncertain. In an experimen- Kreulen et al.112 reported a photo- surface is concerned119. tal study comparing shear bond graphic evaluation of the margins Clinically, the exact timing of strength of 36 composite resin of 245 Class II amalgam restora- the different stages of bonding as restorations placed either with tions placed by three dentists. The recommended by the manufacturer cotton rolls or under rubber dam, principle variable influencing is often very difficult. For exam- no significant differences were marginal adaptation was the dentist. ple, parts of the dentine may be noted between the two groups127. In addition, improvement of the etched for the same amount of In another study using the same marginal adaptation by an occlusal time as the enamel because the protocol, microleakage was assessed. bevel was discussed compared with precise differentiation between the This study concluded that the use non-bevelled margins. two substrates is not always possi- of rubber dam isolation resulted in Investigations published before ble. Excessive etching may result in less microleakage at the enamel- 1992 on the possible relationship demineralisation depths that are resin interface128. between marginal fracture and greater than monomers can effec- 115,119 Class I and Class II cavity prepara- tively penetrate , and cause Patient factors tions for amalgam has been severe collapse of the collagen Intraoral location reported in a previous paper, and 119 meshwork . The depth of demin- As for wear, bite force is probably will not be discussed further113. eralisation is dependent on etching a significant aetiological factor Fukushima et al.114 reported a time and phosphoric acid concen- regarding the extent of material study on the early marginal break- 120 tration , while the thickness of the deterioration. As a result of rela- down of 432 posterior composite monomer penetration, or ‘hybrid’, tively high bite forces in the first resin restorations. It was deter- layer is a function of conditioning molar region, it can be assumed mined that smaller cavities, greater 121 time . However, the implications that more marginal fractures will bulk of material at the margin of these variables on long-term occur in this location. (especially in functional cusp areas), clinical outcomes remain uncertain. In a study of 88 composite resin and well-finished margins without Isolation restorations placed by nine dental overfilling seem to reduce the Desiccation of the demineralised students, it was observed after two occurrence of marginal fracture. dentine causes collapse of the and three years that marginal integ- Material handling and proce- collagen meshwork, which impedes rity was significantly better in dures the proper infiltration of the premolars compared to that in Successful bonding is associated primer121. Therefore, a wet bonding molars100,101. with several technique-related technique is recommended122,123. Berg and Derand129 reported factors. The use of adhesives is However, there is a wide range of data on 51 out of originally 115 technique sensitive because of interpretations of ‘wet’124,125, with porcelain inlays made with the complex multi-step application no clear guidelines in manufactur- Cerec technique after five years in techniques38,115. Careful manage- ers’ directions for use. While the 46 patients. No significant differ- ment of the status of the collagen negative consequences of excessive ences in marginal ditching were meshwork is important to prevent air-drying are well documented for detected between molars and it from disintegration or collapse acetone-based systems122,123, the premolars. and thereby ensuring optimal resin results for water-based systems are Jokstad29 did not find any strong penetration116. variable125. relationship between marginal A clinical technique, commonly Contamination of the etched degradation and intraoral location referred to as ‘wet bonding’, has enamel surface with saliva prior to after five years observation of Class been recommended especially for the placement of a resin-based II amalgam restorations. Only the adhesive systems that utilise water- material significantly reduces the lower premolars showed less

FDI Commission, Jokstad et al.: Quality of dental restorations 130 marginal degradation compared to dentists, perceived causes of resto- years. The conclusions from this the other tooth groups. Osborne ration failure were ranked by study was that the type of amal- and Gale130 reported that the patient-related factors (45 per cent), gam alloy used had no association marginal fracture of high-copper dentist-related (35 per cent) and with restoration survival108,109. Van amalgam restorations could not be material choices (20 per cent)136. An Noort and Davis142 observed in a related to the intraoral location amusing secondary finding was that five-year prospective study the after fourteen years service. Inter- these estimates were for restora- survival of 2,399 Class III and 1,093 actions between tooth position and tions in general, while the percen- Class V chemically-activated ante- width indicated that lower tages were 48, 26 and 26 per cent rior composite resin restorations in premolars with conservative resto- respectively when dentists addressed 26 general dental practices, that the rations exhibited the least fracture the causes of failure of the restora- differences in clinical performances at the margins, and upper tions they had made themselves. between six materials was small. In premolars with a wide preparation The following sections present a cross-sectional study, 75 private exhibited the most. Osborne and the effects of the numerous practitioners evaluated 1,147 two- Gale131 reported that the marginal dependent and independent vari- to-four years old anterior restora- degradation of 429 Class II amal- ables influencing the quality of tions of 25 different materials gams after two years was less in restorations, notably the operator; according to the CDA system. With lower premolars than in the other the operative techniques and instru- the exception of one composite posterior teeth. ment used; the material; the location; resin, no obvious differences in the Goldberg et al.132 studied 475 type; size; initial and short-term quality of dental restorations were restorations over 1.5 years. Using technical excellence of the restora- observed33. ANOVA analyses, these investiga- tion and patient factors. tors compared marginal fracture Operator factors scores among different subgroups, Among various clinical factors categorised by intraoral location and General performance affecting restoration performance, found more fractures in molars than Material factors an operator association is frequently in premolars. Differences in composition and detected in multicentre and cross- Oral environment physical properties sectional studies (Table 1). Controlled Derand133 assessed restorations of Subtle differences in physical prop- clinical studies are usually designed four amalgam alloys in 163 teeth erties within specific material to avoid such operator effects, and after 2.5 years. The patients were groups may be considered to have different research groups have divided into three levels of biting a small effect on clinical perform- employed various strategies (see force. It was found that marginal ance in general practice settings. A section on statistical issues) to fractures increased with increasing particular exception is perhaps com- control these effects. bite force for the conventional posite resin cements for indirect Most of the relevant papers alloys, but that the relationship was restorations, where the microfilled offer no explanation of the not significant for the three non- cements seem to be superior to observed variation in operator gamma-2 alloys. cements with larger fillers14,136, effect, although some authors stress although conflicting results have the necessity of specific training for been reported138. Two longitudinal dental personnel using new materi- Restoration failure and multicentre studies involving 24 als. It is also possible that an clinical factors dentists in seven clinics revealed only indirect patient association may have Technical excellence of restorations minor differences amongst six influenced an apparent operator deteriorates in clinical service and composite resins after three and association. Whether the experience may or may not be linked to resto- five years139,140. Dunne and Millar141 of the operator can be associated ration failure. Certain investigators, reported the evaluation of 315 with technical excellence is uncer- including those of Harris134 and porcelain labial veneers in 96 tain. For example, Hawthorne and Owens135, reflect a common opin- patients, fitted up to five years Smales150 reported that the survival ion that materials themselves are previously in two teaching hospi- for composite resin restorations often the least of the problems and tals. Increased problems and failure was best for the most recent gradu- that most restoration failures can rates were associated with veneers ates. By contrast, Shaini et al.151 be attributed to poor attention to where inappropriate luting agents commented that the poorest detail in cavity preparation and were employed, that is, luting results were seen in relation to the material handling. However, this cements not dedicated to veneer inexperienced operators. Of course, view can at best be regarded as cementation. In studying over 1,544 appropriate clinical training and expert opinion, and is linked to the amalgam restorations, 1,213 resto- experience are necessary prerequi- failure criteria. In a survey of 571 rations remained after 15 fifteen sites for favourable clinical outcomes.

International Dental Journal (2001) Vol. 51/No.3 131

Table 1 Clinical studies that have investigated a possible association between restoration performance and operator

Reference Centres/dentists1 Restorations2 Operator variation observed (application) after years3 Longitudinal studies Pilebro et al. (1999)143 12d 374 glass cermets (tunnel) 3 yrs: yes Köhler et al. (2000)87 3c/12d 104 composites (Class II) 5 yrs: not reported Rasmusson et al. (1998)86 3 yrs: yes Kreulen et al. (1998)109 3d 1544 amalgams – Class II 15 yrs: yes Gruythuysen et al. (1996)108 15 yrs: yes Akerboom et al. (1993)107 10 yrs: yes Meijering et al. (1998)144 7d 180 ceramic (veneers) 2.5yrs: no Plasmans et al. (1998)145 3d 300 amalgams (complex) 9 yrs: no Wilson et al. (1996)146 5c 172 amalgams (Class II) 5 yrs: no Wilson and Norman (1991)147 12c 958 composites (Class II) 5 yrs: yes Letzel (1989)72 12c 232 amal. +932 compos. (Class I and II) 4 yrs: yes Phantumvanit et al. (1996)148 3d 446 glass ionomer cement (ART) 3 yrs: no Rasmussen and Lundin (1995)140 7c/24d 247 light cured composites (Class II) 5 yrs: yes Lundin et al., 1990139 3 yrs: yes Retrospective studies Wendt et al. (1998)149 11c 6012 amalgams and composites 5–13 yrs: yes Smales and Hawthorne (1996)150 3c/20d 404 restorations, 100 patients, 25 yrs: yes and no Hawthorne and Smales (1997)56 regular attenders for 25 years Shaini et al. (1997)151 ‘Several’ 372 ceramic veneers 6.5 yrs: yes Mahmood and Smales (1994)152 4c 1588 amalgams, composites, inlays 25 yrs: yes Smales (1991)153 ‘Many’ 950 composites 18 yrs: no Smales (1991)154 ‘Many’ 1476 amalgams 18 yrs: yes 1d= number of dentists in study, c= number of centres in study 2ART = Atraumatic Restorative Treatment, tunnel = tunnel preparation with glass-ionomer 3yrs = observation years, yes/no= operator associated/not associated with restoration performance

Cavity design differences in the failure rate longitudinal study of 242 tunnel The relationship between cavity between moderate and large resto- restorations in 142 individuals, morphology and restoration quality rations were observed. the cumulative survival was 81 per is uncertain because of opposing Köhler et al. reported in a five- cent after two years and 64 per or controversial results. A system- year study of 63 Class II composite cent after 3.5 years. Secondary atic review of restoration longevity resin restorations similar failure caries caused replacement of 50 concludes that large amalgam levels in teeth with conservative and per cent of the restorations, while restorations would appear to with larger conventional study marginal ridge fractures constituted survive as long as small amalgam designs87. 26 per cent of the failures. The restorations. Moreover, the inves- Burke et al.156 examined the statistical analyses revealed that tigators suggested that the evidence reasons for replacement and median success was related neither to that two-surface restorations survive age of 4,608 restorations reported the radiographic stage of initial longer than three-surface restora- by 73 vocational dental practition- approximal caries nor to type of tions is inconclusive5. This conclusion ers and their trainers. The median preparation technique158. Several is supported by most studies, while age of the amalgam restorations studies have revealed that technique other studies suggest differences in ranked from Class I>V>II (7.4 to sensitivity is high concerning tunnel longevity and clinical quality 6.6 yrs), for composite resin resto- preparations. Strand et al.159 showed depending on morphology. rations Class III>II and V>IV>I that the complexity of the prepara- For Class II composite resin (5 to 3.3 yrs), and for glass-ionomer tion and operator experience were restorations, special cavity prepa- cement restorations Class III>IV> the principal determinants of rations have been appraised V (4.8 to 3.2 yrs). survival in a three-year study of clinically, but they seem to have a Raskin et al.157 reported on a 161 glass-ionomer cermet cement limited influence on the long-term ten-year longitudinal study of 100 tunnel restorations. failure rates92,93. light-cured posterior composite Stoll et al.160 reviewed the clini- Lundin and Koch155 reported resin restorations. Class and size of cal performance of 3,518 cast the outcomes after ten years of 117 restoration were not found to restorations placed in 890 patients Class I and II restorations made significantly influence the survival. between 1963 to 1993 in a dental from two different composite Tunnel restorations gained in school in Germany. They found posterior materials. Only minor popularity in the early 1990s. In a that the ten-year survival for Class

FDI Commission, Jokstad et al.: Quality of dental restorations 132

I inlays was lower than that for the and 1,093 Class V chemically-acti- than multi-surface restorations. other types of inlays, that is two-, vated anterior composite resin Moreover, multisurface restorations three- and four-surface inlays. restorations assembled from 26 including the occlusal surface In study of over 1,544 amal- general dental practices indicated survived significantly longer than gam restorations, 1,213 restorations that the overall probability of did those including the facial or remained after fifteen years. It survival at five years was 10 per lingual surface. appeared as if the three-surface cent higher for Class V restorations restorations had less favourable than for Class III restorations142. Material handling and clinical outcomes compared to Smales and Gerke166 evaluated procedures two-surface restorations after 15 700 anterior composite resin Factors associated with material years. Also, the provision of a 90o restorations over four years. Signi- handling and procedures that may cavosurface angle combined with ficantly more failures occurred in affect the incidence of margin fail- a cavity wall finish reduced the risk Class IV and V preparations. Of ures of amalgam restorations of failure of amalgam restorations, all failures, 81 per cent were from include trituration time106, use of compared to larger cavosurface Class V preparations, which may rubber dam169,170, condensation angles108,109. reflect undue reliance on dentine- techniques171, and the carving, Prati et al.161 reported three-year bonding systems for restoration burnishing and polishing tech- data on 116 Class III and V poly- retention in premolar non-carious niques172. The effect of burnishing acid-modified composite resin cervical lesions. amalgam restoration margins is (‘compomer’) restorations. They Fritz et al.167 reported the long- difficult to estimate, and nearly found no statistical differences with term outcome of 2,717 cast impossible to quantify since the respect to the USPHS criteria restorations provided for 548 ‘surface treatment’ is influenced by between the Class III and V resto- patients during 1960–1989. Rela- factors such as burnishing load, rations. tively minor differences in the 15 direction of the strokes, number In a cross-sectional appraisal of year survival were noted for four of strokes, beginning time after 520 cast restorations in 56 patients sizes of casts: single surface (65 per trituration and the size of the made between one to 40 years cent), two-surface (60 per cent), burnisher172. previously, the restorations includ- three-surface (68 per cent) and To what extent cavity varnishes ing more than two surfaces were inlays and onlays (70 per cent). and their thicknesses promote associated with less favourable Investigations published before marginal failures is unknown. It is outcomes of quality and survival162. 1992 on the association between conceivable that some varnishes The outcome after three years Class I and Class II cavity prepara- may be incorporated into the amal- of 446 restorations placed by tions for amalgam and restoration gam along the margin, and thereby one dentist and two dental nurses survival has been reported in a reduce the strength in these areas. in 282 patients using the ART previous paper and will not be Thus, there is a theoretical possibil- technique was reported by discussed further113. ity that the type or amount of Phantumvanit et al.148. The survival Wilson and Norman147 reported varnish may be related to margin was lower for occlusal surface five-year findings of an 11-centre fracture. However, clinical data on restorations compared to those in trial of a posterior composite resin. such a relationship is sparse, and other surfaces. The findings were based on data existing data are not conclusive. In Friedl et al.163,164 carried out a collected from 649 (68 per cent) one longitudinal study it was cross-sectional study in which 102 of the 958 restorations originally revealed that application of a dentists provided information placed. Chi-square analyses indi- varnish or silver suspension did not about 3,375 composite resin and cated that of the independent influence the risk of long-term 5,240 amalgam restorations. The variables investigated, size of restoration failure107–109. failed restorations with four restoration had the greatest asso- Letzel et al.171 assessed the type surfaces had a lower median age ciation with clinical performance. of condensation instrument, together compared to the other types of In a study of 950 anterior with patient and operator on the restorations. composite resin restorations over performance of a single amalgam Jokstad et al.165 reported on a sixteen years there were significantly alloy over 2.5 years. The authors cross-sectional study of 8,310 more failures with the Class IV reported an association between restorations a marked association compared to the Class III restora- failure and the patient and the between the age of the restorations tions153. operator, but there were too few and both the types and the size of Bentley and Drake168 reported a failures to establish an association the restorations. study of 1,207 restorations placed with condensation instrument. Data from a five-year prospec- by students in 70 patients. Single- However, the authors did not indi- tive study of the of 2,399 Class III surface restorations lasted longer cate how ‘failure’ was assessed.

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Isolation up to 63 months previously in two were no clinically significant differ- The debate about the necessity of teaching hospitals. The use of rub- ences present in the initial high using rubber dam in operative ber dam could not be associated quality of the restorations, or in dentistry has been ongoing with with survival. their later survivals, which could be variable intensity for many decades. The consequence of using either directly related to the use of In this context it should perhaps be rubber dam or cotton roll isola- rubber dam. emphasised that working without tion on clinical deterioration was In a survey where the clinical rubber dam does not necessarily reported by Smales169,170. In one handling properties of glass- allow saliva contamination during study, 546 polished amalgam and ionomer cements were addressed, operative procedures. 148 anterior enamel-bonded compo- Knibbs and Plant173 attributed the Raskin et al.157 reported a ten- site resin restorations were evaluated main cause of unsatisfactory resto- year longitudinal study of 100 over periods of up to 15 years. He rations in deciduous teeth made by Class I and II composite resin concluded that although a statisti- 17 general dental practitioners to restorations in a group of selected, cally significant difference was poor handling of the material, prin- predominantly young patients found between the two isolation cipally by moisture contamination. under highly controlled conditions. methods for marginal fracture of Van Dijken and Horstedt174 The method of isolation was not the composite resins, the clinical assessed 35 patients who received found to significantly influence clini- relevance of this difference was one hybrid and one microfilled cal performance and survival. questionable. In the second paper composite resin restoration placed Dunne and Millar141 reported the survival of the restorations was in anterior teeth with and without the evaluation of 315 porcelain related to the possible influence of rubber dam. After one year the labial veneers in 96 patients, fitted six other clinical parameters. There marginal adaptation was investi-

Table 2 Clinical studies reporting a relationship between restoration performance and intraoral location

Reference Restorations/ Restoration types Obs. period General performance patients (years) Longitudinal Köhler et al., 200087 63/45 Posterior composite 5 No statistically significant difference between premolars and molars, and between maxillary and mandibular teeth Lundin and Koch 2000155 117/65 Posterior composite 10 Restorations in premolars had a higher failure rate than in molars Pyk and Mejare, 1999158 242/142 Glass cermets – tunnel 3.5 Failure occurred about five times as often in molars as in premolars Raskin et al., 1999157 100/ Posterior composite 10 Location not found to influence survival Donly et al., 1999176 72/18 Gold cast and composite 7 The acceptable restorations were located mainly inlay in the premolars Prati et al., 1998161 116/ Class III and V polyacid- 3 No association with respect to the USPHS criteria mod. composite and intra-oral location Geurtsen and Schoeler, 1209/ Class I and II composite 1–4.5 More restorations with rating Alpha in premolar 1997177 teeth compared to molar teeth Gruythuysen et al., 1213/ Class I and II amalgam 15 The type of tooth had no association with 1996108 survival Smales and Gerke, 700/ Class III and V composite 4 More failures occurred in premolar teeth com- 1992166 pared to other locations Jokstad, 199229 468/ Class II amalgam 10 No effects of intraoral location detected Retrospective Pelka et al., 1996162 520/56 Cast 1–40 Molars had less favourable outcomes of quality and survival compared to premolars Drake et al., 199061 1207/70 All types 1–20 No statistically significant differences were Bentley and Drake, observed. Mandibular incisive restorations lasted 1986168 longer than maxillary Cross-sectional McDaniel et al., 2000178 706/ Class I and II amalgam ns Mandibular first (36%) and second (20%) molars accounted for most fractures among cuspal- coverage restorations Jokstad et al., 1994165 10091/575 All types >10 The restoration age is possibly influenced by intra-oral location Kerschbaum et al., /1841 Fixed prostheses 1–15 An anterior placement and the lower jaw associ- 1991179 ated with a lower survival

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Table 3 Clinical studies reporting a relationship between restoration performance and gender and age.

Reference Restorations/ Restoration types Obs. period General performance patients (application) (years) Longitudinal Pyk and Mejare, 1999158 242/142 Glass cermet (tunnel) 3.5 Success rate was not related to patient age Plasmans et al., 1998145 300/ Amalgam (complex) 8.5 Restorations more prone to failure in patients >30 yrs old than in younger ones Prati et al., 1998161 116/ Class III/V polyacid – 3 No association between USPHS criteria and modified composite patient age and gender Phantumvanit et al., 1996148 446/282 Glass-ionomer (ART) 3 No differences between ART restorations in children and adults Gruythuysen et al., 1996108 1213/ Class I and II amalgam 15 20% of the study restorations were replaced in males, 16% in females Jokstad, 199229 468/ Class II amalgam 10 Survival associated with patient age, but sample included caries-susceptible children Smales and Gerke, 1992166 700/ Class III and V composite 4 Significantly more failures occurred among the elderly patients Retrospective Hawthorne and Smales, /100 Amalgam and composite 1–40 Lowest survival rates in the 0–20 and 61+ year 1997150 age groups Pelka et al., 1996162 520/56 Cast 1–40 No association between patient age and out- comes of quality and survival Mahmood and Smales, /1588 All types 1–15 Restoration survival was superior in female 1994152 patients Dunne and Millar, 1993141 315/ Porcelain (veneer) 5 Patient age and gender could not be associated with failure Bentley and Drake, 1986168 1207/70 All types 1–20 Survival less favourable for patients >60 yrs old compared to the younger patients. No differences between males and females Cross-sectional Mjör et al., 200036 6761/ Amalgam and composite 1–30 Minor differences noted in longevity between male and female patients Glantz et al., 1993180 /77 Fixed prosthesis 1–15 No differences regarding fracture, loss of retention and/or dental caries between age subgroups Dawson and Smales, 1992181 1918/100 Amalgam and composite 1–16 Survival lower in the oldest of three age groups. A small gender difference also noted Smales, 1991153 950/ Anterior composite 1–16 Median survival 7 yrs in age group <20 yrs and >60 yrs, 12 yrs in group 21–60 yrs. More failures seen in the oldest group Smales, 1991154 1476/ Amalgam 10 Patient age had a significant association for one of five alloys Kerschbaum et al., 1991179 /1841 Fixed prosthesis 1–15 A lower survival of fixed prostheses was associated with higher age group (especially if the patient was older than 70 yrs) Kroeze et al., 1990182 /600 All types ns The prevalence of unsatisfactory restorations tended to be higher with increasing age gated and no differences were terised these patients. and intraoral location were usually observed. The findings related to an carried out as secondary analyses. association between restoration It is impossible to know if no such performance and patient factors are relationships are reported because Patient factors summarised in Tables 2 and 3. no secondary analyses have been Collins et al.175 concluded, after an The majority of the studies carried out, or if the relationships eight-year longitudinal study of describe a minor difference. How- were negative and thus omitted in posterior composite resin restora- ever, as for many of the other the text (Figures 4). tions, that there was evidence to alleged associations to clinical factors confirm the importance of the one must be aware of publication Oral environment influence of the patient, since many bias. Moreover, most clinical studies Reduced salivation and xerostomia of the observed failures occurred were designed to address specific are associated with older patients, among few patients. However, no clinical problems. Issues such as side effects of drug therapy and details were reported that charac- influence of operator, patient factors cancer treatment. Consequently,

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Figure 4 (a–e). Old composite resin restorations remaining in situ due to patient satisfaction. Other patients, as well as clinicians, might well consider the restorations ‘unacceptable’. caries risk increases significantly. ionomer cement and 100 per cent Caries activity might be expected Wood et al.183 studied 54 pairs of of the amalgam restorations to affect the performance of Class V amalgam and glass- survived after six months. For the restorations; however, there are few ionomer cement restorations over subgroup of eight non-fluoride data on this aspect. In a longitudi- two years in 36 xerostomic cancer users survivals were approximately nal study of 242 tunnel restorations patients. Survival times were very 100 per cent and 24 per cent. Thus, in 142 individuals, the cumulative short (8.5 months) for all restora- the degree of fluoride use was proportion of successful restora- tions. Among the individuals using associated with the rate of restora- tions was 81 per cent after two fluoride, 8 per cent of the glass- tion failure. years and 64 per cent after 3.5 years.

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Secondary caries caused replacement patient attendance or experience of general practice settings, it has been of 50 per cent of the restorations, dentist. Restoration survival was not observed that dentists do not but statistical analyses revealed no influenced significantly by whether, necessarily replace restorations even association between caries activity or not, any replacements were when one or more features have and replacement158. made by the dentist who placed been graded as unacceptable Strand et al.159 observed in a three- the initial restorations. according to the USPHS/CDA year study of 161 glass-ionomer Regularly attending patients are criteria140,186–190. Thus many dentists cermet cement tunnel restorations probably more dental health practice a treatment philosophy that there were significantly more conscious than irregular attenders. where the discrepancy is observed failures among patients with a high Furthermore, at recalls, dentists rather than effecting an immediate caries activity. correct minor discrepancies that are operative intervention. Interestingly, Restoration survival was strongly believed to put the prognosis of a the same longitudinal studies also influenced by caries activity in a restoration at risk. Therefore, reveal that restorations will perform ten-year longitudinal study of Class improved restoration longevity is satisfactorily for many years in spite II amalgam restorations29. The 210 more likely in regular attenders. of ‘unacceptable’ USPHS/CDA patients in the study were divided However, Jokstad et al.165 did not scorings. into high, medium and low caries detect this difference in a cross- One main conclusion from a activity, depending on the incidence sectional study of 8,310 restorations, fifteen-year longitudinal study of of primary and secondary caries where similar restoration ages were 1,213 Class II amalgam restora- lesions during the first eight years recorded for the regular and tions was that the short-term of a 10 year study of amalgam irregular attenders. marginal performance was not an restorations. However, some caution Mahmood and Smales152 com- indication of long-term survival, and was expressed in interpreting these pared longevity of dental restora- that there was a lack of a valid data, as the study sample included tions in selected patients from predictive parameter107–109. a group of caries-susceptible different practice environments in In a longitudinal study of Class children. two countries, private practices in V composite resins, the authors Bentley and Drake168 reported Pakistan and a dental hospital in reported that it was apparent that on a study of 1,207 restorations Australia. In both countries, resto- the results after two years of placed by students in 70 patients. A ration survival was significantly observation could not be used to subset of the population (19 per improved when patients attended predict the three-year results191. cent) with a disproportionately infrequently for treatment, and Smales and Webster188 attemp- higher failure rate accounted for when the patient routinely changed ted to determine the relationship 56 per cent of all failed restora- dentist. between the deterioration and the tions. The authors speculated that In an examination of the survival later failure of a very large number it may have been a reflection of of 1,918 restorations in an Australian of amalgam and anterior compos- higher caries activity, but the military population, no differences ite resin restorations examined over precise nature of this group in survival as a function of frequency periods of up to sixteen years. remained uncertain. A subsequent of attendance or frequency of Assessments were made of the analysis of the study material iden- change of dentists were reported181. deterioration in various character- tified only minor differences of Kroeze et al.182 examined, in a istics of restorations that were salivary risk markers for caries national epidemiological survey, the thought to predict later failure. For between patients in the high- and restoration quality of 600 dentate amalgam, there was a significant low-failure groups184. adults. The authors reported that association found between surface the restoration quality could be tarnishing and failure. Marginal frac- Patient attendance related to the frequency of visits to ture and marginal staining were not Hawthorne and Smales150 related a dentist. significantly associated with any of survival for amalgam and compos- A re-examination of 720 dentate the three failure modes. For the ite resin restorations with patient Scottish residents who had taken composite resins there were signi- attendance in a retrospective study part in a dental health survey five ficant associations between the of five types of restorations placed years previously suggested superior surface roughness, marginal fracture by 20 male dentists in 100 adult restoration longevity among the and colour mismatch. However, patients. There were no significant patients who had not changed surface and marginal staining were effects on restoration survival from dentist frequently185. not associated with any of the three change of dentist, and generally only failure modes. Many restorations one or two types of restorations Does technical excellence assessed as being unsatisfactory had their survivals influenced predict failure? continued to function on average significantly by frequency of In several longitudinal studies in for a further two to three years

International Dental Journal (2001) Vol. 51/No.3 137 before being replaced, often for saliva and caries, material-to-cavity cavity walls remains unknown, as unrelated reasons. adaptation, quality and quantity well as the interaction mechanism The median function period of of exogenous bacterial products, between the potentially detrimen- restorations can possibly be restoration sealing and variable tal substances in the space and the predicted by a Weibull distribution patient pain thresholds196,197. tooth tissues. Even the characteris- function. However, Smales et al.192 Post-operative sensitivity after tics of the bacteria in, or adjacent reported, after applying such a cementation may be associated with to, the gap have not been firmly theoretical model on three restora- a deformation of the abutment established. It is clear that the tive materials, that this is problem- following high pressure or misalign- surface chemistry of the material atic if the model includes slowly ment of the casting during cemen- significantly influences the micro- deteriorating restoration features. tation. The hypersensitivity results ecological environment201. However, from fluid movement within the it is unclear if this is due to a local dentinal tubules198. toxic effect of possible compo- Specific replacement nents released from the restorative reasons material, or if it is indirectly due to Allergy Material factors an effect on the initial biofilm Given the enormous number of The previous belief that pulp composition that is formed on the dental restorations placed world complications following restorative restoration surface. wide, the incidence of adverse treatment were either the conse- Anecdotal sources have reported reactions seems exceedingly small. quence of insufficient removal of that in some practices, alarming Researchers have tried to estimate bacteria in the dentine or to toxic numbers of endodontic procedures the population risk of adverse effects from the material was chal- have become necessary because of reactions to materials used in lenged approximately 10 years ago. pulp damage after prosthesis cemen- 202 dentistry193, but the accurateness of In a consensus report from 1992, tation . Third-party payment such estimates of risk remains it was stated that much of the companies report that many teeth uncertain. However, there are in all previous work on pulpal reactions receiving crowns require endodon- populations a minority of individuals to restorative procedures and tic therapy within five years. It is that responds negatively to various materials had up to then been uncertain if this can be related to a extrinsic and intrinsic substances, flawed because of leakage of gradual shift of use from conven- including biomaterials found to be bacteria and their products around tional zinc phosphate cements to of acceptable biocompatibility filling materials199. The general view alternative cements and/or cemen- according to International Organi- today is that most restorative tation techniques. sation for Standardisation (ISO) materials do not per se cause pulp standards. All dental restoratives damage as long as they are prop- Operator factors have the potential to cause adverse erly handled, but problems will effects, even when used correctly. develop if the handling procedures Cavity design Higher risks of adverse reactions are not followed to ensure optimal The remaining dentine thickness is are present if the material is not adaptation to the cavity walls200. An a critical factor in the development properly stored or handled, for exception is perhaps glass-ionomer of pulp damage given the large example, incorrect proportioning, cements when applied in a very surface area of open dentine contamination, inadequate polymer- close proximity with the pulp195. tubules close to the pulp. Dentine isation, date expiration, incorrect Poor adaptation between a tubules may provide diffusion storage temperature and/or humi- restoration and remaining tooth channels for noxious substances, dity. Several comprehensive review tissues increases the risk for endo- which diffuse toward the pulp articles194,195 proceedings and consen- dontic complications given the where they can activate the immune sus statements on the subject of potential leakage of detrimental system, provide chemotactic biocompatibility of materials can substances. A number of highly stimuli, cytokine production, and be found in the dental literature. sophisticated laboratory techniques elicit pulpal inflammation116. Post- has been developed to measure operative hypersensitivity, on the adaptation, but the association with other hand, seems to occur in some Endodontic complications clinical significance remains uncer- individuals regardless of the depth Postoperative sensitivity is an tain. Thus, quantitative data from of the prepared cavity203. outcome that is a complex combi- laboratory leakage studies do not The incidence of pulpal compli- nation of the effect of the extent give sufficient information to cations following crown and bridge and depth of the initial caries predict clinical performance. The work was discussed by Valderhaug lesion, cavity preparation depth, environmental conditions in the et al.190 in a report describing the period of dentine exposure to microspace between restoration and results of a longitudinal clinical

FDI Commission, Jokstad et al.: Quality of dental restorations 138 study of initially 158 fixed prosthe- Concerns over possible II composite resin inlays and amal- ses made by senior dental students microleakage and postoperative gam restorations207. 25 years previously. The results sensitivity with amalgam restora- Age and gender indicated that the frequency of pulp tions have led many practitioners During function, secondary and deterioration in association with to use various varnishes and resin- reparative dentine is deposited in bridges tends to be related to the containing lining, or ‘adhesive’ the pulp. At age 55 years, the size of the prosthesis. It can be materials. However, others have volume of the pulp is about 20 per speculated that this can be the questioned the merit of amalgam cent of that at age 25, and contains effect of biomechanical complex- bonding, and the results are only 20 per cent of the blood ity, including factors such as a conflicting205. supply208. This suggests that the complex alignment of preparations Cases of persistent post-opera- pulp’s capacity of recovery decreases with possible iatrogenic tissue tive sensitivity with composite resin with age. However, there are no removal and overtapered abut- restorations following total etching data in the literature reporting the ments; lack of acceptable fit in parts and application of some dentine incidence of endodontic compli- of the casting; tendency to accept adhesives have been reported. This cations as a function of patient age small discrepancies in large, fixed clinical phenomenon can occur following restorative therapy. prostheses compared to single despite careful isolation prior to crowns, and the complications of direct restorative procedures and Oral environment oral hygiene procedures. the use of an incremental build up Anecdotal observations suggest that Periapical complications and technique, as well as after cementa- bruxism may be associated with an vertical root fractures following the tion of indirect restorations in increased risk of pulpal complica- placement of restorations or conjunction with using a composite tions following flexing of the crowns with pulpal or parapulpal resin cement. Problems regarding restorations and gap formation. posts may be considered as iatro- post-operative sensitivity are hypoth- The clinical evidence for this is poor. genic. Cross-sectional studies indi- esised to be related to a deficient In one early in vitro study it was cate that this is perhaps more light-curing source, or incomplete demonstrated that composite resin common than is acceptable. Grieve evaporation of the primer solvents restorations placed in third molars and McAndrew204 examined radio- prior to application of the bonding exhibited increased microleakage graphically 327 post-retained crowns agent. Alternative suggestions are when an antagonist was present for length of post, length of gaps, cracks in enamel related to compared to none209. The author remaining root filling, periapical polymerisation stresses, fracture of concluded that bacterial leakage condition, fit and angulation of tooth substance at the restoration around restorations in cavities the post and quality of root filling. cavity interface and polymerisation surrounded by enamel would most Most root fillings were judged to shrinkage followed by hydraulic often be the result of stress in the be unsatisfactory, and there was forces induced during mastication restored tooth during occlusion and no radiographic evidence of any on the dentinal tubule fluid follow- articulation. The study has not been root filling in nearly 10 per cent of ing flexure of the restoration195,206. duplicated using modern dentine cases. bonding systems, so it is uncertain Investigations published before to what extent the conclusion is 1992 on the possible relationship Patient factors applicable to newer composite resin between Class I and Class II cavity Intraoral location materials. preparations for amalgam and In a study of 88 composite resin adverse effects on the pulp has restorations over two years it was been reported in a previous paper, observed that the postoperative Does technical excellence and will not be discussed further113. symptoms were significantly lower predict failure? in premolars compared to molars101. A clear relationship between endo- Material handling and Borgmeijer et al.196 reported post- dontic complications and criteria procedures operative sensitivity after placing for technical excellence of dental The principles for prevention of 244 Class II restorations of restorations has not been demon- pulpal damage during preparation composite resin and amalgam. Post- strated. Several review papers have with rotating instruments were operative sensitivity occurred more suggested that such a relationship outlined many years ago, and are often in the molars than in the exists, but this is substantiated still valid today. Key factors are premolars although the difference mostly with laboratory and frictional heat and adequate cool- was not statistically significant. The microleakage studies210. In one clini- ing, excessive dehydration and air research group reported that this cal study the radiographic quality blast, and vibration and high finding had also been observed in of the root filling and the appear- speed46. another study of 240 indirect Class ance of the apical one-third of

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1,010 endodontically treated teeth where significant changes in the Material handling and was scored211. This was related to microbial ecosystem following procedures the presence of open margins, introduction of unfavourable char- Indirect restorations may be recurrent decay or overhangs acteristics of the restorations were overcontoured or overextended if detected in radiographs. By calcu- observed217. Finally, experimental the impression of the preparation lating the odds ratios of periapical evidence of a causal relationship is deficient. One paper reported inflammation as a function of the has been confirmed in numerous that there was little evidence that root-filling and restoration quali- animal studies. established guidelines for the ties, the authors concluded that preparation of teeth for porcelain restoration qualities are more laminate veneers were being important than root-filling quality. Material factors applied in full in general dental prac- Although this finding may give rise Multiple studies have compared the tices221. Other papers conclude that to concerns there are many meth- periodontal response to different the general quality of impressions odological issues that can be raised, dental materials, but only small for crowns received at commercial and scientifically sound research differences have been detected dental laboratories may be a cause designs are needed to substantiate provided that the restoration surface for concern222,223. Johnson et al.224 the hypothesis. Indeed, a recent is smooth218,219. No studies have reported a wide variation of qual- identical study resulted in contra- been located in the literature link- ity between three-unit bridges made dictory results212. ing periodontal problems to specific from different commercial dental physical properties of materials. laboratories. Lack of a satisfactory A speculative suggestion is that prescription, representative of Periodontal problems restorations made from materials which may be used by clinicians, The research focused on dental with high creep values will extrude was singled out as an important restorations and periodontal disease out of the cavity as a result of explanatory factor. is a good example of how the occlusal stress, and thus cause plaque criteria for causation as established retention with periodontal disease by Hill have been applied succes- as a consequence. However, no Patient factors sively to clarify the relationship clinical data substantiate this The most important aetiological between the two factors213. There concept. factor in periodontal disease is the is consistent association for several presence of microbial plaque. epidemiological studies between Unless the patient can establish restorations with and without Operator factors plaque control the risk of develop- discrepancies and indicators of peri- Cavity design ing periodontal disease is high, odontal disease214,215. Strength of In general, the proportion of restor- regardless of the technical excel- association and degree of expo- ations with poor margins gingivally, lence of a restoration. The fact that sure has also been demonstrated. correlates with the gingivoaxial oral health maintenance is a major For example, Lang et al.215 observed location, and thus contributes more significant factor in avoiding peri- a close relationship between an to periodontal disease than resto- odontitis and caries has been inflammatory response to poor rations placed away from the established repeatedly since the margins and increasing sizes of over- gingival sulcus215,216. In one clinical mid-1970s225. Grasso et al.214 hangs. Hill’s criteria of temporality study, no improvement in gingival concluded after a cross-sectional has been verified in numerous stud- status was noted following the study including 291 patients that ies, showing that the periodontal removal of overhangs. It was plaque control measures were prob- tissues around restored teeth have hypothesised that this was due to a ably more important in reducing more gingival inflammation than correlation between, on one side, periodontal disease than improv- the periodontal tissues around intact the axial location of the restoration ing the technical excellence of the teeth in intra- and inter-patient margin, and, on the other side, the restorations. comparisons. The criteria for inter- dimensions of the overhangs and No studies have been identified vention effect was demonstrated gaps220. in the literature linking periodontal in a study by Coxhead216, who Investigations published before problems to restoration properties reported that following removal 1992 on the possible relationship as indirectly influenced by specific of restoration overhangs on 50 between Class I and Class II cavity patient factors. patients, the conditions of the peri- preparations for amalgam and odontal tissues improved signifi- adverse effects on the periodon- cantly. A biological plausibility and tium have been reported in a Does technical excellence coherence of results has been previous paper, and will not be predict failure? established in experimental studies discussed further113. It is difficult to separate the effects

FDI Commission, Jokstad et al.: Quality of dental restorations 140 of various local aetiological factors, are asked their opinion of aesthetics, that amongst the direct restorative when assessing the association it comes as little surprise, that tooth- materials, the composite resins have between periodontal disease and coloured restorations are preferred. the best long term clinical perform- restorations. Reported restoration Numerous clinical studies have ance regarding aesthetics234–236. Some parameters include the axiogingival confirmed strong patient acceptance differences among the composite location of the restoration margin, of tooth-coloured inlays. Rimmer resins have also been reported: the location of the contact area and and Mellor229 evaluated patients’ • Among conventional chemically the axial contour of the restora- perceptions of different types of cured composite resins, resto- tion. Other factors are the plaque fixed anterior restorations. Respon- rations with macrofillers discol- retentive ability, chemical state and dents thought that crowns and fixed our more over time compared roughness of the restorative mate- prostheses with normal margins to the same composite resin rial, the occurrence and size of were of a higher technical standard, containing microfillers189. overhangs and crevices, and the and those restorations were pref- • Chemically cured composite resins possible contributing effects of a erable to crowns with metal discolour more than light-cured restoration on an adjacent tooth. margins. The shade and colour of over time, probably because of Adverse effects on the soft the restorations were the most different polymerisation initia- tissues have been attributed either to important factors in the partici- tors232. improper contact areas with food pants’ assessments. • Most restorative materials increase impaction226 or to details such as Abrams et al.230 compared the opacity and lightness after a surface roughness, contour gaps and assessment of quality by 117 patients period intraorally following overhangs. Within limits, it appears after two dentists had assessed their water absorption, but this varies that surface roughness does not restorations. The authors observed considerably between various lead to gingival changes218,219,227. that when the patients and dentists’ products237. There is general consensus that perceptions of the quality of the all factors that enhance the dental restorations were compared, Operator factors accumulation of plaque promote no relationship existed. It was periodontal disease. Therefore, concluded that patients and Material handling and procedures cavity designs that increase the dentists employ different criteria The aesthetic limits of restorations prevalence of restoration discrep- and priorities when judging quality in anterior teeth are determined ancies indirectly cause supportive of dental care. The logical view of tissue breakdown. The prevalence aesthetics of dental restorations is mainly by : of gingival restoration margin related to the patient perspective, • The size and nature of the lesion discrepancies varies among different notably to what extent do dental • The characteristics of the filling materials reports. One major reason is the lack restorations deviate from the appear- The technique of application of common assessment techniques ance of sound teeth? (Figure 5) • The age of the filling and a common terminology. • • The oral environment231. Material factors It is self-evident that an optimal Aesthetics Several tests have been devised to material handling and restoration process should be followed to The topic of aesthetics includes screen materials at risk for bulk ensure a satisfactorily aesthetic result. both the qualities of shape and discolouration. These tests employ Numerous papers have detailed appearance228. Shape depends on the high intensity light sources and/or techniques necessary to create aesthe- operator’s ability to contour and liquids with high chromaticity to tically satisfactorily restorations finish the surface, as well as the evaluate colour stability. No tests focusing on variables such as long material’s wear resistance. Appear- exist that correlate laboratory find- bevels, polishing, anatomic and ance depends primarily on material ings with clinical observations of surface sharpening, multi-layering optical properties of colour and discolouration. The complex events techniques, sufficient veneering and translucency. Metamerism, (a differ- producing restoration discoloura- application of subsurface tints. No ence in colour appearance that varies tion in the oral environment are clinical studies, however, have tested with the light source) is also a poorly understood. Bulk and the relative importance of these vari- common concern in aesthetic dentis- marginal discolouration varies ous procedures on the aesthetic out- try. The same concern exists for considerably among different types comes in a long-term perspective. fluorescence of materials and teeth. of dental materials, and within Many would argue that a highly dental material groups such as polished, anatomically correct cast- composite resins189,231,232 and glass- Patient factors ing or amalgam restoration is ionomer cements233. Oral environment aesthetically pleasing. When patients In general, there is consensus In a clinical study over 18 months

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e Figure 5 (a–e). ‘Quality’ has a different meaning for different individuals, patients and dentists alike. of composite veneers and artificial tion was most often recorded extent of surface staining239. resin teeth the effects of consump- among smokers. Significant corre- tion behaviour, such as coffee, tea lations were also found between and smoking, and cleaning habits the patients’ consumption of alco- Does technical excellence on discolouration was evaluated. holic beverages and bulk and predict failure? No significant influence on discol- surface discolouration of the resto- Although the initial aesthetics of ouration could be detected238. rations. restorations of tooth-coloured Qvist and Strom88 observed 52 On the basis of a clinical study materials can be outstanding, a last- pairs of Class III composite resins it has been suggested that local oral ing outcome requires a material that over 11 years. Surface discoloura- hygiene may play a role in the has a high proportion of polymer-

FDI Commission, Jokstad et al.: Quality of dental restorations 142 ised matrix. Restorations with an the cavity244. No reference in the be assumed this occurs at least insufficiently polymerised matrix literature has been found as to esti- occasionally with a possible detri- will discolour faster than those with mates of the incidence of the two mental effect on restoration strength. a well-polymerised matrix, and for occurrences. To what extent this accelerates light-cured materials this depends, material deterioration remains among other things, on an accept- unknown. able light intensity. There are a large Material factors Of the 15 studies inclu-ded in number of variables (instrumenta- Mjör245 compared reasons for replace- a systematic review of CEREC tion, manipulative, restorative) that ment of restorations with those restorations, comparable results in also influence the degree of conver- from another study recorded 16 terms of fracture rates were seen in sion of monomer to polymer. years previously. The proportion studies undertaken in general prac- Rarely are restorations well cured, of replacements of amalgam resto- tice and university environments15. which is partly because many rations due to bulk fracture had Malament and Socransky247 dentists use light-curing units with remained much the same over the observed 1,444 restorations made low light intensities240. The intensity period, which suggest little effect from Dicor glass-ceramic over 14 output from a lamp in a light- of the improvements in amalgam years, and found no significant curing unit deteriorates over time, alloy compositions. On the other difference between the bulk frac- and the minimum acceptable light hand, a significant relationship ture of inlay and onlay restorations. intensity level is 300mW/cm2. between the zinc and copper The fracture incidence improved Unfortunately, there seems to be a contents of amalgam alloys and significantly when restorations were low awareness among dentists of bulk fractures was reported by acid-etched before luting. There the need for maintenance and regu- Letzel et al.69 on the basis of a was no significant difference lar checking of light intensity as longitudinal study over 15 years. between acid-etched Dicor resto- part of a quality management The authors attributed this to the rations that were placed on programme241. superior corrosion resistance of the shoulder or chamfer preparations, non-gamma-2 (high-copper) amal- nor did the thickness of the resto- gams compared to conventional ration measured at the mid-axial Material deterioration alloy compositions. point of each surface relate to frac- Material deterioration includes bulk For composite resin restorations ture incidence. and marginal fracture, as well as there has been a notable decrease Letzel et al.69 reported a signifi- excessive wear or dissolution of in the relative frequency of replace- cant association between amalgam the material. Excessive dissolution ments as a result of degradation alloys and bulk fractures over an is seldom seen when materials and wear, and an increase in the observation period of five to 15 which comply with ADA or ISO replacements following bulk and years. Although not much was standards are correctly used. In marginal fractures, which is attrib- commented on in their report, a particular, the presence of saliva uted to changes of material table showed a marked association during material placement may have composition245. between operator and incidence of a strong negative effect on the Tyas246 reported three-year obser- bulk fracture. resistance to deterioration, for vations of 102 Class IV restora- Lemmens et al.248 reported an example glass-ionomer cement242. tions of four composite resins. analysis of 176 fractured amalgam Excessive wear of luting cements Significant correlations (P < 0.01) restorations and concluded that may occur if the cement margin is were found between surface chip- there was a statistically significant wide. Modern composite resin ping/bulk fracture and fracture influence of the dentist on the inci- cements seem to resist wear better toughness, elastic modulus and dence of bulk fracture. than conventional cements243. Cements tensile strength. Moreover, there may also begin to disintegrate was a trend towards an association under luted restorations during between incisal wear and both elas- Cavity design deformation of the restoration, tic modulus and inherent flaw size. Wilson et al.146 reported on a five- initiating and propagating cracks centre study for the five-year leading to cement fracture. outcome of 232 restorations. Large Bulk fracture is a common reason Operator factors restorations consistently deterio- for restoration replacement, and it It is difficult to assess the influence rated more than moderate-sized is often associated with caries. of important operator factors such ones, with respect to class of Caries may either have preceded as poor cavity adaptation, extent restoration or type of tooth the fracture, or have developed of porosities and extent of contam- restored. In a cross-sectional study rapidly after fracture if a remnant ination of the material during of approximately 2,500 amalgam of a broken restoration remains in handling on the restoration. It can restorations bulk fractures were

International Dental Journal (2001) Vol. 51/No.3 143 most prevalent in fillings with three significant effect on deterioration it is misleading to calculate and or four surfaces163. of occlusal marginal adaptation describe wear levels in terms of In a three-year study of 438 over five years. This appeared micrometre/year255. It is probable Class I restorations of glass- greatest in the large Class I and that wear decreases over time, ionomer cement, composite resin both small and large Class II amal- because the more wear-resistant and amalgam, loss of material gam restorations in molars. This adjacent enamel surface protects the and surface cracking or crazing finding led the authors to suggest remaining material surface to an appeared to a greater extent in large that future longitudinal studies increasing extent256. conventional preparations, and should include assessment of especially among glass-ionomer occlusal function, diet and chewing cement restorations249. patterns. Caries The possible relationship between In a longitudinal clinical study There is no reason to consider bulk fracture risk and Class I and of ceramic inlays over three years secondary caries as any different Class II cavity preparations for Åberg et al.251 reported that of from primary caries257. It is a local- amalgam has been reported in a the fractured inlays, two-thirds ised disease caused by a local previous paper, and will not be occurred in patients with signs of accumulation of mechanically discussed further113. bruxism. undisturbed bacterial biomass. In a retrospective study after Several facts should be examined 10–15 years on the quality of 793 in this regard. First, even when Patient factors restorations, bulk fractures in amal- there is a very close adaptation Intraoral location gam restorations were recorded between a restoration and tooth, Malament and Socransky245 found primarily in patients with severe there is still more than enough space fewer fractures of Dicor restora- bruxism170. The levels of oral health for bacterial ingrowth. Second, there tions in female than in male and smoking were also included in is little evidence of ‘undetectable patients. The highest fracture level the analyses, but no influence of microleakage’ causing secondary was observed in second molars. either was found. caries. Third, most papers have Mjör and Jokstad187 examined Klausner et al.252 recorded the reported only weak evidence of a the clinical performance of 274 reasons for replacements of resto- relationship between marginal amalgam, glass-ionomer cermet rations. For bulk fracture, 43 per discrepancies and secondary caries. cement and composite resin resto- cent of restorations were 10 years Fourth, in spite of hundreds of rations over five years in small Class of age or older, while 80 per cent laboratory microleakage studies, no II cavities. The majority of the bulk were older than four years. The correlation with secondary caries fractures, which were mostly in authors commented that if faulty has been established. Fifth, ground glass-ionomer cermet cement occlusion or thin pulpal-occlusal sections of restored teeth with restorations, were located in the sections of amalgam were the prin- secondary caries often reveal upper molars. cipal reasons for isthmus fracture, subsurface lesions unrelated to the In a 10 year longitudinal study then these fractures should have cavity wall. Finally, some clinical of 468 amalgam restorations, become evident at an earlier time. data suggest that the occurrence of Jokstad29 reported findings that secondary caries is a localised contrasted with the results by phenomenon related to the condi- Lemmens et al.243. Only one of 27 Does technical excellence tions for evolution of cariogenic fractured restorations was located predict failure? plaque, rather than a universal in lower premolars. No effect of Few clinical studies have addressed attack along the entire interface the intra-oral location on bulk the correlation between material between tooth and restoration257. fracture was observed. deterioration and duration of Thus, secondary caries may On the basis of longitudinal clinical service. Early occlusal develop in the presence of cari- studies over seven years, including marginal fractures, may69,106,248 or ogenic plaque, but will never 176 fractured amalgam restorations, may not188,253,254 correlate with develop if cariogenic plaque is it was suggested that restorations further material deterioration. absent regardless of the technical in the mandibular teeth and espe- Jokstad29 observed 468 amalgam excellence of the restoration. A cially in the premolars were very restorations of five alloys placed in discussion of which restoration susceptible to bulk fracture248. 210 patients for 10 years. Marginal detail constitutes a major or a fractures after relatively short clini- minor ‘focus’ of plaque retention cal service were associated with later appears from this aspect to be an Oral environment bulk fracture. academic discussion. It is the Wilson et al.146 reported that the Wear is not linear over time. It patient’s oral hygiene habits that will presence of occlusal contacts had a has therefore been suggested that determine if caries develops, not

FDI Commission, Jokstad et al.: Quality of dental restorations 144 whether the restoration can be previous paper, and will not be In a 10 year longitudinal study considered as ‘excellent’, ‘adequate’ discussed further113. of 468 amalgam restorations, the or ‘deteriorated’. most important factor that could Patient factors be associated with the development In a clinical evaluation of 63 Class of secondary caries was the Material factors II composite resin restorations over patient’s yearly DFT increment29. The increased popularity of restora- five years, 8 of the 11 patients with tive materials that release fluoride restorations that failed because of is in part explained by the belief caries and marginal defects had Does technical excellence that secondary caries can somehow higher counts of mutans strepto- predict failure? be prevented by incorporating this cocci at baseline compared to the Roulet104 stated categorically that component. The anticariogenic remaining patients. This led the marginal integrity is an important properties of glass-ionomer cement authors to suggest that the caries parameter for restoration longev- restorations are not strongly sub- activity should be managed to avoid ity, since recurrent caries and pulpal stantiated by clinical investigations13. future secondary caries87. disease is associated with marginal On the other hand, the lack of In a study of 4,294 children gaps. However, the gap size per se strong evidence of an anticario- observed over three years, the inci- may not play any role in secondary genic potential may stem from dence of secondary caries be asso- caries initiation. What is of impor- clinical studies conducted in academic ciated with some oral hygiene tance is whether it promotes environments on selected patients parameters259. Water rinsing after formation of cariogenic plaque, with minimal caries risk instead of brushing and the use of a beaker which encompasses additional vari- in ‘real-life’ general practices. for rinsing was associated with ables besides just gap size. It is In a longitudinal study of 274 secondary caries. Also, subjects who theoretically possible that the quan- large Class II open-sandwich resin- brushed less often than twice a day tity and quality of the plaque modified glass-ionomer cement developed more secondary caries formation around restorations may restorations over three years, no than the others did. be a better prognostic marker of secondary caries was noted, despite Clarkson and Worthington260 restoration longevity than various a large number of participating reported that in a group of 270 criteria of technical excellence201. patients with high caries risk258. In adults an association was seen The alleged correlation between these patients, a far higher caries between caries, most commonly marginal fractures and recurrent frequency around the other restora- secondary caries, and attendance. caries is controversial. Two factors tives was recorded, leading the The irregular attenders experienced should be considered in this context. authors to suggest a possible more caries than did the regular What is the association between the anticariogenic effect of this material. attenders. location of the defect and location van Dijken261 has carried out of secondary caries? What is the several longitudinal clinical studies relationship between the size of the Operator factors where part of the study design has defects and secondary caries? No Several textbooks advise that been to classify the patient accord- reports have been identified that because of polymerisation shrink- ing to few or many caries risk demonstrate a correlation between age, the location of the gingival factors, based on the net effect of occlusal discrepancies and marginal margin for posterior composite microbial counts, oral hygiene, sali- adaptation on the approximal resin restorations should be placed vary flow levels, buffer values, and surfaces, which are the areas where at least one millimetre, when possi- fermentable carbohydrate intake32. secondary caries lesions prevail. ble, from the enamel-cement However, the difference between Therefore, it is difficult to under- margin. Several cross-sectional these two groups has only been stand how marginal fractures on studies imply that this rule is not reported in two studies. In a six the occlusal surface can be related followed by general practitioners. year longitudinal study of 150 to a higher risk of secondary caries. However, it has not been possible tooth-coloured restorations, all While some authors report to identify in the literature any clini- restorations which subsequently associations between marginal frac- cal studies that have associated this developed secondary caries (n=7), ture and secondary caries262, others characteristic of the cavity design except for one, were from the high- do not263,264. Other laboratory with the development of second- caries-risk group261. In another six experiments suggest that a correla- ary caries. year study of seven anterior tion does not seem to exist between The possible relationship between composite resins, a markedly higher the size of the crevice and second- secondary caries risk and Class I increment of caries was recorded ary caries265, or describe only a and Class II cavity preparations for among the patients with many correlation in extremely cariogenic amalgam has been reported in a caries risk factors32. environments266.

International Dental Journal (2001) Vol. 51/No.3 145

Staining around both amalgam267 tooth regardless of material. The Operator factors 268 and tooth-coloured restorations processes involved regarding the Cast restorations, especially inlays is considered unreliable in the diag- way in which tooth strength is or dowels with improper fit, cause nosis of active recurrent caries. associated with choice of restora- stress that increases the risk of tooth 269 Hewlett et al. reported that 86 tive material, adaptation and the fracture. Strain can also be intro- per cent of 822 restorations with microstructural relationship at the duced if high pressure is used or marginal defects revealed no tooth-material interface are contro- misalignment of the casting occurs secondary caries on radiographs. versial. This can be explained by during cementation. Also, it has This led the author to suggest that the fact that the incidence of tooth been suggested that tooth prepara- the replacement of all restorations fractures is relatively low, which tion using eccentric or worn burs with defects related to a perceived impedes the execution of clinical increase the risk of crack propaga- risk of secondary caries would studies. Our understanding of the tion in the tooth. constitute overtreatment. relationship between clinical factors The possible relationships between After observing 468 amalgam and tooth fractures is therefore to tooth fracture risk and Class I and restorations of five alloys placed in a large extent based on extrapola- Class II cavity preparations for 29 210 patients for ten years, Jokstad tion of case descriptions and amalgam have been reported in a 273–275 reported that those restorations laboratory findings . previous paper, and will not be with early marginal fractures could discussed further113. not be correlated with later devel- opment of secondary caries. Material factors In an observational longitudinal Thermal dimensional stability, hygro- Patient factors study, an increased prevalence of scopic expansion and setting/ Most tooth fractures originate in secondary caries was recorded in polymerisation shrinkage of resto- the 30–50 year age group and in the restorations with the poorest rative materials, as well as exces- teeth with large intracoronal resto- 270 margin fracture scores . sive loading, have been related to rations or caries. Fractures of 1,65,73 A longitudinal clinical study over stress build-up in tooth tissues . contralateral teeth are common275. 10 years demonstrated no differ- The stress will be best tolerated by All factors that cause high strain on ences in secondary caries levels dentine due to its elasticity, while tooth tissue increase the risk of between a spherical amalgam alloy infractions may develop in the crack-line development and cusp and a non-gamma-2 alloy, despite enamel. The material-caused stress fractures. Examples are bruxism, differences in marginal deteriora- applies to restorative materials that lack of occlusal support following 271 tion during the first years . do not exceed the limits according loss of teeth, malocclusion, supra- 272 Goldberg et al. examined to the existing material test stand- contacts or frequent intake of 1,556 restorations in 87 patients in ards. An in vitro investigation has coarse foods. Cusp fractures and a cross-sectional study. The preva- demonstrated fractures of ceramic crack lines in the posterior teeth lence of secondary caries was crowns with cores made from are most frequently observed on correlated with the marginal frac- resin-modified glass-ionomer cement balancing cusps, which are subjec- ture scores and indices of the materials. It was hypothesised that ted to lateral chewing forces (that patients’ oral health. Using log- the fractures were caused by hygro- is, the lingual cusps in the mandi- 276 linear analyses, the investigators scopic expansion . Several manu- ble and buccal cusps in the maxilla). suggested that there was a signifi- facturers do not recommend this Ellis et al.274 reported a meta- cant relationship between these class of material for core builds or analysis of the influence of patient three factors. as a luting cement for full-ceramic age on tooth fracture and conclu- restorations. ded that incomplete tooth fractures Several papers postulate that Tooth fracture are uncommon in students attend- infractions in enamel and cusp ing an emergency clinic. It was Tooth fractures include cusp frac- fractures in teeth restored with noted that complete fractures might tures, dentine cracks, incomplete amalgam are caused by an expan- occur at any age, while it appears dentine fractures, crack lines, and sion associated with heat or with that incomplete fractures are asso- cracked tooth syndrome. Some use chemical reactions in the alloy, or ciated with older age groups. the term ‘infraction’ when the crack corrosion of the amalgam. How- line is limited only to the enamel. ever, there is no clinical docu- There is general consensus that a mentation of such relationship. Does technical excellence restored tooth is stronger than a Furthermore, no standardisation predict failure? non-restored tooth with caries, but tests have been devised to screen No papers were found that report that a tooth with an intracoronal materials for this alleged expan- any association between clinical restoration is weaker than an intact sion. observations of technical excellence

FDI Commission, Jokstad et al.: Quality of dental restorations 146 of restorations versus the incidence tures) to poor bonding, which is relatively high proportion of loss, of later tooth fractures. an indirect indication of improper as a result of changes in the charac- tooth preparation or material ter of the dentinal surface. handling. It has been suggested that Heymann et al.287 reported on Loss of restoration the effectiveness of dentine bond- the determinants of failure of bonded Loss of entire restoration is limited ing, and thus the retention of composite resin restorations in non- mostly to Class V restorations, restorations, is influenced by carious cervical lesions. A strong especially when placed without operator factors such as cavity association between patient age and cavity preparation. Loss of other preparation relative to the active restoration loss was identified, types of restorations would only caries process, technique for mate- which was attributed to the greater occur due to inappropriate selection rial application, and procedures for tooth flexure in older patients, and of material, improper preparation polishing282. the smooth, sclerotic nature of ‘old’ of the tooth before restoration, Cavity design dentine. violation of biomechanical princi- Vital dentine is continuously remod- Oral environment ples for designing the restoration, elling its microstructure to respond In a recount of a clinical experience mishandling the material, or a to physiological and pathological after placing 3,500 porcelain combination of these factors. changes. Therefore, bonding may veneers over 15 years, Friedman281 encounter differences such as distinguishes between three fracture Material factors sclerotic dentine, hypersensitive types, and suggests the aetiological dentine (with open tubules), caries- mechanism for each type. The Deviations from the manufactur- affected areas, superficial dentine author ascribed static fracture lines er’s direction for use may lead to with few tubules, or deep dentine and cohesive fractures to excessive decreased clinical performance. This layers close to the pulp283. loading. has been reported in a three-year McCoy et al.191 noted in a three- study of resin-modified glass- Isolation Cervical composite resin restora- year longitudinal study of Class V ionomer cements placed in cervical composite resin restorations that cavities, where retention was tions placed with isolation either with rubber dam or with cotton some restorations were lost from associated with surface wetting teeth with marked signs of occlusal following variations in the powder/ rolls suggested no statistically significant differences in retention wear, supporting earlier reports of liquid ratio at the time of place- higher loss of restorations among 277 after two years of service. Thus, ment . bruxers compared to non-bruxers288. Much discussion has taken place loss of retention was not different on the importance of the modulus when a careful cotton roll tech- of elasticity of polymeric materi- nique was used as a moisture Does technical excellence als278. There are diverging views on control method, as long as saliva predict failure? its relevance, and this confusion typi- contamination was avoided174. There are no known papers that fies our poor understanding of have reported any association tooth biomechanics. There is also between clinical observations of an ongoing discussion about which Patient factors technical excellence of restorations material is most appropriate for Gender and age versus later loss of restorations. non-carious cervical lesions. Is It has been suggested that bonding composite resin, glass-ionomer to sclerotic dentine is less reliable cement, polyacid-modified compos- than to young dentine, at least with Orthodontic changes and ite or resin-modified glass-ionomer older restorative materials284. Two temporomandibular joint cement the optimal material of recent clinical studies have refuted problems choice279,280? the hypothesis285,286. In these stud- Composite resins placed during ies, lower failure frequencies were 1970–1980 had relatively poor seen in the oldest age groups and resistance to wear when used in the Operator factors the restorations placed in sclerotic posterior occlusal segments. In spite Although presented as anecdotal dentine had an almost equal failure of this, products were sold in large evidence, Friedman281 recounts his rate compared to the ones placed quantities and used for this clinical experiences after placing a in non-sclerotic lesions. purpose by many general practi- substantial number of porcelain McCoy et al.191 suggested, after tioners. Annual wear of 30–60mm veneers (n=3,500) over 15 years. a three-year longitudinal study of was reported, raising concerns for The author attributes the three main Class V composite resin restora- possible hypereruption of oppos- failure reasons (debonding, marginal tions, that a high proportion of old ing teeth and mesial migration of discolouration and adhesive frac- patients in the study contributed to teeth distal to those undergoing loss

International Dental Journal (2001) Vol. 51/No.3 147 of approximal contact289. Despite highest possible technical excel- patient classifications. Although concerns that composite resins were lence, and (5) aim to accomplish such systems tend to appear sim- unsuitable for surfaces exposed to the pre-set objectives that you as a plistic, they highlight the fact that heavy masticatory forces, there dentist and patient have agreed on. patients’ personalities, values and were no reports that extensive use The most relevant issue is the evalu- priorities differ considerably. Mod- led to tooth misalignments or ation of the technical excellence ern health care places great empha- temporomandibular joint problems of dental restorations as part of sis on patient satisfaction as a crite- caused by occlusal changes. the first step: making a correct rion for quality. However, the The resistance to wear of diagnosis. Main objectives are to theoretical principles of patient sat- correctly handled modern materi- recognise a pathological condition, isfaction are complex and corre- als has now been markedly understand the patient’s problem late poorly with criteria for techni- improved. Thus, the risk of large and identify risk markers of cal excellence commonly used by generalised wear and potential progressive oral disease. The tech- dentists292. pathological joint changes and nical excellence of restorations is, temporomandibular problems are at this stage, of secondary impor- minor. However, the potential tance. Estimating risk for oral exists if materials are handled disease incorrectly, following eating disor- Assessment of risk markers of oral ders or harmful occupational Patient dissatisfaction disease is detailed in at least one environments, or if new restora- Patient dissatisfaction with a partic- excellent textbook on risk and oral tive materials are applied that have ular restoration is easy to detect. It diseases293, and within textbooks not been adequately tested for includes complaints about pain, on cariology46,267,294,295 and period- clinical wear. aesthetics, surface roughness, contour, ontology296,297. Briefly, risk assessment detectable margins, supraocclusion associated with susceptibility to oral or food retention. As long as the disease consists of determining Treatment decisions and contributing factor is identified and factors related to the patient’s technical excellence corrected, there is no problem. social and medical history, plaque The planning of restorative treatment However, if the patient’s dissatis- control, saliva and clinical signs of consists of a series of interactive faction is with a restoration that disease. Estimating the risk for oral exchanges of information between meets all criteria for technical disease progression can be assessed the dentist and the patient. Lack of excellence the situation is more at the patient, tooth and site levels. awareness of a patient’s complaints complicated. Then patient infor- At the patient level, the key oral and expectations can lead to mation and ethical considerations disease risk markers are the pres- unnecessary conflicts, a situation must prevail, tempered by existing ence of a systemic disease, irregular cherished by sensational news local or national legislative prec- dental attendance, prior caries media. A common principle in edents or regulations. The patient history, periodontal problems, plaque marketing is ‘do/say the right thing must always be advised of the and/or bleeding scores, medica- to the right people at the right potentially iatrogenic damage asso- tion side effects and saliva quantity time’. This quotation can be ciated with restoration replacement, and quality. Other risk markers may improved for our purposes by such as risk of pulp deterioration refine decisions about interventions. refining the words into the dental and increased cavity dimensions, For example, information on social strategy. Optimal dental treatment as well as the possibility of no deprivation, active oral disease in of patients consists of: (1) At the improvement in spite of restora- siblings or low dental IQ and right time, (2) offer the right treat- tion replacement. history of repeated interventions ment, (3) to the right patient, (4) in Some studies have attempted to may be relevant factors. the right way, (5) with the right categorise or distinguish patient For periodontal disease, presence results. characteristics versus expectations of residual pockets and cigarette The interpretation into dental of dental treatment. Several taxono- smoking are additional factors to terms is (1) make the correct diag- mies have been presented. Håkestam be considered when assessing risk nosis at the outset, (2) explain to et al.290 suggests there are three while additional factors for address- the patient the options and suggest groups: the aesthetic, the cost ing risk for future caries are dietary the best alternative, (3) take into conscious and the longevity- habits, frequency of sugar intake, consideration the patient’s priori- focussed. Lutz and Krejci291 availability of snacks and use of ties and preferences, (4) carry out categorised the patients as in orally fluorides. the restorative intervention accord- ‘functional’, ‘presentable’, ‘healthy’, At the tooth and site levels, risk ing to correct procedures and ‘beautiful’ and ‘metal-free’ groups. factors include residual periodontal material handling to ensure the Other studies have applied further support, inflammatory parameters

FDI Commission, Jokstad et al.: Quality of dental restorations 148

Table 4 Intervention strategies based on combining a risk assessment for oral disease and the technical excellence of the patient’s restorations. The codes used in the CDA evaluation system criteria31 are included to enhance the interpretation of the table (see Table 5 for abbreviations)

1. Consider consequences of monitoring, correcting, removing or replacing restoration in case of: Caries Caries along restoration margin (VCAR) Radiographic evidence of caries/voids Margin Retained excess cement (TCEM) Restoration overhang/surplus (TOV) Other Tooth 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 examination 2a. 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 with or can contribute to disease or can contribute to disease 2. Consider consequences of monitoring, correcting or 2. Consider consequences of monitoring, correcting or replacing restoration replacing restoration Surface Surface Fractured, rough or pitted or irregular, flaking or has Fractured, rough or pitted or irregular, flaking or has gross porosities gross porosities (SRO)(TGI)(TPIT)(VSF)(VFK)(VGP) (SRO)(TGI)(TPIT)(VSF)(VFK)(VGP) Contour Contour Exposed dentine or base (TDE)(TBA) Contact slightly open or faulty (SCO)(TCO) Undercontoured cervical area approximally (SPX)(TPX) Undercontoured cervical area approximally (SPX)(TPX) Margin Margin Ditch or gap along the margin (SCR)(TMD) Ditch or gap along the margin (SCR)(TMD) Discoloured margin (SDIS)(TPEN) Other Traumatic occlusion (VTO) 3. Limit intervention to monitoring – unless the patient is dissatisfied. Contour Undercontoured 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 of approach and/or treatment-index ration replacement. ecological niches with difficult to concept should be applied to Table 4 suggests how the techni- access sites such as furcations, and specific clinical conditions and cal excellence of restorations should the presence of iatrogenic factors preventive-restorative options to be appraised clinically in light of such as restoration discrepancies. estimate the probable outcomes298. risks of oral disease. The wording Information gathered by clinical In the introduction, a definition of the criteria parallels descriptions monitoring and continued multi- of the quality of restorations used in the CDA evaluation level risk assessment produces an emphasised the risk of jeopardis- system31 and textbooks cited at the estimate of the oral health status of ing the integrity of remaining start of this section. Table 5 shows an individual, and risk of oral dental-related tissues. Patients with the CDA quality evaluation rating disease progression at a particular indications of severe caries or peri- system and USPHS criteria for tooth or site. It is not until this odontal disease require more evaluation. stage that concern about the tech- attention to possible detrimental It must be emphasised that the nical excellence of one or more characteristics of restorations considerations of the consequences particular restorations should be compared to patients with no signs of monitoring, correcting, removing addressed. Thus, the risk level for of disease. The concept of such an or replacing an existing restoration oral diseases must in a systematic approach is consistent with the must be but one component of the way first be recognised, and then treatment decision philosophy management of oral disease. Further coupled with treatment options practised by many clinicians. The requirements to justify operative that are consistent with the poten- clinician always has three options in intervention should include patient tial future caries increment or deciding on a strategy for interven- understanding of risks and prog- periodontal disease. It has been tion. Either to ignore the current nosis, assessment of aetiology and suggested that a decision-tree status, to adjust or repair, or resto- the instruction of preventive proce-

International Dental Journal (2001) Vol. 51/No.3 Table 5 Relationship between the CDA and the USPHS criteria for evaluation of dental restoration systems30,31.

Surface and color Anatomic form Margin Integrity R: Range of excellence Restoration is of satisfactory quality and is expected to protect tooth and surrounding tissue CDA USPHS CDA USPHS CDA USPHS Surface 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 the No irritation of adjacent translucency of adjacent adjacent teeth and soft anatomic form or is slightly which explorer will penetrate. restoration tissue is occurring tooth tissues tissues with good individual flattened. It may be over- Satisfies principles of margin There is no mismatch in anatomic form contoured. When the side of placement wherever possible. The explorer does not catch when color or translucency (The restoration must be the explorer is placed No discoloration on margin drawn across the surface of the between restorations and examined without using a tangentially across the between restoration and restoration toward the tooth, or, if the adjacent teeth* mouth mirror) restoration, it does not touch tooth structure* explorer does catch there is no visible two opposing cavosurface crevice along the periphery of the line angles at the same time restoration

There is no visual evidence of marginal discoloration difference from the color of the restorative material and from the color of the adjacent tooth structure

S: Range of acceptability Restoration is of acceptable quality but exhibits one or more features that deviate from ideal CDA USPHS CDA USPHS CDA USPHS SRO Surface of restoration The restoration does not SOCO Restoration over- A surface concavity is SCR Visible evidence of There is visual evidence of marginal is 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 the can be polished translucency of adjacent excess material can be explorer is placed tangentially with no evidence of decay; tooth structure and the restoration, but SMM Slight mismatch tooth tissues, but the removed) across the restoration, the repair can be made or is the discoloration has not penetrated FDI Commission,Jokstad between shade of mismatch is within the normal SUCO Restoration slightly explorer touches two unnecessary (visible ditching along the restoration in a pulpal restoration(s) and adjacent range of tooth shades undercontoured opposing cavosurface line along the margin not direction tooth 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 is the normal range of tooth locally(not in toto)) exposed SDIS Discoloration on margin visible evidence of a crevice, into which color, shade and/or SMR Marginal ridges slightly between restoration and the explorer penetrates, indicating that translucency) undercontoured tooth structure* the edge of the restoration does not SCO Contact slightly open adapt closely to the tooth structure.

et al. SFA Facial flattening present The dentin and/or the base is not SLG Lingual flattening present exposed, and the restoration is not

: Qualityofdental restorations SAF Anatomic form of pontic mobile may cause food retention; no irritation of soft tissue SOC Occlusal contour not continous with that of cusps and planes SPX Interproximal cervical area slightly undercontoured 149 International Dental Journal(2001)Vol.51/No.3 T: Replace or correct for prevention 150 Restoration is not of acceptable quality. Future damage to tooth or surrounding tissue is likely to occur CDA USPHS CDA USPHS CDA USPHS TGI 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, deep not related to anatomy and match the shade and undercontoured substance so that a surface cannot be properly repaired discoloration adjacent to the restoration not subject to correction translucency of the adjacent TOCO Restorations grossly concavity is evident and the TPEN Penetrating discoloration (but not directly associated with TMM 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 crevice range of color, shade, or and translucency TOV There is marginal cement defect that extends to the dentoenamel translucency* overhang junction TAF Anatomic form of pontic TMD visible ditching along TPIT Surface deeply pitted, likely to result in food the margin extending to the There is visual evidence of marginal irregular grooves (not related retention, causing irritation to DE junction discoloration at the junction of the tooth to anatomy) cannot be soft tissue or caries in TMB ditching along the structure and the restoration that has refinished abutments margin extending to the penetrated along the restoration in a center base pulpal direction TDE Dention is exposed TBA base is exposed TOC A occlusion is affected TPX contact is faulty – self-correction unlikely

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