Long-term Performance of Refurbished Amalgam Restorations: 10-year Follow-up.

PURPOSE: This prospective, blinded clinical trial assessed the performance of amalgam restorations that were refurbished, replaced, or not treated. MATERIALS AND METHODS: Twenty-three patients were included, ages 18-80 years, with 63 amalgam restorations that had one or more defects in their clinical features, such as defective anatomic form, roughness and/or luster according to United State Public Health Service (USPHS) criteria. Restorations were randomly assigned to either refurbishment (A: n = 21), replacement (B: n = 21) or untreated (C: n = 21) groups. Two calibrated examiners evaluated the restorations at baseline (Kappa = 0.74) and after 10 years (Kappa = 0.84), according to eight parameters: anatomy, roughness, luster, secondary caries, marginal adaptation, occlusal contact, marginal staining and tooth sensitivity. Wilcoxon tests were performed for within-group comparisons, and Friedman tests were used for multiple within-group comparisons. The Mantel-Cox test was used to compare survival curves. RESULTS: After 10 years, 49 restorations (77.8%) were assessed (group A: n = 19; group B: n = 13; group C: n = 17). Over a decade, the three groups showed similar clinical performances for all studied parameters: anatomy (p = 0.410), roughness (p = 0.930), luster (p = 0.984), secondary caries (p = 1.0), marginal adaptation (p = 0.433), occlusal contact (p = 0.33), marginal staining (p = 0.470), and tooth sensitivity (p = 0.784). CONCLUSIONS: Amalgam restorations that have defective anatomic form, roughness and/or luster performed similarly for all studied parameters, whether they were refurbished, replaced or left untreated after 10 years in patients with low and intermediate caries risk. Most of the restorations were classified as clinically acceptable after ten years. Restorations in all three groups tended to deteriorate over time.

Does refurbishing composites lead to short-term effects or long-lasting improvement?

PURPOSE: To evaluate the clinical performance of refurbished resin composite restorations compared to untreated (negative control) restorations over a period of 10 years. METHODS: 26 subjects (having a total of 52 composite restorations) were recruited. All restorations in the refurbished group showed clinical features rated bravo according to modified USPHS criteria. Untreated restorations were those that had been deemed acceptable (alpha or bravo rated); these were used as controls. Two examiners performed assessments at baseline and during the 5th and 10th years after the intervention. Wilcoxon tests were performed for within-group comparisons, Friedman tests were used for multiple within-group comparisons, and Mann Whitney tests were used for between-groups comparisons. Kaplan-Meier survival curves were calculated, and the Mantel-Cox test was used to compare curves. P < 0.05 was considered statistically significant. RESULTS: In both groups, 10-year scores were significantly different from baseline scores in all clinical parameters except secondary caries. There were no statistically significant differences in the survival analysis of groups (log-rank test, P = 0.376). Refurbishing treatment improved the anatomy, roughness, luster, and marginal adaptation of restorations with a short-term effect, with most properties rated acceptable after 10 years of clinical service. The clinical characteristics were similar for all groups at the 10th year.

Fluorides leaching from restorative materials and the effect on adjacent teeth.

OBJECTIVE: Placing a Class II restoration in a tooth changes the local environment, including that for the adjacent tooth. Apart from the change to a less- or non-cariogenic environment for the restored tooth, the effect of leachable components from a restoration in the adjacent tooth should be taken into consideration. METHOD: Practice-based clinical studies comprising of 1341 unrestored proximal surfaces in contact with Class II restorations using different restorative materials were reviewed to assess the effect on the caries development on the adjacent teeth. The caries status of the adjacent un-restored proximal surface was assessed as being clinically sound, having active caries with or without cavitation, or having arrested caries. Restorations from nine clinicians were reviewed. They had attended annual meetings where all aspects of the investigation had been discussed. The surfaces were followed for up to eight years. RESULTS: A reduced rate of caries development and progression were found on surfaces in contact with fluoride releasing materials like glass ionomers, resin modified glass ionomers and compomers compared to surfaces in contact with amalgam. CONCLUSION: Fluoride releasing materials reduce the development and progression of primary caries on adjacent proximal surfaces.

The longevity of different restorations in primary teeth.

BACKGROUND AND AIM: This paper reviews three published papers and adds results from a fourth study which aimed to determine which restorative material would be the best alternative(s) to amalgam (AM) in primary teeth. DESIGN: All studies had a practice-based design and were part of the routine treatment of children and adolescents. The clinicians were assigned which materials to use in a randomised matter in the first three studies which lasted for 7-8 years. In the fourth study conducted 4 years after the initial studies, the clinicians were free to select the restorative materials. RESULTS AND CONCLUSIONS: Resin modified glass ionomer (RMGI) and compomer (COM) restorations showed similar longevity compared with AM, whereas conventional GI restorations showed significantly shorter longevity. The studies indicated that the 'new and improved' materials based on in vitro tests did not always show enhanced clinical properties. In the last study, where clinicians freely selected the restorative materials they used in their practices, seven used COM, one used conventional GI materials and one used a combination of the two types of material.

Morphological characterization and permeability of attrited human dentine.

OBJECTIVE: Dentine is a vital tissue that can be changed by physiological and pathological condition. The purpose of this study was to clarify the morphology and permeability of dentine that changed by wearing process. METHODS: Twenty extracted human molars with enamel attrition and dentine was exposed and 20 intact human extracted third molars that had not reached occlusion were used. Ten teeth per each group were observed under light microscope (LM) and transmission electron microscope (TEM). Remaining 10 teeth per each group were subjected for evaluation of dentine permeability. RESULTS: Under LM, the transparent dentine and reactionary dentine were found in the attrition group but were not found in the group unaffected by attrition. When the transparent dentine were examined under the TEM, it was found that dentinal tubules were partially or completely occluded by growth of peritubular dentine or by precipitation of needle-like or rhombohedral crystals in transparent dentine. In reactionary dentine, tubular dentine structures that were comparable to those in secondary physiologic dentine were observed whereas atubular dentine demonstrated occlusion of tubules by high mineral substances or by peritubular dentine under the TEM. Permeability of dentine from worn teeth was less than those from unoccluded teeth significantly. CONCLUSION: Change in dentine by wear resulted in the formation of reactionary dentine and transparent dentine that illustrated various types and degrees of tubular occlusion. These decrease the dentine permeability.

Caries and restoration prevention.

BACKGROUND: The authors analyzed studies of decayed, missing and filled (DMF) rates for surfaces and teeth in Norway published during the last 30 years. The result of active fluoride therapy combined with a change in criteria for when to place restorations led to a marked reduction in the need for restorations. METHODS: The authors reviewed independent, cross-sectional DMF studies of representative samples of young adults performed every 10 years during the period 1973 through 2006. The clinicians involved in the studies used standardized and calibrated methods. The authors of this article also reviewed an additional series of studies collecting DMF data from representative samples of 15-year-old adolescents that also had been carried out independently from 1979 through 1996. In these studies, the investigators examined clinical records and bitewing radiographs with attention to progression of carious lesions and restorative treatments. RESULTS: The authors noted a marked reduction in the mean decayed, missing and filled surface (DMFS) scores from 1973 through 2006 in the two adult groups. They also found a significant decrease in treatment of caries. The reduction was most marked after the mid-1990s. They noted that the most dramatic change in the data from the 15-year-olds resulted from a change in the treatment criteria during the 1980s. Approximal lesions in enamel were monitored by the investigators of those studies in combination with the use of fluoride toothpaste. CONCLUSION AND CLINICAL IMPLICATIONS: A caries treatment approach based on active caries-preventive treatment and restrictive criteria for restoration placement are good bases for reducing the need for restorations as shown in cross-sectional studies reviewed.

Increasing the longevity of restorations by minimal intervention: a two-year clinical trial.

UNLABELLED: This investigation assessed the effectiveness of alternative treatments for the replacement of amalgam and resin-based composite restorations. Sixty-six patients (age 18 to 80 years, mean = 26.6) with 271 (amalgam [n = 193] and resin-based composite [n = 78]) defective restorations were randomly assigned to one of five different treatment groups: A) Repair (n = 27); B) Sealing of margins (n = 48); C) Refurbishing (n = 73); D) Replacement (n = 42) and E) Untreated (n = 81). USPHS/Ryge criteria were used to determine the quality of the restorations. Two calibrated examiners (Cohen's Kappa 0.74) assessed the restorations independently at the beginning of the study (baseline) and at two years after treatment using seven parameters from the USPHS/Ryge criteria (Marginal Adaptation, Anatomic Form, Roughness, Marginal Stain, Occlusal Contact, Secondary Caries and Luster). RESULTS: Two-hundred and fifty-six restorations (178 amalgam and 78 resin-based composite) were examined at the two-year recall exam. The sealing of marginal defects showed significant improvements in marginal adaptation (p < 0.05). Refurbishing of the defective restorations significantly improved anatomic form (p < 0.0001), luster (p < 0.016), marginal adaptation (p < 0.003) and roughness (p < 0.0001). The repair significantly improved anatomic form (p < 0.002) and marginal stain (p < 0.002). Replacement showed significant improvements for all parameters (p < 0.05). The Untreated group showed significant deterioration on marginal adaptation (p < 0.013). CONCLUSIONS: The two-year recall examination showed that sealant, repair and refurbishing treatments improved the clinical properties of defective amalgam and resin-based composite restorations by increasing the longevity of the restorations with minimal intervention.

CAD/CAM restorations and secondary caries: a literature review with illustrations.

UNLABELLED: The literature related to failures of CAD/CAM restorations, with emphasis on secondary caries, is presented. A good approximal fit of the restoration is important to prevent plaque accumulation that may lead to secondary caries. CAD/CAM restorations allow inspection of the approximal fit prior to cementation and it may explain the relatively few failures due to secondary caries. The longevity of these restorations approaches that of gold restorations. CLINICAL RELEVANCE: The requirement for CAD/CAM restorations has advanced to a stage where high quality restorations with excellent anatomy and fit can be produced. The failure rate is relatively low compared to directly placed restorations.

Recommendations for conducting controlled clinical studies of dental restorative materials. Science Committee Project 2/98--FDI World Dental Federation study design (Part I) and criteria for evaluation (Part II) of direct and indirect restorations including onlays and partial crowns.

About 35 years ago, Ryge provided a practical approach to the evaluation of the clinical performance of restorative materials. This systematic approach was soon universally accepted. While that methodology has served us well, a large number of scientific methodologies and more detailed questions have arisen that require more rigor. Current restorative materials have vastly improved clinical performance, and any changes over time are not easily detected by the limited sensitivity of the Ryge criteria in short-term clinical investigations. However, the clinical evaluation of restorations not only involves the restorative material per se but also different operative techniques. For instance, a composite resin may show good longevity data when applied in conventional cavities but not in modified operative approaches. Insensitivity, combined with the continually evolving and nonstandard investigator modifications of the categories, scales, and reporting methods, has created a body of literature that is extremely difficult to interpret meaningfully. In many cases, the insensitivity of the original Ryge methods leads to misinterpretation as good clinical performance. While there are many good features of the original system, it is now time to move on to a more contemporary one. The current review approaches this challenge in two ways: (1) a proposal for a modern clinical testing protocol for controlled clinical trials, and (2) an in-depth discussion of relevant clinical evaluation parameters, providing 84 references that are primarily related to issues or problems for clinical research trials. Together, these two parts offer a standard for the clinical testing of restorative materials/procedures and provide significant guidance for research teams in the design and conduct of contemporary clinical trials. Part 1 of the review considers the recruitment of subjects, restorations per subject, clinical events, validity versus bias, legal and regulatory aspects, rationales for clinical trial designs, guidelines for design, randomization, number of subjects, characteristics of participants, clinical assessment, standards and calibration, categories for assessment, criteria for evaluation, and supplemental documentation. Part 2 of the review considers categories of assessment for esthetic evaluation, functional assessment, biological responses to restorative materials, and statistical analysis of results. The overall review represents a considerable effort to include a range of clinical research interests over the past years. As part of the recognition of the importance of these suggestions, the review is being published simultaneously in identical form in both the Journal of Adhesive Dentistry and Clinical Oral Investigations. Additionally, an extended abstract will be published in the International Dental Journal, giving a link to the web full version. This should help to introduce these considerations more quickly to the scientific community.

A clinical evaluation of a self-etching primer and a giomer restorative material: results at eight years.

BACKGROUND: The authors evaluated the performance of a giomer restorative material (Beautifil, Shofu, Kyoto, Japan) with a self-etching primer (FL-Bond, Shofu) for posterior restorations. MATERIALS AND METHODS: Two clinicians placed 26 Class I restorations and 35 Class II restorations in 31 patients ranging in age from 21 to 62 years (mean age, 34 years). Inclusion criteria required patients to have molar-supported permanent dentition free of any edentulous spaces and no clinically significant occlusal interference, as well as one or more permanent molars or premolars requiring new or replacement Class I or II restorations. Two of the authors examined the restorations using modified U.S. Public Health Service/Ryge criteria for color match, marginal adaptation, anatomy, surface roughness, marginal staining, interfacial staining, proximal and occlusal contacts, secondary caries, postoperative sensitivity and luster. RESULTS: The two authors examined all restorations at the one-year recall visit, 58 at the two-year visit, 47 at the three-year visit, 39 at the four-year visit and 41 at the eight-year visit (16 Class I and 25 Class II restorations). During the eight-year period, they detected no changes with respect to surface roughness, postoperative sensitivity or secondary caries. The majority of changes recorded were for marginal adaptation at occlusal (29 percent) and proximal (16 percent) surfaces and marginal staining at occlusal (15 percent) and proximal (32 percent) surfaces. The McNemar test showed significant changes between baseline and the eight-year evaluation only for marginal adaptation at occlusal surfaces (P = .0047) and marginal staining at proximal surfaces (P = .04). None of the restorations failed. CONCLUSION: Most of the restorations maintained good quality during the observation period. CLINICAL IMPLICATIONS: Beautiful restorative material and FL-Bond bonding system, when placed in Class I and II preparations, achieved clinically acceptable results after eight years of service.

The safety of nickel containing dental alloys.

Nickel is a constituent of many dental alloys. This paper reviews mainly papers published after 1985 with regards to biological reactions to nickel in dentistry. Nickel is an allergen, but there is no evidence that individual patients are at a significant risk of developing sensitivity solely due to contact with nickel-containing dental appliances and restorations. Hypersensitivity reactions to nickel are only likely to occur with prior sensitization from non-dental contacts and even these are rare. Clinical evidence has been presented to show that small doses of nickel, e.g. from dental appliances, may induce tolerance to this allergen. The papers reviewed report low rates of release of nickel from dental alloys. Some nickel compounds, which are mildly cytotoxic, have been implicated as carcinogens by inhalation in industrial settings, but these compounds are not present in dentistry-related operations, including dental technology procedures. Nickel-containing alloys and compounds have not been associated with increased cancer risk by oral or dermal routes of exposure. It is concluded that, subject to use according to established techniques, nickel-containing dental alloys do not pose a risk to patients or members of the dental team.

Two-centre evaluation of a resin composite/ self-etching restorative system: three-year findings.

PURPOSE: This two-centre study evaluated the clinical performance of Class I and Class II restorations of the giomer material Beautifil, placed using Fluorobond, a self-etching adhesive system, to determine the suitability of the test system as an alternative for the restoration of posterior teeth. MATERIALS AND METHODS: A total of 108 restorations, comprising 72 Class II and 36 Class I restorations, was placed predominantly in molars (82%). Evaulations using modified USPHS/Ryge criteria were conducted at baseline and thereafter at 6 months and 1, 2, and 3 years. Die stone replicas of the restored teeth were examined retrospectively. RESULTS: A total of 5 restorations was found to fail during the study-- 3 in the first year and 2 during the third year of the study. Occlusal marginal adaptation was less than ideal at baseline in 11% of cases, primarily as a consequence of overcontouring, as observed in the die stone replicas. The combined percentage Alpha ratings at 3 years were: colour match, 98%; marginal adaptation (occlusal), 78%; marginal adaptation (proximal), 97%; anatomic form (occlusal), 99%; anatomic form (proximal), 95%; surface roughness (occlusal), 100%; surface roughness (proximal), 100%; marginal staining (occlusal), 90%; marginal staining (proximal) 81%; interfacial staining (occlusal), 99%; interfacial staining (proximal), 100%; contacts (occlusal), 95%; contacts (proximal), 93%; sensitivity, 100%; secondary caries, 100%; lustre of restoration, 100%. CONCLUSION: It is concluded that the 3-year performance of Fluorobond-bonded Beautifil for Class I and II restorations demonstrated some marginal changes, but most of the direct evaluation ratings were > 90% Alpha, with the performance observed being similar in the two centres.

Repair strength of dental amalgams.

This study tested the hypothesis that newly triturated amalgam condensed vertically on old amalgam was essential for establishing a bond between the new and old amalgams. Twelve rectangular bars were prepared with Dispersalloy and Tytin to establish their baseline flexure strength values. An additional 12 specimens were made and separated into 24 equal halves. All fracture surfaces were abraded with a flat end fissure bur. Twelve surfaces were paired with the original amalgam, and the remaining 12 surfaces were repaired with a different amalgam. At first, freshly triturated amalgam was condensed vertically on the floor of the specimen mold (Group A). The majority of specimens repaired with Group A failed to establish bond at the repair interface. All repair surfaces were abraded again and prepared by a second method. A metal spacer was used to create a four-wall cavity to facilitate vertical condensation directly on the repair surface (Group B). The specimens were stored in ambient air for seven days prior to flexure testing. The strength of specimens repaired with Group B ranged from 26% to 54% of the baseline specimens. ANOVA showed that amalgams repaired with a different amalgam yielded higher strength values than those repaired with the original amalgam, and the baseline specimens exhibited significantly higher strength values than all the repaired specimens.

2-year clinical evaluation of alternative treatments to replacement of defective amalgam restorations.

OBJECTIVE: To investigate the effectiveness of alternative treatments for replacing defective amalgam restorations through a prospective longitudinal cohort clinical study. METHODS: Forty-five patients aged 21 through 77 (mean=56) years with 113 defective amalgam restorations, which were independently diagnosed during treatment planning, participated in the study. These patients were assigned to 5 treatment groups: repair (n=20), sealing of defective margins (n=23), refurbishing (n=23), replacement (n=23) and no-treatment (n=24). The replacement and no-treatment groups served as comparison groups and received random assignment. Two clinicians examined the restorations (n=113) prior to and after the assigned treatment and at subsequent recalls, using a modified Ryge Criteria that included marginal adaptation, anatomy, contact, post-operative sensitivity and secondary caries. RESULTS: At 1- and 2-year recalls, 79 (70%) and 74 (65%) restorations were examined. Kruskal-Wallis Test showed significant differences for marginal adaptation and anatomic form for both 1- and 2- year recall exams (p<.05). The repair and replacement groups had significant differences when compared to the no-treatment group. CONCLUSIONS: Defective restorations that have a Bravo rating for clinical characteristics other than marginal integrity and anatomical form do not need to be immediately replaced.

Alternative treatments for resin-based composite and amalgam restorations with marginal defects: a 12-month clinical trial.

This clinical trial sought to evaluate the effectiveness of alternative treatment for replacing amalgam and resin-based composite restorations with marginal defects. The study recruited 66 patients with 271 restorations. Each restoration was assigned randomly to one of five groups: Sealant, Refurbishing, Repair, Replacement, and Untreated. Two clinicians evaluated the restorations according to USPHS/Ryge criteria at baseline (Kappa 0.74) and one year after the treatment (Kappa 0.81). The scoring of the margins improved (from bravo to alfa) after the experimental treatments. None of the treatments showed significant degradation of the margins during the 12-month observation period.

Clinical diagnosis of recurrent caries.

BACKGROUND: The clinical diagnosis of recurrent caries is the most common reason for replacement of all types of restorations in general dental practice. Marked variations in the diagnosis of the lesions have been reported. The prevention of recurrent lesions by the use of fluoride-releasing restorative materials has not been successful. TYPES OF STUDIES REVIEWED: The author focused on practice-based studies in the literature. These studies are not scientifically rigorous, but they reflect "real-life" dental practice. Few experimental studies on recurrent carious lesions in vivo have been reported, but bacteriological studies indicate that the etiology is similar to that of primary caries. RESULTS: Recurrent carious lesions are most often located on the gingival margins of Class II through V restorations. Recurrent caries is rarely diagnosed on Class I restorations. The diagnosis is difficult, and it is important to differentiate recurrent carious lesions from stained margins on resin-based composite restorations. Over-hangs, even minute in size, are predisposed to plaque accumulation and the development of recurrent caries. The development of recurrent lesions is unrelated to microleakage. CLINICAL IMPLICATIONS: As recurrent carious lesions are localized and limited, alternative treatments to restoration replacement are suggested. Polishing may be sufficient. If not, exploratory preparations into the restorative material adjacent to the localized defect can reveal the extent of the lesion. Such explorations invariably show that the lesion does not progress along the tooth-restoration interface. The defect, therefore, may be repaired in lieu of being completely replaced. Repair and refurbishing of restorations save tooth structure. These simple procedures also increase the life span of the restoration.

Four-year clinical evaluation of a self-etching primer and resin-based restorative material.

PURPOSE: To evaluate the performance of a universal resin-based restorative material (Beautifil) in combination with a self-etching primer (Fluorobond) for posterior restorations. METHODS: 61 restorations, 26 Class I and 35 Class II, were placed by two clinicians in 31 patients under rubber dam isolation. Two other calibrated clinicians evaluated the restorations using USPHS/Ryge criteria observing the following characteristics: color match, marginal adaptation, anatomy, roughness, marginal staining, interfacial staining, contact, secondary caries, and luster. Chi-Square and Fisher's Exact Test were used for statistical analysis (alpha=0.05). RESULTS: All the restorations were assessed at baseline and alpha scores predominated for all criteria. All restorations were examined at the 1-year recall examination. 58 restorations were examined at the 2-year recall (23 Class I and 35 Class II), 47 (16 Class I and 31 Class II) at the 3-year recall. The present 4-year report covers 39 restorations (12 Class I and 27 Class II). Marginal adaptation, staining, anatomy, and color matching constitute the majority of the recorded changes. Chi-Square and Fisher's Exact Test of the frequency of clinical rating of each characteristic showed that there were no statistically significant differences at each recall with respect to the baseline observations (P> 0.05), except for occlusal marginal stain. Statistical significance was detected for the occlusal marginal stain at 1-year (P= 0.06), 2-year (P= 0.01) and 4-year (P= 0.002) when compared to baseline data.

The effect of mechanical undercuts on the strength of composite repair.

BACKGROUND: The authors conducted an in vitro study to test the hypothesis that undercuts prepared in old composite restorations could improve the strength between the restoration and a flowable composite as repair material. METHODS: The authors used three composites to fabricate cylinders as repair substrates. The etched-only group was ground, etched, dried and built up with a flowable composite. For the undercut group, the authors introduced arrays of fissures on the surfaces before preparing the specimens for subsequent buildup in the manner described for the etched-only group. They made nonrepaired cylinders for baseline measures of strength. They sliced all finished cylinders into slender bars with a diamond saw. Flexure strength values were determined by a three-point-bending test. RESULTS: Nonrepaired bars exhibited statistically significantly higher flexure strength values than did repaired bars, as determined by Wilcoxon rank sum test. Two-way general linear model showed that both material (P < .0001) and undercut (P = .0207) exhibited a statistically significant influence on the repaired flexure strength. Repair substrate with elastic modulus close to that of repair material exhibited a greater percentage of recovery of the respective cohesive strength. Compared with the etched-only group, the undercut group yielded a higher mean flexure strength with one composite but a lower mean flexure strength with the other two. Examination of the fractured surfaces showed that a significant number of undercuts were filled only partially. CONCLUSION: Flexure strengths of repaired specimens always were lower than the cohesive flexure strengths of the materials being repaired. Undercuts did not generally improve repair strength. CLINICAL IMPLICATIONS: Small undercuts on the surface of composite often are difficult to fill completely, resulting in areas of stress concentration that result in no improvement in the repair strength.

Teaching students the repair of resin-based composite restorations: a survey of North American dental schools.

BACKGROUND: The purpose of this study was to evaluate whether North American dental schools teach students to repair resin-based composite, or RBC, restorations and to compare the findings with those from similar European surveys. MATERIALS AND METHODS: The authors mailed a 15-item questionnaire to 64 dental schools in the United States, Canada and Puerto Rico. The survey asked whether the school taught repair of RBC restorations and inquired about the respondent's experience with such procedures. Questions also elicited reasons why schools taught or did not teach repair, information in regard to relevant decision-making processes, criteria for deciding whether to perform repairs and the nature of the instruction (theoretical, practical, preclinical or clinical). RESULTS: Fifty-two (81 percent) of 64 schools participated in the survey. Thirty-seven (71 percent) of the respondents reported that they taught undergraduate students repair techniques as an alternative to replacing failing RBC restorations. Twenty-seven (73 percent) of these 37 schools reported that such teaching was at the clinical level, while only three schools (8 percent) reported that it was included in formal lectures as part of preclinical courses. The major reasons given for teaching students how to repair RBC restorations were tooth structure preservation and reduction of potentially harmful effects on the pulp. Indications included the correction of marginal defect and marginal discoloration. CONCLUSIONS: More than one-half of the respondents reported that they taught repair of RBC restorations and that patients were willing to accept such treatment. Most schools considered the repair of RBC restorations to be a definitive measure and reported that, on average, expected a repaired RBC restoration to have a longevity of four years.