Bond strength of repaired amalgam restorations.

This in vitro study investigated the interfacial flexural strength (FS) of amalgam repairs and the optimal combination of repair materials and mechanical retention required for a consistent and durable repair bond. Amalgam bricks were created, each with 1 end roughened to expose a fresh surface before repair. Four groups followed separate repair protocols: group 1, bonding agent with amalgam; group 2, bonding agent with composite resin; group 3, mechanical retention (slot) with amalgam; and group 4, slot with bonding agent and amalgam. Repaired specimens were stored in artificial saliva for 1, 10, 30, 120, or 360 days before being loaded to failure in a 3-point bending test. Statistical analysis showed significant changes in median FS over time in groups 2 and 4. The effect of the repair method on the FS values after each storage period was significant for most groups except the 30-day storage groups. Amalgam-amalgam repair with adequate condensation yielded the most consistent and durable bond. An amalgam bonding agent could be beneficial when firm condensation on the repair surface cannot be achieved or when tooth structure is involved. Composite resin can be a viable option for amalgam repair in an esthetically demanding region, but proper mechanical modification of the amalgam surface and selection of the proper bonding system are essential.

Dental students' ability to assess their performance in a preclinical restorative course: comparison of students' and faculty members' assessments.

Dental education consists of both theoretical and practical learning for students to develop competence in treating patients clinically. When dental students encounter practical courses in their first year as a new educational experience, they must also learn to evaluate themselves. Self-evaluation is an essential skill to learn for dental professionals to keep increasing their competence over the course of their careers. The aim of this study was to compare the assessment scores of second- and third-year dental students and the faculty in two consecutive preclinical practical exams in restorative dentistry courses in a dental school in Turkey. Faculty- and student-assigned scores were calculated from two consecutive preclinical examinations on tooth restorations performed on both artificial casts and phantom patients. The students were formally instructed on grading procedures for tooth preparations, base and restoration placement, and polishing criteria. After each step, each item was assessed by faculty members, the student, and another student. The results indicated that the initial differences between second-year students' assessments of their own preclinical practical ability and that of the faculty decreased among the third-year students. Self-evaluation scores did not indicate whether the third-year students tended to over- or underestimate the quality of their own work. However, the second-year students not only overestimated themselves but thought they were above average. The results point to the need to develop students' self-insight with more exercises and practical training.

A study of primary teeth restored by intracoronal restorations in children participating in an undergraduate teaching programme at Cork University Dental School and Hospital, Ireland.

AIM: To study the outcomes for restored primary molar teeth; to examine outcomes in relation to tooth type involved, intracoronal restoration complexity and to the material used. DESIGN: Retrospective study of primary molar teeth restored by intracoronal restorations. A series of restored primary molar teeth for children aged 6-12 years was studied. The principal outcome measure was failure of initial restoration (re-restoration or extraction). Three hundred patient records were studied to include three equal groups of primary molar teeth restored with amalgam, composite or glass ionomer, respectively. Restorative materials, the restoration type, simple (single surface) or complex (multi-surface) restoration, and tooth notation were recorded. Subsequent interventions were examined. Data were coded and entered into a Microsoft Excel database and analysis undertaken using SPSS v.18. Statistical differences were tested using the Chi square test of statistical significance. RESULTS: Of the 300 teeth studied, 61 restoration failures were recorded with 11 of those extracted. No significant differences were found between outcomes for upper first, upper second, lower first or lower second primary molars. Outcomes for simple primary teeth restored by intracoronal restorations were significantly better than those for complex intracoronal restorations (P = 0.042). Teeth originally restored with amalgam accounted for 19.7% of the 61 failures, composite for 29.5%, while teeth restored with glass ionomer represented 50.8% of all restoration failures. The differences were significant (P = 0.012). CONCLUSIONS: The majority (79.7%) of the 300 restored primary teeth studied were successful, and 3.7% teeth were extracted. Restorations involving more than one surface had almost twice the failure rate of single surface restorations. The difference was significant. Significant differences in failure rates for the three dental materials studied were recorded. Amalgam had the lowest failure rate while the failure rate with glass ionomer was the highest.

[Evaluation of the quality of proximal restorations with plastic materials: radiographic study]. / Evaluation de la qualité des restaurations proximales aux matériaux plastiques. Etude radiographique.

AIM: To assess the quality of proximal coronary restorations and bring out the factors influencing this quality. MATERIAL AND METHOD: A transversal study on 160 radiographs of proximal coronary restorations was conducted at the University Center of Dental Consultation and Treatment of Rabat. Restorations were evaluated according to the modified USPHS criteria. Four variables were studied: restoration material, treated tooth, cavity type and location of treatment in order to identify the influencing factors. RESULTS: Forty five per cent of the evaluated proximal coronary restorations required replacement. The main cause of failure was recurrent caries in 36% of cases, followed by the absence of the contact point (24.4%), unacceptable proximal coronary outline (13.8%), and finally dentin exposure (6.9%). Thus, it turned out that there is a difficulty to restore correctly posterior proximal cavities especially using amalgam and a high rate of recurrent caries at both the anterior and posterior teeth. CONCLUSION: Both a clinical and a radiographic evaluation after each proximal restoration would be recommended to reduce failure.

New science challenges old notion that mercury dental amalgam is safe.

Mercury dental amalgam has a long history of ostensibly safe use despite its continuous release of mercury vapor. Two key studies known as the Children's Amalgam Trials are widely cited as evidence of safety. However, four recent reanalyses of one of these trials now suggest harm, particularly to boys with common genetic variants. These and other studies suggest that susceptibility to mercury toxicity differs among individuals based on multiple genes, not all of which have been identified. These studies further suggest that the levels of exposure to mercury vapor from dental amalgams may be unsafe for certain subpopulations. Moreover, a simple comparison of typical exposures versus regulatory safety standards suggests that many people receive unsafe exposures. Chronic mercury toxicity is especially insidious because symptoms are variable and nonspecific, diagnostic tests are often misunderstood, and treatments are speculative at best. Throughout the world, efforts are underway to phase down or eliminate the use of mercury dental amalgam.

A 24-month evaluation of amalgam and resin-based composite restorations: Findings from The National Dental Practice-Based Research Network.

BACKGROUND: Knowing which factors influence restoration longevity can help clinicians make sound treatment decisions. The authors analyzed data from The National Dental Practice-Based Research Network to identify predictors of early failures of amalgam and resin-based composite (RBC) restorations. METHODS: In this prospective cohort study, the authors gathered information from clinicians and offices participating in the network. Clinicians completed a baseline data collection form at the time of restoration placement and annually thereafter. Data collected included patient factors, practice factors and dentist factors, and the authors analyzed them by using mixed-model logistic regression. RESULTS: A total of 226 practitioners followed up 6,218 direct restorations in 3,855 patients; 386 restorations failed (6.2 percent) during the mean (standard deviation) follow-up of 23.7 (8.8) months. The number of tooth surfaces restored at baseline helped predict subsequent restoration failure; restorations with four or more restored surfaces were more than four times more likely to fail. Restorative material was not associated significantly with longevity; neither was tooth type. Older patient age was associated highly with failure (P < .001). The failure rate for children was 4 percent, compared with 10 percent for people 65 years or older. Dentist's sex and practice workload were associated significantly with restoration longevity. CONCLUSIONS: In this prospective cohort study, these factors were significantly predictive of failure for amalgam and RBC restorations: patient's age, a higher number of surfaces restored at baseline, the dentist's sex and the practice workload. Material choice was not significantly predictive in these early results. Practical Implications. If clinicians can recognize and identify the risk factors associated with early restoration failure, more effective treatment plans may be offered to the patient.

Development of strength in dental silver amalgam.

OBJECTIVES: To characterize the development of strength during the setting process of dental silver amalgam in the context of 'early strength' measurements for standards compliance testing in relation to patient instructions, and demonstrate the applicability of the Hertzian 'ball on disc' method. MATERIALS AND METHODS: Sixteen dental silver amalgam products were tested using the 'ball on disc' protocol at 1, 2, 3, 4 and 24h after setting at 37°C in air. The mixed materials were packed into a tapered steel disc mold (10mm diameter, 3mm thick) resting on a glass surface, slightly overfilled and carved level with a sharp edge, then ejected at ∼10min and placed immediately into an incubator at 37°C. Testing was in Hertzian mode, using a 20mm steel ball, with the specimen resting on a disc of glass-filled polyamide (E=10GPa) at a cross-head speed of 0.2mm/min on a universal testing machine (E3000, Instron). The load at first crack was recorded, as was the number of radial cracks produced. RESULTS: Radial cracking into 2-5 pieces, in a clinically-relevant (non-explosive) mode was observed in all cases. Considerable variation in setting rate between products, as indicated by the development of load at failure with time, was found. The distribution of normalized failure load values overall was lognormal (Weibull was excluded). The RMS coefficient of variation overall was 12.4%. SIGNIFICANCE: The ball-on-disc test provides a facile, relevant measure of the strength of dental silver amalgam, and is viable as a standards compliance test. Early strength testing at a minimum of 2h is suggested.

The influence of a short training program on the clinical examination of dental restorations.

PURPOSE: To investigate how a simple restoration evaluation training program affected restoration replacement decision making by a group of 16 dentists. METHOD: The clinical examination of 66 dental restorations in nine female patients was carried out by two groups of dentists: one having previously received training in restoration assessment. The results of these assessments were compared to a gold standard for restoration integrity determined by two experienced clinicians applying US Public Health Service criteria. All evaluations were completed under controlled clinical conditions with standard equipment and lighting. The results of the clinical examinations between the trained (test) group and the untrained (control) group were compared to each other and the gold standard. RESULTS: The trained group scheduled fewer restorations for replacement (6.00±3.01 and 9.71±3.15; p=0.034), in a shorter time (27.86±3.45 mins and 36.71±3.74 mins; p=0.003) and showed greater agreement with the study's gold standard for restoration replacement (0.85±0.27 and 0.79±0.06; p=0.002). CONCLUSION: Within the limits of this study, examiner training can significantly improve the reliability of restoration replacement decision making by dentists.

An application of Harrell's C-index to PH frailty models.

Frailty models are encountered in many medical applications, yet little research has been devoted to develop measures that quantify the predictive ability of these models. In this paper, we elaborate on the concept of the concordance probability to clustered data, resulting in an 'Overall Conditional C-index' or bfC(O, C) and an 'Overall Marginal C-index' or C(O, M) . Both Overall C-indices can be split up into a 'Between Conditional' or C(B, C) and a 'Between Marginal C-index' or C(B, M) and into a 'Within Conditional' or C(W, C) and a 'Within Marginal C-index' or C(W, M) . For PH frailty models of the power variance family, C(W, C) and C(W, M) are equivalent resulting in one 'Within C-index' C(W) . We propose an application of Harrell's C-index to estimate the proposed indices within a likelihood and a Bayesian context and the performances of their point estimates and confidence/credible intervals are compared in an extensive simulation study. This simulation study shows that the point estimates of C(W) and C(B, M) perform good within both a likelihood and Bayesian context but that the point estimates of C(B, C) show less bias for the Bayesian approach than for the likelihood approach. The 95 per cent confidence/credible intervals also possess good coverage properties, given that the point estimates perform good. The performance of the C-indices is evaluated on a real data set.

Re-intervention in glass ionomer restorations: what comes next?

AIM: The aim of this study is to report the subsequent treatment provided, over the 11 years' data available, when a re-intervention was considered clinically necessary on a glass ionomer (GI) restoration. METHODS: A detailed sample of treatment records of patients has been established at the Dental Practice Division of the NHS Business Services Authority, consisting of records containing directly placed restorations for adult patients from January 1991. This database contains the records of over half a million restorations. For each direct restoration placed, the subsequent history of that tooth was consulted, for the period up to December 2001, and the restorations divided into three groups: amalgam, composite and GI, the latter being subdivided into anterior teeth, premolars, and molars. RESULTS: Data on 164,036 directly placed restorations were analyzed. Results indicated that, for amalgam and composite restorations, the subsequent treatment was likely to be another restoration in the same material. For GI (24,947 restorations), only one third of restorations, overall, were followed by another GI. In anterior teeth, GI restorations were more often followed by composite than by GI, this trend increasing with increasing time interval since restoration. For premolar teeth, the GI restoration was most likely to be followed by another GI within 4 years, with an increasing trend towards re-intervention by an amalgam or composite in older restorations. For molar teeth, GI restorations were more likely to be followed by an amalgam restoration. CONCLUSION: For GI restorations, on re-intervention, there is variation in the next restoration material used according to tooth position and time interval to re-intervention. GI restorations in anterior and molar teeth are not likely to be followed by another GI restoration.

Influence of the temperature, volume and type of solution in the mercury vaporization of dental amalgam residue.

One of the qualitative methods for the identification of mercury vapor is what it occurs as a way of chemical reaction between palladium chloride and metallic mercury. Palladium chloride ribbons with yellowish coloration put in contact with the vaporized mercury of dental amalgam residue, liberates palladium and forms mercury chloride in your surface, and starts to have black coloration; this form identify the presence of the mercury vapor in the system. This work studies the influence of temperature, volume and type of barrier-solution in the vaporization of mercury during the period of storage of dental amalgam residues, aiming to establish the best conditions for storage of these residues. It was found that for all tested solutions, the longest storage times without any occurrence of mercury vaporization were obtained in the lowest temperatures tested and the largest solution volumes of barrier-solution. The radiographic effluent presented bigger efficacy in the reduction of the volatilization, increasing the period when the residue was stored, however the analysis of this solution after the vaporization test showed the presence of organic mercury. These results show that water is the most efficient barrier against the vaporization of mercury, since it did not result in organic mercury formation in the effluent solution from the storage process.

Implementation of revolutionary legislation for informed consent for dental patients receiving amalgam restorations.

Mercury is one of the most dangerous environmental toxins. Realizing the environmental dangers of mercury, the Norwegian Minister of the Environment and International Development, Erik Solheim, has therefore prohibited the use of mercury in products in Norway. This ban will include dental filling materials (amalgam) and measuring instruments, as well as other products. This ban is valid from January 1, 2008. Sweden announced a similar ban, and dentists in Denmark will no longer be able to use mercury in fillings after April 1, 2008. It is indeed unfortunate that the United States has not taken a leadership role in enacting Informed Consent Legislations for patients receiving dental amalgam restorations. Informed Consent Legislations have been enacted by Maine, California, Connecticut, and Vermont.