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.

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.

[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.

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.

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.

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.

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.

Tensile creep of dental amalgam.

Rather than the usual compressive dental creep, various types of one week old dental amalgams were continuously monitored in tensile creep. Testing was done at 37, 45 and 50 degrees C, in a specially designed apparatus capable of 0 to 60 degrees C while maintaining a constant true tensile stress of 17 MPa. For the first time, the classical four stages of creep were observed at elevated temperatures in the low Cu amalgams, including creep rupture. The high Cu systems displayed only transient creep up to 50 degrees C and no rupture. Approximately one half the stress was needed in tension to provide the equivalent creep in compression.

Elastic and fracture properties of dental direct filling materials.

Five dental direct filling materials were tested in tension and compression in order to define their stress-strain behaviour for both types of applied stress. In addition, fracture toughness was determined from three-point bending tests. Linear and non-linear stress-strain behaviour was observed, and the response was specific for each material and also to the type of applied stress. Fracture resistance was also found to be material specific, which was related to differences in composition.

Amalgams made from liquid Hg-In.

The addition of indium to amalgam appears to reduce the mercury vapour above fillings during setting. In the present work the structure and the physical properties of amalgams with In additions to the mercury up to 30 vol.% have been investigated. No new phase or undissolved in could be detected by X-ray diffraction and scanning electron microscopy studies. Energy dispersive spectroscopy measured 4 at.% In in the gamma 1-phase of an amalgam with 20 vol.% In added to the mercury. At the same time, the Ag/Hg ratio was substantially increased compared with amalgam having no In addition. The compression strength decreased with increasing In content, and for amalgam with as much as 30 vol.% In added to the mercury, it fell below the minimum requirement of ISO 1559 (Alloys for dental amalgam, International Organization for Standardization, Geneva, 1986). An abrupt drop of the load at the onset of failure and cracks running through the gamma 1-phase, as well as the eta-phase, indicates embrittlement of these phases with increasing In content.

Corrosion test for dental amalgam.

A corrosion test for dental amalgam, based on controlled potential coulometry, provides an index of corrosion susceptibility. A special cell was designed, and optimum test conditions were determined. The test can be used for the rating of amalgams, and in studies of the effect of variables on the corrosion resistance.

Influences of clinical factors on marginal adaptation and residual mercury content of amalgam.

Clinical factors affecting residual mercury and marginal adaptations of amalgam restorations in a private practice environment were investigated. Findings, converted to ridit values, indicated that influencing factors are the training level of the dental assistants, type of amalgamator, accuracy of the timing device, and method of condensation.

A 30-month clinical evaluation of the influence of finishing and size of restoration on the margin performance of five amalgam alloys.

The influence of finishing and size of the restorations using five amalgam alloys (Aristaloy, Dispersalloy, Oraloy, Sybraloy, and Tytin) was evaluated at 30 mo. when size of the restoration was considered, Dispersalloy displayed the best margin performance. Oraloy, Sybraloy, and Tytin were inferior to Dispersalloy and were grouped together. Aristaloy was inferior to all other alloys in the study. When the aspect of finishing was considered, Dispersalloy and Sybraloy evidenced excellent margin performance when unfinished. Aristaloy showed the worst margin performance of all the alloys in the study when unfinished, but showed remarkable improvement in margin performance when finished.

Standardizing evaluations of the clinical marginal fracture of amalgam.

In this study, we investigated both inter-examiner and intra-examiner differences in the evaluation of the marginal fracture characteristics of dental amalgam restorations. Evaluations were made by matching intra-oral photographs of the occlusal surfaces of clinical restorations to a reference set of clinical photographs illustrating increasing amounts of marginal fracture. Four amalgam alloys and five examiners provided the data base. Differences in marginal fracture indices were found among examiners and between evaluation times for the same examiners. However, these differences were reduced significantly after application of a standardization procedure.

Effects of cement bases on the stresses in amalgam restorations.

A computerized dental model was used to study the stress induced in a Class 1 amalgam restoration when supported by bases of varying materials and thickness. Under the same load, the maximum tensile stresses and deflections in the amalgam restoration increased at least threefold with a zinc oxide-eugenol base as compared with a ZnPO4 cement base.

Evaluation of key parameters in a potentiostatic corrosion test for dental amalgam.

OBJECTIVES: Participation in a Round Robin study of potentiostatic corrosion test guidelines for dental amalgam was undertaken for the purpose of developing an accurate set of draft guidelines. METHODS: Dispersalloy, sybraloy, aristalloy, phasealloy, and tytin were used as the amalgam specimens. They were prepared following the guidelines, then coupled to a copper wire, cemented into glass tubes, and polished to a 600-grit finish. A corrosion cell was prepared using a carbon counter-electrode, a standard calomel electrode (SCE) as the reference electrode, and amalgam as the working electrode. A 37 degrees C solution of 10 g/l NaCl with a minimum volume of 300 ml was used. Within 5 min of polishing, the open circuit potential (OCP) was recorded for 10 min. Next, the specimen was polarized to 0 mV versus SCE, and the currents were recorded for a 24-h time period. Corrosion results were analyzed statistically with one-way ANOVA (p < 0.05) and the multiple comparisons Student-Newman-Keuls post-hoc test. RESULTS: Problems that occurred with evaporation, beaker size, carbon electrode length, SCE cap removal, glass tube fracture, polishing technique, and fresh electrolyte are easily avoidable with further explanation or reminder notes. Observations made concerning starting time, initial OCP recording, millivoltage, and solution temperature were determined to be necessary for the accuracy of test results. Analysis of results should include clarification of units, and graph interpretations. Finally, the number of specimens per amalgam should be increased from one to three so that statistical analysis can be performed. Using three specimens per amalgam, the method revealed corrosion susceptibility as measured by the improved test: aristalloy > sybraloy > (dispersalloy, phasealloy, tytin). SIGNIFICANCE: Having run the initially proposed guidelines, a number of clarifying changes were made so that the corrosion susceptibilities of five dental amalgams could be clearly differentiated.