Effect of burn-out temperature on magnetic keepers in cast noble metal alloy posts.

STATEMENT OF PROBLEM: Early loss of magnetic keepers in cast gold posts is seen in clinical practice. PURPOSE: The purpose of this vitro study was to investigate the effect of burn-out temperature on the retention of magnetic keepers in cast gold alloy and on the thickness of the oxide layer at the keeper-alloy interface. MATERIAL AND METHODS: One hundred and five keepers (Magfit EX) were cast with gold alloy (Protor 3) at 3 different burn-out temperatures: 500 degrees C, 600 degrees C, or 700 degrees C (n=35). To test for retention of keepers, 60 specimens (n=20) were tested to failure in tension mode in a universal testing machine (UTM); 45 specimens (n=15) were sectioned, and the interface was evaluated under a scanning electron microscope (SEM). Tensile force data were analyzed with 1-way ANOVA, and SEM data were analyzed with 1-way repeated measures ANOVA. Bonferroni multiple comparisons were performed for post hoc analysis (alpha=.05). RESULTS: Retention of the keepers was significantly higher at lower burn-out temperatures (P<.001). The retention of the keepers became unpredictable and immediate failures were observed at a burn-out temperature of 700 degrees C. Oxide formation at the keeper-alloy interface was significantly less at lower burn-out temperatures (P<.001). CONCLUSIONS: A burn-out temperature of 500 degrees C for casting the Magfit EX keeper with type IV high-strength gold alloy is recommended.

A retrospective clinical evaluation of two-unit cantilevered resin-bonded fixed partial dentures.

BACKGROUND: The authors conducted a study to examine the clinical performance of two-unit cantilevered resin-bonded fixed partial dentures (RBFPDs) that were inserted at The Prince Philip Dental Hospital, University of Hong Kong. METHODS: The authors recalled patients who had received two-unit cantilevered RBFPDs at least 24 months before the recall examination. The authors recorded the following data: patient's sex and age, operator's experience, prosthesis cementation date, endodontic treatment if performed, bone support, tooth mobility, the presence of shim-stock contacts on the abutment or pontic in intercuspal position, and the presence of aproximal axial contacts adjacent to the prosthesis. They also recorded the date of any debonding with subsequent treatment. They asked the patients qualitative questions about their prostheses. RESULTS: A total of 269 prostheses were placed in 214 patients and had a mean service life of 51.7 months +/- 19.5 months standard deviation, with a range of 13.2 to 141.6 months. Of 14 failed prostheses, 12 debonded, resulting in a success rate of 94.8 percent and clinical retention rate of 95.5 percent. No discernable rotation or drifting of the abutments was apparent in any of the prostheses. Overall patient satisfaction with RBFPDs was good, with an average assessment score of 8.5. CONCLUSIONS: The authors observed a 95.5 percent clinical retention rate of 269 two-unit RBFPDs, with no apparent drifting of the abutments. Longer-term follow-up studies are required. CLINICAL IMPLICATIONS: Two-unit RBFPDs are conservative and clinically retentive prostheses in the short to medium term.

Rehabilitation of amelogenesis imperfecta using a reorganized approach: a case report.

Amelogenesis imperfecta is a genetic disorder that causes defective enamel development in both the primary and permanent dentitions. Significant tooth structure damage often results in various pulpal symptoms, occlusal disharmony, impaired function, and esthetic disfigurement. These problems pose great challenges to the clinician when rehabilitating patients with amelogenesis imperfecta. This case report describes an uncomplicated and logical way to reorganize, temporize, and completely restore an extensively damaged dentition caused by amelogenesis imperfecta.