Effect of ultrasonic vibration on the removal of posts cast in different metal alloys

The aim of this experiment was to evaluate the relative efficacy of ultrasonic instruments on the removal of posts cast in alloys with different stiffness (nickel-chromium and silver-tin alloys). Sixty roots of extracted bovine incisor teeth were sectioned, prepared and randomly divided into 4 groups (n=15): groups 1 and 2 received posts cast in Ni-Cr and groups 3 and 4 received posts cast in Ag-Sn. All posts were cemented with zinc phosphate cement. Groups 2 and 4 received ultrasonic vibration for 12 minutes. The force necessary for post removal was measured by an Instron universal testing machine. Data were statistically analyzed with ANOVA and when significant differences were found, means were compared using Tukey's intervals with a confidence level of 95%. The mean force (kgf) to remove posts of group 1 (67.84± 15.31) was statistically greater than groups 2 (46.95± 10.85), 3 (48.53± 8.49) and 4 (41.25± 11.40). There was no statistically significant difference among groups 2, 3 and 4. The ultrasonic vibration was effective in reducing the force required to remove posts cast in Ni-Cr (about 31% of reduction), but had little effect on posts cast in Ag-Sn (about 15% of reduction). Posts cast in Ni-Cr were also more retentive then posts cast in Ag-Sn when they were not submitted to ultrasonic vibration.

Otimização de sobredentaduras implantossuportadas: relato de caso clínico / Optimization of implant-retained overdentures: case report

A utilização de implantes para suportar sobredentaduras está comprovada por vários autores na literatura. Inúmeros sistemas de abutments estão disponíveis no mercado; a escolha depende de fatores que variam de acordo com o quadro clínico presente. A retenção e a estabilidade são requisitos fundamentais a qualquer sistema. Em alguns casos, a facilidade de inserção da prótese em posição pelo paciente pode-se tornar um fator determinante nesta escolha. A descrição e a utilização de um novo abutment, o sistema Locator, são relatadas neste trabalho.