Comparative analysis of different joining techniques to improve the passive fit of cobalt-chromium superstructures.

STATEMENT OF PROBLEM: The influence of different joining techniques on passive fit at the interface structure/abutment of cobalt-chromium (Co-Cr) superstructures has not yet been clearly established. PURPOSE: The purpose of this study was to compare 3 different techniques of joining Co-Cr superstructures by measuring the resulting marginal misfit in a simulated prosthetic assembly. MATERIAL AND METHODS: A specially designed metal model was used for casting, sectioning, joining, and measuring marginal misfit. Forty-five cast bar-type superstructures were fabricated in a Co-Cr alloy and randomly assigned by drawing lots to 3 groups (n=15) according to the joining method used: conventional gas-torch brazing (G-TB), laser welding (LW), and tungsten inert gas welding (TIG). Joined specimens were assembled onto abutment analogs in the metal model with the 1-screw method. The resulting marginal misfit was measured with scanning electron microscopy (SEM) at 3 different points: distal (D), central (C), and mesial (M) along the buccal aspect of both abutments: A (tightened) and B (without screw). The Levene test was used to evaluate variance homogeneity and then the Welsch ANOVA for heteroscedastic data (α=.05). RESULTS: Significant differences were found on abutment A between groups G-TB and LW (P=.013) measured mesially and between groups G-TB and TIG (P=.037) measured centrally. On abutment B, significant differences were found between groups G-TB and LW (P<.001) and groups LW and TIG (P<.001) measured mesially; groups G-TB and TIG (P=.007) measured distally; and groups G-TB and TIG (P=.001) and LW and TIG (P=.007) measured centrally. CONCLUSIONS: The method used for joining Co-Cr prosthetic structures had an influence on the level of resulting passive fit. Structures joined by the tungsten inert gas method produced better mean results than did the brazing or laser method.

Planejamento digital em cirurgia ortognática: precisão, previsibilidade e praticidade / Digital surgical treatment planning: accuracy, predictability and practicity

A cirurgia ortognática deixou de ser um procedimento com finalidade exclusivamente funcional e a estética facial consagrou-se como um dos objetivos mais importantes da Cirurgia e da Ortodontia. A evolução dos conceitos envolvidos no diagnóstico e plano de tratamento em Cirurgia Ortognática tem sido imensurável. As metas para o tratamento dos pacientes tornaram-se mais amplas, levando ao desenvolvimento de novos instrumentos de diagnóstico. Dentre eles, destaca-se o planejamento cirúrgico digital, o qual proporciona maior previsibilidade e padronização de toda sequência clínica, além de ser um método extremamente preciso. Considerando a análise clínica soberana e imprescindível ao planejamento de sucesso, a proposição neste artigo foi evidenciar pontos importantes na análise clínica e na predicção digital, e apresentar um caso clínico, cujo tratamento foi executado seguindo as linhas mais modernas em termos de análise facial e planejamento cirúrgico digital