ABSTRACT
O objetivo desse estudo foi avaliar a adaptação marginal e a precisão do assentamento protético de cilindros plásticos e de cilindros plásticos com base usinada, fundidos em estruturas protéticas de liga de cobalto-cromo (Co-Cr). Em um modelo semicircular à base de poliuretano, quatro implantes de hexágono externo com conexões protéticas do tipo minipilar foram instalados, sendo oito sensores elétricos colados na superfície superior do bloco. A partir desse modelo foi realizado um índex sobre o qual foram confeccionadas dez barras segmentadas em acrílico, utilizando-se cilindros calcináveis e cilindros sobrefundíveis (n = 5). Depois de fundidas em centrífuga manual com liga de Co-Cr Biosil e soldadas convencionalmente, as estruturas tiveram os espaçamentos verticais entre cilindros e análogos avaliados sob microscopia de luz e as microdeformações determinadas por meio da extensometria. Os resultados foram analisados com o teste de análise de variância (p = 0,636) e teste t Student (p = 0,325), não apresentando diferenças estatísticas significantes. Concluiu-se que os cilindros sobrefundíveis não conferiram às barras nas quais foram fundidos maior adaptação marginal e passividade de assentamento que os cilindros plásticos calcináveis.
The aim of the present study was to evaluate the vertical and passive fit of plastic burnout cylinders and plastic cylinders with a pre-machined cobalt-chromium collar cast in implant-supported frameworks. Four external hex cylindrical implants and their respective conical abutments were placed in an experimental semicircular model on which eight-element strain gauges were attached in close proximity to the implants. The master model was duplicated originating an index that was used to wax-up ten standard bars segmented in four sections (n = 5) and to allow the measurements under an optical microscope. The segments were cast in Co-Cr alloy and soldered conventionally. Initially, the structures were submitted to optical measurements. An average misfit value was assigned for each group and the Analysis of Variance was applied (p = 0.636). Later, each structure was tightened to the master model and the stress generated was recorded. The mean strain developed at each group was calculated and the Student´s t test was applied (p = 0.325). No significant statistical differences were found. It can be concluded that pre-machined Co-Cr cylinders could not offer better vertical fit or passive fit when compared to plastic burnout cylinders.