Strain Gauge: study of strain distributions around three Morse taper prosthetic connections with offset positioning in machined and plastic copings under vertical load / Extensometria: estudo das microdeformações ao redor de três conexões protéticas cone Morse, com posicionamento compensado (offset) em coifas usinadas e plásticas sob carga vertical

ABSTRACT

The aim of this study was to evaluate through strain gauge the strain distribution occurred around 3 Morse taper implants with positioning offset, by varying the types of copings: plastic and machined. Microunit prosthetic abutments were connected onto the implant platforms. Ten frameworks composed of 3 copings were casted in cobalt-chromium alloy as single block (Co-Cr). Half of the copings were machined (n=5) and half were made of plastics (n=5). Four strain gauges were placed into the polyurethane block tangential to the 3 implants. The frameworks were fixed at their respective sites with the aid of a retaining screw with torque of 20 N.cm, achieve with a mechanical torquemeter. The vertical load of 30 Kg was applied through a spherical point of 2 mm diameter for 10 s, onto each one of the 3 screws of the framework through a device for load application The records of the strain reading were submitted to ANOVA and Tukey tests (5%). There were statistically significant differences (p=0.0174) between the coping type used (machined and plastic). The micro strain mean values were: point C at the machined coping 282.5 μm (±120.8), point B at the machined coping 229.5 μm (±76.1), point A at the machined coping 209.8 μm (±55.0), point C at the plastic coping 155.0 μm (±30.5), point B at the plastic coping 146.2 μm (±25.8) and point A at the plastic coping 130.36 μm (±21.83). It was concluded that there was a significant difference between the coping types, once the plastic coping exerted smaller micro strain on Morse taper implants than the machined copings.

RESUMO

O objetivo deste trabalho foi avaliar por meio da extensometria as microdeformações ocorridas ao redor de 3 implantes cone Morse com posicionamento compensado (offset) inseridos em um bloco de poliuretano. Sobre a plataforma dos implantes foram conectados pilares protéticos microunit. Dez supra estruturas constituídas por 3 coifas foram fundidas em monobloco com liga de Cobalto-Cromo (Co-Cr), sendo que metade das supra estruturas foram utilizadas coifas usinadas (n=5) e a outra metade de coifas plásticas (n=5). Quatro extensômetros foram colocados no bloco de poliuretano tangenciando os três implantes. As supra estruturas foram fixadas nos respectivos locais com o parafuso de retenção com torque de 20 N.cm, obtidos com um torquímetro mecânico. A carga estática vertical de 30 Kg foi aplicada com uma ponta esférica de 2 mm de diâmetro durante 10 s, sobre cada um dos 3 parafusos da supra estrutura utilizando o dispositivo de aplicação de cargas. Os registros foram submetidos ao teste ANOVA e Tukey (5%). O resultado estatístico mostrou que houve diferença significante (p=0,0174) para o efeito de aplicação de carga. Os valores médios de microdeformação: ponto C na coifa usinada 282.5 μm (±120.8), ponto B na coifa usinada 229.5 μm (±76.1), ponto A na coifa usinada 209.8 μm (±55.0), ponto C na coifa plástica 155.0 μm (±30.5), ponto B na coifa plástica 146.2 μm (±25.8) e ponto A na coifa plástica 130.36 μm (±21.83). Concluiu-se que a coifa que exerceu menor microdeformação em implantes cone Morse foram as coifas plásticas