Overdentures: effect of marginal misfit and prosthetic abutment on stress induced in cp Ti implantssuported systems and on destorque of prosthetic screws

Abstract

The aim of this study is to analyze the mean of vertical misfit of overedentures bars casted in cp Ti; to evaluate prosthetic screws detorque and the stresses induced in the implants and in the adapted and unadapted bars. It will be casted 20 cp Ti bars retained by two implants, using 2 prosthetic abutments (n=10) (UCLA and microunit), which will be evaluated marginal misfit inherent in the casting procedure using a comparator microscope. The misfit quantification will follow the test of the single screw (10 Ncm). It will be made 40 índex (20 adapted and 20 unadapted/ each abutment). Crossing variables (abutment and misfit) it will be originated 4 groups: G1- microunit (M)/ adapted (A); G2- UCLA (U) / A; G3- M/ misfit (D); G4- U/D. The misfit will be standardized by interposing a metal ring of 200 µm between pillar A abutment and prosthetic coping. In the index will be evaluated the misfit level using the same protocol used to analyze the misfit after casting. The measurements of tensions will be made by strain gauges fixed in the replicas and in the bars, after retorque of prosthetic screws (10 Ncm). The strength used to detorque the titanium prosthetic screws will be evaluated using a digital torque meter with 0.1 Ncm of precision (Torque Meter TQ-8800; Lutron, Taipei, Taiwan)