Loosening torque of prosthetic screws in metalaceramic or metalaacrylic resin implant-supported dentures with different misfit levels

The aim of this study was to evaluate the effect of the prosthesis material (metalaacrylic resin or metalaceramic) on loosening torque of the prosthetic screws in an implant-supported mandibular denture under two levels of vertical misfit. Ten frameworks were fabricated with commercially pure titanium, and five of them received acrylic resin and acrylic artificial teeth as veneering material and the other five were veneered with porcelain. Two levels of vertical fit were also created by fabricating 20 cast models to obtain four experimental groups according to the prosthesis material and misfit: Group 1 (metalaacrylic resin prosthesis with a passive fit); Group 2 (metalaacrylic resin prosthesis with a non-passive fit); Group 3 (metalaceramic prosthesis with a passive fit); and Group 4 (metalaceramic prosthesis with a non-passive fit). Two hundred prosthetic titanium-alloy screws were divided in 40 sets (five screws per set, n=10). After 24 h, the loosening torque of the screws was evaluated using a digital torque meter. The results were submitted to two-way ANOVA analysis of variance followed by a Tukey's test ( alpha =0.05). The mean values and standard deviations for each group were G1=7.05 (1.64), G2=5.52 (0.90), G3=6.46 (1.34), and G4=4.35 (0.99). Overall, the prosthesis material and misfit factors showed a statistically significant influence on the loosening torque (p