Influence of Screw Surface Treatment on Retention of Implant-Supported Fixed Partial Dentures.

The aim of this study was to assess the effect of a diamond-like carbon (DLC) coating on the removal torque of prefabricated implant screws after cyclic loading. Four groups with two crowns supported by two implants (n = 5) were obtained according to splinted and nonsplinted prosthesis, using titanium or DLC screws (splinted crowns with titanium screw [STi], splinted crowns with DLC screw [SC], nonsplinted crowns and titanium screw [NSTi], and nonsplinted crowns and DLC screw [NSC]). The prosthetic screws were tightened at 32 Ncm and retightened, and the specimens were submitted to 106 mechanical cycles (4 Hz/98 N). After cyclic loading, loosening torque was evaluated, and the final measurements were performed. Data were analyzed by two-way analysis of variance and Tukey's test (α = .005). There was statistically significance in the interaction of screw × splinting (P = .003). For the group that used titanium screws, NSTi showed smaller removal torque compared with STi. It was concluded that the use of the DLC coating screws in nonsplinted prosthesis maintain the torque after cyclic loading.