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.
Figure 1. Virtual planning crowns in CAD/CAM, simulating region of the posterior mandible. Figure 2. (a) Splinted crowns, (b) nonsplinted crowns, (c) titanium screws, and (d) neotorque screw (diamond-like carbon cover).
Casting process. (a) Crowns at the end of the closure process, ready to be included. (b) Crowns attached to the sprues. (c) Crowns with inclusion of the coating material. (d) Crowns after casting and polishing.
(a) Crowns in position with its analogs, ready for inclusion. (b) Samples fixed on a solid base and ready to receive the resin. (c) Device of each sample after adding the resin. (d) Contact point of the assessment of nonsplinted samples.
Figure 5. Evaluation of device removal torque. (a) Adjustable device for the digital switch setting. (b) Adjustable platform to hold the specimens. (c) Torquemeter connected to a data link receiver and software. (d) Capturing in real time any movement of screw loosening. Figure 6. Samples under cyclic load with two loading tips focusing in the center of each crown.
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