Effect of Surface Modifications of Abutment Screws on Reverse Torque Values: An In Vitro Study

Purpose: To investigate the reverse torque values of abutment screws subjected to various surface modifications. Materials and Methods: Sixty abutment screws were divided into two groups of 30 each: with thermomechanical cycling (240,000 cycles) and without thermomechanical cycling. Each group was then divided into three subgroups according to surface treatment: nontreated (NT, n = 10); anodic oxidation (AO, n = 10); and diamond-like carbon (DLC) coating (DLC, n = 10). All abutment screws were tightened to 30 Ncm using a digital torque meter. The reverse torque values of the abutment screws with and without thermomechanical cycling were then measured. The percentage of deviation (PERDEV) for reverse torque values was calculated. Two-way analysis of variance followed by Tukey Honest Significant Difference test were used for intergroup comparisons. Results: Significant differences were found among the PERDEV values of the groups based on thermomechanical cycling and surface treatment (P .001 for each). A significant interaction was found between surface treatment and thermomechanical cycling (P .001). Conclusion: Reverse torque values of abutment screws were found to be higher after surface treatments. The abutment screws with AO exhibited the lowest torque value loss in groups with and without thermomechanical cycling.