Effect of Screw Channel Angulation on Reverse Torque Values of Dental Implant Abutment Screws

Purpose: To compare the reverse torque values (RTVs) of abutment screws tightened from three different angles.

Materials And Methods: Implant abutment screws (n = 48), abutments (3), and regular platform implant analogs (3) were divided into three angulation groups (n = 16/group). Custom guides of 0°, 10°, and 20° were fabricated to verify driver angulation. The implant components for each group were assembled and all screws torqued to 35 Ncm using a universal screwdriver in a manual torque wrench at the appropriate angle. Torque was reapplied 10 minutes after initial torque. A digital gauge was then used to measure reverse torque at a position parallel (0°) to the implant analog. RTVs were recorded and compared using one-way ANOVA and Tukey HSD post-hoc comparisons (α = 0.05).

Results: All mean RTVs fell below the targeted torque value of 35Ncm, with some values in each angulation group 10% below of the target value. Mean RTVs in descending order from targeted torque value were: 10° group = 32.07 ± 0.97 Ncm, 0° group = 31.16 ± 1.12 Ncm, and 20° group = 30.08 ± 0.88 Ncm. One-way ANOVA revealed significant differences between angulation groups (F = 15.954, p < 0.001). Tukey HSD post hoc comparisons revealed that the mean RTVs of the three angulation groups were significantly different from each other (0° vs. 10°: p = 0.033; 0° vs. 20°: p = 0.011; 10° vs. 20°: p < 0.001).

Conclusions: All RTVs did not reach the targeted torque value of 35 Ncm. Mean screw RTVs were significantly influenced by screwdriver insertion angulation.