Laboratory Evaluation of Torque Loss in Titanium, One-Piece and Two-Piece Zirconia Abutments Under Cyclic Loading

Background: Screw loosening is one of the most common problems associated with implant-supported prostheses. The type and material of the abutment play an important role in the esthetic appearance of implant-supported restorations. Metal abutments create an unaesthetic grayish halo in the gingival margin of the implant due to the reflection of light from the surface of titanium abutment. Zirconia is highly popular for the fabrication of abutments due to its optimal color, along with the quality of light transmission and its resistance. The present study aimed to evaluate the torque loss in titanium and one- and two-piece zirconia abutments under cyclic loading. Methods: In general, ۲۴ abutments in three groups (n=۸) of one- and two-piece zirconia abutments, and titanium abutments were evaluated in this experimental study. The abutments were attached to the analog of fixtures with ۳۰ N/cm torque and the samples were subjected to loads applied to the center of abutments at ۳۰° angle. After cyclic loading, the removal torque value was measured for each abutment and its numerical mean was calculated as well. Finally, the groups were compared using SPSS۱۶ via ANOVA and Games-Howell tests at a ۰.۰۵ level of significance. Results: The mean removal torque value was ۲۳.۹۲۵, ۲۳.۹۱۳, and ۲۲.۵۳۸ N/cm in titanium and two- and one-piece zirconia abutments, respectively, with no statistically significant difference in between (P>۰.۰۵). Conclusions: The highest mean removal torque value belonged to prefabricated titanium abutments while the lowest value was related to one-piece zirconia abutments.