Effect of Loading Angles on Abutment Screw Loosening: In Vitro Study.

AIM: Biomechanical performance is a critical factor in the long-term success of dental implants, with abutment screw loosening being a common clinical issue. This study aimed to examine the impact of abutment screw design and external load loading angles on abutment screw loosening. MATERIALS AND METHODS: Abutments and abutment screws with 30 degrees , 60 degrees , 90 degrees , and 180 degrees fitting tapers were fabricated and tested for preload and initial loosening torque. Subsequently, dynamic loosening tests were conducted at loading angles of 15 degrees , 30 degrees , and 45 degrees . Finite element analysis (FEA) was used to calculate the stress and strain distribution of the abutment screws. RESULTS: The findings indicated that large-taper abutment screws exhibit a higher preload, whereas small-taper abutment screws demonstrate greater loosening torque values. Additionally, as the loading angle increases, the loosening torque value decreases, and the stress and strain values of the abutment screw increase. CONCLUSIONS: Abutment screws with smaller taper heads exhibited superior resistance to loosening. Moreover, the anti-loosening performance of the abutment screws decreased with higher external load loading angles.