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A Comparison of Abutment Screw Loosening in 24-Degree Angulation-Correcting and Straight Implants: An In Vitro Study
Purpose:
To compare abutment screw loosening in 24-degree angulation-correcting and straight implants subjected to nonaxial cyclic loading.
Materials And Methods:
Seven external connection 24-degree angulation-correcting implants (AI) and seven external connection straight implants (SI) were embedded in acrylic resin within a brass housing. A hemispherical titanium fatigue abutment was secured to each implant using a titanium abutment screw tightened to 32 Ncm. Each implant-abutment complex was positioned within a tooth wear machine and subjected to 1,000,000 cycles of 50-Ncm nonaxial loading to simulate 1 year of function. The abutment screw removal torque values were measured before and after cyclic loading, and the differences were statistically analyzed using two-way ANOVA and post hoc pairwise Dunn tests. Scanning electron microscopy and finite element analyses were performed to assess the wear of the abutment screws.
Results:
The mean torque loss for the AI group was 21.44% (P < .001) compared to 24.56% (P < .001) for the SI group. There was a statistically significant difference between the AI and SI groups (P = .006).
Conclusions:
Both groups exhibited significant abutment screw loosening. Within the limitations of this study, 24-degree angulation-correcting implants resisted screw loosening significantly more than straight implants.
