Implant placement with more than 25° angle and use of customized abutments are still challenging in implant dentistry. Also, casting is still the most commonly used method for fabrication of customized abutments.
This study evaluated the effect of angulation and type of abutment (castable and cast-to) on torque loss and fracture resistance after cyclic loading.
Two implants were mounted with 0 and 30° angle on a gypsum model. Castable and Cast-to abutments were casted by cobalt-chromium alloy on each implant (10 samples in 4 groups). Rotational freedom was measured by a video-measuring microscope. The reverse torque values before and after cyclic loading (500,000 cycles) were measured by a digital torque-meter. Abutments were subjected to fracture resistance test in a universal testing machine. Data were analyzed using the Kruskal Wallis, two-way ANOVA and repeated measures tests.
Difference between castable and cast-to abutments regarding rotational freedom was not significant. Torque loss in castable abutments was significantly greater than cast-to abutments before and after cyclic loading (P < 0.05). The effect of abutment angle on torque loss before and after cyclic loading was not significant.
Irrespective of the abutment angle, torque loss was significantly higher in castable groups. Considering the high fracture resistance, abutment fractures were not clinically an issue.
Keywords: Abutments, Casting, Fracture, Implant, Reverse torque, Rotational freedom.