Comparison of screw retention of nine abutment systems: a pilot study

Fracturing or loosening of abutment and retaining screws is a frequent occurrence. This study was designed to evaluate the retaining ability of nine abutment systems. Abutment and retaining screws were secured to the appropriate implant using a digital torque gauge, with the abutment screws placed at 30 N-cm and the retaining screws at 10 N-cm. Removal torque was recorded three times for each sample 10 minutes after initial placement, 20 minutes after retightening, and 24 hours after retightening. There was no statistical difference in removal torque relative to time or repeated tightening. Of the nine abutment systems, three were statistically less retentive as compared with the most retentive system. The retaining screws were less retentive as compared with the abutment screws. For maximum retention the elimination of retaining screws from the restorative design and using 30 N-cm of torque for the abutment screws is suggested.