Study of the Abutment Screw threads of Internal Hexagon and Morse Taper Connection Implants and their loosening after Fatigue Testing

Aims: To evaluate the length of the thread portion and the distance between the thread pitches of internal hexagon (IH) and morse taper (MT) connection screws and their loosening after fatigue testing. Methodology: Ten IH and ten MT implants received abutments torqued 20 N.cm. The implant-abutment sets were subjected to fatigue by mechanical cycling. After testing the removal torque of the abutments was measured and the abutments and screws were analyzed by scanning electron microscopy. Results: Student's t-test showed there was no significant difference between the removal torque values among the groups (p=0.609). The length of the screw thread portion of the IH connection was significantly longer than that of the MT connection (p<0.001). There was no significant difference between the groups regarding the distance between the threads of the screws.  (p=0.734). Conclusion: The thread portion of screws in the internal hexagon connection was larger than that of screws in the morse taper connection. However, the distance between thread pitches and the removal torque values under fatigue testing were similar for screws in both types of connections.