Effect of tightening and opening cycles on final detorque values of abutment screw in internal hex connection and internal Morse hex connection

Abstract

Introduction: screw loosening is The most common complication that is being reported regularly in dental implants. It seems that tightening and loosening of the abutment screw repeatedly have an effect On its loosening resistance. limited studies have been done on Different implant systems that have reported different results in relation to detorque changes after tightening and loosening cycles. the aim of this study is to determine the effect of tightening and opening cycles on final detorque values of abutment screw in Internal Hex connection and Internal Morse Hex connection. Materials and Methods: In this study, two different systems of implant with internal hex connection (SIC system) and internal morse hex connection (Dentis system) were investigated. Ten samples were prepared from each system; the abutment screws were tightened with a torque of 25 N.cm. then the screws were loosened. the detorque was measured by a digital torquemeter. This was repeated 8 times for specimens of both systems. detorque values were recorded and the final detorque of cycles of 2 , 6 and 8 were compared using the repeated measure analysis in each system and Independent t-test between tow systems. The statistical significance of P-value was less than 0.05. Statistical analysis was performed using SPSS17 software. Results: The highest detorque was at the first cycle and in SIC system with 23.1 ± 1.72 and the lowest detorque was at the eighth cycle and in Dentis system was reported at 17.6 ± 3.41. results of repeated measurement test showed a significant statistical difference between the amount of detorque in the opening and tightening cycles of abutment screw (P-value = 0.001). The mean values of the final detorque at 2nd and 6th cycles of tightening and opening in the internal morse hex connection (Dentis system) were lower than internal hex connection (SIC system). Results of Independent t-test showed no significance statistical diffrence in final detorque between tow connections. Conclusion: The amount of final detorque of the abutment screws in both Dentis and SIC systems decreases with increasing number of cycles. There is no significance statistical diffrence in final detorque between tow systems.