Chulalongkorn University Dental Journal

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Background/Objective To evaluate the effect of three screw-tightening methods on the screw loosening resistance of two dental implant systems. Materials and methods Fifteen Simple Line II dental implants and 15 CU dental implant abutments were screw tightened to their implant fixtures to the manufacturerûs recommended torque using three tightening methods (method 1: tightening the screw one time, method 2: tightening the screw and retightening the screw after 10 min, method 3: tightening the screw, loosening the screw, retightening the screw, and then retightening the screw after 10 min). After a 106-cycle fatigue test, the reverse torque values were measured. The screw loosening resistance (the reverse torque value) was expressed as the percentage of the initial tightening torque. The Kruskal-Wallis and Conover-Inman tests were used to compare the screw loosening resistance at the 95% confidence level. Results Method 1 demonstrated the significantly lowest screw loosening resistance in both dental implant systems. Methods 2 and 3 showed no significant differences in screw loosening resistance in either dental implant system. The Simple Line II implant system exhibited a significantly higher screw loosening resistance than that of the CU dental implant system when comparing the same method. Conclusion The highest screw loosening resistance was achieved by screw retightening. However, screw loosening before a second retightening did not increase the screw loosening resistance compared with that achieved from the first screw retightening. The Simple Line II dental implant system showed a significantly higher screw loosening resistance compared with the CU dental implant system.



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