Evalution of various techniques of preload application on final detorque values of abutment screw

Abstract

Intruduction: abutment screw loosening in posterior single crowns is the most common problem which can be addressed by the adequate preload as well as proper anti-rotational properties at the implant and abutment joints which appear to be the two key solutions to handle such problem. Since studies on how to apply preload have generally used opening and closing of abutment screw once prior to the final torque, in this study, we decided to investigate the effect of applying more than one force cycle on the final detorque before final tightening of the screw. Materials and Methods: In this study, three different methods of opening and closing of abutment screws were compared and their effects on the final detorque of abutment screws were investigated as well. Using a plaster, the fixtures were mounted in plaster blocks up to the second thread of the upper surface of the plaster block. A torque gauge was used to apply sufficient force to each abutment screw. Reverse torque value in screw was measured using a Digital Torque Meter. Oneway ANOVA test was used to compare detorque values in three times the force applied. Statistical analysis was performed using SPSS17 software. P < 0.05 was considered as the significance level. Results: The highest detorgue value was in the third stage with the mean of -20.41 ±1.62, and the lowest value was in the second stage with the mean of -17.16 ± 4.74. In the first stage, detorgue value was also equal to -17.58. ANOVA test was used to compare the detoqrue values in the three stages studied. According to the results of the present study, the value of the test statistic associated with detorque value in each step was less than the significance level of the test (0.05). Conclusion: According to the results of the evaluation of the tested data, it can be said that applying torque once or twice does not make any differences in the detorque value of abutment, while torque application in three stages increases detorque value, and therefore provides greater resistance to loosening.