Biomechanics in terms of rotation angles and torques of implant-abutment screw tightening and loosening: Effects of implant types, contamination and sandblasting

Biomechanics in terms of rotation angles and torques of implant-abutment screw tightening and loosening: Effects of implant types, contamination and sandblasting Purpose.The purpose of this study is to analyze the biomechanical differences in rotation angle-torque according to the type of implant and to compare the effects of contamination and sandblasting on the removal torque value (RTV) of abutment screws.Materials and methods.For this study, an automated device for tightening and loosening implant screws was developed, and each 15 implant-abutment complexes of external and internal connection type were prepared, divided into three groups according to the surface treatment of the screw: control group (no treatment), experimental group-1 (artificial saliva contamination and chlorhexidine (CHX) rinsing), and experimental group-2 (artificial saliva contamination, CHX rinsing, and subsequent 50 m Al 2 O 3 sandblasting).First-RTV was measured for each group, followed by different post-treatment procedures for the screws, and then Second-RTV was measured.During the procedure, the removal torque value and rotation angle vs. time were recorded at a 20 data/s.A standardized protocol was followed for all the tightening and loosening procedures: screw was tightened with 30 Ncm torque and maintained for 5 s, and then rotated in the reverse direction until the torque value reached 0 Ncm.After 10 min of rest period, the screws were loosened to initial point.Results.Statistical analysis of measured data revealed that the internal connection type showed significantly higher First-RTV compared to the external connection type, however, no significant differences in Second-RTV were found.Both experimental groups 1 and 2 showed a decrease in RTVs for both implant types, while the control group showed a decrease in RTV only for the internal type.The internal connection type required a significantly larger rotation angle during the tightening and loosening process.Conclusion.