Evaluation of Tightening Protocols for Transmucosal Abutments: An In Vitro Study

Abstract

Purpose: The aim of the study is to evaluate the different tightening protocols for Nobel, On1 abutment. Materials and Methods: The study used 50 Nobel Biocare™ implants, 50 On1 Base Xeal, and 40 On1 Universal Abutments, divided into five groups of 10 implants each. One group (control) received only the On1 Base to determine if the On1 Universal Abutment's tightening protocols affect the reverse tightening value on the On1 Base. The other four groups underwent different tightening protocols for the On1 Universal Abutment screws. Each implant was mounted in autopolymerized splint resin, and the On1 Base was attached and tightened to 35 Ncm. The control group's input and reverse tightening were measured using a digital torque device. The four different tightening protocols for the other groups were: Tightening the abutment screw once, tightening the abutment screw twice consecutively, tightening the abutment screw twice with a 10-minute interval and Tightening, counter-tightening, and re-tightening the abutment screw. All implants were stored at room temperature, and the RTVs were measured and compared to the control group. Results: For the On1 abutment, the highest mean (RTV) was 32.0 Ncm for the 2x 10 protocol, followed by 31.9 Ncm for TCT, and 31.1 Ncm for 2x without waiting. The single tightening (1x) protocol had the lowest mean RTV of 29.4 Ncm, which was statistically significant. Regarding the On1 base, there were statistically significant differences in RTVs between the control group and the other groups (P < .05), with the control group having a mean RTV of 28.0 Ncm. However, no statistically significant differences were found among the other groups. Conclusions: Within the limitations of this study, significant differences were observed among the various tightening protocols for the final abutment screw of the On1 abutment. Therefore, Tightening the On1 abutment screw more than one time, improves the clamping force. Additionally, any removal or loosening of the final abutment screw significantly affected the RTV of the On1 base abutment screw and should be retightened.