Efficacy of Several Retightening Protocols for Maintaining Clamping Force in the Implant-Abutment Joint: An In Vitro Pilot Study

Purpose: Stability of an implant-supported restoration is an ultimate measure of the success of the procedure. It has been recommended by some to retighten the abutment screw for maintenance of the crown on the implant. The purpose of this study was to evaluate the usefulness of two retightening protocols to maintain the clamping force. Materials and Methods: Three groups of slip-fit implants (MIS 4.3 by 10.5) were compared. The first group was only tightened once (group C). In the second group (group R10M), the screw was retightened after 10 minutes. The third group (group R2W) was retightened after 2 weeks of simulated functional loading. After completion of individual protocols, all specimens were loaded for 100,000 cycles. After the loading, all specimens had the remaining torque audited. Results: The mean torque loss for group C was 6.10 (± 5.13) Ncm. Group R10M was 2.03 (± 3.018) Ncm, and group R2W was 0.30 (± 0.483) Ncm. A one-way analysis of variance (ANOVA) recorded significant differences among the groups (P = .003). Multiple pairwise comparisons between groups by Tukey test recorded significant differences between group C vs group R10M (P = .035) and group C vs group R2W (P = .002). There was no significant difference in torque loss between groups R10M and R2W (P = .509). Conclusion: Within the parameters of this in vitro investigation, it was concluded that both retightening after 10 minutes (P = .035) and after 2 weeks (P = .002) was equally effective. Parole chiave: clamping force, embedment relaxation, preload, slip fit connection, torque