Effects of wobbling angle on the stability measures of orthodontic mini-implants during insertion and removal procedures

Abstract

Objective: To investigate the effects of wobbling angle on the stability measures of orthodontic mini-implants (OMIs) during insertion and removal procedures in artificial bone blocks. Materials and Methods: A total of 36 OMIs (self-drilling type, cylindrical shape, 7 mm in length, 1.45 mm in diameter) were allocated into three groups according to the amount of wobbling angle (W-0 degrees, W-2 degrees, and W-4 degrees groups; N=12 per group). The OMIs were installed and subsequently removed from artificial bone blocks (Sawbone) using a driving torque tester with a uniform speed of 28 rpm. Insertion peak time (IPT), maximum insertion torque (MIT), total insertion energy (TIE), near-peak insertion energy (NPIE), maximum removal torque (MRT), and near-peak removal energy (NPRE) were measured. Results: The W-4 degrees group showed the longest IPT and highest TIE and NPIE, followed by the W-2 degrees and W-0 degrees groups (W-0 degrees < W-2 degrees < W-4 degrees, all P < .001). The W-2 degrees and W-4 degrees groups showed significant increase in MIT compared with the W-0 degrees group (W-0 degrees < [W-4 degrees,W-2 degrees]; P < .001). Although there was no significant difference in NPRE among the three groups, the W-4 degrees group showed a decrease in MRT compared with the W-0 degrees and W-2 degrees groups (W-4 degrees < [W-2 degrees,W-0 degrees]; P < .05). Although the W-4 degrees group showed a 14.5% (2.9 Ncm) increase in MIT compared with the W-0 degrees group, there was only a 6% (1.3 Ncm) decrease in MRT from the W-0 degrees group to the W-4 degrees group. Conclusion: Slight wobbling during the OMI insertion procedure may be acceptable in terms of the stability measures of OMIs during insertion and removal procedures.