Influence of the changes in arch width on postsurgical relapse after mandibular setback surgery with minimal orthodontics.

Purpose: Most reports on the surgery-first approach in patients with skeletal Class III malocclusion have focused on skeletal changes and treatment efficacy. This study sought to evaluate the association between the transverse changes of arch dimension and postsurgical relapse of the mandible after mandibular setback surgery (MS) with minimal orthodontic preparation (MO) without extractions (N).

Materials And Methods: This was a retrospective cohort study. The sample consisted of patients with skeletal Class III malocclusion who underwent MS-MO/N. Primary outcome variables were horizontal, vertical, and angular changes of the mandibular position (mandibular relapse). Predictor variables included changes in the transverse width of the upper and lower arches. Lateral cephalograms and study models were obtained and measured before (T0) and 1 month (T1), 3 months (T2), and 6 months (T3) after surgery. Descriptive, paired t test, repeated measures analysis of variance, and a generalized estimating equation with Bonferroni correction were computed.

Results: The sample consisted of 12 patients (7 female and 5 male; mean age, 19.83 ± 2.37 yr). Significant anterior and superior movements and counterclockwise rotation of the mandible were noted from T1 to T3. Despite dental decompensation from T1 to T3, there were no significant postsurgical changes in arch width. In addition, there was no correlation between the forward and upward movements of the mandible and changes of arch width. However, the counterclockwise rotation of the mandible was correlated with the changes in the upper inter-first premolar width (UIP1W) and lower inter-first molar width (LIM1W) over time.

Conclusion: The changes in arch width had no association with horizontal and vertical relapses of the mandible. Only changes in UIP1W and LIM1W showed an association with angular relapse of the mandible.