Factors related to relapse after mandibular setback surgery with minimal presurgical orthodontics

Publication date: Available online 3 January 2019

Source: Journal of Oral and Maxillofacial Surgery

Author(s): Tae-Hyun Choi, So-Hyun Kim, Pil-Young Yun, Young-Kyun Kim, Nam-Ki Lee

Abstract

Purpose

The aims of this study were to compare the presurgical conditions, surgical changes, and postsurgical changes between skeletal Class III patients with different degrees of horizontal relapse after mandibular setback surgery (MS) with minimal presurgical orthodontics (MPO), and to identify the factors contributing to this relapse.

Materials and Methods

For this retrospective study, 33 consecutive patients who underwent MS-MPO were selected. Lateral cephalograms were taken preoperatively (T0), 1 month after surgery (T1), and at orthodontic debonding (T2). Subjects were divided into low relapse (LR, n=18; relapse < 1 mm) and high relapse (HR, n=15; relapse > 2 mm) groups based on the cephalometric distance of mandibular horizontal relapse. The paired t test, the independent t test, and Pearson's correlation analysis were used to evaluate surgical (T0 to T1) and postsurgical changes (T1 to T2) in the skeleto-dental variables, and to explore the relationship between surgical changes and horizontal relapse.

Results

Compared with the LR group, the HR group exhibited more upward movement with counterclockwise rotation of the mandible from T1 to T2. The HR group presented at T0 with a more prognathic mandible, greater vertical facial height, and a positive overbite. In addition, the HR group presented more posterior movement with clockwise rotation of the mandible, increased overjet, and decreased overbite from T0 to T1. Horizontal relapse of the mandible was positively correlated with the amount of setback and clockwise rotation of the mandible, as well as the change in overjet, and was negatively correlated with the change in overbite.

Conclusions

Mandibular instability was related to the extent of setback and clockwise rotation of the mandible, decreased overbite, and increased overjet during MS-MPO.

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