Craniomaxillofacial deformities/sleep disorders/cosmetic surgery
Evaluation of Postoperative Mandibular Positional Changes After Mandibular Setback Surgery in a Surgery-First Approach: Isolated Mandibular Surgery Versus Bimaxillary Surgery

https://doi.org/10.1016/j.joms.2018.09.008Get rights and content

Purpose

The aim of this study was to compare postoperative positional changes in the mandible after isolated mandibular surgery (IMS) or bimaxillary surgery (BMS) in a surgery-first approach (SFA).

Materials and Methods

The authors designed and implemented a retrospective cohort study composed of patients who underwent mandibular setback surgery using the SFA. Surgical and postoperative changes were evaluated using lateral cephalograms taken 1 month before surgery (T0), 1 week after surgery (T1), and immediately after debonding of orthodontic appliances (T2; 16.6 ± 8.7 months after surgery). To predict postoperative mandibular positional changes from the increase in vertical dimension (VD) in surgical occlusion, the mandible was rotated counterclockwise to the preoperative VD on the lateral cephalogram at T1, and resultant mandibular positional changes were measured. To evaluate actual postoperative mandibular positional changes between each time point and compare them between the 2 groups, independent t test, paired t test, and repeated-measures analysis of variance were performed.

Results

Thirty patients were evaluated (16 in IMS group and 14 in BMS group). The 2 groups showed significant time-course mandibular positional changes from T0 to T1 and from T1 to T2 within each group (point B, P < .001), although no statistically significant differences were observed between groups. There was no statistically relevant difference between groups in the predicted and actual postoperative rotational movements. In addition to the mandibular forward movement that resulted from postoperative mandibular counterclockwise rotation, additional horizontal relapse occurred.

Conclusion

The present findings suggest that the mandible exhibits notable postoperative forward movement during postoperative orthodontic treatment, regardless of the extent of the orthognathic surgery in the SFA, and it is necessary to consider mandibular forward movement from the VD increase in surgical occlusion and additional relapse during the treatment planning stage.

Section snippets

Study Design and Sample

The authors designed and implemented a retrospective cohort study to address the research purpose. This study was approved by the institutional review board of the Chonnam National University Dental Hospital (Gwangju, Korea; CNUDH-2018-0002). The study population was composed of patients who underwent mandibular setback surgery using bilateral sagittal split ramus osteotomy (BSSO) with or without Le Fort I osteotomy at the Department of Oral and Maxillofacial Surgery of the Chonnam National

Results

Thirty patients (20 male and 10 female; mean age, 21.1 yr; age range, 17 to 29 yr) who met the inclusion criteria were recruited for the study. All patients received postoperative orthodontic treatment; 16 patients (IMS group; mean age, 22.2 yr; range, 18 to 29 yr) underwent an isolated mandibular setback surgery; 14 patients (BMS group; mean age, 19.9 yr; range, 17 to 26 yr) underwent mandibular setback surgery combined with Le Fort I osteotomy. Although there was no statistical difference in

Discussion

This study was conducted to evaluate postoperative positional changes in the mandible after mandibular setback surgery using the SFA. The study's hypothesis was that the extent of the orthognathic surgery would have a marked effect on postoperative stability. The specific aims were to compare postoperative mandibular forward movement after mandibular setback surgery between the IMS and BMS groups. In this study, the 2 groups showed clinically relevant postoperative mandibular forward movement

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    This study was supported by a grant (CRI18011-1) from the Chonnam National University Hospital Biomedical Research Institute.

    Conflict of Interest Disclosures: None of the authors have any relevant financial relationship(s) with a commercial interest.

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