Objective To investigate the effects and alterations in soft and hard tissues in the lower third of the facial structure in patients exhibiting facial asymmetry following bilateral sagittal split ramus osteotomy (BSSRO) with genioplasty, and to examine the correlation between the changes observed in soft and hard tissues.

Methods A total of 31 patients with facial asymmetry who underwent BSSRO with genioplasty were divided into mild-deviation group (n=17) and severe-deviation group (n=14). Multidimensional imaging evaluation was performed preoperatively, and at 3 and 6 months postoperatively. Three-dimensional reconstructions of oral and maxillofacial cone beam CT (CBCT) date were performed using Mimics Medical 21.0. The 3-matic Medical 13.0 was employed to measure key indicators such as hard tissue landmarks or soft tissue width. Statistical analyses of the data, including calculation of the mean, standard deviation, correlation analysis as well as significance test, were performed using SPSS 23.0.

Results Compared with the preoperative period, there were significant differences in the bilateral mental foramen width, bilateral gonion width, and the asymmetry coefficient of the submental point and mental foramen (Mf) in patients with mild deviation (P < 0.05). Additionally, there were significant differences in the width of the deviated-side oral commissure at 3 months and the width of the contralateral oral commissure at 6 months after surgery (P < 0.05); in patients with severe deviation, there were significant differences in the width of the deviated-side oral commissure, bilateral mental foramen width, and the asymmetry coefficient of the submental point and Mf (P < 0.05), and there were significant differences in the width of the contralateral oral commissure, the contralateral Go-Go'distance at 3 months and the asymmetry coefficient of the gonion point at 6 months after surgery (P < 0.05). In addition, from preoperative stage to 6 months after surgery, there was significant correlation between the changes in the facial soft and hard tissues of patients with mild and severe deviation (P < 0.05), and there were differences in the correlation between the two groups (P < 0.05).

Conclusion BSSRO with genioplasty can significantly improve the facial symmetry in patients with unilateral mandibular asymmetry and there is a correlation between the changes of soft and hard tissues in the lower facial third from pre-operation to 6 months post-operation.