Improved lip esthetics in patients with skeletal Class III malocclusion and facial asymmetry after isolated mandibular orthognathic surgery

Asymmetry of the lips severely affects facial esthetics and is often one of the chief complaints of orthognathic patients, especially those with Class III malocclusion. The objectives of this study were to investigate the changes in lip symmetry in patients with mandibular prognathism and deviation and the relationships between jaw hard tissue and lip soft-tissue changes.Three-dimensional facial scan and cone-beam computed tomography scan data of 30 orthodontic-orthognathic patients treated with bilateral sagittal split ramus osteotomy were combined to conduct the research. Paired-sample t test and Pearson correlation coefficient were applied to compare the differences in the same variable before and after the orthognathic surgery and the potential correlations between the changes in hard and soft variables. To explore the important hard tissue variables influencing the lip soft-tissue changes, linear regression analysis was performed.Although there was significant upper lip asymmetry presurgery, the upper lip asymmetry was corrected postsurgery. Surgical correction of the mandibular deviation was also accompanied by lengthening of the bilateral philtrum crests. Improvement in lip asymmetry and lengthening of the philtrum crests were primarily related to the transverse correction of the mandible rather than sagittal changes. The corresponding prediction formulas were established.The isolated mandibular bilateral sagittal split ramus osteotomy surgery can substantially improve the upper and lower lip asymmetry in patients with mandibular prognathism and deviation, but one should be wary of the unesthetic effects associated with lengthening of the philtrum crests.