Three-dimensional analysis of lip soft tissue changes and related jaw changes in patients with skeletal class III malocclusion and facial asymmetry.

OBJECTIVE

To investigate three-dimensional soft tissue changes of lips and related jaw changes in patients with skeletal class III malocclusion and facial asymmetry using cone-beam computerized tomography (CBCT).

METHOD: This study included 46 CBCT scans of patients with aforementioned character before (T1) and 6-12 months after orthognathic surgery (T2). Subjects were divided into 2 groups according to two types of orthognathic surgery namely, the one-jaw surgery group who underwent bilateral sagittal splint ramus osteotomy (BSSRO) and the two-jaw surgery group who underwent Le Fort I osteotomy and BSSRO. Mimics 19.0 software are used for model reconstruction, landmark location and three-dimensional cephalometric analysis. Descriptive statistics and correlation analyses are used to investigate jaw hard tissue and lip soft tissue changes.

RESULTS

In one-jaw group, the mandible shows changes in contour and position (p < 0.05), and the surgery causes changes of lip structure on the deviated side. While in two-jaw group, jaws only show changes in spatial position, and surgery changes contour of bilateral lips and nasolabial angle (p < 0.05). At the same time, lip symmetry increases significantly in both groups postoperatively.

CONCLUSIONS

Orthognathic surgery can improve lip aesthetics in patients with skeletal class III malocclusion and facial asymmetry. However, changes induced by two surgical approaches are different. Surgeons should have a clear acquaintance with this difference to deal with different situations.