Delayed Soft Tissue Changes after Clockwise Rotation of the Maxillo-Mandibular Complex

The purpose of this study was to evaluate delayed soft tissue changes of the maxilla-mandibular complex MMC using three-dimensional (3D) cone-beam computed tomography after clockwise repositioning orthognathic surgery.This study included 21 patients that underwent maxilla-mandibular complex clockwise rotational orthognathic surgery by 1 doctor from January 2015 to June 2019. Radiographic images (panorama, lateral cephalogram, posteroanterior view, and conebeam computed tomography) were taken and 3D analysis was performed using the Invivo 5 (Anatomage Inc, Santa Clara, CA) to acquire 3D images before surgery, immediately after surgery, at 6 months after surgery and 21 months after surgery. The 9 soft tissue landmarks were measured and compared in terms of postoperative changes in transverse, vertical, and anteroposterior directions. The points were at the outer commissure of the eye fissure (Exocathion; Exc_r, Exc_l), at the midline of both the nasal root and the nasofrontal suture, analogous to bony N (soft tissue nasion; N), the most prominent point on the nasal tip (Pronasale; Prn), the most lateral point in the curved baseline of each ala, indicating the facial insertion of the nasal wing base (Alare curvature; Ac_r, Ac_l), the most lateral point on the soft tissue contour of each mandibular angle (Soft tissue Gonion; Go_r, Go_l), and the most inferior midpoint on the soft tissue contour of the chin (soft tissue menton; Me).The most prominent point of the nasal tip (Prn) moved 1.36 mm upward and 1.55 mm forward in the vertical and anteroposterior planes immediately after surgery. However, there were no significant changes in Ac_r and Ac_l even immediately after surgery. Both soft tissue gonions shifted downward and forward between immediately after surgery and 6 months after surgery. However, no significant change was observed in the value of any of the 9 soft tissue points between 6 months and 21 months after surgery ( P value < 0.05).No significant changes were observed between 6 and 21 months after surgery, which suggests no delayed soft tissue changes occur in surgically treated patients after the resolution of surgically-related facial edema and swelling and postsurgical remodeling of hard tissue in overlying soft tissue.