The Extent of Chin Ptosis and Lower Incisor Exposure Changes Following the Osseous Genioplasties

The incision and dissection of the mentalis muscles are inevitable to access the osteotomy line during genial surgery. As the mentalis muscles elevate the central lower lip and support the lip vertically, inadvertent scarring or lengthening of these muscles may lead to lip incompetence and may increase the lower incisor exposure (LIE) that will cause an unaesthetic result. The aim of this study was to evaluate the extent of lip ptosis, LIE, and other soft-tissue changes following different types of osseous genioplasty procedures. Twenty-nine patients (18 females, 11 males) were included in this study. Patients were classified into 3 groups with respect to their genial movement type as genial setback (n = 10), genial advancement (n = 10), and vertical reduction (n = 9). Preoperative and postoperative lateral cephalograms were analyzed to evaluate the horizontal and vertical soft-tissue changes of the lower lip and chin in the 3 genioplasty groups. The statistical evaluations were performed with regression analysis. The mean increase in the LIE was 1.88 mm. Lower incisor exposure and soft-tissue thickness at pogonion were increased significantly in all patients (P < 0.05). Statistically significant differences for lower lip length and vertical position of soft-tissue supramentale values were detected in patients who underwent vertical reduction genioplasty (P < 0.05). Genioplasty procedures requiring the mentalis muscle release cause a 1.88-mm increase in LIE. Vertical positional alterations of the lower lip were especially observed following the vertical reduction genioplasty. Clinician should aware of this consequence in the course of treatment planning.