Aesthetic Changes in Lip Profile following Advancement Genioplasty

Abstract

This study examined the aesthetic changes in the labiomental fold profile after advancement genioplasty. We presented a Cartesian system, based on symphyseal landmarks, to compare both hard and soft tissue changes occurring after advancement genioplasty. This technique was then utilized to compare quantitatively the soft tissue changes in patients who have had advancement genioplasty with or without bone grafts in the anterior osteotomy site. Thirty-one consecutive patients who had undergone advancement horizontal mandibular osteotomies (HMOs) for the correction of a deficient chin in the period 1989 through 1994 were included in this study. All patients underwent HMO either with or without the insertion of a freeze-dried rib to contour the osteotomy step defect. The majority of patients underwent additional procedures, including Le Fort I osteotomy (LFI) and bilateral sagittal split osteotomy (BSSO), alone or in combination. In the grafted group, after the segment was fixed, a split-thickness freeze-dried rib graft was contoured and secured in the anterior osteotomy site with 2-mm position screws. Cephalograms were taken at two time periods: preoperatively and 1 year postoperatively. The cephalograms were traced, and bony landmarks in the mandibular symphysis were identified: genion, infradentale, and B point. These points were chosen because they were not affected by any surgical procedure. A Cartesian coordinate system was then derived from the preoperative tracings and superimposed on the 1-year postoperative tracings. The depth of the labiomental fold was measured from the soft tissue chin profile. The data were analyzed with a Student's t-test to test the hypothesis that horizontal advancement of the mandibular symphysis produced unfavorable aesthetic changes in the labiomental sulcus in patients with no graft in the anterior osteotomy site. The significance level to reject the null hypothesis was set at P < 0.05. The mean change in the sulcus depth for nongrafted HMOs was 2.22 mm, while the mean change in sulcus depth for grafted HMOs was −2.79 mm. A positive change represented a deepening of the labiomental fold. The mean difference between the two groups was 5.00 mm (P < 0.0001). The amount of advancement did not correlate with sulcus depth changes in either group (no graft, r2 = 0.012, P = 0.72; with graft, r2 = 0.03, P = 0.15). Significant change occurred at the deepest point of the labiomental fold. The mean change there in patients with no graft was 0.59 mm (P = 0.4); for grafted patients it was 3.42 mm (P < 0.0001). The mean difference between the two groups was 2.83 mm (P = 0.0017). Changes at lower incisor, lower lip, and soft tissue pogonion were not significantly different between the two groups. We found that the sulcus depth deepens significantly after advancement genioplasty when no graft is placed in the anterior osteotomy site. The significant change occurs at the depth of the sulcus, the site of the anterior step, and does not correlate with the amount of advancement.