Soft Tissue Changes after Setback Surgery with and without Reduction Genioplasty

Soft tissue changes in the chin were compared between patients undergoing sagittal split ramus osteotomy (SSRO) for mandibular setback with and without reduction genioplasty. Twenty patients with symmetrical skeletal Class III malocclusion were examined. Twelve underwent SSRO alone (group I), and 8 underwent SSRO combined with reduction genioplasty (group II). Reduction genioplasty was performed by two horizontal osteotomies, removing the bony wedge, and posterosuperior movement of the inferior segment of the chin. Lateral cephalograms were obtained preoperatively and 6 months postoperatively. Pre- to postoperative changes in the positions of hard-tissue points (B-point [B], pogonion [Ng], and menton [Me]) and soft-tissue B-point [sB], soft-tissue pogonion [sPog], and menton [sMe] were measured on the cephalograms. The ratio of the soft tis-sue movement to the hard tissue movement was also calculated. Though superior movement of Me was significantly larger in group II than in group I, there were no significant differences in the superior movement ratios of sMe to Me between the two groups. However, the posterior movement ratio of sPog to Pog was significantly larger in group I than in group H. These results suggest that the reduction genioplasty performed by two horizontal osteotomies, removing the bony wedge, and posterosuperior movement of the inferior segment of the chin had little effect on the posterior movement of the chin. Therefore, in patients with skeletal class III malocclusion, reduction genioplasty should be applied mainly to vertical shortening of the chin.