Three-dimensional evaluation of soft tissue change gradients after mandibular setback surgery in skeletal Class III malocclusion

Abstract

Objective: To evaluate whether mandibular setback surgery (MSS) for Class III patients would produce gradients of three-dimensional (3D) soft tissue changes in the vertical and transverse aspects. Materials and Methods: The samples consisted of 26 Class III patients treated with MSS using bilateral sagittal split ramus osteotomy. Lateral cephalograms and 3D facial scan images were taken before and 6 months after MSS, and changes in landmarks and variables were measured using a Rapidform 2006. Paired and independent t-tests were performed for statistical analysis. Results: Landmarks in the upper lip and mouth corner (cheilion, Ch) moved backward and downward (respectively, cupid bow point, 1.0 mm and 0.3 mm, P , .001 and P , .01; alar curvature-Ch midpoint, 0.6 mm and 0.3 mm, both P , .001; Ch, 3.4 mm and 0.8 mm, both P , .001). However, landmarks in stomion (Stm), lower lip, and chin moved backward (Stm, 1.6 mm; labrale inferius [Li], 6.9 mm; LLBP, 6.9 mm; B9, 6.7 mm; Pog9, 6.7 mm; Me9, 6.6 mm; P , .001, respectively). Width and height of upper and lower lip were not altered significantly except for a decrease of lower vermilion height (Stm-Li, 1.7 mm, P , .001). Chin height (B9-Me9) was decreased because of backward and upward movement of Me9 (3.1 mm, P , .001). Although upper lip projection angle and Stm-transverse projection angle became acute (Ch Rt -Ls-Ch Lt , 5.7u; Ch Rt -Stm-Ch Lt , 6.4u, both P , .001) because of the greater backward movement of Ch than Stm, lower lip projection angle and Stm-vertical projection angle became obtuse (Ch Rt -Li-Ch Lt , 10.8u; LsStm-Li, 23.5u, both P , .001) because of the larger backward movement of Li than labrale superius (Ls). Conclusions: Three-dimensional soft tissue changes in Class III patients after MSS exhibited increased gradients from upper lip and lower lip to chin as well as from Stm to Ch. (Angle Orthod. 2010;80:896-903.)

Evaluation of canting correction of the maxillary transverse occlusal plane and change of the lip canting in Class III two-jaw orthognathic surgery

“…Lim et al 7 found that 3D soft tissue changes in Class III patients after mandibular setback surgery exhibited increased gradients from the upper lip and lower lip to the chin as well as from the stomodium to the mouth corner. Kim et al 8 suggested that there were significant increases in the upper lip length and decreases in the lower lip length in the large setback, hypodivergent, and genioplasty groups in Class III cases with mandibular setback surgery.…”

“…Therefore, 3D facial scanning can be regarded as a useful and accurate method with which to measure soft tissue change. Lim et al 7 and Kim et al 8 evaluated soft tissue change in 3D facial scanning images according to the skeletal movement of lateral cephalograms after one-jaw orthognathic surgery (mandibular setback only) in cases involving skeletal Class III malocclusion.…”

3D Assessment of Orthognathic Surgical Outcomes

“…Both one-and two-jaw orthognathic surgeries for Class III correction result in forward and upward movement of the nasal tip (Jung et al, 2009;Lim et al, 2010;Park et al, 2012a) that results from remodeling of the perioral musculature (Jung et al, 2009). The other primary change in nasal esthetics after two-jaw surgery results from malpositioning that 3D imaging now is able to detect more precisely.…”

“…Even with isolated mandibular setback, the upper lip moves backward (Hershey & Smith, 1974;Suckiel & Kohn, 1978;Sung et al, 2000;Lim et al, 2010;Kim et al, 2012) because both the upper and lower lips are influenced by the protruded mandibular incisors. With the posterior positioning of the mandible, the maxillary incisors rather than the mandibular incisors begin to provide the main support for the upper lip, resulting in an overall reduction in the sagittal projection of the upper lip (Lim et al, 2010). In contrast, due to the LeFort I advancement in two-jaw surgery, the upper lip moves forward (Jensen et al, 1992;Kim et al, 2012).…”

“…The ideal positioning of the jaws through orthognathic surgery does not always result in an ideal soft tissue appearance because the patient's facial soft tissue does not respond to movement of the underlying skeletal tissues in a 1 : 1 ratio (Lim et al, 2010;Ryckman et al, 2010). Therefore, surgical treatment objectives must focus on the desired soft tissue outcome (Sarver, 1998), rather than on the correction of skeletal discrepancies only.…”