You-Sun Lee1, Young-Kyun Kim2, Pil-Young Yun3, Brent E Larson4, Nam-Ki Lee5. 1. Clinical Instructor, Department of Orthodontics, Seoul National University Bundang Hospital, Seongnam, Republic of Korea. 2. Professor, Department of Oral and Maxillofacial Surgery, Seoul National University Bundang Hospital, Seongnam; Department of Dentistry and Dental Research Institute, School of Dentistry, Seoul National University, Seoul, Republic of Korea. 3. Associate Professor, Department of Oral and Maxillofacial Surgery, Seoul National University Bundang Hospital, Seongnam, Republic of Korea. 4. Associate Professor, Division of Orthodontics, School of Dentistry, University of Minnesota, Minneapolis, MN. 5. Associate Professor, Department of Orthodontics, Seoul National University Bundang Hospital, Seongnam, Republic of Korea. Electronic address: nklee@snubh.org.
Abstract
PURPOSE: Most studies on the surgery-first approach focused on skeletal relapse compared with conventional surgery. The objective of this study was to compare the stability of skeletal Class III patients with 2 different vertical facial types after mandibular setback surgery (MS) with minimal orthodontic preparation (MO). MATERIALS AND METHODS: In this retrospective study, the patients were recruited from a population that had undergone MS. Consecutive patients were selected based on the following inclusion criteria: skeletal Class III malocclusion with mandibular prognathism, MO without extraction for less than 6 months, and sagittal split ramus osteotomy. The vertical facial types of the patients were classified based on the Frankfort mandibular-plane angle (FMA). Lateral cephalograms were taken at the presurgical stage, at 1 month after surgery (T1), and at the debonding stage (T2). To evaluate surgical changes (T1 - presurgical stage) and relapse (T2 - T1), the linear, angular, and dental measurements were analyzed using a paired t test and an independent t test. RESULTS: The 26 patients were divided into 2 groups: normal-angle group (n = 14; mean FMA, 23.58°) and high-angle (HA) group (n = 12; mean FMA, 30.26°). From T1 to T2, the normal-angle and HA groups showed significant forward and counterclockwise rotation of the mandible (distance between pogonion and perpendicular line to Frankfort horizontal plane from sella, 1.71 mm and 1.51 mm, respectively; distance between menton and perpendicular line to Frankfort horizontal plane from sella, 1.91 mm and 1.60 mm, respectively; angle between articulare-menton line and Frankfort horizontal plane, -0.55° and -0.89°, respectively). The HA group showed a significant upward movement of the mandible (distance from Frankfort horizontal plane to pogonion, -1.13 mm; distance from Frankfort horizontal plane to menton, -0.78 mm). However, there was no significant difference in the skeletal-dental changes between the 2 groups from T1 to T2. CONCLUSIONS: The vertical facial types of Class III patients with similar prognathic mandible and dental patterns may not cause any differences in the relapse pattern after MS-MO.
PURPOSE: Most studies on the surgery-first approach focused on skeletal relapse compared with conventional surgery. The objective of this study was to compare the stability of skeletal Class III patients with 2 different vertical facial types after mandibular setback surgery (MS) with minimal orthodontic preparation (MO). MATERIALS AND METHODS: In this retrospective study, the patients were recruited from a population that had undergone MS. Consecutive patients were selected based on the following inclusion criteria: skeletal Class III malocclusion with mandibular prognathism, MO without extraction for less than 6 months, and sagittal split ramus osteotomy. The vertical facial types of the patients were classified based on the Frankfort mandibular-plane angle (FMA). Lateral cephalograms were taken at the presurgical stage, at 1 month after surgery (T1), and at the debonding stage (T2). To evaluate surgical changes (T1 - presurgical stage) and relapse (T2 - T1), the linear, angular, and dental measurements were analyzed using a paired t test and an independent t test. RESULTS: The 26 patients were divided into 2 groups: normal-angle group (n = 14; mean FMA, 23.58°) and high-angle (HA) group (n = 12; mean FMA, 30.26°). From T1 to T2, the normal-angle and HA groups showed significant forward and counterclockwise rotation of the mandible (distance between pogonion and perpendicular line to Frankfort horizontal plane from sella, 1.71 mm and 1.51 mm, respectively; distance between menton and perpendicular line to Frankfort horizontal plane from sella, 1.91 mm and 1.60 mm, respectively; angle between articulare-menton line and Frankfort horizontal plane, -0.55° and -0.89°, respectively). The HA group showed a significant upward movement of the mandible (distance from Frankfort horizontal plane to pogonion, -1.13 mm; distance from Frankfort horizontal plane to menton, -0.78 mm). However, there was no significant difference in the skeletal-dental changes between the 2 groups from T1 to T2. CONCLUSIONS: The vertical facial types of Class III patients with similar prognathic mandible and dental patterns may not cause any differences in the relapse pattern after MS-MO.