Jihyun Lee1, Yong-Il Kim2, Dae-Seok Hwang3, Ki Beom Kim4, Soo-Byung Park5. 1. Postgraduate student, Department of Orthodontics, Pusan National University Hospital, Busan, South Korea. 2. Assistant professor, Department of Orthodontics, Dental Research Institute, Pusan National University Dental Hospital, Busan, South Korea. Electronic address: kimyongil@pusan.ac.kr. 3. Assistant professor, Department of Oral & Maxillofacial Surgery, Pusan National University Hospital, Busan, South Korea. 4. Associate professor, Department of Orthodontics, Center for Advanced Dental Education, St Louis University, St Louis, Mo. 5. Professor, Department of Orthodontics, Pusan National University Dental Hospital, Yangsan, South Korea.
Abstract
INTRODUCTION: The purposes of this study were to investigate the relationship between occlusal vertical dimension (VD) changes and postsurgical skeletal changes in the surgery-first approach and to derive regression models for the final mandibular setback at B-point. METHODS: This retrospective study included 40 patients (16 men, 24 women; ages, 22.6 ± 4.0 years) who had undergone a bimaxillary surgery-first approach. Using cephalograms generated from cone-beam computed tomography representing the presurgical, postsurgical, and posttreatment stages, skeletal landmarks in the maxilla and mandible were investigated to derive multivariate linear regression-based prediction models. Additionally, a patient classification based on the VD was established and verified to generate regression models for the classified groups. RESULTS: For the nonincreased VD group, the surgical setback of B-point was its predictor for the final mandibular setback (R(2) at 92%). Meanwhile, the final mandibular setback of the increased VD group was predicted according to the surgical upward movement of pogonion, the postsurgical horizontal position of A-point, and the postsurgical vertical position of the coronoid process (R(2) at 94%). CONCLUSIONS: The results of this study support the clinical observation that the more increased the vertical occlusal dimension after surgery, the less predictable the position of B-point at the posttreatment stage.
INTRODUCTION: The purposes of this study were to investigate the relationship between occlusal vertical dimension (VD) changes and postsurgical skeletal changes in the surgery-first approach and to derive regression models for the final mandibular setback at B-point. METHODS: This retrospective study included 40 patients (16 men, 24 women; ages, 22.6 ± 4.0 years) who had undergone a bimaxillary surgery-first approach. Using cephalograms generated from cone-beam computed tomography representing the presurgical, postsurgical, and posttreatment stages, skeletal landmarks in the maxilla and mandible were investigated to derive multivariate linear regression-based prediction models. Additionally, a patient classification based on the VD was established and verified to generate regression models for the classified groups. RESULTS: For the nonincreased VD group, the surgical setback of B-point was its predictor for the final mandibular setback (R(2) at 92%). Meanwhile, the final mandibular setback of the increased VD group was predicted according to the surgical upward movement of pogonion, the postsurgical horizontal position of A-point, and the postsurgical vertical position of the coronoid process (R(2) at 94%). CONCLUSIONS: The results of this study support the clinical observation that the more increased the vertical occlusal dimension after surgery, the less predictable the position of B-point at the posttreatment stage.