Yu-Fang Liao1,2,3,4, Piengkwan Atipatyakul5, Yi-Hsuan Chen6,7,8, Ying-An Chen7,8,9, Chuan-Fong Yao7,8,9, Yu-Ray Chen5,7,8,9. 1. Graduate Institute of Dental and Craniofacial Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan. yufang@cgmh.org.tw. 2. Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, No. 123, Dinghu Road, Guishan District, Taoyuan, 333, Taiwan. yufang@cgmh.org.tw. 3. Craniofacial Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan. yufang@cgmh.org.tw. 4. Craniofacial Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan. yufang@cgmh.org.tw. 5. Graduate Institute of Dental and Craniofacial Science, College of Medicine, Chang Gung University, Taoyuan, Taiwan. 6. Department of Craniofacial Orthodontics, Chang Gung Memorial Hospital, No. 123, Dinghu Road, Guishan District, Taoyuan, 333, Taiwan. 7. Craniofacial Research Center, Chang Gung Memorial Hospital, Linkou, Taiwan. 8. Craniofacial Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan. 9. Department of Plastic and Reconstructive Surgery, Chang Gung Memorial Hospital, Linkou, Taiwan.
Abstract
OBJECTIVES: Surgery-first orthognathic surgery is rarely used in class III asymmetry due to concerns of reduced skeletal stability from unstable surgical occlusion. This study aimed to evaluate if skeletal stability after surgery-first orthognathic surgery is related to virtual surgical occlusal contact or surgical change. MATERIALS AND METHODS: We studied 58 adults with class III asymmetry, consecutively corrected by Le Fort I osteotomy and bilateral sagittal split osteotomy using a surgery-first approach. Dental casts were manually set to measure virtual surgical occlusal contact including contact distribution, contact number, and contact area. Cone-beam computed tomography taken before treatment, 1-week post-surgery, and after treatment was used to measure surgical change and post-surgical stability of the maxilla and mandible in translation (left/right, posterior/anterior, superior/inferior) and rotation (pitch, roll, yaw). The relationship between skeletal stability and surgical occlusal contact or surgical change was evaluated with correlation analysis. RESULTS: Significant instability was found in the mandible but not in the maxilla. No correlation was found between the maxillary or mandibular stability and surgical occlusal contact (all p > 0.01). However, a significant correlation was found between the maxillary (roll and yaw) or mandibular (shift, roll and pitch) stability and its surgical change (all p < 0.001). CONCLUSIONS: In correction of class III asymmetry with surgery-first bimaxillary surgery, the skeletal stability is not related to the virtual surgical occlusal contact, but surgical skeletal change. CLINICAL RELEVANCE: Planned over-correction is a reasonable option for correction of severe shift or roll mandibular asymmetry in bimaxillary surgery for class III deformity.
OBJECTIVES: Surgery-first orthognathic surgery is rarely used in class III asymmetry due to concerns of reduced skeletal stability from unstable surgical occlusion. This study aimed to evaluate if skeletal stability after surgery-first orthognathic surgery is related to virtual surgical occlusal contact or surgical change. MATERIALS AND METHODS: We studied 58 adults with class III asymmetry, consecutively corrected by Le Fort I osteotomy and bilateral sagittal split osteotomy using a surgery-first approach. Dental casts were manually set to measure virtual surgical occlusal contact including contact distribution, contact number, and contact area. Cone-beam computed tomography taken before treatment, 1-week post-surgery, and after treatment was used to measure surgical change and post-surgical stability of the maxilla and mandible in translation (left/right, posterior/anterior, superior/inferior) and rotation (pitch, roll, yaw). The relationship between skeletal stability and surgical occlusal contact or surgical change was evaluated with correlation analysis. RESULTS: Significant instability was found in the mandible but not in the maxilla. No correlation was found between the maxillary or mandibular stability and surgical occlusal contact (all p > 0.01). However, a significant correlation was found between the maxillary (roll and yaw) or mandibular (shift, roll and pitch) stability and its surgical change (all p < 0.001). CONCLUSIONS: In correction of class III asymmetry with surgery-first bimaxillary surgery, the skeletal stability is not related to the virtual surgical occlusal contact, but surgical skeletal change. CLINICAL RELEVANCE: Planned over-correction is a reasonable option for correction of severe shift or roll mandibular asymmetry in bimaxillary surgery for class III deformity.