Abstract：
OBJECTIVE: Facial asymmetry is common in Class III patients requiring orthognathic surgery. This study aimed to analyze jaw bone position after surgical-orthodontic treatment in three types of skeletal Class III asymmetry patients.
METHODS: The retrospective study included 30 Class III patients who underwent surgical-orthodontic treatment comprising LeFort I osteotomy and bilateral sagittal split osteotomy (BSSO) without genioplasty. Cone-beam computed tomography (CBCT) images obtained before surgery (T1) and after post-surgical orthodontic treatment (T2) were superimposed with voxel-based registration. Patients were classified into three groups based on T1 CBCT scans. Groups 1 and 2 exhibited menton and ramus deviated to the same side. Menton deviation was larger than ramus width asymmetry in group 1, while the reverse was true for group 2. Group 3 had menton deviation contralateral to the side with greater ramus width.
RESULTS: Menton deviation after treatment was improved in all groups. Ramus width asymmetry and coronal ramus angle difference decreased in groups 1 and 2. Neither improvement nor deterioration of ramus width asymmetry was noted for group 3. Comparing to groups 1 and 2, group 3 had greater roll and yaw rotations of distal segment, more upward pitch of proximal segment on chin deviation side, and largest inward yaw as well as backward translation of proximal segment on non-deviation side.
CONCLUSIONS: The positional changes of osteotomy segments differed among three types of mandibular asymmetry. Special attention should be given to the atypical mandibular asymmetry with mandibular body and ramus deviating to opposite directions during surgical correction of jaw deflection.
METHODS: The retrospective study included 30 Class III patients who underwent surgical-orthodontic treatment comprising LeFort I osteotomy and bilateral sagittal split osteotomy (BSSO) without genioplasty. Cone-beam computed tomography (CBCT) images obtained before surgery (T1) and after post-surgical orthodontic treatment (T2) were superimposed with voxel-based registration. Patients were classified into three groups based on T1 CBCT scans. Groups 1 and 2 exhibited menton and ramus deviated to the same side. Menton deviation was larger than ramus width asymmetry in group 1, while the reverse was true for group 2. Group 3 had menton deviation contralateral to the side with greater ramus width.
RESULTS: Menton deviation after treatment was improved in all groups. Ramus width asymmetry and coronal ramus angle difference decreased in groups 1 and 2. Neither improvement nor deterioration of ramus width asymmetry was noted for group 3. Comparing to groups 1 and 2, group 3 had greater roll and yaw rotations of distal segment, more upward pitch of proximal segment on chin deviation side, and largest inward yaw as well as backward translation of proximal segment on non-deviation side.
CONCLUSIONS: The positional changes of osteotomy segments differed among three types of mandibular asymmetry. Special attention should be given to the atypical mandibular asymmetry with mandibular body and ramus deviating to opposite directions during surgical correction of jaw deflection.
摘要：
目的：面部不对称在需要正颌手术的III类患者中很常见。本研究旨在分析三种类型的III类骨骼不对称患者在手术-正畸治疗后的颌骨位置。
方法：回顾性研究包括30例III级患者，这些患者接受了手术-正畸治疗，包括LeFortI截骨术和双侧矢状面劈开截骨术（BSSO），而没有进行基因成形术。手术前（T1）和手术后正畸治疗（T2）获得的锥形束计算机断层扫描（CBCT）图像与基于体素的配准叠加。根据T1CBCT扫描将患者分为三组。第1组和第2组表现出门神和支偏向同一侧。第1组的Menton偏差大于支宽度不对称，而第2组的情况则相反。第3组对侧有较大的分支宽度。
结果：各组治疗后Menton偏差均有改善。第1组和第2组的支宽度不对称性和冠状支角度差减小。第3组没有发现支宽度不对称性的改善或恶化。与第1组和第2组相比，第3组远端侧倾和偏航旋转更大，下巴偏离侧的近端向上的螺距更大，和最大的向内偏航以及向后平移近端在非偏离侧。
结论：三种下颌不对称类型的截骨节段的位置变化不同。在下颌偏转的手术矫正过程中，应特别注意下颌不对称，下颌体和支向相反方向偏离。
方法：回顾性研究包括30例III级患者，这些患者接受了手术-正畸治疗，包括LeFortI截骨术和双侧矢状面劈开截骨术（BSSO），而没有进行基因成形术。手术前（T1）和手术后正畸治疗（T2）获得的锥形束计算机断层扫描（CBCT）图像与基于体素的配准叠加。根据T1CBCT扫描将患者分为三组。第1组和第2组表现出门神和支偏向同一侧。第1组的Menton偏差大于支宽度不对称，而第2组的情况则相反。第3组对侧有较大的分支宽度。
结果：各组治疗后Menton偏差均有改善。第1组和第2组的支宽度不对称性和冠状支角度差减小。第3组没有发现支宽度不对称性的改善或恶化。与第1组和第2组相比，第3组远端侧倾和偏航旋转更大，下巴偏离侧的近端向上的螺距更大，和最大的向内偏航以及向后平移近端在非偏离侧。
结论：三种下颌不对称类型的截骨节段的位置变化不同。在下颌偏转的手术矫正过程中，应特别注意下颌不对称，下颌体和支向相反方向偏离。
