Objective:To evaluate the feasibility of three-dimensional measurement in the study of jaw stability in patients with skeletal Class Ⅲ malocclusion after orthognathic surgery, and to analysis the jaw relapse of risk factors.Methods:Patients with skeletal Class Ⅲ malocclusion who underwent bimaxillary surgery in Department of Oral and Maxillofacial Surgery, Nanjing Stomatological Hospital, from July 2019 to December 2019 were included. CT data at 1 week preoperative (T0), 3 days after surgery (T1), and 6-12 months after surgery (T2) were collected respectively. The 3D model was constructed by 3D Slicer, and the movement of maxilla and mandible after surgery was measured by Geomagic Qualify. The paired student t-test, Wilcoxon rank sum test and Pearson correlation was performed in this study. P<0.05 was considered statistically significant. Results:A total of 15 patients were included, including 5 males and 10 females. The age is from 18 to 25 year old. The average age is 21.3. In horizontal direction, the RGo coordinate has significant difference between T1[(-50.47±4.44) mm] and T2[(-50.06±4.66) mm] ( t=2.948, P=0.011), while all other landmarks have no significantly statistic difference. In the anteroposterior direction, there were significant differences for all maxillary landmarks between T1 with T2 ( P< 0.05). The relapse rates at point of A, Rp, Lp, RMF and LMF were 37.7 %(1.36/3.61), 35.7%(1.15/3.22), 25.4%(0.84/3.31), 26.9%(0.84/3.12), 14.0%(0.41/2.92), respectively. There were significant differences in all mandibular landmarks between T1 with T2 ( P<0.01). The relapse rates at point of B, Pog, Gn, Me, RGo and LGo were respectively 36.9%(1.75/4.74), 53.9%(2.45/4.55), 55.5%(2.72/4.90), 61.7%(2.90/4.70), 85.3%(2.20/2.58), 93.4%(2.40/2.57). The distance of skeletal relapse movement was significantly correlated with the surgery-induced distance ( r: 0.572-0.736, P<0.05). In the vertical direction, there was no significant difference of maxillary landmarks between T1 with T2 ( P > 0.05). For B, Pog, Gn and Me points, there were statistically significant differences ( P< 0.01). From T1 to T2, the mandible has tendency of counter-clockwise rotation. Conclusions:The three-dimensional measurement can accurately reflect the three-dimensional changes of jaw in patients with skeletal Class Ⅲ malocclusion after bimaxillary surgery. No significantly statistic relapse was in horizontal direction, while obvious relapse was occurred in anteroposterior directions. The counter-clockwise rotation of mandible was shown in vertical direction.

Objective:To evaluate the feasibility of three-dimensional measurement in the study of jaw stability in patients with skeletal Class Ⅲ malocclusion after orthognathic surgery, and to analysis the jaw relapse of risk factors.Methods:Patients with skeletal Class Ⅲ malocclusion who underwent bimaxillary surgery in Department of Oral and Maxillofacial Surgery, Nanjing Stomatological Hospital, from July 2019 to December 2019 were included. CT data at 1 week preoperative (T0), 3 days after surgery (T1), and 6-12 months after surgery (T2) were collected respectively. The 3D model was constructed by 3D Slicer, and the movement of maxilla and mandible after surgery was measured by Geomagic Qualify. The paired student t-test, Wilcoxon rank sum test and Pearson correlation was performed in this study. P<0.05 was considered statistically significant. Results:A total of 15 patients were included, including 5 males and 10 females. The age is from 18 to 25 year old. The average age is 21.3. In horizontal direction, the RGo coordinate has significant difference between T1[(-50.47±4.44) mm] and T2[(-50.06±4.66) mm] ( t=2.948, P=0.011), while all other landmarks have no significantly statistic difference. In the anteroposterior direction, there were significant differences for all maxillary landmarks between T1 with T2 ( P< 0.05). The relapse rates at point of A, Rp, Lp, RMF and LMF were 37.7 %(1.36/3.61), 35.7%(1.15/3.22), 25.4%(0.84/3.31), 26.9%(0.84/3.12), 14.0%(0.41/2.92), respectively. There were significant differences in all mandibular landmarks between T1 with T2 ( P<0.01). The relapse rates at point of B, Pog, Gn, Me, RGo and LGo were respectively 36.9%(1.75/4.74), 53.9%(2.45/4.55), 55.5%(2.72/4.90), 61.7%(2.90/4.70), 85.3%(2.20/2.58), 93.4%(2.40/2.57). The distance of skeletal relapse movement was significantly correlated with the surgery-induced distance ( r: 0.572-0.736, P<0.05). In the vertical direction, there was no significant difference of maxillary landmarks between T1 with T2 ( P > 0.05). For B, Pog, Gn and Me points, there were statistically significant differences ( P< 0.01). From T1 to T2, the mandible has tendency of counter-clockwise rotation. Conclusions:The three-dimensional measurement can accurately reflect the three-dimensional changes of jaw in patients with skeletal Class Ⅲ malocclusion after bimaxillary surgery. No significantly statistic relapse was in horizontal direction, while obvious relapse was occurred in anteroposterior directions. The counter-clockwise rotation of mandible was shown in vertical direction.