目的: 应用头颅侧位片和锥形束计算机体层摄影术(cone-beam computed tomography, CBCT)评价骨性Ⅱ类高角错患者术前正畸的下前牙去代偿效果和牙槽骨改建情况。方法: 从2017年1月至2022年8月在北京大学口腔医院完成术前正畸及正颌手术的骨性Ⅱ类高角错患者中, 筛选出30例术前正畸前后拍摄了头颅侧位片和CBCT的患者。测量术前正畸前后与下前牙角度及线距相关的头影测量项目, 包括: 下中切牙(L1)长轴-眶耳平面角(L1-Frankfort horizontal plane angle, L1-FH)、L1长轴-下颌平面角(L1-mandibular plane angle, L1-MP)、L1长轴-鼻根点-下齿槽座点连线交角(L1-nasion-supramental angle, L1-NB)、L1切缘到鼻根点-下齿槽座点连线的垂直距离(L1-NB线距)等。利用CBCT测量并评估术前正畸前后下前牙唇/舌侧骨开裂长度(d-La/d-Li)及骨开裂/骨开窗发生情况的变化。采用Pearson相关性分析, 评价L1的d-Li变化量与年龄、术前正畸疗程及治疗前头影测量项目之间的相关性, 筛选出与术前正畸牙周风险相关的因素。结果: 经过术前正畸治疗, L1-FH、L1-MP、L1-NB、L1-NB线距分别变化了11.56°±5.62°、-11.13°±5.53°、-11.57°±5.43°、(-4.99±1.89) mm, 差异均具有统计学意义(P < 0.05)。180个测量牙位中, 45个术前正畸前(T0)唇侧存在骨开裂/骨开窗, 而术前正畸后(T1)不再骨开裂/骨开窗; 142个T0时舌侧不存在骨开裂/骨开窗, 而T1时出现了骨开裂/骨开窗。术前正畸后下侧切牙(L2)、下尖牙(L3)及下前牙(L1+L2+L3)的d-La分别减小了(0.95±2.22) mm、(1.20±3.23) mm及(0.68±2.50) mm, 且差异均具有统计学意义(P < 0.05);术前正畸后L1、L2、L3及L1+L2+L3的d-Li分别增加了(4.43±1.94) mm、(4.53±2.35) mm、(3.19±2.80) mm及(4.05±2.46) mm, 差异均具有统计学意义(P < 0.05)。L1的d-Li变化量与治疗前的L1-FH值成正相关(r=0.373, P=0.042)。结论: 骨性Ⅱ类高角错患者在减数双侧下颌第一前磨牙后经过完善的术前正畸可以实现较为理想的下前牙去代偿效果, 但下前牙舌侧牙周风险升高。这种风险可能与治疗前下前牙相对眶耳平面的唇倾程度相关, 在进行正畸-正颌联合治疗设计时应重点关注。

Objective: To evaluate the decompensation effectiveness and alveolar bone remodeling of mandibular anterior teeth after preoperative orthodontic treatment in high-angle patients with skeletal class Ⅱ malocclusion using lateral cephalogram and cone-beam computed tomography (CBCT). Methods: Thirty high-angle patients with skeletal class Ⅱ malocclusion who had received preoperative orthodontic treatment and orthognathic surgery in Peking University School and Hospital of Stomatology between Ja-nuary 2017 and August 2022 and had taken lateral cephalogram and CBCT before and after preoperative orthodontic treatment were selected. Items were measured with lateral cephalogram including: The lower central incisor (L1)-Frankfort plane angle (L1-FH), the L1-mandibular plane angle (L1-MP), the L1-nasion-supramental angle (L1-NB) and the vertical distance from the incisal edge of lower central incisor to NB line (L1-NB distance), etc. The incidence of dehiscence/fenestration and the length of dehiscence at labial side (d-La) and lingual side (d-Li) were measured using CBCT. Pearson correlation analysis was used to evaluate the correlation between the changes of d-Li of L1 and age, duration of preoperative orthodontic treatment and the cephalometric measurements before preoperative orthodontic treatment to screen out risk factors affecting the periodontal risk of preoperative orthodontic treatment in high-angle patients with skeletal class Ⅱ malocclusions. Results: After preoperative orthodontic treatment, L1-FH, L1-MP, L1-NB and L1-NB distances changed by 11.56°±5.62°, -11.13°±5.53°, -11.57°±5.43° and (-4.99±1.89) mm, respectively, and the differences were all statistically significant (P < 0.05). Among the 180 measured mandibular anterior teeth, 45 cases with labial dehiscence/fenestration before preoperative orthodontic treatment (T0) had no longer labial dehiscence/fenestration after preope-rative orthodontic treatment (T1); 142 cases without lingual dehiscence/fenestration at T0 had lingual dehiscence/fenestration at T1. After preoperative orthodontic treatment, the d-La of lower lateral incisors (L2), lower canines (L3) and lower anterior teeth (L1+L2+L3) decreased by (0.95±2.22) mm, (1.20±3.23) mm and (0.68±2.50) mm, respectively, and the differences were statistically significant (P < 0.05); the d-Li of L1, L2, L3 and L1+L2+L3 increased by (4.43±1.94) mm, (4.53±2.35) mm, (3.19±2.80) mm and (4.05±2.46) mm, respectively, and the differences were statistically significant (P < 0.05). The increase of d-Li of L1 was positively correlated with L1-FH (r=0.373, P=0.042). Conclusion: This study showed that high-angle patients with skeletal class Ⅱ ma-locclusion could achieve ideal decompensation effect of mandibular anterior teeth after preoperative orthodontic treatment with bilateral mandibular first premolars extracted, but the lingual periodontal risk of mandibular anterior teeth was increased. This risk could be correlated to L1-FH before preoperative orthodontic treatment, which should be paid more attention in the design of orthodontic-orthognathic surgical treatment.