Liu Lijuan, Liu Yuting, Guo Kai, Ma Haojie, Yang Fanghong
Department of Orthodontics, Weifang People's Hospital, Shandong Second Medical University, Weifang, Shandong Province, China.
Department of stomatology, Weifang maternal and Child Health Hospital, Weifang, Shandong Province, China.
PLoS One. 2025 May 7;20(5):e0322551. doi: 10.1371/journal.pone.0322551. eCollection 2025.
The camouflage treatment of skeletal class III malocclusion can include both premolar extraction and mandibular third molar extraction-based approaches. This study aimed to compare an all four second premolar extraction approach with a mandibular third molar extraction and temporary anchorage devices (TADs)-based approach for compensatory orthodontic treatment in mild to moderate skeletal class III malocclusion.
31 subjects (mean age = 19.65 ± 3.91 years, male = 12, female = 19) with skeletal class III malocclusion were included in this retrospective, observational study. Lateral cephalograms taken before and after treatment were used to perform measurements for 7 dental indicators, 9 skeletal indicators, and 5 soft tissue indicators. Statistical analyses were performed to compare the cephalometric measurements between groups.
The patients' profiles were improved after treatment, and molars reached a neutral occlusal relationship. Dental cephalometric measurements showed that mandibular incisor to mandibular plane angle (IMPA) (-7.73 ± 4.72°), lower incisor-Nasion-B point angle (L1-NB angle) (-8.36 ± 4.57°),and the lower incisor-Nasion-B point distance (L1-NB distance) (-2.02 ± 1.42 mm) all significantly reduced (P < 0.05) in the premolar extraction group, while the changes were non-significant in the mandibular third molar extraction group, and the between-group differences were significant. The angle between the long axis of upper incisors and that of lower incisors (U1-L1) increased significantly (7.76 ± 8.55°) in the premolar extraction group but decreased significantly in the mandibular third molar extraction group (-4.64 ± 5.96°) (P < 0.05). Skeletal cephalometric measurements showed that Sella-Nasion-B point angle (SNB), decreased (premolar extraction group: -1.43 ± 0.87°, mandibular third molar extraction group: -0.71 ± 0.73°), A point-Nasion-B point angle (ANB) increased (premolar extraction group: 1.01 ± 0.86°, mandibular third molar extraction group: 1.22 ± 0.93°) and Wits increased (premolar extraction group: 1.39 ± 0.93 mm, mandibular third molar extraction group: 1.00 ± 0.60 mm) significantly in both groups, P < 0.05; with a significantly larger decrease in SNB in the premolar extraction group (P < 0.05). Soft tissue measurement items showed lower lip eversion (LL-E) decreased (premolar extraction group: 1.77 ± 1.61 mm, mandibular third molar extraction group: 0.76 ± 1.14 mm) and Lip Difference increased (premolar extraction group: 2.30 ± 0.58 mm, mandibular third molar extraction group: (2.01 ± 0.52 mm) significantly in both groups (P < 0.05), with between-group differences non-significant. Analysis of co-variance accounting for the pre-treatment values as the covariate, showed significant effects of the treatment group for the parameters IMPA, L1-NB (mm), L1-NB (°), U1-L1(°), SNA, SNB, and Wits value.
For mild and moderate skeletal class III malocclusion patients, both premolar extraction and mandibular third molar extraction with TAD-based approaches showed good clinical outcomes. The premolar extraction group showed greater SNB angle and compensatory lingual inclination of the lower incisors, along with significant reduction in OP-SN angle in the mandibular third molar extraction group, which contributed to the counterclockwise movement of the occlusal plane. Soft tissue changes mainly included improvements in lower lip protrusion with no significant differences noted between the two groups.
骨性III类错牙合畸形的掩饰性治疗可包括拔除前磨牙和基于拔除下颌第三磨牙的方法。本研究旨在比较全口四颗第二前磨牙拔除方法与基于拔除下颌第三磨牙及临时支抗装置（TADs）的方法在轻中度骨性III类错牙合畸形代偿性正畸治疗中的效果。
本回顾性观察研究纳入了31例骨性III类错牙合畸形患者（平均年龄=19.65±3.91岁，男性12例，女性19例）。治疗前后拍摄的头颅侧位片用于测量7项牙齿指标、9项骨骼指标和5项软组织指标。进行统计分析以比较两组间的头影测量结果。
治疗后患者的面部轮廓得到改善，磨牙达到中性咬合关系。牙齿头影测量显示，前磨牙拔除组的下颌切牙与下颌平面角（IMPA）（-7.73±4.72°）、下切牙-鼻根点-B点角（L1-NB角）（-8.36±4.57°）以及下切牙-鼻根点-B点距离（L1-NB距离）（-2.02±1.42mm）均显著减小（P<0.05），而下颌第三磨牙拔除组的变化不显著，两组间差异有统计学意义。前磨牙拔除组上切牙长轴与下切牙长轴之间的夹角（U1-L1）显著增大（7.76±8.55°），而下颌第三磨牙拔除组则显著减小（-4.64±5.96°）（P<0.05）。骨骼头影测量显示，两组的蝶鞍-鼻根点-B点角（SNB）均减小（前磨牙拔除组：-1.43±0.87°，下颌第三磨牙拔除组：-0.71±0.73°），A点-鼻根点-B点角（ANB）均增大（前磨牙拔除组：1.01±0.86°，下颌第三磨牙拔除组：1.22±0.93°），Wits值均增大（前磨牙拔除组：1.39±0.93mm，下颌第三磨牙拔除组：1.00±0.60mm），P<0.05；前磨牙拔除组的SNB减小更显著（P<0.05）。软组织测量项目显示，两组的下唇外翻（LL-E）均减小（前磨牙拔除组：1.77±1.61mm，下颌第三磨牙拔除组：0.76±1.14mm），唇差值均增大（前磨牙拔除组：2.30±0.58mm，下颌第三磨牙拔除组：（2.01±0.52mm），P<0.05，两组间差异无统计学意义。以治疗前值作为协变量的协方差分析显示，治疗组对IMPA、L1-NB（mm）、L1-NB（°）、U1-L1（°）、SNA、SNB和Wits值等参数有显著影响。
对于轻中度骨性III类错牙合畸形患者，拔除前磨牙和基于TADs拔除下颌第三磨牙的方法均显示出良好的临床效果。前磨牙拔除组的SNB角更大，下切牙有代偿性舌倾，而下颌第三磨牙拔除组的OP-SN角显著减小，这有助于咬合平面逆时针旋转。软组织变化主要包括下唇前突改善，两组间无显著差异。
