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目的:应用有限元分析法比较螺旋扩弓器前方牵引与无托槽隐形矫治器联合前方牵引治疗对替牙列骨性Ⅲ类错 上颌骨、上牙列的影响，以期为替牙期骨性Ⅲ类错 应用无托槽隐形矫治器提供临床参考。 方法:选取1例2024年1月于第四军医大学口腔医院正畸科就诊的替牙列骨性Ⅲ类错 患者（男性，10岁）的口腔颌面部锥形束CT资料，建立三维有限元模型。设计扩弓器前牵组（A组）和无托槽前牵组（B组），均设置双侧前磨躯扩弓0.25 mm，前方牵引力值分别为2.94 N（工况1）和4.90 N（工况2）。分析两种工况下两组模型上颌骨、上牙列的初始位移趋势。 结果:两种工况下两组上颌骨均表现为顺时针旋转、唇向位移趋势；无托槽前牵组上颌骨唇向位移更明显，为同种工况下扩弓器前牵组的2~3倍。两种工况下两组上颌牙列均表现为近中、颊向移动和前牙伸长、后牙压低趋势。工况1和工况2条件下，无托槽前牵组中切牙唇向位移量（-0.065、-0.089 mm）均大于扩弓器前牵组（-0.024、-0.024 mm）。两组工况下，冠状向上扩弓器前牵组后牙接近颊向整体移动（冠根位移比约为1∶1），无托槽前牵组则为颊向倾斜移动（冠根位移比约为2∶1）。随前牵力值增加，无托槽前牵组上颌骨、上牙列的位移趋势增加比扩弓器前牵组更明显。两种工况下无托槽前牵组前牙段牙周膜静水压力、牙槽骨等效应力均高于扩弓器前牵组，且主要集中于切牙唇侧颈部区域。结论:无托槽隐形矫治器联合前方牵引可对上颌骨产生向前的力量，但可伴上前牙唇倾，可作为替牙期骨性Ⅲ类错 矫形治疗措施的一种选择。

Objective:To observe the improvement of the growth and development of the maxilla and the upper dentition with clear aligners combined with anterior protractor for mixed dentition patients with Class Ⅲ skeletal malocclusion.Methods:A three-dimensional finite element model was established for Class Ⅲ mixed dentition patients with clear aligners combined with maxillary protractor. 4 groups of working conditions were set: Group A1: screw expander with protractor extended the arch horizontally by 0.25 mm and 300 g forward pull force; Group A2: screw expander with protractor extended the arch horizontally by 0.25 mm and 500 g forward pull force; Group B1: clear aligners with protractor expanded the arch horizontally by 0.25 mm and 300 g forward pull force; Group B2: clear aligners with protractor expanded the arch horizontally by 0.25 mm and 500 g forward pull force. The initial displacement trend of maxilla and maxillary dentition in each working condition was evaluated.Results:In the four groups, all maxilla showed clockwise rotation and labial inclination. The labial inclination of the maxilla was more significant in clear aligners with protractor group, about 2-3 times that in the fixed anterior retractor group. Maxillary dentition showed mesial and buccal displacement, with anterior teeth extrusion and posterior teeth intrusion. The labial displacement of incisor teeth of clear aligner with protractor group in sagittal direction was greater than that in screw protractor group. In the horizontal direction, the posterior teeth of screw protractor group moved close to the buccal bodily direction, while those of clear aligners with protractor group moved tilted towards the buccal direction. The forward displacement trend of maxilla and maxillary dentition in the 4 groups was more obvious with the increase of the anterior protractor value.Conclusions:clear aligner combined with anterior traction can produce the bony effect of maxillary development/growth, which can promote the maxillary growth forward and downward along the original growth direction in mixed dentition patients, and is an effective orthopedic treatment for skeletal Class Ⅲ malocclusion.