Ma Y N, Qiang R Y, Jin Z L
Department of Orthodontics, School of Stomatology, The Fourth Military Medical University, State Key Laboratory of Oral & Maxillofacial Reconstruction and Regeneration, National Clinical Research Center for Oral Diseases, Shaanxi Clinical Research Center for Oral Diseases, Xi'an 710032, China.
Zhonghua Kou Qiang Yi Xue Za Zhi. 2024 Sep 9;59(9):919-926. doi: 10.3760/cma.j.cn112144-20240516-00207.
To compare the effects of expansion screw with maxillary protractor and clear aligners combined with maxillary protractor on the maxilla and maxillary dentition of mixed dentition patients with class Ⅲ skeletal malocclusion using finite element analysis, further providing clinical guidance for clear aligner treatment. A finite element model was established based on maxillofacial cone-beam CT data of a 10-year-old boy with mixed dentition, class Ⅲ skeletal malocclusion, who visited Department of Orthodontics, School of Stomatology, The Fourth Military Medical University in January, 2024. The expander with protractor group (group A) and the clear aligners with protractor group (group B) were divided. The arch was extended by 0.25 mm in both groups, and the forward pull force was 2.94 N (working condition 1) and 4.90 N (working condition 2), respectively. The initial displacement trend of maxilla and maxillary dentition in two groups under two working conditions were evaluated. Under two working conditions, the maxilla of both groups showed clockwise rotation and labial inclination. The labial inclination of maxilla was more significant in clear aligners with protractor group, about 2.2-3.0 times that of expander with protractor group under the same working condition. Maxillary dentition showed mesial and buccal displacement, with anterior teeth extrusion and posterior teeth intrusion in two groups under two working conditions. Under the working condition 1 and 2, the labial displacement of central incisor of clear aligners with protractor group (-0.065, -0.089 mm) were greater than that in expander with protractor group (-0.024, -0.024 mm). Under two working conditions, the posterior teeth of expander with protractor group moved close to the buccal bodily direction, while those of clear aligners with protractor group moved tilted towards the buccal direction in the horizontal direction. The forward displacement trend of maxilla and maxillary dentition in clear aligners with protractor group was more obvious than expander with protractor group with the increase of the forward pull force. Under two working conditions, the anterior teeth' s hydrostatic stress of periodontal membrane and the equivalent stress of alveolar bone in clear aligners with protractor group were higher than those in expander with protractor group, mainly concentrated on the labial cervical region of the incisor. Clear aligners combined with maxillary protractor can produce forward force on the maxilla, but labial inclination occurs in the anterior teeth. It can be an effective orthopedic treatment strategy for mixed dentition patients with class Ⅲ skeletal malocclusion.
为采用有限元分析比较扩弓螺旋器联合上颌前牵引器与透明矫治器联合上颌前牵引器对Ⅲ类骨性错牙合混合牙列患者上颌骨及上颌牙列的影响，进一步为透明矫治器治疗提供临床指导。基于一名2024年1月就诊于第四军医大学口腔医学院正畸科的10岁混合牙列、Ⅲ类骨性错牙合男孩的颌面锥形束CT数据建立有限元模型。分为扩弓器联合前牵引器组（A组）和透明矫治器联合前牵引器组（B组）。两组均将牙弓扩展0.25 mm，前牵引力分别为2.94 N（工况1）和4.90 N（工况2）。评估两组在两种工况下上颌骨及上颌牙列的初始位移趋势。在两种工况下，两组上颌骨均表现为顺时针旋转及唇倾。透明矫治器联合前牵引器组上颌骨唇倾更明显，在相同工况下约为扩弓器联合前牵引器组的2.2 - 3.0倍。上颌牙列表现为近中及颊向位移，两组在两种工况下均出现前牙伸长及后牙压低。在工况1和2下，透明矫治器联合前牵引器组中切牙的唇向位移（-0.065，-0.089 mm）大于扩弓器联合前牵引器组（-0.024，-0.024 mm）。在两种工况下，扩弓器联合前牵引器组后牙向颊侧整体方向移动，而透明矫治器联合前牵引器组后牙在水平方向上向颊侧倾斜移动。随着前牵引力增大，透明矫治器联合前牵引器组上颌骨及上颌牙列的前向位移趋势比扩弓器联合前牵引器组更明显。在两种工况下，透明矫治器联合前牵引器组中切牙牙周膜的静水压力及牙槽骨的等效应力均高于扩弓器联合前牵引器组，主要集中在切牙唇侧颈部区域。透明矫治器联合上颌前牵引器可对上颌骨产生前向力，但前牙出现唇倾。对于Ⅲ类骨性错牙合混合牙列患者，它可以是一种有效的正畸治疗策略。
