无托槽隐形矫治器配合微种植钉远移磨牙的三维有限元研究

Three-dimensional finite element study of combined use of micro-implant anchorage and invisible orthodontic appliance for distally displaced molars

目的 应用三维有限元模型研究无托槽隐形矫治器配合不同植入位置微种植钉远移磨牙时的初始上颌前牙位移及尖牙区应力分布情况。方法 选取于2021-02-16在大连市口腔医院正畸科就诊的需采用无托槽隐形矫治器行远移磨牙非减数正畸治疗的1例女性患者作为建模对象。构建三维有限元模型,模拟微种植钉位于第二前磨牙与第一磨牙之间、第一磨牙与第二磨牙之间,分别距离牙槽嵴顶4、6、8、10 mm的8种工况,并在微种植钉与尖牙唇面的舌侧扣之间加载1.47 N正畸力。分析加力1 s后8种工况的上颌前牙位移及尖牙牙周膜应力分布情况。结果 8种工况中,上颌中切牙均呈现牙冠唇向、牙根腭向的位移趋势;上颌中切牙牙冠唇向位移量随微种植钉高度的增加而减小,且微种植钉位于相对近中(上颌第二前磨牙与第一磨牙之间)时产生的位移量更小。8种工况中,上颌尖牙均呈现牙冠唇向、牙根腭向的位移趋势,且牙冠呈现唇倾趋势;上颌尖牙牙周膜最小主应力绝对值随微种植钉高度的增加而增大,且微种植钉位于相对近中时产生的最小主应力更大。结论 无托槽隐形矫治器配合微种植钉远移上颌磨牙时,配合本实验8种工况中相对近中的更高位微种植钉利于切牙转矩控制,配合相对远中的低位微种植钉利于维护尖牙区牙周组织健康。

Objective To investigate the effect of different micro-implant anchorage(MIA)positions on the molar displacement trend and stress distribution of anterior teeth when applying invisible orthodontics appliance combined with MIA by using three-dimensional finite element model.Methods One female patient requiring non-decreasing orthodontic treatment of distally displaced molars with invisible orthodontics appliance who visited the Department of Orthodontics of Dalian Stomatological Hospital on 2021-02-16 was selected as the modeling subject.A three-dimensional finite element model was constructed to simulate 8 working conditions with MIA located between the second premolar and the first molar,between the first molar and the second molar,and at 4,6,8,and 10 mm away from the top of the alveolar ridge,respectively,and 1.47 N orthodontic force was loaded between the MIA and the lingual clasps on the labial surfaces of the cuspids.The displacement of the maxillary anterior teeth and the distribution of the periodontal stress in the cuspids in the 8 working conditions after 1 s of loading were analyzed.Results In all eight conditions,the maxillary mesial incisors showed a trend of displacement in the labial direction of the crowns and palatal direction of the roots;the labial displacement of the crowns of the maxillary mesial incisors decreased with the increase in the height of the micro-implant anchorage,and the displacement was smaller when the anchorages were located in the relatively proximal mesial area(between the maxillary second premolar and the first molar).The maxillary cuspids showed a trend of displacement in the labial direction of the crowns and palatal direction of the roots,and the crowns showed a trend of labial inclination.The absolute values of the minimum principal stresses in the periodontium of the maxillary cuspids increased with the increase in the height of the micro-implant anchorages,and the minimum principal stresses were greater when the micro-implant anchorages were located in the relatively proximal center.Conclusion When the invisible orthodontic appliance is used with MIA for distal displacement of maxillary molars,the higher MIA position in the relatively proximal mesial region is good for the torque control of incisors,and the lower MIA position in the relatively distal mesial region is good for the maintenance of periodontal tissues in the cuspal region in the eight conditions of the present experiment.