Abstract: Objective    To investigate the Von Mises stress values and the initial displacement of maxillary molar with mini-implants at different locations. Methods    Select a male patient who visited the Department of Stomatology at Xiamen Haicang Hospital on May 11，2022 due to the extension of the left maxillary first molar as the model. The three dimensional finite element model was constructed to simulate 6 situations；mini-implants were placed at 10 mm from alveolar ridge in palatal sides；the mini-implants were placed at different locations in vestibular sides（between the roots of the first and second molars or the second premolar and first molar）and different height（7，8，9 mm from alveolar ridge）；1 N backward force was exerted on palated and vestibular sides to analyze the initial displacement and Von Mises stress values of maxillary first molar. Results    The higher mini-implant position caused the lower Von Mises stress values and less palatal tipping of the maxillary first molar under the same force and location of mini-implant. The Von Mises stress values at the region of second premolar and first molar are less than the first and second molars from vestibular sides at the same height of alveolar ridge. Conclusion    When using mini-inplants to lower the maxillary first molar，as the implant height increases，the stress on the maxillary first molar gradually decreases and tends to move towards overall depression. Moreover，when implants are implanted between the maxillary first molar and the second premolar，a balanced stress distribution can be obtained.

Key words: mini-implant, 3D finite element analysis, intrusion, maxillary first molar

摘要： 目的    研究颊腭侧微种植体在不同近远中向位置及不同牙槽骨高度下，压低上颌第一磨牙时的应力分布及初始位移。方法    选取2022-05-11于厦门市海沧医院口腔科因左上颌第一磨牙伸长就诊的1例男性患者作为建模对象。构建三维有限元模型，模拟在腭侧距牙槽嵴顶10 mm，在颊侧分别为上颌第一磨牙和上颌第二磨牙之间及上颌第一磨牙和上颌第二前磨牙之间，且距牙槽嵴顶分别为7、8、9 mm的位置植入微种植体的6种工况，并对颊腭侧各施加1 N的压力。分析上颌第一磨牙各取值点的初始位移及牙周膜、牙根应力分布情况。结果    在力的大小不变，腭侧微种植体位置不变时，随着颊侧微种植体高度的增加，上颌第一磨牙所受应力逐渐减小，牙齿逐渐趋向整体压低；在相同牙槽嵴高度下，颊侧微种植体位于上颌第一磨牙与上颌第二前磨牙之间时，上颌第一磨牙所受的等效应力小于微种植体在上颌第一磨牙和上颌第二磨牙之间。结论    采用颊腭侧微种植体压低上颌第一磨牙时，在一定范围内随着微种植体植入高度的增加，上颌第一磨牙所受应力逐渐减小，并逐渐趋向于整体移动；且颊侧微种植体在上颌第一磨牙与上颌第二前磨牙之间时更能获得平衡的应力分布。

关键词: 微种植体, 三维有限元分析, 压低, 上颌第一磨牙