无托槽隐形矫治器推上颌第二磨牙向后的三维有限元分析

Three-dimensional finite-element-analysis on pushing back maxillary second molar via invisible appliance withoutbrackets

目的研究无托槽隐形矫治器在推磨牙向后过程中生物力学机制,为正畸临床治疗提供思路。方法采集身体健康志愿者的影像数据,运用计算机软件进行三维重建,得到上颌牙列、牙槽骨、牙周膜及矫治器的有限元模型。根据是否配合Ⅱ类牵引分为2组进行比较分析。结果被远移磨牙牙冠产生了远中颊向、压入位移趋势,牙周膜应力最大处在远中牙颈部。上前牙在此过程中产生了近中唇向、压入的位移趋势,增加Ⅱ类牵引后前牙在三维方向上的位移量均减小,上前牙牙周膜所受应力大小及面积均减小。结论隐形矫治技术推磨牙远移过程中配合Ⅱ类牵引使上前牙区牙周膜唇侧受力减小,能有效抑制上前牙唇倾。

Objective This research explores the biomechanics of the invisible appliance in the process of pushing the second molar backward. The study provides useful advises for orthodontic treatment. Methods The three-dimensional image data were collected from an healthy volunteer. The finite-element models of the maxillary dentition,alveolar bone,periodontal ligament and appliance reconstruction was produced by computer software. All models are divided into two groups according to whether cooperate with class Ⅱ traction. Results The crowns of the second molars had a distal,buccal movement tendency. The greatest stress in periodontal ligament is on the distal cervical of tooth. The upper anterior displacement in three-dimensional direction is reduced in the group of class Ⅱ traction. The stress intensity and area in the periodontal ligament of the upper anterior teeth are reduced. Conclusion The stress on the labial periodontal ligament of upper anterior teeth are reduced in the process of pushing the second molars backwards if cooperated with class Ⅱ traction. Thus the upper anterior teeth labial inclination can be effectively restrained.