矩形附件在矫正尖牙扭转中作用的有限元分析

Three-dimensional finite element analysis of the role of rectangular attachment in correcting canine torsion

目的通过有限元分析法探究矩形附件在隐形矫治中矫正上颌尖牙扭转的作用。方法实验分为无附件的空白对照组和不同尺寸及放置方向的矩形附件组,建立左上颌尖牙、矩形附件及与之相适应的矫治器等有限元模型;将各组矫治器以尖牙牙体长轴为旋转中心轴,施加一个2°顺时针旋转位移;在Mentat软件中进行模拟运算,观察各组模型随附件的改变发生的应力、位移变化。结果①无论有无附件,尖牙位移及牙周膜应力分布趋势一致,但附件组的尖牙位移值及牙周膜各种应力值均大于未使用附件组,其中3 mm垂直附件组的最大位移值为无附件组的8.42倍;②同尺寸的矩形附件放置方向不同时,4 mm和5 mm组水平向放置的最大位移值均大于垂直向,而3 mm组两种放置方向相差不大;当矩形附件水平向放置时,尖牙最大位移值:3 mm组>4 mm组>5 mm组,而当垂直向放置时变化不大。结论①矩形附件的使用不会改变初戴矫治器瞬间尖牙的移动方式,仅是在矫治器矫正尖牙扭转时起了协同作用;②矩形附件水平向放置相对垂直向放置更有利于矫治器矫正上颌尖牙的扭转,随着附件水平宽度的增加,其协同作用越明显。

Objective To explore the role of rectangular attachment in correcting maxillary canine torsion in clear aligner by finite element analysis.Methods There were blank control group without attachments and rectangular attachment group with different sizes and directions in this experiment.The three-dimensional finite element model of the left maxillary canine,rectangular attachment with different situation according to the rectangular attachment group and the models of clear aligners were established.Two degrees clockwise rotation of the tooth axis was applied to the clear aligner.The simulation was performed in the MSC.Marc.Mentat software to observe the changes in stress and displacement of each model with the change of the attachment.Results①The trend of canine displacement and periodontal membrane stress distribution was consistent with or without the attachment,but the canine displacement values and periodontal membrane stress values of the rectangular attachment group were larger than those of the blank control group.The maximum displacement value of the canine with 3 mm-vertical rectangular attachment was 8.42 times of that without the attachment.②When the rectangular attachments of the same size were placed in different directions,the maximum displacement values of the horizontal placement of the 4 mm and 5 mm groups were larger than the vertical direction,and the two placement directions of the 3 mm group were not much different;When the attachment was placed horizontally,the maximum displacement of the canine was 3 mm>4 mm>5 mm,but it did not change much when placed vertically.Conclusion①The use of rectangular attachments do not change the way of movement of instant canines.It only plays a synergistic role when the appliance corrects the torsion of the canine.②The horizontal attachment of the rectangular attachment is more favorable to correct maxillary canine torsion.The synergy is more obvious as the horizontal width of the attachment increases.