Forsus推上颌第一磨牙向远中瞬时移动趋势的力学仿真分析

The mechanical simulation analysis of instantaneous distal moving trend of the maxillary first molar in forsus

目的:构建具有一定粘弹塑性的Forsus推上颌第一磨牙向远中三维有限元模型,仿真模拟Forsus推上颌第一磨牙远中瞬时移动趋势,探讨Forsus远中移动上颌第一磨牙有利的加载方式,为临床应用提供一定的参考依据。方法:选择恒牙早期安氏Ⅱ类错畸形男性患者1名,螺旋CT扫描头颅后,经Mimics8.0、Abaqus6.5构建Forsus推上颌第一磨牙向远中的三维有限元模型,模拟单纯加载Forsus远中力、加载Forsus远中力+抗倾斜力矩、复合加载Forsus远中力+抗倾斜力矩+抗旋转力矩三种不同载荷作用下上颌第一磨牙的瞬时移动过程(加载合力大小300g,作用点位于冠颊面中心,加载时间为1s),经Abaqus6.5分析上颌第一磨牙远中移动的有利加载方式。结果:Forsus推上颌第一磨牙向远中时,不同的加载方式所产生的牙周膜应力分布不同。单纯加载Forsus远中力时,上颌第一磨牙发生较严重倾斜移动;加载Forsus远中力+抗倾斜力矩(Mt/F=9)时,上颌第一磨牙发生较严重扭转;复合加载Forsus远中力+抗倾斜力矩(Mt/F=9)+抗旋转力矩(Mr/F=5)时,上颌第一磨牙牙周膜韧带远中面承受的应力最小,第一磨牙近似远中平动。结论:Forsus导下颌向前时,在上颌第一磨牙处辅以一定的抗倾斜力矩和抗旋转力矩,可获得较有利的磨牙远中平动效果。

Objective： To simulate the instantaneous distal moving trend of the maxillary first molar based on the three-dimensional finite element model（ 3-FEM ） of Forsus distalizing the maxillary first molar with some visco-elastic-plastic characters and explore the favorable loading mode of molar distal movement in Forsus in order to provide biomechanical basis for clinical practice. Methods： A male patient with Class Ⅱ malocclusion was selected. The 3-FEM of Forsus distalizing the maxillary first molar was built through spiral CT scanning, Mimics8.0, and Abaqus6.5 software. This study simulated instantaneous distal moving process of the maxillary first molar under three dif- ferent loading modes （ loading force was 300 g, point of force was on the center of the crown＇ s buccal surface, loading time was 1 s ）, which included a distalizing force, a distalizing force ＋ counterrotation moment, a distalizing force ＋ countertipping moment ＋ counterrotation moment. Results： When Forsus distalized the maxillary first molar, different loading modes lead to different PDL stress distributions. When the model was added by a distalizing force, the maxillary first molar would be relatively seriously inclined; when added by a distalizing force ＋counterrotation moment （ Mt/F =9 ）, the maxillary first molar would be relatively seriously rotated and when added by a distalizing force ＋ countertipping moment（ Mt/F =9 ） ＋ counterrotation moment（ Mr/F = 5 ）, the distal surface of the PDL would bear the lightest stress, and the first molar would achieve approximate translation movement.Conclusion： When mandible is guided forward by Forsus, the maxillary first molar would achieve better molar translation effect if added certain countertipping and counterrotation moment .