滑动法内收下前牙过程中力学行为的有限元分析

Finite element analysis of mechanical characteristics during retracting mandibular incisors through sliding mechanics

目的:模拟临床加载力系统,研究应用种植体内收下前牙过程中,不同方向载荷作用下,牙及弓丝力学行为的变化。方法:建立含有托槽、弓丝、牵引钩、种植体的下牙列及下颌骨有限元模型。连接牵引钩上的点与种植体中心点来确定矫治力的方向,并通过改变牵引钩高度或种植体高度来改变矫治力的作用点和方向。分析计算每组加载力对牙的三维瞬间移动趋势、牙周膜的单元应力、弓丝的节点最大位移。采用SPSS13.0软件包对数据进行统计学分析。结果:经统计学分析,种植体高度及牵引钩高度的变化与各牙角位移及牙周膜应力间均有相关性(P<0.01),各牙在不同种植体高度,随着牵引钩高度变化而移动。随着牵引钩高度的增加,中切牙、侧切牙的移动趋势逐渐由近中舌侧倾斜变化为近中唇侧倾斜,而尖牙则向远中舌侧倾斜;第二前磨牙向近中舌侧倾斜;第一磨牙的近远中根均表现为远中颊侧倾斜。且远中倾斜角度随着前牙牵引钩高度的增加而减小。全牙弓牙周膜的最大应力始终出现在侧切牙的唇侧根尖1/3处;而尖牙、第一磨牙的牙周膜最大应力分别集中于牙槽嵴顶、根分叉处。结论:在临床治疗中,可通过改变前牙牵引钩的高度来实现前牙内收时的不同移动趋势,种植体支抗可有效控制后牙前移。

PURPOSE： To analyze the mechanical characteristic changes of teeth and arch under different loading direction during retracting mandibular incisors through implant, simulating clinical loading system. METHODS： Threedimensional finite element model, including brackets, archwire, crampable hooks and implants, was reconstructed. The force direction was determined by connecting the points in crampable hook and the center point of implant, and the force point and force direction were changed with the adjustment of the height of crampable hook and the height of implant, Then three-dimensional movement trend of teeth, stress distribution in periodontal membrane and the largest displacement of archwire nodes in each group were calculated and analyzed. SPSS13.0 software package was used for statistical analysis. RESULTS： It was found that the height of implant and the height of erampable hook were correlated with the movement of teeth and stress distribution in periodontal membrane （P〈0.01）. The movement trend of teeth in the condition of different height of implant and different height of crampable hook was illustrated as follows：（1）with the height increase of crampable hook, the movement trend of the central and lateral incisors varied from mesial lingual tipping to mesial labial tipping. However, canines tipped distally and lingually; the second premolars tipped mesially and lingually, and the first molar roots tipped distally and buccally with decreasing tipping angle. （2） The largest stress distribution in the whole arch was located in the labial apical one-third area of the lateral incisors, while that of canines and the first molars was located in the alveolar ridges and root bifurcations. CONCLUSIONS： These findings indicate that the different movement trend during retracting anterior teeth can be achieved through the adjustment of the height of crampable hook, and implant anchorage can effectively control anterior movement of the posterior teeth.Supported by Research Fund of Bureau of Science and Technology of Nantong City（Grant No.S40023）.