Jeon P D, Turley P K, Moon H B, Ting K
Section of Orthodontics, University of California, Los Angeles, USA.
Am J Orthod Dentofacial Orthop. 1999 Mar;115(3):267-74. doi: 10.1016/s0889-5406(99)70328-8.
The aim of this study was to simulate the stress response in the periodontium of the maxillary first molar to different moment to force ratios, and to determine the moment to force ratio for translational movement of the tooth by means of the finite element method. The three-dimensional finite element model of the maxillary first molar consisted of 3097 nodes and 2521 isoparametric eight-node solid elements. The model was designed to dissect the periodontal ligament, root, and alveolar bone separately. The results demonstrate the sensitivity of the periodontium to load changes. The stress pattern in the periodontal ligament for a distalizing force without counterbalancing moments showed high concentration at the cervical level of the distobuccal root due to tipping and rotation of the tooth. After various counterrotation as well as countertipping moments were applied, an even distribution of low compression on the distal side of the periodontal ligament was obtained at a countertipping moment to force ratio of 9:1 and a counterrotation moment to force ratio of 5:1. This lower and uniform stress in the periodontal ligament implies that a translational tooth movement may be achieved. Furthermore, high stress concentration was observed on the root surface at the furcation level in contrast with anterior teeth reported to display high concentration at the apex. This result may suggest that the root morphology of the maxillary first molar makes it less susceptible to apical root resorption relative to anterior teeth during tooth movement. The stress patterns in the periodontal ligament corresponded with the load types; those on the root appeared to be highly affected by bending and the high stiffness of the root.
本研究的目的是通过有限元方法模拟上颌第一磨牙牙周组织对不同力矩与力比值的应力反应，并确定牙齿平移运动的力矩与力比值。上颌第一磨牙的三维有限元模型由3097个节点和2521个等参八节点实体单元组成。该模型旨在分别剖析牙周膜、牙根和牙槽骨。结果表明牙周组织对负荷变化敏感。在没有平衡力矩的远中向力作用下，牙周膜中的应力模式显示，由于牙齿的倾斜和旋转，远中颊根颈部水平处应力高度集中。在施加各种反向旋转和反向倾斜力矩后，当反向倾斜力矩与力的比值为9:1、反向旋转力矩与力的比值为5:1时，牙周膜远中侧获得了均匀分布的低压缩应力。牙周膜中这种较低且均匀的应力意味着可以实现牙齿的平移运动。此外，与报道的前牙根尖处应力高度集中相反，在根分叉水平的牙根表面观察到高应力集中。这一结果可能表明，在上颌第一磨牙牙齿移动过程中，相对于前牙，其牙根形态使其根尖吸收的易感性较低。牙周膜中的应力模式与负荷类型相对应；牙根上的应力模式似乎受弯曲和牙根高刚度的影响很大。
