Where is the center of resistance of a maxillary first molar? A 3-dimensional finite element analysis
Where is the center of resistance of a maxillary first molar? A 3-dimensional finite element analysis
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DOI：
10.1016/j.ajodo.2020.04.033
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发表时间：
2021-08-26
影响因子：
3
通讯作者：
Upadhyay, Madhur
中科院分区：
文献类型：
--
作者：
Gandhi, Vaibhav;Luu, Bill;Upadhyay, Madhur
介绍：阻力中心（C-Res）被认为是预测牙齿运动的基本参考点。准确的估计可以大大提高正畸牙齿移动的效率。只有少数研究评估了上颌第一磨牙的C-Res；然而，大多数研究的样本量较低（个位数），使用理想化模型，或涉及二维分析。本研究的目的是：(1)确定上颌第一磨牙C-Res的三维位置，(2)在大样本中评估其变异性，(3)研究从两个方向施加正畸负荷对C-Res位置的影响。方法：对25例患者（平均年龄20.8±8.7岁）50颗上颌磨牙进行锥形束ct扫描。对锥束ct体图像进行分割，提取三维生物结构。将分割的结构进行清洗并转换为最大边缘长度为1mm的四面体三角形组成的虚拟网格模型。牙块包括磨牙和牙周韧带，平均有7753 +/- 2748个节点和38355 +/- 14910个四面体单元。使用专门的软件对模型进行预处理，以创建装配并分配材料属性、交互条件、边界条件和负载应用。施加特定载荷，并使用定制算法分析应力和应变以定位C-Res。测量了C-Res与磨牙颊面几何中心和磨牙根三分叉的关系。结果：上颌第一磨牙C-Res的平均位置相对于磨牙颊面几何中心为4.94 +/- 1.39 mm，相对于磨牙根分叉处为2.54 +/- 2.7 mm，相对于龈面几何中心为7.86 +/- 1.66 mm，相对于龈面三分叉处为0.136 +/- 1.51 mm （P < 0.01）。在前后（y轴）和垂直（z轴）平面上，C-Res与根分化(P
Introduction: The center of resistance (C-Res) is regarded as the fundamental reference point for predictable tooth movement. Accurate estimation can greatly enhance the efficiency of orthodontic tooth movement. Only a handful of studies have evaluated the C-Res of a maxillary first molar; however, most had a low sample size (in single digits), used idealized models, or involved 2-dimensional analysis. The objectives of this study were to: (1) determine the 3-dimensional (3D) location of the C-Res of maxillary first molars, (2) evaluate its variability in a large sample, and (3) investigate the effects of applying orthodontic load from 2 directions on the location of the C-Res. Methods: Cone-beam computed tomography scans of 50 maxillary molars from 25 patients (mean age, 20.8 +/- 8.7 years) were used. The cone-beam computed tomography volume images were manipulated to extract 3D biological structures via segmentation. The segmented structures were cleaned and converted into virtual mesh models made of tetrahedral triangles having a maximum edge length of 1 mm. The block, which included the molars and periodontal ligament, consisted of a mean of 7753 +/- 2748 nodes and 38,355 +/- 14,910 tetrahedral elements. Specialized software was used to preprocess the models to create an assembly and assign material properties, interaction conditions, boundary conditions, and load applications. Specific loads were applied, and custom-designed algorithms were used to analyze the stress and strain to locate the C-Res. The C-Res was measured in relation to the geometric center of the buccal surface of the molar and the trifurcation of the molar roots. Results: The average location of the C-Res for the maxillary first molar was 4.94 +/- 1.39 mm lingual, 2.54 +/- 2.7 mm distal, and 7.86 +/- 1.66 mm gingival relative to the geometric center of the buccal surface of the molar and 0.136 +/- 1.51 mm lingual (P 0.01) relative to the trifurcation of the molar roots. In the anteroposterior (y-axis) and the vertical (z-axis) planes, the C-Res showed significant association with root divergence (P