Luu Bill, Cronauer Edward Anthony, Gandhi Vaibhav, Kaplan Jonathan, Pierce David M, Upadhyay Madhur
Division of Orthodontics, University of Connecticut Health.
Private Practice, Miami, FL.
J Vis Exp. 2020 Apr 8(158). doi: 10.3791/60746.
The center of resistance (CRES) is regarded as the fundamental reference point for predictable tooth movement. The methods used to estimate the CRES of teeth range from traditional radiographic and physical measurements to in vitro analysis on models or cadaver specimens. Techniques involving finite element analysis of high-dose micro-CT scans of models and single teeth have shown a lot of promise, but little has been done with newer, low-dose, and low resolution cone beam computed tomography (CBCT) images. Also, the CRES for only a few select teeth (i.e., maxillary central incisor, canine, and first molar) have been described; the rest have been largely ignored. There is also a need to describe the methodology of determining the CRES in detail, so that it becomes easy to replicate and build upon. This study used routine CBCT patient images for developing tools and a workflow to obtain finite element models for locating the CRES of maxillary teeth. The CBCT volume images were manipulated to extract three-dimensional (3D) biological structures relevant in determining the CRES of the maxillary teeth by segmentation. The segmented objects were cleaned and converted into a virtual mesh made up tetrahedral (tet4) triangles having a maximum edge length of 1 mm with 3matic software. The models were further converted into a solid volumetric mesh of tetrahedrons with a maximum edge length of 1 mm for use in finite element analysis. The engineering software, Abaqus, was used to preprocess the models to create an assembly and set material properties, interaction conditions, boundary conditions, and load applications. The loads, when analyzed, simulated the stresses and strains on the system, aiding in locating the CRES. This study is the first step in accurate prediction of tooth movement.
阻力中心（CRES）被视为可预测牙齿移动的基本参考点。用于估计牙齿阻力中心的方法多种多样，从传统的放射学和物理测量到模型或尸体标本的体外分析。涉及对模型和单颗牙齿进行高剂量微型计算机断层扫描（micro-CT）的有限元分析技术已显示出很大的前景，但对于更新的、低剂量和低分辨率的锥形束计算机断层扫描（CBCT）图像的研究却很少。此外，仅描述了少数特定牙齿（即上颌中切牙、尖牙和第一磨牙）的阻力中心；其余牙齿在很大程度上被忽视了。还需要详细描述确定阻力中心的方法，以便于复制和进一步研究。本研究使用常规CBCT患者图像来开发工具和工作流程，以获得用于定位上颌牙齿阻力中心的有限元模型。通过分割处理CBCT体图像，以提取与确定上颌牙齿阻力中心相关的三维（3D）生物结构。使用3matic软件对分割后的对象进行清理，并将其转换为最大边长为1mm的由四面体（tet4）三角形组成的虚拟网格。这些模型进一步转换为最大边长为1mm的四面体实体体积网格，用于有限元分析。使用工程软件Abaqus对模型进行预处理，以创建装配体并设置材料属性、相互作用条件、边界条件和载荷应用。分析载荷时，模拟系统上的应力和应变，有助于定位阻力中心。本研究是准确预测牙齿移动的第一步。
