Department of Mechanical Engineering, UMN, Minneapolis, MN, United States; Minnesota Dental Research Center for Biomaterials and Biomechanics, UMN, Minneapolis, MN, United States.
School of Dentistry, UMN, Minneapolis, MN, United States.
J Mech Behav Biomed Mater. 2022 Oct;134:105404. doi: 10.1016/j.jmbbm.2022.105404. Epub 2022 Aug 1.
Clear thermoplastic aligners have become popular in orthodontics, but the biomechanics of these devices is not well understood. Neither is the tooth movement induced by such devices. The aim of this study was to develop and validate finite element (FE) models for clear thermoplastic teeth aligners for orthodontic force prediction.
FE models were created from Micro-CT scans of an aligner and a model arch of teeth with one of the incisors tipped buccal-lingually by 2.4°. The models were uniformly meshed with 0.3-mm long elements. Linear-elastic mechanical properties provided by the material manufacturers were used. Fitting of the two components was simulated using Abaqus's interference fit, followed by frictional surface-to-surface interaction. The assembled FE model was validated by comparing its prediction for the teeth-aligner gaps and aligner surface strains with experimental data. The experimental teeth-aligner gaps were obtained from the Micro-CT scans whereas the aligner surface strains were measured using a 2-camera digital image correlation (DIC) system.
Good agreement between prediction and measurement was obtained for both the teeth-aligner gaps and aligner surface strains. The linear regression between prediction and measurement for teeth-aligner gaps sampled at different positions had a R value of 0.99. The mean difference between prediction and measurement for the aligner surface strains (von Mises) over 1544 nodes on the labial side and 1929 nodes on the lingual side was 0.07% and 0.01%, respectively, both being lower than the mean background noise.
A FE model for clear thermoplastic teeth aligners has been successfully developed and validated. The model can therefore be used with confidence to predict the forces and moments applied to teeth by the aligners, thus improving our understanding of the biomechanics of such devices and the tooth movement they induce.
透明热塑矫正器在正畸领域已得到广泛应用，但人们对这些器械的生物力学特性及其所产生的牙齿移动知之甚少。本研究旨在开发和验证用于预测正畸力的透明热塑牙齿矫正器有限元（FE）模型。
FE 模型由透明矫正器和带有一颗切牙颊舌向倾斜 2.4°的牙齿模型的 Micro-CT 扫描创建。模型采用 0.3mm 长的单元均匀网格化。使用材料制造商提供的线性弹性机械性能。使用 Abaqus 的过盈配合模拟两个组件的配合，然后是摩擦表面到表面的相互作用。通过将其预测的牙齿-矫正器间隙和矫正器表面应变与实验数据进行比较来验证组装的 FE 模型。实验中的牙齿-矫正器间隙是从 Micro-CT 扫描中获得的，而矫正器表面应变是使用双相机数字图像相关（DIC）系统测量的。
牙齿-矫正器间隙和矫正器表面应变的预测与测量均吻合良好。在不同位置采样的牙齿-矫正器间隙的预测与测量之间的线性回归 R 值为 0.99。在唇侧的 1544 个节点和舌侧的 1929 个节点上，预测与测量的矫正器表面应变（von Mises）的平均值差异分别为 0.07%和 0.01%，均低于平均背景噪声。
成功开发并验证了用于透明热塑牙齿矫正器的 FE 模型。因此，可以放心使用该模型来预测矫正器施加到牙齿上的力和力矩，从而提高我们对这些器械的生物力学特性及其所诱导的牙齿移动的理解。
