Department of Mechanical Engineering, Indiana University Purdue University Indianapolis (IUPUI), Indianapolis, IN, USA.
Department of Mechanical Engineering, Department of Oral Facial Genetics, Indiana University Purdue University Indianapolis, Indianapolis, IN, USA.
Int J Numer Method Biomed Eng. 2019 Mar;35(3):e3169. doi: 10.1002/cnm.3169. Epub 2018 Dec 10.
Finite element (FE) method's correctness depends heavily on modeling method. This study aimed at determining whether the interfaces at bracket-wire and between teeth can be simplified for multi-teeth FE analysis.
A three-dimensional FE model of a mandible was created from cone-beam computed tomography scan. Due to symmetry, only a half of the mandible was modeled, which consisted of five teeth (first premolar extraction and only first molar), brackets and archwire, periodontal ligament (PDL), cortical bone, and cancellous bone. All the bone, teeth, and PDL were considered to be isotropic and linear. The En-masse retraction case was simulated. A detailed model, which has contact elements between the bracket and archwire and between teeth, was developed to allow relative motion at the interfaces. A model with simplified interfacial conditions, which does not allow the relative motion, was also created. The stresses and displacements as results of the treatment on these two models were calculated and compared.
The stress and displacement distributions from the detailed model were more close to reality based on the expected displacement pattern of the clinical case than from the simplified model. The maximum stresses from the two methods were also different. The highest stress from the detailed model is twice as high as from the simplified model.
The detailed model provides much more reasonable results than the simplified model. Thus, the simplified model should not be used to replace the detailed model if the stress magnitude and highest stress location are the expected outcomes.
有限元（FE）方法的正确性在很大程度上取决于建模方法。本研究旨在确定在多牙 FE 分析中，托槽-弓丝和牙齿之间的界面是否可以简化。
从锥形束 CT 扫描创建下颌骨的三维 FE 模型。由于对称性，仅对下颌骨的一半进行建模，包括五颗牙齿（第一前磨牙拔除，仅第一磨牙）、托槽和弓丝、牙周膜（PDL）、皮质骨和松质骨。所有的骨、牙和 PDL 都被认为是各向同性和线性的。模拟了整体后移情况。开发了一个具有详细模型的模型，该模型在托槽和弓丝之间以及牙齿之间具有接触元素，以允许界面相对运动。还创建了一个具有简化界面条件的模型，该模型不允许相对运动。计算并比较了这两种模型的治疗结果的应力和位移。
基于临床病例的预期位移模式，详细模型的应力和位移分布比简化模型更接近实际情况。两种方法的最大应力也不同。详细模型的最高应力是简化模型的两倍。
详细模型比简化模型提供了更合理的结果。因此，如果期望得到应力大小和最高应力位置等结果，则不应使用简化模型替代详细模型。
