Background & objective

This study aims to analyze the stress distributions in temporomandibular joints (TMJs) during the left and right protrusions and explore the mechanical reasons for these stress distributions.

Methods

Computed tomography and magnet resonance images of 5 asymptomatic subjects were used to reconstruct the bone and soft tissue of the maxillofacial models with a pair of detailed TMJs. An optical motion-track system captured the left and right protrusions of the subjects. Inhomogeneous material properties were assigned to the models according to the gray value of the images. Then, the captured data were inputted as the loadings of the finite element models. Different from previous studies, a more relaxed position was used as the initial position of the jaw, which could better mimic the internal loads with lower initial stress.

Results

The stresses on the discs for all the subjects during the motions were under the fracture stress. The stress distributions exhibited an obvious asymmetry. Among them, three subjects had a contralateral-greater stress distribution during both left and right lateral protrusions. The greater stresses always lay in the left disc for one subject, and another subject had an ipsilateral-greater stress distribution during the motions. Besides, the stress distributions in a single disc were various due to the different nature of movements.

Conclusion

Excessive stretch and squeeze, which was originated from great and little condylar displacements towards fossa during the motions, had a negative influence on the stresses in discs. Thus, the detections about the condylar displacement, even biomechanical analysis, were necessary to provide dynamically biomechanical information in the treatment of TMJ associated dysfunctions.

中文翻译：

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颞下颌关节在侧向突出过程中的生物力学响应：3D有限元研究。

背景与目标

这项研究旨在分析左右突突期间颞下颌关节（TMJ）的应力分布，并探讨造成这些应力分布的力学原因。

方法

使用计算机断层扫描和5个无症状受试者的磁共振图像，通过一对详细的TMJ重建颌面部模型的骨骼和软组织。光学运动跟踪系统捕获了对象的左右突起。根据图像的灰度值将不均匀的材料属性分配给模型。然后，将捕获的数据输入为有限元模型的载荷。与以前的研究不同，下颌的初始位置使用了更放松的位置，可以更好地模拟内部载荷，初始应力较低。

结果

运动过程中所有受试者的椎间盘上的应力都处于断裂应力之下。应力分布表现出明显的不对称性。其中，三名受试者在左侧和右侧外侧突起处都有对侧较大的应力分布。对于一个受试者，左椎间盘始终施加更大的应力，而在运动过程中，另一个受试者的同侧应力分布更大。此外，由于运动性质的不同，单个圆盘中的应力分布也各不相同。

结论

过度的拉伸和挤压是由于运动过程中great窝向颅窝的位移大而小，对椎间盘的应力有负面影响。因此，对于con突移位的检测，甚至生物力学分析，对于动态治疗TMJ相关功能障碍的生物力学信息都是必需的。