关节盘移位对颞下颌关节内应力分布的影响

目的 通过对不同关节盘移位的数值模拟，探究各种移位情况下颞下颌关节（temporomandibular joint,TMJ）内各结构的应力分布规律。方法 依据CT图像，建立包含下颌骨、全牙列、关节盘和关节软骨的正常TMJ三维有限元模型；参考关节盘前、后、外、内移位的临床特征，建立对应的4个模型。关节盘与关节软骨间考虑接触，用缆索元模拟下颌韧带和关节盘附着，施加正中咬合荷载。结果 前移位将导致关节盘中带产生过高的压应力，达到3.23 MPa；后、内、外移位时关节盘的整体应力水平比前移位和正常TMJ高；各种移位都使关节结节后斜面的应力值大幅度增加，但对髁突关节面的影响却不大。结论 各种移位都将导致关节盘和关节结节后斜面产生过高的应力，且后、内、外移位更为危险，更容易造成关节结构和功能的损伤。

Effects of disc displacement on stress distributions in temporomandibular joint

Objective To investigate stress distributions on temporomandibular joint (TMJ) with different disc displacements through numerical simulation. Methods A three-dimensional finite element model of normal TMJ including the mandible, teeth, discs and articular cartilage was established according to CT images of a volunteer with asymptomatic joints. Base on the model, four corresponding models with the anterior, posterior, lateral and medial displacement of the disc were developed. Contact elements were considered to simulate the interaction between the discs and articular cartilages of the condyle and the temporal bone. Cable elements were used to simulate the ligaments and attachments of the disc. The muscle forces and boundary conditions corresponding to the centric occlusions were applied on the models. Results The maximum compressive stress occurred at the intermediate zone due to the anterior displacement of the disc, which was as high as 3.23 MPa. The stresses in the model with the posterior, lateral and medial displacements of the disc were higher than the model with the anterior displacement of the disc and healthy TMJ model. The stresses at the back of the articular eminences in four models with disc displacements were much higher than those in healthy TMJ model. However, the effects of disc displacements on the stresses of the condyles were not obvious. Conclusions Disc displacements could cause higher stresses in the discs and at the back of the articular eminences, especially in the model with the posterior, lateral and medial displacements of the disc, which was likely to cause damage to TMJ structure and function.