Finite element analysis of biomechanical alterations in the temporomandibular joint following mandibular reconstruction

Frictional contact between biological tissues is of critical importance in biomechanics and clinical treatment strategies, which is particularly relevant to diarthrodial joints, where articular cartilage surfaces undergo reciprocal contact loading for thousands of cycles per day. Taking the temporomandibular joint (TMJ) as an example, mandibular resection and reconstruction significantly alters the masticatory system and impacts its biomechanical conditions. Clinical evidence indicates that pain is more frequent in the contralateral TMJ after this kind of surgery. However, there has been limited analysis of TMJ biomechanics following reconstructive surgery to date. Therefore, our study aimed to investigate the effects of masticatory muscle loss on stress distribution in the TMJs, determine an optimum loading region to mitigate excessive stress in the contralateral TMJ, and explore how the frictional change influences the biomechanics of the TMJ. The results demonstrate that the loss of masticatory muscles on the ipsilateral side due to resection can increase contact pressure in the contralateral TMJ and that incisor and ipsilateral dental implant occlusal loading generates the most desired stress patterns in the contralateral TMJ. This study reveals that the excessive contact pressure could increase the real contact area in the joint and further cause a transition from fluid film lubrication to solid contact, leading to increased friction and wear. This work sheds some light on asymmetric anatomy and frictional condition changes arising from surgery, which contribute to stress concentration in the contralateral TMJ and may be associated with degenerative changes. These findings hold significant clinical implications for selecting an optimal and patient-specific occlusal loading to mitigate excessive contact pressure and potential damage in the articular joint.