Temporomandibular joint reconstruction: From alloplastic prosthesis to bioengineering tissue

Pain and dysfunction of the temporomandibular joint (TMJ) may affect more than 10 percent of the adult people in developed countries. TMJ is a unique jaw joint with both rotational and translational movements while masticating, swallowing or speaking. During masticatory function, the both-side joints work in harmony with adjacent structures including masticatory muscles, teeth (occlusion), tongue, etc. and sustain heavy and repeated bite force or loading. The function of the articular disc is the absorption of the compression load to the joint and is susceptible to displacement forward due to the increase of the friction coefficient and the degeneration of the collateral ligaments. An anteriorly displaced disc will lead to higher compressive and tangential stresses in the posterior band of the disc and to a fibrotic change or eventual perforation of that zone of the disc. The disease thus may progress to a more severe stage of degenerative osteoarthritis, and joint replacement is indicated for the destructed disease entity. TMJ prosthesis has evolved for more than 50 years and served to restore the function of temporomandibular joint disorder (TMD) patients. There are some limitations in the function of the implanted TMJ prosthesis, such as lack of translational motion of the condyle and reduction in opening of the mouth. Recent advances in tissue engineering may provide an alternative to traditional strategies to repair and regenerate the TMJ. For the patient or defect-specific purpose, a three-dimensional (3D) image-based design and multi-phasic tissue fabrication technique is under development and could offer a sophisticated approach to the TMJ reconstruction. The biomechanical analyses of the TMJ prosthesis and the newly developed bioengineering constructs are still very rare. Study of the biomechanism of TMJ could improve our knowledge in the pathogenesis of TMD and success in the regeneration of TMJ.