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Biomaterials in TMJ replacement613IntroductionThe temporomandibular joint (TMJ), is a relatively complex joint, consisting of an upper and lower compartment, separated by a fibrocartilaginous disk. Both rotational and translational motions allow for the opening and closing of the mouth, mastication, talking, and other activities.Although the prevalence of TMJ diseases is high, treatment using a TMJ prosthesis remains relatively rare.(1,2) According to Sidebottom et al. (3), up to 80% of all patients seen by a specialist can be treated with a more conservative approach, such as rest and anti-inflammatory medications. Less than 10% of all patients in a specialist center will present the need for arthroscopy or arthrocentesis, and even fewer patients will require open surgery. TMJ replacement is widely accepted as end-stage therapy, which should only be considered for certain well-specified indications when previous, more conservative (noninvasive) treatments have been proven unsatisfactory.(4) This widespread highly prudent approach is partly the result of overuse of surgery in the past, in combination with catastrophic experiences with early alloplastic TMJ replacements (e.g., the Vitek-Kent prosthesis). (5–11) Indications for total joint replacement include the following: inflammatory arthritis involving the TMJ, recurrent fibrosis or bony ankylosis after failed tissue grafts (bone and soft tissue), failed alloplastic joint reconstruction, or loss of vertical mandibular height or a proper occlusal relationship because of bony resorption, trauma, developmental abnormalities, or pathological lesions.(5–10) For a TMJ prosthesis to be successful, it must achieve good imitation of the function of the joint, a close fit between the prostheses and host bone, and a reasonable lifetime, which should equal that of other prostheses. Furthermore the prosthesis should reduce the suffering and disability of the patient, not be unduly expensive, and not require excessive treatment.(5,10,12,13)Although the problems with the Vitek-Kent prosthesis were later determined to be due to inappropriate material selection, leading to the formation of severe wear debris and subsequent osteolysis, the Nikolas de Meurechy NW.indd 61 05-06-2024 10:14