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Biomaterials in TMJ replacement673Current alloplastic total temporomandibular joint prosthesesAt the time of writing, two total TMJ devices have received US FDA-approval: The Biomet/Lorenz Microfixation TMJ Replacement System (Fig. 4), and the TMJ Concepts Patient-Fitted Total TMJ Replacement System. (Fig. 5). The first system, as the Christensen system, uses a stock prosthesis that is available in different standard sizes. During surgery, the best fit is selected based on the patient’s anatomy, and after the necessary alterations are made to the host bone, the components are attached with screws.(5,7,8,35,38,39) By contrast, the TMJ Concepts system is a custom-made and patient-fitted prosthesis. First, the prosthesis is fabricated using CAD/CAM technology based on a maxillofacial computed tomography scan of the patient. Next, a stereolithographic model of the patient’s skull is printed, from which the final components are designed and manufactured. Through this custom design, the prosthesis can be altered to the patient’s specific anatomy, including jaw abnormalities and jaw position. Additionally, the fixation screw positions can be optimized, taking into account the patient’s anatomical structures, such as the inferior alveolar nerve. As will be further discussed below, optimizing the positioning and contact with the bone can greatly improve the stability of the prosthesis.(6,9,35,38,40) The two systems also differ with respect to the materials used for the various components, as shown in the overview of these materials presented in Table 1. The Biomet/Lorenz system , which received FDA approval as an investigational device in 1995 and full approval in 2005(7,41), employs a cast CoCrMo ramal component, in which the medial surface is coated with a plasma-sprayed Ti coating. This enables bone ingrowth to improve integration into the host bone (osseointegration). The fossa, on the other Fig. 4: Biomet/Lorenz Microfixation TMJ Replacement SystemNikolas de Meurechy NW.indd 67 05-06-2024 10:14