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Biomaterials in TMJ replacement913PEEK has many advantageous biomaterial properties, such as good biocompatibility and bone formation capacity.(88,90) Furthermore, Sagomonyants et al.(90) reported good boney fusion around an implanted PEEK, equaling the in vitro bone formation capacity of Ti. Furthermore, PEEK is radiolucent, which is beneficial for x-ray imaging of an implant. PEEK is also highly resistant to gamma and electron beam radiation, processes used for sterilization; compared to UHMWPE, for example, the quantity of free radicals produced during irradiation is much less and the radicals that are generated will decay quickly.(88) As such, PEEK is less prone to oxidative degradation due to chain scission, which is initiated by free radicals. While unaltered PEEK has an elastic modulus of 3–4 GPa, the addition of carbon fibers can increase its elastic modulus, so it matches that of both cortical and trabecular bone.(88,91) This carbon fiber-reinforced PEEK (CFR-PEEK) also exhibits improved mechanical properties. Compared to untreated PEEK, CFR-PEEK has greater tensile strength and a higher fatigue limit but similar bone formation capacity and biocompatibility.(88,90)When considering PEEK and CFR-PEEK as an articulating bearing surface, data in the field of CMF surgery are extremely scarce, but data are available for orthopedic hip and knee TJR. A systematic review by Li et al.(92) included a total of 20 clinical and/or biochemical articles and 3 scientific reports, published between 1990 to 2013. Of 20 studies, 17 showed that wear resistance was superior for CFR-PEEK compared with UHMWPE, when used as a bearing surface in hip joint simulations, regardless of whether the opposite articulating material was a ceramic material or metal alloy. Less clear were the results concerning knee joint simulations. While Scholes and Unsworth(93) reported favorable results for using CFRPEEK in knee TJR, Wang et al.(91) reported that UHMWPE was a more suitable bearing surface in the knee joint simulation and concluded that CFR-PEEK should not be used as a bearing surface in knee TJR. Grupp et al.(94) concluded that while CFR-PEEK reduced wear compared with PEEK, it is still unclear whether wear is considerably reduced compared with UHMWPE. Similar to Wang et al.(91), Brockett et al.(95) concluded that, despite better results for CFR-PEEK, both PEEK and CFR-PEEK Nikolas de Meurechy NW.indd 91 05-06-2024 10:14