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Chapter 13338the material and FBGCR, as was the case for both Silastic® and Proplast® implants.(10–15) In addition, the materials should have high strength, excellent fatigue and wear resistance, and fracture toughness, for the implant to have proper longevity.(7,16,17) The materials need to be stiff enough so that no micromotions of the implant components can occur, yet at the same time show a sufficiently high elastic modulus, preferably as close as possible to bone, to prevent stress shielding and underlying bone resorption.(7,16,18) If these criteria are not met, proper osseointegration and implant longevity will not result. When evaluating the 27 TMJR that were being developed or available for placement in 2019, three TMJR had a stainless steel (SS) ramal component.(1) While SS alloys such as 316L have good fatigue and tensile strength properties and are significantly cheaper and easier to manufacture compared to titanium, allowing for a lower production cost, our literature analysis revealed that SS has the lowest corrosion resistance amongst the most common biomaterials. This makes it susceptible to stress corrosion, cracking, and crevice corrosion, rendering it unsuitable as a bearing prosthetic material. While the corrosion resistance can be improved through passivation, the elastic modulus of 190-210 GPa is significantly higher than that of human bone, making the material significantly prone to stress shielding, making it an unsuitable material for prosthetic use.(19) The TMJR developed by Genovesi (20) used a polyether ether ketone (PEEK) ramal component. Our narrative literature analysis revealed this to be an interesting material with good biocompatibility and bone formation capacity.(21,22) Through reinforcement with carbon fibers, the elastic modules can be increased to mimic that of bone and the tensile strength can be improved as well. However, as an articulating material, both PEEK and carbon-reinforced PEEK showed significantly worse wear resistance compared to UHMWPE in knee TJR, making it unsuitable as an articulating prosthetic TMJR material.(23,24) Seven out of 27 systems used a cobalt chrome (CoCr) or cobalt chrome molybdenum (CoCrMo) condylar head and three systems used a complete CoCr ramal component.(1) While CoCr and CoCr alloys have excellent wear resistance, high strength and fatigue resistance, there are 2 main Nikolas de Meurechy NW.indd 338 05-06-2024 10:15