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Chapter 13340The use of β-Ti alloys such as Titanium-Niobium-Zirconium-Tantalum alloys could be considered. Not only do these alloys have an elastic modulus that is close to that of bone, they also have a higher corrosion resistance and better friction wear resistance.(16,33,35) However, this increased friction wear resistance is still too little to serve as an articulation surface.(16,35) Although research is being done to further improve wear resistance, by for instance adding boride to the alloy or using laser surface treatment, this research remains experimental, with unclear results.(35–38) Thus, this approach was not opted for. Instead of altering the alloy composition, we choose to modify the implant’s surface, allowing for several intended effects such as improved wear resistance, improved or reduced cellular adhesion, as well as the promotion of biological responses such as osteosynthesis.(16,33,39–41) Through application of a hard, wear-resistant protective coating such as titanium nitride (N) or diamond-like carbon (DLC) on the articulating surfaces of the implant, it is possible to significantly improve the tribological properties. Bütow was the first to release a TiN TMJR in 1994.(1,42) Since then, a second Nitride-coated TMJR has been released by OrthoTin (Whippany, NJ, USA). Whilst nitriding the titanium surface leads to better wear and corrosion resistance, as well as biocompatibility, our literature analysis revealed that the process in which the coating is applied is highly significant.(39,40,43) Physical vapour deposition is most often used to coat the implant surface, yet delamination due to adhesive failure has been seen in orthopedic implants. This was also seen by Kerwell et al.(44) during the explantation of 2 Bütow TMJR. Alternatively, plasma nitriding can be used, yet corrosion fatigue properties diminish with increased processing time. In comparison, DLC-coatings are chemically inert and boast high bioand hemocompatibility and corrosion resistance, as well as a low friction coefficient and high hardness.(16,41,45–48) Besides a high hardness, a very smooth surface can also be obtained with DLC, resulting in excellent wear resistance.(47,48) Due to the high hardness of the DLC layer however, as well as the difference in thermal expansion coefficient between the DLC-coating and the underlying Ti, deformation of the underlying Ti could occur under higher loads, resulting in insufficient support of the DLCNikolas de Meurechy NW.indd 340 05-06-2024 10:15