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Chapter 388The general consensus regarding surface roughness is that while surfaces directly in contact with bone are preferentially roughened to promote cell adhesion (micro-topography) or bone ingrowth (macro-topography), smooth surfaces are preferred wherever adhesion of bacteria should be avoided. With respect to wettability, hydrophilic surfaces are preferred, as these seem to have a beneficial effect on cell spreading, while limiting the attachment of bacteria.(77) In addition, introducing inorganic materials (such as hydroxyapatite) or biomolecules at the implant surface that mimic the natural bone interface can lead to improved osseointegration. In addition to triggering appropriate biological responses, surface modifications of Ti are also being considered to improve its wear resistance, thereby allowing its use in articulating surfaces.(19,48,59,76,78) Application of a thin, hard, wearresistant protective coating material, such as titanium nitride (TiN), titanium carbide (TiC), or diamond-like carbon (DLC), can significantly improve the tribological properties of Ti-based implants. TiN has shown favorable effects with respect to biocompatibility, as well as wear and corrosion resistance.(19,48,79) It should be noted, however, that the strength and durability of the coating are very dependent on the coating process. Physical vapor deposition (PVD) is the most commonly used technique for creating a TiN coating, yet several studies in the field of orthopedic surgery have noted increased third body wear due to delamination of the TiN coating. This has been attributed to the lack of chemical reactions or diffusion phenomena between substrate and coating during PVD, resulting in adhesive failure.(78,79) Alternatively, plasma nitriding can be applied; however, it has been reported that as processing time increases, corrosion fatigue properties are diminished. With respect to corrosion, nitrogen-ion implantation has been shown to be the preferred technique over plasma nitriding, even if no differences are observed between both techniques in wear properties.(19) Very little research has been conducted regarding TiN coatings in the field of TMJ surgery. Kerwell et al.(80) reported delamination in two explanted TiNcoated TMJ TJR devices, which had resulted in wear and corrosion of the TiN coating; unfortunately, the authors provided no information regarding which technique was used for the coating process. Nikolas de Meurechy NW.indd 88 05-06-2024 10:14