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Chapter 9256yet available. An important aspect to testing is sensitization. Should allergy or sensitization susceptibility be tested? Specific immunoglobulin E (IgE) antibodies are produced after prior exposure to a substance that consequently becomes an allergen. Hence, should patch testing be repeated after 3 months to ensure that the original test has not sensitized the candidate to that substance? Is epicutaneous sensitization possible, or is intradermal testing mandatory? T-lymphocytes are constantly observed surrounding titanium debris in tissues. Titania microparticles can act as adjuvants to drive antigenic T helper 2 cell differentiation and the IgE response. Should titania microparticles be injected intradermally to rule out hypersensitivity?A second remark that has to be made with concern to the use of titanium alloys is the material’s poor abrasion/wear resistance. While compression forces are on average 66 N/cm2 in a TMJ, shear forces do play a greater role.(12,38) Even more so by restoring the lateral pterygoid muscle (LPM) function, as all movements, including protrusion and lateralization, remain simultaneously present. Despite the low forces generated, low friction and a hard coating are advised for the condylar head to prevent wear of the opposing fossa component, which usually consists of softer polyethylene. The latter can be achieved by using a diamond-like carbon coating (DLC).(39) DLC is an amorphous carbon composed of a mixture of sp3 and sp2 carbon bonds with various levels of hydrogen. Coatings of materials within the DLC family can be fabricated based on hydrogen content, the addition of metallic and nonmetallic doping elements, the presence of interlayers, and the choice of bonding and deposition methods. These parameters can be controlled for the engineering of a broad range of thin (1–5 µm) coatings with a hardness of 8–80 GPa or higher. Diamond is the hardest known material to date, with 70–150 GPa Vickers hardness. The coefficient of friction, surface finish, and application temperature can also be manipulated. After the application of the coating, a polishing process can be used to increase the tribological properties of the prosthesis.(40)Delayed delamination from its substrate because of corrosion poses a serious issue for implant stability. Delamination occurs because of the dissolution of the silicon-adhesion-promoting interlayer and has been Nikolas de Meurechy NW.indd 256 05-06-2024 10:14