Surface wear in a custom manufactured temporomandibular joint prosthesis

The wear of a novel temporomandibular joint (TMJ) prosthesis was evaluated in an animal model. The prosthesis consisted of an additively manufactured titanium alloy (Ti₆ Al₄ V) mandibular condyle and glenoid fossa created through selective laser melting, with a machined vitamin E-enriched ultra-high molecular weight polyethylene (UHMWPE) surface attached to the fossa. Thirteen TMJ prosthesis were implanted in sheep, six of which had condylar heads coated with HadSat® diamond-like carbon (H-DLC). Euthanasia took place after 288 days, equaling 22 years of human mastication. Linear and volumetric wear analysis of the fossa was performed by optical scanning. The condylar head surfaces were assessed by scanning electron and confocal laser microscopy. The average linear UHMWPE wear, when combined with the coated condyle, was 0.67 ± 0.28 mm (range: 0.34-1.15 mm), not significantly differing (p = .3765, t-test) from the non-coated combination average (0.88 ± 0.41 mm; range: 0.28-1.48 mm). The respective mean volumetric wear volumes were 25.29 ± 11.43 mm³ and 45.85 ± 22.01 mm³ , not significantly differing (p = .1448, t-test). Analysis of the coated condylar surface produced a mean Ra of 0.12 ± 0.04 μm and Sa of 0.69 ± 0.07 μm. The non-coated condylar surface measured a mean Ra of 0.28 ± 0.17 μm and Sa of 2.40 ± 2.08 μm. Both Sa (p = .0083, Mann-Whitney U test) and Ra (p = .0182, Mann-Whitney U test), differed significantly. The prosthesis exhibits acceptable wear resistance and addition of the H-DLC-coating significantly improved long-term condylar surface smoothness.