In vitro biomechanical simulation testing of custom fabricated temporomandibular joint parts made of electron beam melted titanium, zirconia, and poly-methyl methacrylate

Abstract

Total alloplastic temporomandibular joint (TMJ) replacement has become common. This in vitro study aimed to evaluate wear response of custom-fabricated electron beam melted titanium (EBM-Ti), zirconia, and acrylic TMJ parts when subjected to biomechanical simulation testing. Eighteen prosthetic TMJ parts (condyle, glenoid fossa) were custom-fabricated using computer aided design and manufacturing (CAD/CAM) techniques based on patient's radiographic images. Biomechanical simulation testing of TMJ parts (in different combinations) were done in a modified chewing simulator (108,000 cycles, 1 Hz frequency, 45-60 N compression, strokes-downward 0.15-0.25 s/horizontal, 0.4-0.5 s/upward, 0.25-0.45 s/displacement, 1.5-2.0 mm). Qualitative analysis using scanning electron microscopy revealed wear facets on leading edges of vertical and horizontal simulation strokes. Measurement of pre-test and post-test weights of TMJ parts revealed non-significant reduction in weights due to wear. EBM-Ti and acrylic TMJ glenoid fossae articulating against zirconia condyles during simulation testing had significantly higher wear, evidenced by greater mean reduction in weights. Based on results of this preliminary study, custom-fabricated alloplastic prosthetic TMJ are a viable alternative to stock alloplastic joints. While EBM-Ti and acrylic are suitable biomaterials for custom-fabrication, use of zirconia results in greater wear and requires further studies to optimize their role in customized alloplastic TMJ.