Fracture toughness estimation for the TMJ disc.

J contour integral fracture toughness of the temporomandibular (TMJ) disc was estimated from a computational model based on fracture load data derived from experimental tests. The computational model involved a stress analysis of TMJ disc specimens with cracks oriented parallel and perpendicular to the primary collagen fiber axis within the intermediate zone of the disc. The results demonstrated differences occurred between crack orientations when an orthotropic model was used. Fracture toughness was much lower for a crack oriented parallel to the collagen fiber direction than that for a crack oriented perpendicularly. Thickness, crack size, and anisotropy ratio were observed as additional variables affecting the fracture toughness of the TMJ disc. Future model enhancements may be achieved by considering the poroviscoelastic nature of the TMJ disc.