Collagen structure and biomechanical properties of the goat temporomandibular joint disc

OBJECTIVE: To establish objectively biomechanical criteria for temporomandibular joint disc tissue engineerings. METHODS: Eight temporomandibular joint discs from a four-month-old goat were separated completely. A cylindrical sample with diameter of 3 mm in the anterior, intermediate, and posterior bands was obtained, and the samples underwent pre-compression test with three cycles under a speed of 0.025 mm · s⁻¹. With the end condition for the maximum load of less than 4.9 N and 1.5 mm compression displacement, the formal compression test was performed with the same speed. Moreover, this test obtained the stress-strain relationship and elastic modulus of each disc band. Ultrastructure and collagen fiber orientation of the district zone were observed by scanning electron microscope and polarized light microscope. RESULTS: 1) The physiological strain range of an articular disc was within 10%, and the quasilinear constitutive equation of articular disc tissues can be fitted with the polynomial function: y = ax + bx² + cx³. 2) The elastic modulus of the intermediate disc zone was the largest (P < 0.05). No significant difference existed between the anterior and posterior bands (P = 0.361). 3) Scanning electron microscope and polarized light microscope showed an annular disc collagen network structure, which was the internal part of the goat temporomandibular joint disc. The collagen arrangement of intermediate bands was tensely arranged anterior-posteriorly. The collagen of anterior and posterior bands went through mediolaterally with intersection of anterior-posterior branch fibersd. CONCLUSION: Annular collagen network structure is the basis for goat temporomandibular joint disc compression resistance properties. The intermediate band demonstrated higher compression resistance performance than the anterior and posterior bands.