The viscoelastic properties of the human temporomandibular joint disc

Purpose: This study evaluated the viscoelasticity of the human temporomandibular joint (TMJ) disc by comparing the moduli of elasticity generated by compressing disc specimens under two different loading rates. Materials and Methods: Twelve TMJ disc specimens 4.25 mm +/- 0.15 mm in diameter were obtained from fresh cadavers between 65 and 75 years of age. One group of specimens was subjected to a loading rate of 0.00127 mm/sec, and the other was subjected to a loading rate of 0.000635 mm/sec. Modulus of elasticity was calculated from the stress and strain values obtained from each specimen. Results: When the specimens were subjected to an average 0.00127 mm/sec loading rate, a mean modulus of elasticity of 0.541 N/mm(2) was derived. When an average 0.000635 mm/sec loading rate was used, a mean modulus of elasticity value of 0.211 N/mm(2) was derived. These two mean values were significantly different, as indicated by the results of a one-tailed t-test. Conclusions: Analysis of the data showed that the human TMJ disc specimens became stiffer as the loading rate increased.