Viscoelastic properties of canine temporomandibular joint disc in compressive load-relaxation.

The present study was designed to investigate the mechanical properties and load-relaxation of these discs in compression. Eight discs were used for the experiments. Compression was applied to specimens up to the specified strain, and a series of load-relaxation tests was conducted on each specimen from 0.25% strain to 2.0% strain with 0.25% intervals. The load-relaxation was monitored over a period of 2 min. The elastic moduli of the canine articular discs were 30.9 and 15.8 MPa at t = 0 and 120 sec, respectively, and the discs exhibited near-linear elastic characteristics at each time within a 2-min period. At all strains, the time-dependent load-relaxation curves showed that the load decreased markedly for the initial 30 sec, after which it levelled off after 120 sec with a steady nonzero level. This relaxation feature can be well represented by Kelvin's model. It is concluded that the canine temporomandibular joint disc can be represented as a linear viscoelastic material, and that it plays an important part as a stress absorber under compression.