Biomechanical response of condylar cartilage-on-bone to dynamic shear.

Shear stress can result in fatigue, damage, and irreversible deformation of the mandibular condylar cartilage. However, little information is available on its dynamic properties in shear. We tested the hypothesis that the dynamic shear properties of the condylar cartilage depend on the frequency and amplitude of shear strain. Ten porcine mandibular condyles were used for dynamic shear tests. Two cartilage-bone plugs were dissected from each condyle and tested in a simple shear sandwich configuration under a compressive strain of 10%. Sinusoidal shear strain was applied with an amplitude of 1.0, 2.0, and 3.0% and a frequency range between 0.01 and 10 Hz. The magnitudes of the shear dynamic moduli were found to be dependent on the frequency and the shear strain amplitude. They increased with shear strain. tan delta ranged from 0.2 to 0.4, which means that the cartilage is primarily elastic in nature and has a small but not negligible viscosity. In conclusion, the present results show that the shear behavior of the mandibular condylar cartilage is dependent on the frequency and amplitude of the applied shear strain. The observed shear characteristics suggest a significant role of shear strain on the interstitial fluid flow within the cartilage. Copyright 2007 Wiley Periodicals, Inc.