VISCOELASTIC CHARACTERISATION OF BOVINE NASAL SEPTUM AS MODEL FOR TMJ DISC MECHANOBIOLOGY

Abstract

Animal models have shown that artificially induced temporomandibular joint (TMJ) disc displacement or perforation affect histology and biochemistry of joint cartilage, leading to osteoarthritic changes. However, it is still unclear whether TMJ disc cartilage fails simply due to wear or is degraded by a biological response to mechanical loading.

In order to gain insight into TMJ cartilage mechanobiology, a system reproducing the dynamic TMJ compression effects on live tissues was developed. Bovine nasal septum (BNS) cartilage was chosen as a convenient tissue model. However, little information is available in the literature on its material properties. Aim of this study was to determine BNS material properties using a viscoelastic model and verify its suitability as model for TMJ disc cartilage.

Cartilage samples were harvested from the central part of BNSs of young, healthy animals. Stress-relaxation tests in unconfined compression were performed on cylindrical plugs samples, obtained by means of biopsy punches. A 10% strain (strain rate 0.01 mm/s) was applied and held for 30 minutes.

Stress was estimated from the compressive force data and the initial cross-sectional area. Experimental data were fit to a mathematical model in MATLAB. Experimental results show a highly viscoelastic behavior of the BNS, with a maximum average stress of 0.73 ± 0.14 MPa and relaxed stress of 0.21 ± 0.03 MPa. The numerical model shows good correspondence to the experimental data (R2=0.96). The average values for the instantaneous and relaxed elastic moduli are E0= 7.72 MPa and ER= 2.30 MPa, in the same order of magnitude as the TMJ disc.

We conclude that bovine nasal septum can be modeled as viscoelastic tissue and can be used as a first approximation to study mechanobiology of the TMJ disc.