Tractional forces on porcine temporomandibular joint discs

Tractional forces on the temporomandibular joint (TMJ) disc predispose tissue fatigue. This study tested the hypotheses that tractional forces: (1) increased with stress-field velocity (V) and aspect ratio (AR, contact area diameter/cartilage thickness), and compressive strain (μ); and (2) varied depending on cartilage thickness. Porcine TMJ discs (n = 187) received a 10-N vertical static load via an acrylic indenter for 1, 5, 10, 30, or 60 sec, followed by movement. Physical data were recorded and analyzed by quadratic regression relations and a likelihood ratio test. Results showed non-linear increases in tractional forces that were positively correlated with increased V, AR, and μ when the stress-field moved onto relatively thicker (R² = 0.83) and thinner cartilage (R² = 0.86). When V was > 27 mm/sec and AR^ĝ€¢μ³, was > 0.09, tractional forces were significantly higher (ĝ‰Currency sign 12% of peak) when the stress-field moved onto thicker cartilage. Stress-field dynamic mechanics and cartilage thickness significantly affected TMJ disc tractional forces. Abbreviations : LVDT = linear voltage differential transformer, PBS = phosphate-buffered physiological saline solution, TMJ = temporomandibular joint, V = velocity, AR = aspect ratio, μ = compressive strain, UNMC = University of Nebraska Medical Center, 1/4_T = tractional coefficient, 1/4 _S = static coefficient of friction.