title: Tractional forces on porcine temporomandibular joint discs.
abstract: 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 (epsilon); 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 epsilon when the stress-field moved onto relatively thicker (R(2) = 0.83) and thinner cartilage (R(2) = 0.86). When V was > 27 mm/sec and AR.epsilon(3), was > 0.09, tractional forces were significantly higher (< or = 12% of peak) when the stress-field moved onto thicker cartilage. Stress-field dynamic mechanics and cartilage thickness significantly affected TMJ disc tractional forces.
authors.affiliation: University of Missouri-Kansas City, School of Dentistry, Departments of Orthodontics & Dentofacial Orthopedics and Oral Biology, 650 East 25 St., Kansas City, MO 64108-2784, USA. nickeljc@umkc.edu
authors.forename: J C
authors.initials: JC
authors.lastname: Nickel
authors.forename: L R
authors.initials: LR
authors.lastname: Iwasaki
authors.forename: M W
authors.initials: MW
authors.lastname: Beatty
authors.forename: D B
authors.initials: DB
authors.lastname: Marx
mesh_terms: D000465:Algorithms; D000818:Animals; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000473:pathology / Q000503:physiopathology; D012399:Rotation; D013314:Stress, Mechanical; D013552:Swine; D019224:Temporomandibular Joint Disc / Q000473:pathology / Q000503:physiopathology*; D014143:Traction