title: Viscoelastic shear properties of porcine temporomandibular joint disc.
abstract: OBJECTIVE
  To investigate the intrinsic viscoelastic shear properties in porcine TMJ discs.
  
  
  METHODS
  Twelve fresh porcine TMJ discs from young adult pigs (6-8 months) were used. Cylindrical samples (5 mm diameter) with uniform thickness (~1.2 mm) were prepared from five regions of the TMJ disc. Torsional shear tests were performed under 10% compressive strain. Dynamic shear was applied in two methods: 1) a frequency sweep test over the frequency range of 0.1-10 rad/s with a constant shear strain amplitude of 0.05 rad and 2) a strain sweep test over the range of 0.005-0.15 rad at a constant frequency of 10 rad/s. Transient stress relaxation tests were also performed to determine the equilibrium shear properties.
  
  
  RESULTS
  As the frequency increased in the frequency sweep test, the dynamic shear complex modulus increased, with values ranging from 7 to 17 kPa. The phase angle, ranging from 11 to 15 degrees, displayed no pattern of regional variation as the frequency increased. The dynamic shear modulus decreased as the shear strain increased. The equilibrium shear modulus had values ranging from 2.6 to 4 kPa. The posterior region had significantly higher values for dynamic shear modulus than those in the anterior region, while no significant regional difference was found for equilibrium shear modulus.
  
  
  CONCLUSIONS
  Our results suggest that the intrinsic region-dependent viscoelastic shear characteristics of TMJ disc may play a crucial role in determining the local strain of the TMJ disc under mechanical loading.
authors: Department of Bioengineering, Clemson University, Clemson, SC, USA.
authors: Y
authors: Y
authors: Wu
authors: J
authors: J
authors: Kuo
authors: G J
authors: GJ
authors: Wright
authors: S E
authors: SE
authors: Cisewski
authors: F
authors: F
authors: Wei
authors: M J
authors: MJ
authors: Kern
authors: H
authors: H
authors: Yao
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D055119:Elastic Modulus; D004548:Elasticity; D008297:Male; D023421:Models, Animal; D012399:Rotation; D013314:Stress, Mechanical; D013552:Swine; D019224:Temporomandibular Joint Disc / Q000033:anatomy & histology* / Q000502:physiology; D054159:Torsion, Mechanical; D014783:Viscosity
keywords: dynamic mechanical testing; porcine animal model; shear modulus; temporomandibular joint disc