title: Static and dynamic loading effects on temporomandibular joint disc tractional forces.
abstract: Mechanical fatigue-related degeneration of the temporomandibular joint (TMJ) disc may be promoted by tractional forces. This study tested the hypotheses that tractional forces following static loading of the TMJ disc: (1) increase with compressive strain at the start of movement, and (2) are velocity-dependent during movement. Sixty-four porcine discs received a 10-N static load via an acrylic indenter for 1 or 30 sec before cyclic movement. Physical data were recorded and analyzed by ANOVA. The results showed that compressive strain and tractional forces were largest for the start of movement following 30 sec of static loading (p <or= 0.0001) and were correlated (R(2) = 0.84). Peak tractional forces were linearly and positively related to velocity of movement (R(2) = 0.85), and were highest during Cycle 1 after 30 sec of loading (p <or= 0.0067). The results demonstrated that tractional forces were strain-related at the start of movement and velocity-dependent during movement.
  
  
  BACKGROUND
  ANOVA = analysis of variance, PBS = phosphate-buffered physiological saline solution, TMJ = temporomandibular joint, mu(T) =tractional coefficient, mu(s) = static coefficient of friction.
authors.affiliation: University of Nebraska Medical Center College of Dentistry, Department of Growth and Development, PO Box 683740, Lincoln, NE 68583-0755, USA. jnickel@unmc.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: M A
authors.initials: MA
authors.lastname: Moss
authors.forename: D B
authors.initials: DB
authors.lastname: Marx
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D002358:Cartilage, Articular / Q000502:physiology*; D019245:Compressive Strength; D003799:Dental Stress Analysis; D017276:Friction; D008409:Mastication / Q000502:physiology; D008410:Masticatory Muscles / Q000502:physiology; D009068:Movement; D009119:Muscle Contraction; D013552:Swine; D019224:Temporomandibular Joint Disc / Q000502:physiology*; D014143:Traction