title: Diagnostic group differences in temporomandibular joint energy densities.
abstract: OBJECTIVE
  Cartilage fatigue, due to mechanical work, may account for precocious development of degenerative joint disease in the temporomandibular joint (TMJ). This study compared energy densities (mJ/mm³) in TMJs of three diagnostic groups.
  
  
  METHODS
  Sixty-eight subjects (44 women, 24 men) gave informed consent. Diagnostic criteria for temporomandibular disorders (DC/TMD) and imaging were used to group subjects according to presence of jaw muscle or joint pain (+P) and bilateral disk displacement (+DD).
  
  
  METHODS
  Subjects (+P+DD, n=16; -P+DD, n=16; and -P-DD, n=36) provided cone-beam computed tomography and magnetic resonance images, and jaw-tracking data. Numerical modeling was used to determine TMJ loads (Fnormal). Dynamic stereometry was used to characterize individual-specific data of stress-field dynamics during 10 symmetrical jaw-closing cycles. These data were used to estimate tractional forces (Ftraction). Energy densities were then calculated as W/Q (W=work done or mechanical energy input=tractional force×distance of stress-field translation, Q=volume of cartilage). anova and Tukey-Kramer post hoc analyses tested for intergroup differences.
  
  
  RESULTS
  Mean±standard error energy density for the +P+DD group was 12.7±1.5 mJ/mm³ and significantly greater (all adjusted p<0.04) when compared to -P+DD (7.4±1.4 mJ/mm³) and -P-DD (5.8±0.9 mJ/mm³) groups. Energy densities in -P+DD and -P-DD groups were not significantly different.
  
  
  CONCLUSIONS
  Diagnostic group differences in energy densities suggest that mechanical work may be a unique mechanism, which contributes to cartilage fatigue in subjects with pain and disk displacement.
authors: Center of Dental Medicine, Clinic of Masticatory Disorders, Removable Prosthodontics, Geriatric and Special Care Dentistry, University of Zurich, Zurich, Switzerland.
authors: L M
authors: LM
authors: Gallo
authors: L R
authors: LR
authors: Iwasaki
authors: Y M
authors: YM
authors: Gonzalez
authors: H
authors: H
authors: Liu
authors: D B
authors: DB
authors: Marx
authors: J C
authors: JC
authors: Nickel
mesh_terms: D000328:Adult; D018771:Arthralgia / Q000503:physiopathology; D001696:Biomechanical Phenomena; D002358:Cartilage, Articular / Q000503:physiopathology*; D003198:Computer Simulation; D054893:Cone-Beam Computed Tomography / Q000379:methods; D005157:Facial Pain / Q000503:physiopathology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted / Q000379:methods; D004204:Joint Dislocations / Q000503:physiopathology; D008279:Magnetic Resonance Imaging / Q000379:methods; D008297:Male; D008954:Models, Biological; D016059:Range of Motion, Articular / Q000502:physiology; D013314:Stress, Mechanical; D019224:Temporomandibular Joint Disc / Q000503:physiopathology; D013705:Temporomandibular Joint Disorders / Q000145:classification* / Q000503:physiopathology; D013706:Temporomandibular Joint Dysfunction Syndrome / Q000503:physiopathology; D014937:Work / Q000502:physiology
keywords: cartilage; fatigue; human; mechanics; temporomandibular joint