title: Anatomic disorders of the temporomandibular joint disc in asymptomatic subjects.
abstract: OBJECTIVE
  This study determined the prevalence and specific anatomic types of disc displacement in asymptomatic versus symptomatic subjects using magnetic resonance imaging (MRI).
  
  
  METHODS
  A detailed MRI assessment was performed on both temporomandibular joints (TMJ) in 76 volunteers and 102 successive patients. Attention was placed on the functional aspects of disc displacement with and without reduction and on the anatomic aspects of disc displacement in the anterior, lateral, medial, anterolateral, and anteromedial directions. These assessments were made by radiologists blinded to the clinical information.
  
  
  RESULTS
  Disc displacement was found in at least one joint in 25 of 76 (33%) of asymptomatic subjects and 79 of 102 (77%) of symptomatic subjects. The anatomic types of disc displacement between groups was not statistically significant (P = .55). However, there was a significant difference between asymptomatic and symptomatic subjects, with an odds ratio of 3.91 for disc displacement with reduction and 42.71 for disc displacement without reduction (P < .001).
  
  
  CONCLUSIONS
  Although there was a 33% prevalence of disc displacement in asymptomatic volunteers, there was a highly significant difference in the prevalence of internal derangement in symptomatic subjects. Bruxing was statistically linked to TMJ disc displacement and could explain the anatomic variation in abnormal disc position.
authors.affiliation: Department of Radiology, University of California Davis Medical Center, Sacramento 95817, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Katzberg
authors.forename: P L
authors.initials: PL
authors.lastname: Westesson
authors.forename: R H
authors.initials: RH
authors.lastname: Tallents
authors.forename: C M
authors.initials: CM
authors.lastname: Drake
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002012:Bruxism / Q000175:diagnosis / Q000453:epidemiology; D002648:Child; D005260:Female; D006801:Humans; D016015:Logistic Models; D008279:Magnetic Resonance Imaging / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D011446:Prospective Studies; D013704:Temporomandibular Joint / Q000473:pathology; D013705:Temporomandibular Joint Disorders / Q000175:diagnosis* / Q000453:epidemiology / Q000473:pathology