title: Discrimination of internal derangement of temporomandibular joint by lateral cephalometric analysis.
abstract: BACKGROUND
  The purposes of this study were to analyze the progress of internal derangement (ID) of the temporomandibular joint (TMJ) and to find critical yardsticks that can be used during lateral cephalometric analysis to identify subjects with potential ID.
  
  
  METHODS
  The sample consisted of 134 women whose primary complaints were malocclusions. They were divided into 5 groups based on the results of magnetic resonance imaging of bilateral TMJs: bilateral normal disc position, unilateral disc displacement with reduction (DDR) and contralateral normal disc position, bilateral DDR, unilateral DDR and contralateral disc displacement without reduction (DDNR), and bilateral DDNR. Thirty-six cephalometric variables from their lateral cephalograms were analyzed with 1-way ANOVA and discriminant analysis to determine the key factors in identifying subjects with TMJ ID.
  
  
  RESULTS
  Backward positioning of the mandible, clockwise rotation of the mandible, proclination of the mandibular incisors, and increase in overjet intensified gradually with the progression of TMJ ID, and the subjects with bilateral DDNR showed the greatest changes in dentofacial morphology. Stepwise variable selection in discriminant analysis identified the following 2 variables: mandibular incisor to Frankfort horizontal plane angle and overjet. Discriminant analysis resulted in the correct classification of 79.1% of the subjects and showed that those with smaller mandibular incisor to Frankfort horizontal plane angles and larger overjets had high possibilities of TMJ ID.
  
  
  CONCLUSIONS
  This study suggests that some cephalometric variables can be used as an auxiliary diagnostic tool to help identify patients with potential TMJ ID.
authors.affiliation: Dental Research Institute and Department of Orthodontics, College of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Sug-Joon
authors.initials: SJ
authors.lastname: Ahn
authors.forename: Seung-Hak
authors.initials: SH
authors.lastname: Baek
authors.forename: Tae-Woo
authors.initials: TW
authors.lastname: Kim
authors.forename: Dong-Seok
authors.initials: DS
authors.lastname: Nahm
mesh_terms: D000293:Adolescent; D000328:Adult; D000704:Analysis of Variance; D002508:Cephalometry / Q000706:statistics & numerical data; D016002:Discriminant Analysis; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000150:complications / Q000000981:diagnostic imaging; D008279:Magnetic Resonance Imaging; D008310:Malocclusion / Q000150:complications / Q000473:pathology; D011237:Predictive Value of Tests; D011857:Radiographic Image Interpretation, Computer-Assisted; D018709:Statistics, Nonparametric; D019224:Temporomandibular Joint Disc / Q000000981:diagnostic imaging / Q000473:pathology*; D013705:Temporomandibular Joint Disorders / Q000150:complications / Q000000981:diagnostic imaging*