title: Influence of temporomandibular joint disc displacement on craniocervical posture and hyoid bone position.
abstract: BACKGROUND
  The purpose of this study was to evaluate craniocervical posture and hyoid bone position in orthodontic patients with temporomandibular joint (TMJ) disc displacement.
  
  
  METHODS
  The subjects consisted of 170 female orthodontic patients who consented to bilateral magnetic resonance imaging of their TMJs. They were divided into 3 groups based on the results of magnetic resonance imaging of their TMJs: bilateral normal disc position, bilateral disc displacement with reduction, and bilateral disc displacement without reduction. Twenty-five variables from lateral cephalograms were analyzed with 1-way analysis of variance to investigate differences in craniocervical posture and hyoid bone position with respect to TMJ disc displacement status. Pearson correlation coefficients were calculated to analyze the relationships between craniofacial morphology and craniocervical posture or hyoid bone position.
  
  
  RESULTS
  Subjects with TMJ disc displacement were more likely to have an extended craniocervical posture with Class II hyperdivergent patterns. The most significant differences were found between patients with bilateral normal disc position and bilateral disc displacement without reduction. However, hyoid bone position in relation to craniofacial references was not significantly different among the TMJ disc displacement groups, except for variables related to the mandible. Pearson correlation coefficients indicated that extended craniocervical posture was significantly correlated with backward positioning and clockwise rotation of the mandible.
  
  
  CONCLUSIONS
  This suggests that craniocervical posture is significantly influenced by TMJ disc displacement, which may be associated with hyperdivergent skeletal patterns with a retrognathic mandible.
authors.affiliation: Postgraduate student, Dental Research Institute and Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Jung-Sub
authors.initials: JS
authors.lastname: An
authors.affiliation: Postgraduate student, Dental Research Institute and Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Da-Mi
authors.initials: DM
authors.lastname: Jeon
authors.affiliation: Researcher, Dental Research Institute and Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Woo-Sun
authors.initials: WS
authors.lastname: Jung
authors.affiliation: Assistant professor, Dental Research Institute and Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Il-Hyung
authors.initials: IH
authors.lastname: Yang
authors.affiliation: Associate professor, Dental Research Institute and Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Won Hee
authors.initials: WH
authors.lastname: Lim
authors.affiliation: Professor, Dental Research Institute and Department of Orthodontics, School of Dentistry, Seoul National University, Seoul, Korea. Electronic address: titoo@snu.ac.kr.
authors.forename: Sug-Joon
authors.initials: SJ
authors.lastname: Ahn
mesh_terms: D000293:Adolescent; D000328:Adult; D002508:Cephalometry / Q000379:methods; D002574:Cervical Vertebrae / Q000473:pathology*; D005260:Female; D006801:Humans; D006928:Hyoid Bone / Q000473:pathology*; D004204:Joint Dislocations / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008312:Malocclusion, Angle Class II / Q000473:pathology; D008334:Mandible / Q000473:pathology; D008335:Mandibular Condyle / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D008875:Middle Aged; D009295:Nasal Bone / Q000473:pathology; D009809:Odontoid Process / Q000473:pathology; D021362:Palate, Hard / Q000473:pathology; D011187:Posture; D063173:Retrognathia / Q000473:pathology; D012399:Rotation; D012886:Skull / Q000473:pathology*; D013701:Temporal Bone / Q000473:pathology; D019224:Temporomandibular Joint Disc / Q000473:pathology*; D013705:Temporomandibular Joint Disorders / Q000473:pathology*; D055815:Young Adult