title: Skeletal differences in patients with temporomandibular joint disc displacement according to sagittal jaw relationship.
abstract: OBJECTIVE
  The present study was designed to analyze the skeletal differences in patients with temporomandibular joint (TMJ) disc displacement (DD), according to the sagittal jaw relationship.
  
  
  METHODS
  We implemented a cross-sectional study design and enrolled a sample of Korean women older than age 17 years. The subjects were classified into 3 groups according to the magnetic resonance images of the bilateral TMJs: bilateral normal disc position (BN), bilateral disc displacement with reduction, and bilateral disc displacement without reduction. Each group was subdivided into 2 groups using the mandibular body length to anterior cranial base ratio as a sagittal jaw parameter: normal-size mandible (NM) and oversized mandible (OM). Seventeen variables from the lateral cephalograms were analyzed using 2-way analysis of variance to analyze the differences in skeletal characteristics with respect to the mandible size and TMJ DD status.
  
  
  RESULTS
  The subjects with TMJ DD generally had a short ramus height and clockwise rotation of the ramus and mandible compared with those with BN in both OM and NM groups. However, significant differences were present in the skeletal characteristics of the TMJ DD patients between the NM and OM groups. Significant backward positioning and rotation of the ramus and mandible were found between BN and bilateral disc displacement with reduction or bilateral disc displacement without reduction in the OM group, while those of the ramus and mandible were found between BN and bilateral disc displacement with reduction or bilateral disc displacement without reduction in the NM group.
  
  
  CONCLUSIONS
  The results of our study suggest that the skeletal characteristics associated with TMJ DD are differently represented according to the sagittal jaw relationship.
authors.affiliation: Seoul National University Dental Hospital, Jongro-Gu, Seoul, Korea.
authors.forename: Il-Hyung
authors.initials: IH
authors.lastname: Yang
authors.forename: Beom-Seok
authors.initials: BS
authors.lastname: Moon
authors.forename: Seung-Pyo
authors.initials: SP
authors.lastname: Lee
authors.forename: Sug-Joon
authors.initials: SJ
authors.lastname: Ahn
mesh_terms: D000293:Adolescent; D000328:Adult; D002508:Cephalometry / Q000379:methods*; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D004204:Joint Dislocations / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008334:Mandible / Q000473:pathology*; D008335:Mandibular Condyle / Q000473:pathology; D008437:Maxilla / Q000473:pathology; D009295:Nasal Bone / Q000473:pathology; D056910:Republic of Korea; D012399:Rotation; D019291:Skull Base / Q000473:pathology; D013701:Temporal Bone / Q000473:pathology; D019224:Temporomandibular Joint Disc / Q000473:pathology*; D013705:Temporomandibular Joint Disorders / Q000473:pathology*; D014716:Vertical Dimension; D055815:Young Adult