title: Is mandibular asymmetry more frequent and severe with unilateral disc displacement?
abstract: OBJECTIVE
  To investigate the prevalence of mandibular asymmetry (MA) within the symptomatic unilateral anterior disc displacement (ADD) patients, and analyze the influence TMJ factors of the MA severity.
  
  
  METHODS
  Patients aged under 20 years old with symptomatic unilateral ADD and asymptomatic volunteers with normal disc-condyle relationship diagnosed by magnetic resonance imaging (MRI) were included in this study. Posteroanterior cephalometric radiographs were taken to measure MA. Condylar height, disc length and disc displacement were measured by MRI. The prevalence and severity of MA were compared between the ADD and the control groups. The correlation between the severity of MA with the amount of condylar height shortage, disc deformity and distance of disc displacement were also evaluated within the ADD group.
  
  
  RESULTS
  There were 165 cases in the unilateral ADD group, and 156 cases in the control group. One hundred and nineteen cases had MA which accounted 72.12% (119/165) in the ADD group; while in the control group, only 25.64% (40/156) exhibited MA. The mean horizontal menton deviation and condylar height shortage in the unilateral ADD group were significantly larger than that in the control group (5.62 mm vs. 4.19 mm; 3.14 mm vs. 1.32 mm, p < 0.01). The severity of MA was significantly correlated with the amount of disc displacement, disc deformity and condylar height shortage (correlation coefficient: 0.80, 0.70, and 0.82).
  
  
  CONCLUSIONS
  MA is much more common and severe in young unilateral ADD patients. The severity of MA is correlated with the height of condyle and the status of the disc.
authors.affiliation: Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Key Laboratory of Stomatology, Shanghai 200011, China.
authors.forename: Qianyang
authors.initials: Q
authors.lastname: Xie
authors.affiliation: Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Key Laboratory of Stomatology, Shanghai 200011, China. Electronic address: yangchi63@hotmail.com.
authors.forename: Chi
authors.initials: C
authors.lastname: Yang
authors.affiliation: Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Key Laboratory of Stomatology, Shanghai 200011, China. Electronic address: dongmeihe119@yahoo.com.
authors.forename: Dongmei
authors.initials: D
authors.lastname: He
authors.affiliation: Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Key Laboratory of Stomatology, Shanghai 200011, China.
authors.forename: Xieyi
authors.initials: X
authors.lastname: Cai
authors.affiliation: Department of Oral Surgery, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Key Laboratory of Stomatology, Shanghai 200011, China.
authors.forename: Zhigui
authors.initials: Z
authors.lastname: Ma
mesh_terms: D000293:Adolescent; D016022:Case-Control Studies; D002508:Cephalometry / Q000379:methods; D002648:Child; D002680:Chin / Q000473:pathology; D002681:China / Q000453:epidemiology; D005146:Facial Asymmetry / Q000145:classification / Q000453:epidemiology*; D006801:Humans; D004204:Joint Dislocations / Q000453:epidemiology*; D008279:Magnetic Resonance Imaging / Q000379:methods; D008335:Mandibular Condyle / Q000473:pathology; D008336:Mandibular Diseases / Q000145:classification / Q000453:epidemiology*; D015995:Prevalence; D011446:Prospective Studies; D019224:Temporomandibular Joint Disc / Q000473:pathology*; D013705:Temporomandibular Joint Disorders / Q000453:epidemiology*; D055815:Young Adult
keywords: Anterior disc displacement; Mandibular asymmetry; Prevalence; Temporomandibular joint