title: The relationship between jaw injury, third molar removal, and orthodontic treatment and TMD symptoms in university students in Japan.
abstract: OBJECTIVE
  To determine the association between temporomandibular disorders (TMD) and experiences of jaw injury, third molar removal, and orthodontic treatment, controlling for confounding factors such as age, sex, emotional stress, and oral parafunction.
  
  
  METHODS
  First-year university students (n = 2,374) were instructed to answer a questionnaire regarding symptoms of TMD, jaw injury, third molar removal, orthodontic treatment, stress, and parafunctional habits. All subjects were classified according to the level of TMD symptoms. Logistic regression was applied to assess the associations of experiences of jaw injury, third molar removal, and orthodontic treatment with presence of TMD symptoms after controlling for age, sex, stress, and parafunctional habits.
  
  
  RESULTS
  Of the 2,374 students, 715 students were TMD symptom-positive. They were classified into 7 groups consisting of those with only clicking (group 1), only pain in the temporomandibular joint (group 2), only difficulty in mouth opening (group 3), clicking and pain (group 4), clicking and difficulty in mouth opening (group 5), difficulty in mouth opening and pain (group 6), and all 3 symptoms (group 7). TMD symptoms were significantly associated with jaw injury. Odds ratios were 2.25, 2.47, 3.38, and 2.01 for groups 2, 3, 6, and 7, respectively. Experience of third molar removal was significantly associated with TMD (odds ratio = 1.81 for group 1). No association was found between orthodontic experience and TMD.
  
  
  CONCLUSIONS
  Experiences of jaw injury and third molar removal might be cumulative and precipitating events in TMD.
authors: Department of Preventive Dentistry, Hokkaido University, Graduate School of Dental Medicine, Sapporo, Japan.
authors: Rahena
authors: R
authors: Akhter
authors: Nur Mohammad Monsur
authors: NM
authors: Hassan
authors: Ruka
authors: R
authors: Ohkubo
authors: Tetsurou
authors: T
authors: Tsukazaki
authors: Jun
authors: J
authors: Aida
authors: Manabu
authors: M
authors: Morita
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D002012:Bruxism / Q000453:epidemiology; D015986:Confounding Factors, Epidemiologic; D003769:Dental Occlusion, Traumatic / Q000453:epidemiology; D005157:Facial Pain / Q000453:epidemiology; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D007568:Jaw / Q000293:injuries*; D008016:Life Change Events; D008297:Male; D008964:Molar, Third / Q000601:surgery*; D009971:Orthodontics, Corrective / Q000706:statistics & numerical data*; D012737:Sex Factors; D013315:Stress, Psychological / Q000453:epidemiology; D013705:Temporomandibular Joint Disorders / Q000453:epidemiology*; D014081:Tooth Extraction / Q000706:statistics & numerical data*