title: [Correlation between circadian rhythm and rapid palatal expansion].
abstract: OBJECTIVE
  To investigate the correlation between circadian rhythm and rapid palatal expansion (RPE).
  
  
  METHODS
  One hundred and eleven consecutive patients (55 males and 56 females) using the same rapid palatal expansion devices were included in the study. The mean age of males was (11.2 ± 2.1) years and the mean age of the females was (11.4 ± 2.7) years, According to the activation time (0, 3, 6, 9, 12, 15, 18 and 21 o'clock), the patients were divided into eight groups. The data were analyzed using Halberg methods for cosinor-rhythmometry and t test.
  
  
  RESULTS
  The results of the tooth movement in eight different groups fitted to a cosine curve. The acrophase and bathyphase appeared at 21 and 9 o'clock, respectively.
  
  
  CONCLUSIONS
  The human circadian rhythm could affect the rapid palatal expansion. This study demonstrated that the best activation time for patients with RPE was around 21 o'clock.
authors.affiliation: Department of Orthodontics, Tongji Hospital, Huazhong University of Science and Technology, Wuhan 430030, China.
authors.forename: Yu-ming
authors.initials: YM
authors.lastname: Bai
authors.forename: Jing
authors.initials: J
authors.lastname: Mao
mesh_terms: D000293:Adolescent; D002648:Child; D002940:Circadian Rhythm; D005260:Female; D006801:Humans; D008297:Male; D010155:Palatal Expansion Technique; D010159:Palate; D014087:Tooth Movement Techniques