title: Timing of Demirjian's tooth formation stages.
abstract: BACKGROUND
  Global differences in Demirjian et al.'s method of assessing dental maturity are thought to be due to population differences.
  
  
  OBJECTIVE
  The aim of this study was to investigate the timing of individual tooth formation stages in children from eight countries.
  
  
  METHODS
  This was a meta-analysis of previously published data from retrospective cross-sectional studies of dental maturity.
  
  
  METHODS
  Data of mandibular permanent developing teeth from panoramic radiographs (Demirjian's stages) were combined from Australia, Belgium, Canada, England, Finland, France, South Korea and Sweden (n = 9002, ages 2-16.99 years). Age-of-attainment was calculated using logistic regression for each group by sex and meta-analysis of the total. Overlapping 95% confidence intervals of the means was interpreted as no significant difference.
  
  
  RESULTS
  Mean ages for each group and total were significantly different in 65 out of 509 comparisons (p < 0.05). Some of these were of small sample size but there was no consistent pattern. Apex closure of the first molar was significantly later in children from Quebec and this might explain differences found in the dental maturity score.
  
  
  CONCLUSIONS
  These results suggest no major differences in the timing of tooth formation stages between these children. This fails to explain previous findings of differences using Demirjian's dental maturity method.
authors.affiliation: Dental Institute, Bart's and The London School of Medicine and Dentistry, Dental Institute, London, UK. h.m.liversidge@qmul.ac.uk
authors.forename: H M
authors.initials: HM
authors.lastname: Liversidge
authors.forename: N
authors.initials: N
authors.lastname: Chaillet
authors.forename: H
authors.initials: H
authors.lastname: Mörnstad
authors.forename: M
authors.initials: M
authors.lastname: Nyström
authors.forename: K
authors.initials: K
authors.lastname: Rowlings
authors.forename: J
authors.initials: J
authors.lastname: Taylor
authors.forename: G
authors.initials: G
authors.lastname: Willems
mesh_terms: D000293:Adolescent; D000375:Aging / Q000502:physiology*; D001208:Asia; D001315:Australia; D002170:Canada; D002648:Child; D002675:Child, Preschool; D005060:Europe; D005260:Female; D006801:Humans; D008297:Male; D012727:Sex Characteristics; D013997:Time Factors; D014070:Tooth / Q000033:anatomy & histology / Q000254:growth & development*