title: Secular trends in the maturation of permanent teeth in 5 to 6 years old children.
abstract: OBJECTIVE
  This investigation aimed to evaluate the secular trend exhibited by developing permanent teeth in 5 to 6 years old southern Chinese children.
  
  
  METHODS
  Four hundred radiographs of children born in the years 1981 (n=200) and 2001 (n=200) were randomly selected, and then age and gender matched. Maxillary and mandibular teeth on the left side were scored. The number of tooth developmental stages (n-tds) for each stage of development and total n-tds in crown and root development was calculated. Logistic regression, X(2) test for occurrence of trend and Fisher's exact test were used to evaluate the variations in n-tds between crown and root maturation and also maturation among different teeth. Dental maturation between boys and girls was also compared.
  
  
  RESULTS
  In the maxillary dentition, children born in 2001 showed advanced dental maturation (odds ratio, 1.29; P=0.001), and girls exhibited earlier maturation than boys (odds ratio, 1.43; P=0.001). In the mandibular dentition, no significant difference between the years was observed (odds ratio, 0.97; P=0.761), however, girls showed accelerated development than boys (odds ratio, 1.26; P=0.002). Variations in maturation were also observed between individual tooth in the same arch and between the arches.
  
  
  CONCLUSIONS
  Children born in 2001 demonstrated accelerated dental development only in the maxillary dentition. Girls born in 1981 and 2001 exhibited advanced maturation than boys. Variations in development among different teeth in the year groups indicate the need for inclusion of all developing teeth to establish a secular change.
authors.affiliation: Paediatric Dentistry & Orthodontics, The University of Hong Kong, Hong Kong. jayakumar83@hotmail.com
authors.forename: Jayakumar
authors.initials: J
authors.lastname: Jayaraman
authors.forename: Hai Ming
authors.initials: HM
authors.lastname: Wong
authors.forename: Nigel
authors.initials: N
authors.lastname: King
authors.forename: Graham
authors.initials: G
authors.lastname: Roberts
mesh_terms: D000367:Age Factors; D002648:Child; D002675:Child, Preschool; D002681:China; D019229:Dentition, Permanent; D005260:Female; D006801:Humans; D008297:Male; D011859:Radiography; D012737:Sex Factors; D012959:Socioeconomic Factors; D014070:Tooth / Q000000981:diagnostic imaging / Q000254:growth & development*