title: [Study on the difference of corresponding age at cervical vertebral maturation stages among different skeletal malocclusions].
abstract: OBJECTIVE
  To compare the difference of corresponding age at cervical vertebral maturation (CVM) stages among different skeletal malocclusions and provide clinic guideline on optimal treatment timing for skeletal malocclusion.
  
  
  METHODS
  Based on ANB angle, 2 575 cephalograms collected from Department of Orthodontics, Peking University School and Hospital of Stomatology from May, 2006 to November, 2014 were classified into skeletal Class I (ANB 0°~5°, 1 317 subjects), Class II (ANB > 5°, 685 subjects) and Class III (ANB < 0°, 573 subjects) groups. CVM stages were evaluated with the modified version of CVM method. Independent sample t test was performed to analyze the difference of age at different CVM stages among various skeletal groups.
  
  
  RESULTS
  Significant gender difference of age was found at CS3 to CS6 for skeletal Class I group (P < 0.05), at CS5 and CS6 for skeletal Class II group (P < 0.05), and at CS3 and CS5 for skeletal Class III group (P < 0.05). At CS3 stage, the average age of male in skeletal Class II and skeletal Class III groups was (11.6 ± 1.5) years old and (10.3 ± 1.9) years old, respectively; the average age of females in those two groups was (11.7 ± 1.3) years old and (9.3 ± 1.5) years old, respectively, and significant difference was found in both comparisons (P < 0.05). Compared average age at CS5 and CS6 between skeletal Class II and skeletal Class III groups [the ages of male was (15.1 ± 1.7) and (16.8 ± 1.6) years old, the ages of male was (14.6 ± 1.2) and (15.7 ± 2.5) years old], significant difference was also found (P < 0.05).
  
  
  CONCLUSIONS
  Significant gender differences were found when evaluated CVM stage and age in skeletal Class I, II and III groups. Significant differences of age at different CVM stage was noted when skeletal Class II was compared with skeletal Class III groups.
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Changyan
authors.initials: C
authors.lastname: Zuo
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Chao
authors.initials: C
authors.lastname: Cong
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing 100081, China.
authors.forename: Shihui
authors.initials: S
authors.lastname: Wang
authors.affiliation: Department of Orthodontics, Peking University School and Hospital of Stomatology, Beijing 100081, China; Email: guyan96@126.com.
authors.forename: Yan
authors.initials: Y
authors.lastname: Gu
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002574:Cervical Vertebrae / Q000254:growth & development*; D002648:Child; D005260:Female; D006801:Humans; D008297:Male; D008311:Malocclusion, Angle Class I; D008312:Malocclusion, Angle Class II; D008313:Malocclusion, Angle Class III; D012737:Sex Factors