title: Dental age assessment in a northern Chinese population.
abstract: BACKGROUND
  Age estimation is imperative in the fields of paediatric dentistry, orthodontics and forensic science. Studies have shown that dental age estimation by the radiological method is reliable and non-destructive. Although Demirjian's method was the most widely used estimation method, in recent studies, the Willems' method has been found to be more accurate. The aim of this study was to compare the accuracy of dental age estimation methods and to modify the Demirjian method to make it more applicable for a northern Chinese population.
  
  
  METHODS
  An assessment was made of 1004 digital orthopantomographs of a northern Chinese population (392 boys and 612 girls) ranging in age from 11 to 18 years old. Dental ages were calculated using both the Demirjian method and the Willems method. Discrepancies between chronological ages and dental ages were statistically analysed by the paired t-test and the Wilcoxon signed rank test. A nonlinear fitting method was applied to construct a mathematical model to modify the Demirjian method.
  
  
  RESULTS
  The Demirjian method underestimated age by 0.47 y in boys and 0.63 y in girls, while the Willems method underestimated age by 0.54 y and 1.01 y in boys and girls, respectively. The mean absolute error was 1.08 y for the Demirjian method and 1.22 y for the Willems method.
  
  
  CONCLUSIONS
  The Demirjian method was more accurate for estimating dental age compared with the Willems method. However, the Demirjian method may not be suitable for the northern Chinese population; therefore, it should be modified so that it can be used for this population.
authors.affiliation: Department of General Dentistry, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, Shanghai, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhai
authors.affiliation: Department of General Dentistry, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, Shanghai, China.
authors.forename: Hyun
authors.initials: H
authors.lastname: Park
authors.affiliation: Department of General Dentistry, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, Shanghai, China.
authors.forename: Junli
authors.initials: J
authors.lastname: Han
authors.affiliation: Department of General Dentistry, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, Shanghai, China.
authors.forename: Haining
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Orthodontics, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, Shanghai, China. Electronic address: smilefang98@hotmail.com.
authors.forename: Fang
authors.initials: F
authors.lastname: Ji
authors.affiliation: Department of General Dentistry, Ninth People's Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai Key Laboratory of Stomatology, Shanghai, China. Electronic address: taojiang_doctor@hotmail.com.
authors.forename: Jiang
authors.initials: J
authors.lastname: Tao
mesh_terms: D000293:Adolescent; D000366:Age Determination by Teeth / Q000379:methods*; D044466:Asian People; D002648:Child; D002681:China; D005260:Female; D006801:Humans; D008297:Male; D015233:Models, Statistical; D019252:Radiography, Dental, Digital; D011862:Radiography, Panoramic
keywords: Demirjian method; Dental age estimation; Modified Demirjian method; Northern Chinese population; Willems method