Application Of Nolla And Willems Dental Age Inference Method In Uygur And Han Population Aged 3-16 In Urumqi City

Objective: To evaluate the applicability and accuracy of Nolla method and Willems method in estimating the chronological age of 3 to 16 years old minors of Uygur and Han in Urumqi.Methods: 1208 orthopantomographs(OPGs)of Uyghur and Han patients aged 3-16 in Urumqi from 2018 to 2021 were collected,including 547 Uyghur(male: 267,female: 280)and 661 Han(male: 347,female: 314).The dental age was obtained according to the stage criteria of Nolla method and Willems method and the age conversion table provided.The dental age and chronological age were analyzed by paired t-test according to method,ethnic group and sex.Results: The average chronological age of Uygur men was(8.81 ± 3.75)years old,and that of women was(9.62 ± 3.68)years old;The average chronological age of Han men was(9.07 ± 3.77)years old,and that of women was(8.96 ± 3.86)years old.Nolla method: Uygur men were underestimated by an average of 0.06 years and women by 0.52 years,and the mean absolute error(MAE)of overall was 0.75 years(0.70 years for men and 0.80 years for women);Han men were underestimated by an average of 0.13 years and women by 0.64 years,and the overall MAE was 0.80 years(0.69 years for men and 0.90 years for women);The average difference between dental age and chronological age is less than 1.00 years old in all age groups except for women aged 15-16 years old,regardless of Uygur or Han.Willems method: Uygur men were overestimated by an average of 0.12 years and women by 0.09 years,and the overall MAE was 0.66 years(0.65 years for men and 0.67 years for women);Han men were overestimated by an average of 0.22 years and women by 0.04 years,and the overall MAE was 0.70 years(0.69 years for men and 0.70 years for women);The average difference between dental age and chronological age is less than 0.50 years in almost all age groups,regardless of Uygur or Han.Conclusion: Willems method has high applicability and accuracy in Urumqi Uyghur and Han population aged3-16 years.Nolla method is applicable to Urumqi Uyghur and Han minority population aged 15-16 years,except for females.Therefore,the establishment of the growth and development curve of permanent teeth maturity and chronological age can provide reference for evaluating the individual permanent teeth development and clinical diagnosis and treatment of Urumqi Uyghur and Han adolescents.