Validity of the Demirjian method for dental age estimation when applied to Norwegian children.

Dental age was studied in a sample of 261 Norwegian children by using the maturity standards of Demirjian & Goldstein (1976) to examine the applicability of these standards as a reference for overall dental maturity in a Norwegian population. The sample comprised 128 boys and 133 girls included in 'the Oslo Growth Material', from whom orthopantomograms (total, 783) had been longitudinally obtained, with intervals of about 3 years and covering 3 age spans (5.5-6.5 years, 8.5-9.5 years, and 11.5-12.5 years), each divided into 3 half-year age groups. Reliability was analyzed by repeated assessments of 134 of the radiographs, and the overall mean difference between duplicate dental age determinations was 0.5 months for intra- and 1.8 months for inter-examiner comparisons. The Norwegian children were generally somewhat advanced in dental maturity compared with the French-Canadian reference sample. Among the boys the mean difference between dental age and chronologic age varied in the different age groups from 1.5 to 4.0 months. Among the girls the difference increased with age, varying from 0 to 3.5 months in the younger age groups (5.5 to 9.0 years) and from 4.5 to 7.5 months in the age groups 9.5 years and above. The variability in individual dental age was marked and increased with age. For the older age groups 95% of the individual age estimates were within +/-2 years of the real age. The applied standards appear to be adequate for studying dental age in groups of children from a Norwegian population. Given the considerable individual variation in dental maturity, estimation of chronologic age in individual children should be supplemented by other indicators of biologic maturity.