Accuracy of the estimation of dental age in comparison with chronological age in a Spanish sample of 2641 living subjects using the Demirjian and Nolla methods

- The Nolla and Demirjian methods are totally reproducible and accurate.
- Nolla method under-estimated age by 0.213 years on average.
- Demirjian method over-estimated age by 0.853 years on average.
- The predictive capacity of the new combined model was found to be 99.2%.

Age estimation is an important procedure in forensic medicine and is carried out for a number of reasons. For living persons, age estimation is performed in order to assess whether a child has attained the age of criminal responsibility, in scenarios involving rape, kidnapping or marriage, in premature births, adoption procedures, illegal immigration, pediatric endocrine diseases and orthodontic malocclusion, as well as in circumstances in which the birth certificate is not available or the records are suspect. According to data from the UNHCR (United Nations High Commissioner for Refugees), the number of people seeking refugee status continued to increase in the last years, driven by the wars in Syria and Iraq, as well as by conflict and instability in Afghanistan, Eritrea and elsewhere. The objective of this study is to compare the accuracy of estimating dental age versus chronological age using the Nolla and Demirjian methods in a Spanish population. A final sample of 2641 panoramic X-rays corresponding to Spanish patients (1322 males and 1319 females) between 7-21 years of age was analyzed. Dental age was assessed using the Nolla and Demirjian methods, establishing comparisons with mean chronological age based on the Student t-test for paired samples, followed by the generation of a linear regression model. Both methods showed slight discrepancy between dental and chronological age. On examining the reproducibility of the Nolla and Demirjian methods, technical errors of 0.84% and 0.62%, respectively, were observed. On average, the Nolla method was found to estimate an age 0.213 years younger than the chronological age, while the Demirjian method estimated an age 0.853 years older than the chronological age. Linear combination of the mean Nolla and Demirjian estimates increased the predictive capacity to 99.2%. In conclusion the Nolla and Demirjian methods were found to be accurate in estimating chronological age from dental age in a Spanish population. The error was found to be greater in males than in females, and involved an over-estimation of age with the Demirjian method and under-estimation of age with the Nolla method. Combination of the Nolla and Demirjian methods for estimating chronological age from dental age affords a predictive capacity of over 99%, and is fast and easy to perform, and inexpensive.