Preliminary study on genetic factors related to Demirjian's tooth age estimation method based on genome-wide association analysis.

The age determination of individuals, especially minors, is critical in forensic research. In forensic practice, dental age estimation is one of the most commonly used methods for determining age as teeth are easy to preserve and relatively resistant to environmental factors. Tooth development is affected and regulated by genetic factors; however, these are not incorporated into current commonly used tooth age inference methods, leading to unreliable results. Here, we established a Demirjian and a Cameriere tooth age estimation-based methods suitable for use in children in southern China. By using the difference between the inferred age and the actual age (MD) as the phenotype, we identified 65 and 49 SNPs related to tooth age estimation from 743,722 loci among 171 children in southern China through a genome-wide association analysis (p<0.0001). We also conducted a genome-wide association study on dental development stage (DD) using the Demirjian tooth age estimation method and screened two sets of SNP sites (52 and 26) based on whether age difference was considered. The gene function enrichment analysis of these SNPs found that they were related to bone development and mineralization. Although SNP sites screened based on MD seem to improve the accuracy of tooth age estimation, there is little correlation between these SNPs and an individual's Demirjian morphological stage. In conclusion, we found that individual genotypes can affect tooth age estimation, and based on different phenotypic analysis models, we have identified some novel SNP sites related to tooth age inference and Demirjian's tooth development stage. These studies provide a reference for subsequent phenotypic selection based on tooth age inference analysis, and the results could possibly be used in the future to make forensic age estimation more accurate.

Combining the third molar mineralization to further improve the accuracy of the Kvaal's method in dental age estimation of subadults in northern China.

The morphological changes based on deposition of secondary dentin and mineralization of the third molar have been proven to be related to chronological age. However, Kvaal's method on the theory of deposition of secondary dentin was controversial with respect to dental age estimation in the recent research. The aim of this study was to combine the parameters of Kvaal's method with relatively high correlation coefficients and mineralization stages of the third molar to improve the accuracy of predicting the dental age of subadults in northern China. A total of 340 digital orthopantomograms of subadults aged from 15 to 21 years were analysed. A training group was used to test the accuracy of the original Kvaal's method and to establish novel methods for subadults in northern China. A testing group was used to compare the accuracy of the newly established methods with the Kvaal's original method and with published method specifically used in northern China. To increase the feasibility of our estimation model, we combined the mineralization of the third molar to build a combined specific formula. The results showed that the combined specific model increased the coefficient of determination to 0.513, and the standard error of the estimate was reduced to 1.482 years. We concluded that the combined specific model based on the deposition of secondary dentin and mineralization of the third molar could improve the accuracy of dental age assessment of subadults in northern China. Key Points: The decrease in the dental pulp cavity based on deposition of secondary dentin is a useful variable for assessing age.A total of 340 orthopantomographs were used in this research, including 278 in training groups and 62 in testing groups.Original Kvaal's method underestimated the dental age for subadults in northern China.The equation of combined specific method constructed in our study was proved more suitable to calculate dental age for subadults in northern China.

Comparing the accuracy of Demirjian and Nolla methods and establishing a new method for dental age estimation in northeastern Chinese children.

Dental age estimation plays an important role in the field of clinic medicine and forensic medicine. The Demirjian and Nolla methods are common scoring methods for dental age estimation but there was no research about the comparison of accuracy of these two methods in northeastern Chinese children. Hence, in this study, we compared the accuracy of these two methods to explore more suitable method for our studied population. We collected 535 orthopantomograms from northern Chinese children aged from 6 to 15 years and divided them into training dataset and testing dataset according to the ratio of 7:3. The dental age of training dataset were estimated using Demirjian and Nolla methods, respectively. The results suggested that the mean differences of these two methods were 0.24 and -0.40 years, and mean absolute difference were 0.65 and 0.59 years. Then to further improve the accuracy of dental age assessment, the new improved formulas and dental age conversion tables were established after analyzing the relationship between the sum scores based on Nolla method and chronology age in training dataset. According to the new method used in testing dataset, the minimum value of mean difference (0.00) and mean absolute difference (0.49) were obtained, which are largely smaller than that of Demirjian and Nolla methods. The new developed method and dental age conversion scales may be more suitable dental age estimation method for northeastern Chinese children.