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Population Variation in Dental Development and Its Effect on Forensic Age Estimation
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Dental development is considered the most accurate method of age estimation in subadults, as this process is less subject to external and internal influences than skeletal development. However, dental development can be affected by secular change, socioeconomic status, sex, and ancestry. Therefore, it is problematic that the established methods for subadult dental age estimation in the United States are based on foreign samples or are outdated. This dissertation has two goals: 1) to create age estimation methods based on dental development from a modern sample of U.S. children; and 2) to analyze the effects of sex and/or ancestry differences in dental development on age estimation. Dental development was evaluated from 1,757 orthopantomograms of individuals ages 5-20 taken between 1972 and 2017, using widely employed scoring systems (Demirjian et al. 1973; Moorrees et al. 1963). Values for intraobserver error suggest that the Demirjian et al. (1973) system is more consistently applied; therefore, these scores are used in subsequent tests. The overall trend is that no significant differences in developmental scores exist between groups. When there are significant differences (α < 0.05), dental development in females is more advanced than males, and Hispanic dental development is more advanced relative to European Americans. There are fewer significant differences between the other ancestry groups, likely as a product of small sample size. Age estimation methods that do and do not account for sex and/or ancestry differences are created from a training subset of the total sample, to evaluate whether group-specific methods of age estimation perform significantly better than general methods. Confidence intervals (CIs) are created for each developmental score for every tooth in the training sample. CIs based on all individuals are comparably accurate to and more precise than CIs based on group-specific subsets. Therefore, the use of CIs based on the whole sample is recommended for age estimation from a single tooth. Linear models are created to estimate age from multiple teeth. Models based on all individuals exhibit comparable accuracy and precision to those based on subsets of sex and ancestry. Estimating sex and ancestry in juveniles can be difficult; therefore, the models based on all individuals are recommended for skeletonized juvenile remains. However, in living individuals, models based on females, males, European Americans, and Hispanics are slightly more accurate and precise than models based on all individuals and are therefore recommended. There are currently no age estimation methods using dental development that are derived from a modern American population. The methods presented here fill that void. Since the analysis of dental development is non-invasive and non-destructive, these age estimation methods can be applied to both the living and the deceased, potentially increasing the accuracy of age estimations in the forensic context in the U.S.