An Analysis of Mincer's Method and UT-Age

Third molars have the most developmental variation of all human dentition, yet Mincer’s method and the computer program UT-Age use third molars to estimate the age of migrants crossing the U.S. border. Most migrants subjected to dental exams are classified as Hispanic. However, the term and reference samples used to estimate age do not account for the possible population variation that the term “Hispanic” can encompass. Additionally, third molar reference samples do not address the possible influence of impaction on third molar development. The objective of this study is to assess the effects of various sources of third molar variation on the application of Mincer’s method and the UT-Age program that are currently employed to assess migrants at the border.

To address this objective, this study tests three hypotheses using radiographs from individuals categorized as Hispanic, possibly Hispanic, and Native American: (1) the development of third molars will vary between groups, sexes, and arches, (2) impaction will influence development, and (3) UT-Age will tend to incorrectly predict whether an individual is 18 or older.

Radiographs from 1,120 individuals provided by the University of New Mexico Orthodontics Case File System and the Arizona Pima County Office of the Medical Examiner were scored using Mincer’s method. These data were then entered into the UT-Age program to arrive at probabilities of legal age. Using the mean ages for each developmental stage, a suite of statistical analyses was conducted to assess effects of third molar variation.

Results show imprecise age association with third molar developmental stages. Significant differences were found in mean ages per developmental stage between the social race groups. Mean ages did not vary between arches, but they did vary between the sexes. Additionally, the mean ages of impacted third molars were found to be older than the mean ages of the non-impacted molars, indicating slowed development of impacted third molars. The UT-Age program was also found to misclassify individuals that had reached 18 years as younger than 18 years. Given these results, Mincer’s method, UT-Age program, and reference samples used are not suitable for living individuals and must be reevaluated.