Unquestionable forensic age investigations are based on statistical models constructed
on a sample containing subjects of identical origin as the examined individual. In
cases where corresponding models are unavailable, the established report has to describe
the possible effects of this unrelated information on the predicted age outcome. The
aim of this study is to collect country specific databases of third molar development
and to verify how the related dental age estimations are influenced if we were to
use dental developmental information only from Belgium or from all collected countries
together. Data containing third molar developmental stages scored following Gleiser
and Hunt (modified by Köhler) were collected from 9 country specific populations (Belgium,
China, Japan, Korea, Poland, Thailand, Turkey, Saudi-Arabia and South-India). Age
predictions were obtained from a training dataset and validated on a test dataset.
Bayes rule using the repeated third molar scores is applied to get age predictions
and prediction intervals. Three age predictions were compared for males and females
separately. For the first prediction, the training dataset contains only Belgian subjects.
For the second prediction, the training dataset for each country consists only of
subjects of the country itself. For the final prediction, subjects from all countries
are pooled into one common training dataset. Besides the (absolute) difference between
the chronological age and the predicted age, specific interest lies in the juvenile-adult
distinction. In the age range from 16 to 22 years 6982 subjects (3189 male and 3793
female) were analyzed. Using information on third molar development from Belgium compared
to information from the country specific databases hardly increased the mean absolute
differences (MAD) and mean squared errors (MSE): the MAD and MSE increased on average
with 0.5 and 2.5 months with maximal increases of, respectively 1.6 and 7.3 months.
Using information from all countries pooled compared to country specific information
provided even on average negligible increases (0.05 and 0.2 months for MAD and MSE,
respectively). For the juvenile-adult discrimination, using information from all countries
instead of country specific information yielded comparable performances. Using Belgium
instead of country specific information increased the percentage of correctly identified
juveniles, but decreased the percentage of correctly identified adults. The adult-juvenile
discrimination based on information used from Belgium provides judicially the best
applied reference.
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