Validation of Cameriere's third molar maturity index (I3M) for forensic age estimation in a Moroccan population: a cross-sectional study.

Abstract

Forensic age estimation in living individuals is a critical component of medicolegal practice, particularly for determining whether a subject has reached the legal age of majority of 18 years. The Third Molar Maturity Index (I3M) proposed by Cameriere et al. provides a quantitative radiographic approach based on the ratio between open apical widths and tooth length of the mandibular third molar, with a widely validated cut-off value of 0.08. However, population-specific validation remains essential, as dental maturation is known to vary across ethnic groups, and to the best of our knowledge, there are no data available for North Africa, and in particular for Morocco. This study aimed to validate the I3M cut-off value of 0.08 for assessing the legal adult age of 18 years in a Moroccan population sample and to identify an optimal population-specific cut-off value using ROC curve analysis. A cross-sectional study was conducted on 629 digital panoramic radiographs from Moroccan patients aged 10 to 36.8 years (333 females, 296 males). The I3M was measured on the lower left third molar (tooth 38). Sensitivity, specificity, accuracy, positive and negative predictive values, likelihood ratios, and the area under the ROC curve (AUC) were calculated. Test ROC analysis was used to determine the optimal cut-off value. Using the standard I3M ≥ 0.08 cut-off, sensitivity was 79.71% (95% CI: 68.31-88.44%), specificity 93.28% (95% CI: 89.46-96.04%), and diagnostic accuracy 90.37% (95% CI: 86.61-93.36%). The AUC was 0.907. An optimal population-specific cut-off of I3M ≥ 0.049 was identified, yielding a sensitivity of 91.3% and specificity of 91.7%. The I3M is a valid and accurate forensic tool for distinguishing minors from adults in the Moroccan population. The standard cut-off of 0.08 demonstrated high specificity, thereby minimizing misclassification of minors as adults. A population-specific cut-off of 0.049 may offer improved balanced diagnostic performance. These findings provide the first I3M reference data for Morocco and support its integration into forensic age estimation protocols in North Africa.