Third molar maturity index for discriminating between adults and minors: validation in an Iranian sample

The life-altering effects of criminal trials necessitate providing reliable methods to distinguish adults (≥18) from minors (< 18). The present study aims to evaluate the accuracy of the third molar maturity index (I3M) introduced by Cameriere et al. (2008) in distinguishing adults from minors in the Iranian population. Panoramic radiographs of 800 Iranian individuals (400 males and 400 females) aged 14-23 were evaluated. The cut-off value of I3M=0.08 was analysed to determine whether the individual is younger or older than 18. All male or female subjects with I3M above 0.7 were below 18 years old. The cut-off value of 0.08 showed a sensitivity of 80.83% and 63.33% and a specificity of 88.12% and 93.12%, respectively, in males and females. The positive predictive values were 91.08% and 93.25%, and the negative predictive values were 75.40% and 62.87%, respectively, for males and females. The Bayes' post-test probability was 94% for females and 92% for males. 83.75% of males and 75.25% of females correctly classified as adults or minors. The most remarkable error rate occurred at 18 years old (67.5 % in females and 57.5% in males). By ROC curve analysis, the population-specific cut-off values of I3M 0.097 for males, 0.116 for females, and 0.099 regardless of sex, were acquired, which improved the sensitivity of discrimination between adults and minors (86.3%, 73.8%, and 78.1 %, respectively). The results showed that I3M is a reliable method for distinguishing between minors and adults in the Iranian population. This method provides a higher accuracy level in identifying individuals under 18 years old. Population-specific I3M cut-off values increased accuracy, sensitivity, and NPV, especially for females. The I3M method produced better results in diagnosing adult males than adult females and a higher accuracy level in identifying individuals under 18.