Third molar maturity index cut-off valueoptimization for legal age of majorityin Indonesian juveniles

Introduction: Third molar maturity index (I 3M ) can be used as a method to provide probability of legal age majority; however, the method's performance is known to be population-specific.Objectives: To assess the performance of I 3M in Indonesian juvenile population using a new cut-off value calculation to determine whether an individual has reached age of 18 years. Material and methods:The sample consisted of 900 panoramic radiographs, with an even distribution of age and sex, from 15 to 23.98 years old.I 3M measurement was calculated by the sum of lengths from inner margins of the tooth apical ends, divided by the tooth length from apical to the end of the highest point of the crown.If apices were closed, the I 3M was counted as 0. Probability of an individual being above or below 18 years old given a certain I 3M was done using logistic regression, and optimal cut-off value was calculated with highest Youden's index value. Results:The utilization of non-sex-specific cut-off value provided an accuracy of 0.88 for both sexes, with a recommended cut-off value of I 3M 0.1.The probabilities of an individual to be above 18 years old were 0.82 and 0.95 if I 3M 0.04 for males and females, respectively.Conclusions: The third molar maturity index can be an effective tool for accurately classifying whether an Indonesian' individual is above or below 18 years old, with a recommended cut-off value of 0.1 for both sexes.