Age estimation at 18-year threshold: comparing Demirjian and Cameriere's methods for Thais

This study aims to compare the accuracy of Demirjian's and Cameriere's methods in determining adult age at the 18-year threshold using mandibular third molars in the Thai population. Panoramic radiograph images of 504 healthy subjects aged between 14 and 23 years were retrospectively collected. The developmental stages of mandibular third molars were evaluated using Demirjian's method, while the maturity index of mandibular third molars (I3M) was assessed using Cameriere's method. Comparing the development of the left and right mandibular third molars, slight differences were observed: the left side developed 0.06 stages faster (p = 0.01) and had an I3M 0.01 higher (p < 0.01). For the 18-year age threshold, Demirjian's Stage H demonstrated a specificity of 1.00 for both sexes on the left mandibular third molar, and 0.97 for males and 1.00 for females on the right. I3M < 0.08 yielded specificities of 0.84 for males and 0.93 for females on the left, and 0.82 for males and 0.91 for females on the right. Reducing the cut-off to I3M < 0.02 improved specificity to 1.00 for both sexes on the left side, and 0.96 for males and 1.00 for females on the right. Notably, using Demirjian's Stage H and I3M < 0.02, the probability of being over 18 years was 1.00 for females on both sides, and 0.96 for males on the left and 1.00 on the right. Our study recommends using an I3M cutoff of <0.02 for adult age assessment in the Thai population, as it achieves high specificity comparable to Demirjian's Stage H, with effective differentiation of adults.