Population-specific validation of the distal root canal width method for forensic age estimation in a Spanish sample.

Forensic age estimation in living individuals is essential in legal and migratory contexts, particularly when assessing whether an individual has reached the age of majority. The method proposed by Roberts et al. evaluates the relative distal root canal width (RCW) of mandibular molars, a parameter measurable only after complete apical closure. This method has not yet been validated in a Spanish population, making its regional evaluation essential due to known population-specific variations in dental maturation. A retrospective cross-sectional study was conducted on 576 digital orthopantomographs of individuals aged 16-24 years presenting with complete apical closure of the mandibular molars LL6, LL7, and LL8. Distal root canal patterns were classified into categories A, B, C, and U. Intra- and inter-observer agreements, association with legal adulthood, diagnostic accuracy, and receiver operating characteristic curves were evaluated. Reproducibility was high (kappa > 0.80). Category RCW-C was the only pattern significantly associated with legal adulthood (odds ratio = 2.58; p = 0.006), showing high specificity (84.6%) and positive predictive value (94.2%), but low sensitivity (31.9%). Area under the curve values ranged from 0.665 in males to 0.616 in females, indicating modest discriminative performance. In conclusion, RCW-C is a specific and reproducible indicator associated with legal adulthood in individuals with fully developed mandibular molars. However, its limited sensitivity underscores that the method should be used only as a complementary tool within a multimodal forensic age estimation protocol.