Assessment of periodontal ligament visibility in third molars for threshold-based forensic age estimation: a cross-sectional study in a Turkish population

Forensic age estimation in living individuals is particularly challenging near legally relevant age thresholds after dental maturation is complete. This study aimed to evaluate the applicability of periodontal ligament (PDL) visibility staging in third molars as a post-maturation marker for threshold-based forensic age estimation, with specific focus on the 21-year age cut-off, in a Turkish population. A retrospective analysis was conducted on 1,049 digital orthopantomograms (OPGs) of individuals aged 15–25 years. PDL visibility in maxillary and mandibular third molars was assessed according to the Olze et al. staging system. Associations between PDL stages, chronological age, sex, and tooth position were analyzed. Diagnostic performance for identifying individuals aged ≥ 21 years was evaluated using receiver operating characteristic (ROC) analysis. Advanced PDL visibility stages were significantly associated with increasing age. Mandibular third molars provided the most informative staging patterns. ROC analysis demonstrated good discriminative accuracy for the 21-year threshold, with an area under the curve (AUC) of 0.79, indicating balanced sensitivity and specificity for threshold-based classification. Substantial intra- and inter-observer agreement confirmed methodological reliability. PDL visibility staging in third molars represents a reliable and reproducible complementary tool for forensic age estimation around the 21-year threshold in a Turkish population. Rather than exact age prediction, this method supports probabilistic decision-making in legally relevant age assessment and may contribute to a multimodal forensic age estimation framework.