Applicability of CBCT-Based Imaging Parameters of the Left Mandibular Molars for Estimating Legal Age Thresholds in Adolescents

Abstract Objective To investigate the applicability of cone beam computed tomography (CBCT)-based imaging parameters of the left mandibular molars for determining whether adolescents have reached the legal age thresholds of 12, 14, and 16 years. Methods CBCT images of 180 adolescents aged 10–18 years were retrospectively collected. Imaging parameters of the left mandibular molars were assessed, including the third molar maturity index (I₃M), apical closure status of the left mandibular second molar (AC_37), and other imaging parameters. Receiver operating characteristic (ROC) curve analysis was performed for the age thresholds of 12, 14, and 16 years. The discriminative performance of each individual parameter and multivariable models was evaluated using the area under the ROC curve (AUC), sensitivity, specificity, and accuracy. Results ROC curve analysis showed that combined model 1, incorporating I₃M and AC_37, demonstrated better discriminative performance than the individual imaging parameters. The AUC values of the model for determining the age thresholds of 12, 14, and 16 years were 0.933, 0.947, and 0.921, respectively. Its sensitivity, specificity, and accuracy exceeded 83% for all three age thresholds. Conclusions A multivariable model based on CBCT imaging parameters of the left mandibular molars can improve the determination of the 12-, 14-, and 16-year age thresholds and may serve as an adjunctive tool for age assessment in adolescents. Clinical registration This study was registered with the National Medical Research Registry Information System (https://www.medicalresearch.org.cn/) (registration number: MR-44-26-026887; registration date: April 17, 2026) and the Chinese Clinical Trial Registry (https://www.chictr.org.cn/) (registration number: ChiCTR2600125689; registration date: May 29, 2026).