CBCT-based retrospective assessment of apical closure timing in permanent second molars

The aim of this cone-beam computed tomography (CBCT)-based retrospective study was to evaluate the age-related prevalence of closed apices in permanent maxillary and mandibular second molars in a Turkish pediatric and adolescent population. Additionally, potential sex-related differences in closed apices were investigated. This study included 357 individuals (714 teeth) aged 12–21 years whose CBCT scans were retrieved from the digital archive. The apical status of permanent second molars was evaluated three-dimensionally using multiplanar reconstruction. According to root development, teeth were classified into two groups: those with closed apices in all roots and those with at least one open apex. Age was categorized into seven groups (12–12.99, 13–13.99, 14–14.99, 15–15.99, 16–16.99, 17–17.99, and ≥ 18 years). Associations between closed apices, age, and sex were analyzed using Pearson’s chi-square test and Fisher’s exact test (p < 0.05). The prevalence of closed apices increased markedly with age in both jaws. Rates were low in the 12–12.99 age group (maxillary 2.1%; mandibular 5.4%), exceeded 60% by 14–14.99 years, and approached completion by 16–16.99 years, reaching 100% in individuals aged ≥ 18 years. Overall, no statistically significant difference was observed between permanent maxillary and mandibular second molars (p > 0.05). However, in the 13–13.99 and 14–14.99 age groups, females demonstrated significantly higher rates of closed apices than males in both jaws; in the 15–15.99 age group, this difference was significant only for permanent maxillary second molars (p < 0.05). Closed apices in permanent second molars show a marked age-related increase and tend to occur earlier in females than in males during certain adolescent age groups. These findings support the use of closed apices in second molars as a reliable indicator for both endodontic treatment planning and forensic age estimation. Knowledge of the relationship between age and sex and the rates of closed apices in permanent second molars play an important role in both forensic dentistry and in endodontic and pediatric treatment planning.