Incidence and predictors of root resorption after delayed replantation of permanent teeth

Root resorption is a common but unpredictable complication after delayed replantation of avulsed permanent teeth. Evidence from real-world settings regarding its long-term incidence and associated clinical factors remains limited. This study aimed to determine the incidence of root resorption and identify clinical factors associated with its occurrence following delayed replantation of permanent teeth in a real-world tertiary care setting. This retrospective cohort study analyzed patients aged 7-30 years who underwent delayed replantation (> 60 min extra-alveolar time) between 2019 and 2022 at a tertiary dental trauma center, with ≥ 12 months of follow-up. Clinical and radiographic data were reviewed, and root resorption was classified according to predefined radiographic and clinical criteria. Multivariable logistic regression was used to identify factors associated with the occurrence of root resorption, while Kaplan-Meier survival analysis and Cox proportional hazards regression were performed to evaluate the time to first root resorption event. Competing-risk analysis was conducted, considering tooth extraction as a competing event. Among 120 eligible patients (mean age 14 ± 5 years), root resorption occurred in 72 teeth (60.0%), including inflammatory (41.7%) and replacement (58.3%) types based on radiographic and clinical classification. Among all delayed replanted teeth, the estimated tooth survival and functional retention rates at 24 months were 78.3% and 68.3%, respectively. Teeth with root resorption showed longer extra-alveolar times, more frequent dry storage, and delayed or absent root canal treatment (all P < 0.01). Multivariable logistic regression identified prolonged extra-alveolar time (> 2 h), dry storage, absence of root canal treatment, and delayed endodontic intervention (> 14 days) as factors associated with a higher occurrence of root resorption. Multivariable logistic regression identified prolonged extra-alveolar time (> 2 h), dry storage, absence of root canal treatment, and delayed endodontic intervention (> 14 days) as factors independently associated with a higher occurrence of root resorption. Root resorption occurred in 60% of delayed replanted teeth in this cohort. Prolonged extra-alveolar time, dry storage, and delayed or absent endodontic treatment were independently associated with a higher occurrence of root resorption. These findings highlight the importance of timely management and appropriate endodontic intervention after delayed replantation; however, the retrospective single-center design limits causal interpretation, and further prospective studies are needed to validate these associations.