Association Between the Presence of Missed Canals, Detected Using CBCT, and Post-Treatment Apical Periodontitis in Root-Filled Teeth: A Systematic Review and Meta-Analysis

Background. Post-treatment apical periodontitis (PAP) is a frequent consequence of root canal treatment (RCT) failure, often caused by untreated missed canals in root-filled teeth (RFT). While cone-beam computed tomography (CBCT) has been used to find these missed canals, the results are controversial. This systematic review and meta-analysis investigates the association between PAP in RFT and missed canals detected via CBCT. Methods. Two independent reviewers searched PubMed, Scopus, Dialnet, and SciELO for relevant articles published up until 17 February 2025. The main outcome was the prevalence of PAP in RFT with and without missed canals detected via CBCT. The overall odds ratio (OR) was calculated using a binary random effects model meta-analysis (OpenMeta Analyst). Risk of bias was assessed using the Newcastle–Ottawa Scale, and certainty was evaluated using GRADE. Results. Eight cross-sectional studies (9983 RFT) were included in the review. The pooled prevalence of PAP was significantly higher in RFT with missed canals (85.1%) than those without (56.3%). The meta-analysis showed a strong association between missed canals and PAP (OR = 7.17, 95% CI = 4.55–11.29), indicating a sevenfold increased likelihood. Maxillary molars, especially first molars, most commonly had missed canals. Heterogeneity was high (I2 = 86%), and evidence certainty was low, due to methodological limitations. Conclusions. Untreated missed canals significantly increase the likelihood of PAP in RFT, highlighting the need for thorough canal detection and treatment. Clinicians should prioritize anatomical knowledge and advanced imaging to minimize treatment failure.