Effects of Procedural Errors on Root Canal Treatment Outcomes: A Retrospective Cohort Study of Cases Treated by Sixth-year Dental Students

Objective: This study assessed the effects of various types of procedural errors arising from root canal instrumentation on initial root canal treatment outcomes. Methods: This retrospective cohort study analysed data from sixth-year dental students performing initial root canal treatment on mature permanent molars between 2015 and 2019. Treatment records and radiographic images were reviewed to identify procedural errors during root canal instrumentation and other potential confounding factors affecting treatment outcomes. Subsequently, uni and multivariate logistic regression analyses were performed to identify predictors of treatment outcomes. Results: A total of 142 teeth (343 roots) met the inclusion criteria, with an average follow-up period of 35.84±16.72 months. According to stringent assessment criteria, overall healing rates were 72.5% for the teeth (103 of 142) and 80.5% for the roots (276 of 343). Multivariate logistic regression analysis revealed that among the procedural errors considered, only errors related to under-instrumentation (root canal deviation and lateral perforation) were significant predictors of treatment outcomes (p=0.002). Conclusion: Root canal treatment outcomes are significantly influenced by procedural errors, particularly those affecting the root canal preparation length. Procedural errors related to under-instrumentation can compromise root canal disinfection and increase the risk of post-treatment disease by up to eightfold.