Predicting early endodontic treatment failure following primary root canal treatment

Background: Understanding when and why endodontic treatments fail could help clinicians make prognoses and thus improve treatment outcomes. This study was aimed to assess potential predictors of early endodontic treatment failure. We explored factors contributing to the failure of initial root canal treatment were explored, with a specific emphasis on evaluating the influence of the time elapsed since the initial treatment. Methods: This retrospective cohort study enrolled 1262 patients who sought endodontic treatment at our department and 175 patients were included for analysis. Potential causes of endodontic treatment failure were investigated, such as inadequate obturation quality, inadequate coronal status, the presence of additional untreated canals, anatomical complexity, instrument separation, iatrogenic perforation, cracks, and endodontic-periodontal lesions. The patients were divided into “short-term” and “long-term” groups depending on the time that had passed since the initial treatment (i.e., < 5 and > 10 years, respectively). The causes of failure in the short-term and long-term group were analyzed and compared using logistic regression analyses. Subgroup analysis was performed according to the number of years since the initial treatment in the short-term group to further investigate the association between the time and cause of failure (i.e., < 1, 2, 3, and 4 years, respectively). Results: Untreated additional canals were present in 21.7% of all cases, and in 36.9 and 6.4% of cases in the short-term and long-term groups, respectively. Multivariable analysis showed that the presence of untreated additional canals was significantly associated with short-term compared to long-term failure. Untreated additional canals were also associated with endodontic failure within 1, 2, 3, and 4 years. Conclusions: The presence of untreated additional canals was a predictor of endodontic failure within 5 years following initial root canal treatment. To optimize long-term prognosis, it is important to detect and treat all root canals during the initial treatment.