INTRODUCTION: This study's aim was to calculate the incidence of first additional endodontic treatment or extraction as the result of an unfavourable endodontic outcome following orthograde root canal treatment (RCT) performed by general dental practitioners (GDPs) during a 10-year period and to identify possible predictors for outcomes.

METHODS: A randomised cohort of 280 individuals (and as many teeth) with an orthograde RCT was followed for over 10 years. Dental records were reviewed, and individuals were recalled when data were missing. The following terminal events indicative of unfavourable endodontic treatment outcome were orthograde retreatment, surgical endodontics, and tooth extractions exclusively due to endodontic reasons. Selected variables related to individuals and treatment (pre-, intra-, and post-operative) were harvested to analyze possible associations with the terminal events. Unadjusted survival analysis and Cox regression analysis were performed and P < 0.05 was considered statistically significant.

RESULTS: Terminal events were registered for 22 teeth/individuals and 17 of these were orthograde retreatments. The cumulative 10-year survival of RCTs was 92.7% (standard error 1.7%), with a higher yearly incidence during the first two years. The univariate analysis identified five factors associated with the outcome. There were too few events to perform a multivariate analysis.

CONCLUSIONS: The mean incidence of additional treatment indicative of unfavourable endodontic outcome was 0.7% per year during the first 10 years, but the mean incidence was greater during the first two years. Five factors were associated with an unfavourable outcome; however, confounders cannot be excluded from the associations.