Long-term Outcomes of Predoctoral Root Canal Therapy: Retreatment and Tooth Loss in a 17-year Institutional Cohort

Nonsurgical root canal therapy (RCT) is predictable; however, some teeth develop post-treatment disease requiring retreatment or extraction. This study evaluated the durability of predoctoral RCT by quantifying retreatment and tooth loss within a single institutional cohort.

This retrospective chart review used Axium records from January 1, 2008, through October 31, 2025. All nonsurgical RCTs in the predoctoral clinic (n = 7,340) were identified. Phase I quantified retreatment frequency. Phase II characterized retreated teeth by diagnosis, radiographic quality, intracoronal core placement, restoration status, and timing. Phase III linked RCTs to extraction codes to assess tooth loss and time-to-event patterns. Descriptive statistics, Kaplan-Meier analyses, and an exploratory two-by-two analysis of retreatments attributed to suspected coronal leakage and restoration status were performed.

Of 7,340 RCTs, 131 teeth underwent retreatment (1.78%) and 531 were extracted (7.23%), yielding a 9.02% combined adverse outcome rate. Retreatment occurred at a median of 1.21 years and was most commonly attributed to suspected coronal leakage, obturation deficiencies, and missed canals. Teeth without documented intracoronal core placement demonstrated earlier retreatment and higher odds of retreatment attributed to suspected coronal leakage without definitive restoration (odds ratio 1.98; 95% confidence interval 0.99-3.97). Extractions occurred at a median of 2.10 years, with no survival differences among tooth types.

Retreatment after predoctoral RCT was uncommon, whereas extraction occurred more frequently. Early retreatments and later extractions represent distinct endpoints, emphasizing durable coronal sealing and timely definitive restoration for long-term tooth retention.