Factors affecting long-term success and survival in non-surgical root canal retreatment; a retrospective cohort study

This retrospective study aimed to evaluate the long-term (≥ 5 years) survival and success rates of nonsurgical root canal retreatment (NSRT) and to determine the prognostic factors associated with these outcomes.

A total of 943 teeth from 740 patients treated with NSRT by two experienced endodontists between January 1, 2015, and January 1, 2020, were reviewed. Based on strict inclusion and exclusion criteria, 408 teeth (376 patients) were included. Clinical and radiographic follow-ups were conducted. Periapical healing was assessed using the periapical index (PAI) by two calibrated examiners. Tooth retention was defined as survival, regardless of periapical status. Treatment success was determined using combined clinical and radiographic criteria. Multivariate logistic regression analysis was used to identify significant predictors.

A total of 408 teeth (376 patients) that met the inclusion criteria were included. The survival and success rates were 73.5%. Among surviving teeth, the success rate was 79%, after a follow-up of 78.5 ± 10.5 months. Restoration type (p < 0.001) and initial root canal obturation quality (p = 0.007) significantly influenced survival. Root or crown fractures accounted for 66.7% of extractions, with restoration type significantly related to extraction reason (p < 0.001). Success was significantly associated with pre-NSRT obturation quality (p = 0.035) and restoration quality (p < 0.001).

Coronal restoration quality and initial obturation status appear to be important predictors of long-term NSRT outcomes.

Observational data from routine endodontic practice help clarify long-term retreatment outcomes by revealing survival and success rates and identifying possible prognostic factors over a follow-up of at least five years.