Four-year Outcome of Nonsurgical Root Canal Retreatment Using Cone Beam Computed Tomography: A Prospective Cohort Study.

INTRODUCTION The purpose of this prospective study was to investigate the 4-year outcome and prognostic factors of nonsurgical root canal retreatment determined by measuring the volumetric change of periapical radiolucencies on cone beam computed tomography (CBCT) scans. METHODS Ninety-seven endodontically treated teeth from 80 patients diagnosed as apical periodontitis and indicated for root canal retreatment were included. Retreatment was performed by 7 endodontic specialists using a standardized treatment protocol. The teeth were re-examined clinically and radiographically 48 to 67 months after retreatment. The volume of preoperative and postoperative periapical radiolucencies on CBCT images was independently measured by 2 examiners. Radiographic outcome is presented in 4 categories: absence, reduction, enlargement, or unchanged. Reduction or enlargement was determined when the volumetric change of radiolucenc was 20% or more. Multivariate logistic regression was performed for predictor analysis. RESULTS Sixty-two teeth (63.9%) from 50 patients returned for follow-up. Fifty-eight teeth were included in the prognostic analysis, all of which were symptom free. The 4 remaining teeth that had been extracted due to fracture were excluded. The total volume of periapical radiolucencies at 4 years postoperatively decreased by 94.6% compared to that preoperatively (P<0.001), with an average reduction of 83.4% (95% CI, 69.2-97.5%). The periapical radiolucencies were determined as absence in 44 teeth (75.9%), reduction in 10 teeth (17.2%), unchanged in 1 tooth (1.7%) and enlargement in 3 teeth (5.2%). Tooth type was identified as an outcome predictor (P<0.05). CONCLUSIONS The 4-year outcome of endodontic retreatment is predictable, with a significant volumetric reduction in periapical radiolucencies.