(PR35) Retreatability of Molars with Curved Canals Using Conventional and Retreatment Files

Abstract: Rotary file systems for non-surgical root canal treatment (NSRCT) are commonly used for non-surgical retreatment (Retx). Contemporary Retx-file systems are designed for safer/faster removal of obturation materials. Currently, limited data on the efficacy of Retx-file systems exists. This study aims to evaluate the efficacy of NSRCT-files and Retx-files for retreatment of curved canals. 140 molars with curved roots were scanned using CBCT. Teeth with existing NSRCT, fractures, calcifications, open apices, and resorption were excluded. Planmeca Romexis® was used to evaluate, map, and classify 145 canals for their curvature. Apical patency with #10 K-files was achieved in 88 canals that were then instrumented to size 30/.04 2 mm short of the apex. Canals were obturated using a single gutta-percha cone and BC Sealer HiFlow. Samples were stored in HBSS at 37oC for one month. Four groups (n=22) were retreated using ProTaper® Gold and Universal Retreatment (PTGD), XP-3D Shaper™ (XP3D), Endo ReStart (ERS), or HyFlex™ Remover (HyFR) systems without solvents. Whether or not patency was achieved in 10 minutes and the time to achieve patency were recorded. Data were analyzed via the generalized linear model with a binomial distribution. Patency rates were 81.8% for XP3D and HyFR, 59.1% for ERS, and 50.0% for PTGD. XP3D and ERS demonstrated significantly lower patency times than PTGD (p < 0.05). No significant differences occurred in patency rate or time between curvature classifications. Compared to PTGD, XP3D and HyFR exhibited significantly higher patency rates while XP3D and ERS exhibited significantly lower patency times for retreatment without solvents.