Resistance of gutta-percha and calcium silicate-based sealer to dislocation after non-surgical root canal retreatment.

Background: Complete removal of calcium silicate-based sealers (CSBSs) during root canal retreatment remains challenging, and the effect of chloroform on the bond strength of these materials remains unclear. This study aimed to evaluate the impact of different retreatment techniques on the dislocation resistance of gutta-percha and CSBS to root canal dentin.

Methods: Extracted single-rooted human teeth were prepared and filled via the single cone technique with gutta-percha and EndoSeal MTA (Maruchi, Wonju, Korea). After four weeks, the samples were divided into five groups: (1) no retreatment, (2) retreatment without chloroform: (3) retreatment with supplementary instrumentation using XP-Endo Finisher R (XPEFR) (FKG Dentaire, La Chaux-de-Fonds, Switzerland), (4) retreatment with chloroform, and (5) retreatment with both chloroform and XPEFR. All the samples were then refilled with gutta-percha and EndoSeal MTA. One-millimeter slices from the mid-root were prepared for the push-out test (n = 15 per group). The bond strength was measured using a universal testing machine, and failure modes were recorded. Statistical analysis was performed using one-way and two-way ANOVA tests.

Results: Compared with all the retreatment groups, the control group presented significantly higher bond strength (9.20 ± 1.44 MPa) (P < 0.001). Push-out bond strength values for groups retreated without chloroform, either with or without using XPEFR, were 3.61 ± 1.27 and 3.18 ± 1.01, respectively. However, bond strength after applying chloroform, with or without supplementary instrumentation using XPEFR, was 3.96 ± 1.51 and 4.41 ± 1.32, respectively. The bond strength was significantly higher in the groups with application of chloroform compared with the other retreated groups (P = 0.022), whereas supplementary instrumentation with XPEFR did not have a significant effect (P = 0.982). The most common mode of bond failure across all groups was cohesive failure.

Conclusion: Within the limitations of this study, the dislocation resistance of EndoSeal MTA and gutta-percha to root dentin decreased after non-surgical retreatment. The application of chloroform during retreatment was associated with higher bond strength, whereas supplementary instrumentation with XPEFR had no significant effect.