Impact of remaining zinc oxide-eugenol-based sealer on the bond strength of a resinous sealer to dentine after root canal retreatment

Aim To evaluate the bond strength of a resin‐based sealer (AH Plus) to root canal dentine after the removal of a zinc oxide‐eugenol–based sealer (Endofill), using different retreatment techniques. Methodology The root canals of sixty‐four maxillary incisors were prepared with ProTaper and filled with Endofill/gutta‐percha. After thermocycling, the roots were randomly assigned according to the retreatment technique (n = 16): (A) ProTaper, (B) ProTaper/xylol, (C) ultrasound and (D) ultrasound/xylol and according to whether an operating microscope (OM) was used or not (n = 8): GI‐ direct vision (DV) and GII‐ indirect through the OM. Eight additional roots were instrumented and filled with AH Plus/gutta‐percha (control). Roots were sectioned to obtain 1‐mm‐thick slices. Slices were used in the push‐out test and in confocal microscopy. Data were submitted to anova and Tukey test (α = 0.05). Results The specimens filled under the OM (2.50 ± 0.90) had higher bond strength values of sealer to root canal walls (P