title: Impact of remaining zinc oxide-eugenol-based sealer on the bond strength of a resinous sealer to dentine after root canal retreatment.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  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 < 0.05). The control group had superior mean adhesion values (4.75 ± 1.47) that were significantly different from the others (P < 0.05). Ultrasound/xylol (2.53 ± 1.00) was superior to ultrasound (2.23 ± 0.72) (P < 0.05), ProTaper (2.20 ± 0.69), ProTaper/Xylol (2.12 ± 0.65), which were similar (P > 0.05). Bond strength was different in all thirds (P < 0.05) and decreased in the following sequence: cervical (3.19 ± 1.18), middle (2.58 ± 1.21) and apical (1.87 ± 0.68). Confocal analysis revealed residues of Endofill in dentinal tubules when the removal protocol was carried out with ProTaper, but not from ultrasound combined with xylol.
  
  
  CONCLUSIONS
  The OM was associated with higher bond strength values for filling material to root canals. The zinc oxide-eugenol-based sealer negatively affected the bond strength of AH Plus to root canal walls, regardless of the retreatment technique.
authors: School of Dentistry, University of Ribeirão Preto, Ribeirão Preto, Brazil.
authors: F J A
authors: FJ
authors: Rached-Junior
authors: M D
authors: MD
authors: Sousa-Neto
authors: A E
authors: AE
authors: Souza-Gabriel
authors: M A H
authors: MA
authors: Duarte
authors: Y T C
authors: YT
authors: Silva-Sousa
mesh_terms: D001840:Dental Bonding / Q000379:methods*; D005054:Eugenol / Q000737:chemistry*; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D018613:Microscopy, Confocal; D012387:Root Canal Filling Materials; D012390:Root Canal Therapy; D015034:Zinc Oxide / Q000737:chemistry*
chemical_list: D012387:Root Canal Filling Materials; D005054:Eugenol; D015034:Zinc Oxide
keywords: bond strength; confocal microscopy; endodontic sealer; retreatment