Push-out bond strengths of the dentine-sealer interface with and without a main cone

Aim To evaluate the push-out bond strength of the dentine-sealer interface with and without main cone for three resin sealers. Methodology Thirty extracted maxillary premolar teeth with two separate canals were prepared using 0.04 taper Profile instruments to size 35-45. Teeth were divided into three groups for filling using AH Plus (TM), EndoREZ((R)) or Resilon((R)) sealers. In each tooth, one canal was filled with a matching single-cone technique, and other was filled with sealer alone. A 1 mm slice of mid-root dentine was prepared for the push-out test. Failure modes after push-out were examined under microscopy and field emission-scanning electron microscopy. Data were analysed using two-way ANOVA and paired t-tests, with significance set at P < 0.05. Results Overall, the epoxy resin-based sealer provided the highest push-out bond strengths. Push-out bond strengths were significantly higher (P < 0.001) when canals were filled with sealer alone than those filled with main cone and sealer (AH Plus (TM) 6.6 and 2.0 MPa, respectively; Resilon((R)) 3.4 and 0.4 MPa; EndoREZ((R)) 0.9 and 0.4 MPa). Sealers appeared to behave differently as thin films in association with a main cone, compared with bulk material. They failed in cohesive mode within the thin film, leaving a layer of sealer on the canal surface. Bulk sealer showed predominantly adhesive failure at the dentine-sealer interface, with a clean dentine wall and with resin tags either partially pulled out or sheared off at the interface. Conclusion Push-out bond strengths of resin sealers were much lower when the sealer was present as a thin layer.