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

To evaluate the push-out bond strength of the dentine-sealer interface with and without main cone for three resin sealers.

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, EndoREZ or Resilon 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.

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 6.6 and 2.0 MPa, respectively; Resilon 3.4 and 0.4 MPa; EndoREZ 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.

Push-out bond strengths of resin sealers were much lower when the sealer was present as a thin layer.