Active application of liquid etching agent improves adhesion of fibre posts to intraradicular dentine.

To assess the effectiveness of an active application of liquid etching, compared with the standard gel formulation on smear layer removal from post space walls and push-out bond strength of luted fibre posts.Human extracted teeth were collected and root filled. After post space preparation and cleaning with 10\% ethylenediaminetetraacetic acid for 30 s, teeth were assigned to four groups (n = 11) according to etching procedure: (i) 37\% phosphoric acid (H3 PO4 ) gel; (ii) 37\% H3 PO4 liquid applied with an endodontic needle; (iii) 37\% H3 PO4 liquid applied with an Endovac; (iv) no etching procedure (control group). Three teeth per group were sectioned longitudinally and prepared for SEM examination to evaluate the presence of smear layer, debris, sealer/gutta-percha remnants, and the number of open tubules. Eight teeth per group were bonded with an etch-and-rinse adhesive, and fibre posts were luted with a resin-based cement. After cutting, specimens were prepared for a push-out test. Data were analysed by anova and post hoc tests (P < 0.05).Improved smear layer removal was obtained in Group 2, followed by Group 1, Group 3, and the control group (P < 0.05). The mean values for the bond strength of the push-out test were: Group 1, 8.3 ± 2.9 MPa (coronal); 7.7 ± 3.0 (middle); 3.3 ±1.9 MPa (apical); Group 2, 7.8 ± 2.1 MPa (coronal); 6.9 ± 3.9 MPa (middle); 3.7 ± 1.3 MPa (apical); Group 3, 9.7 ± 2.8 MPa (coronal); 8.6 ± 2.1 MPa (middle); 6.9 ± 2.3 MPa (apical); and Group 4, 2.9 ± 3.0 MPa (coronal); 2.6 ± 2.0 MPa (middle); 1.1 ± 2.0 MPa (apical).Liquid phosphoric acid applied with an endodontic needle yielded better canal wall smear layer removal and higher bond strength values when an etch-and-rinse system was used.