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

AIM: 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. METHODOLOGY: 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). RESULTS: 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). CONCLUSIONS: 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.