Objective To evaluate the influence of eugenol-containing and resin-containing endodontic sealers on the bond strength of fiber posts using different strategies of root canal irrigation.Methods Forty-eight mandibular premolars were endodontically treated. The specimens were randomly assigned into two groups according to different endodontic sealers. Group A used Endofil (eugenol-containing endodontic sealer), and group B used AH-plus (resin-containing endodontic sealer). After post space preparation, each group was randomly assigned into three subgroups according to the strategies of root canal irrigation (eight premolars in each subgroup). Group A1 and B1:0.9%NaCl irrigation; Group A2 and B2:17% ethylene diamine tetraacetic acid (EDTA)+5.25%NaClO+0.9%NaCl irrigation; Group A3 and B3: ultrasonic agitation associated with 1 7%EDTA+5.25%NaClO+0.9%NaCl. One week after the cementation of fiber posts using RelyXTMUnicem, a push-out test was performed to measure the bond strength of the posts. The microstructure of the root canal surface was examined under scanning electron microscope (SEM).Results The bond strengths of the six groups were as follows: A1 (7.96±2.23) MPa, A2 (9.95±2.89) MPa, A3 (18.88±3.69) MPa, B1 (11.41±3.71) MPa, B2 (14.00±4.04) MPa, and B3 (19.14±3.27) MPa. Statistical analysis revealed a significant interaction between the different endodontic sealers and the strategies of root canal irrigation (PPP>0.05). SEM showed that the root canal in group A3 and B3 achieved the cleanest surface with nearly all dentine tubules opened.Conclusion The eugenol-containing endodontic sealer can impair the bond strength of fiber posts compared with the resin-containing sealer when the root canal is irrigated by 0.9% NaCl or 17%EDTA+5.25%NaClO+0.9%NaCl. No difference was observed between the two sealers when using 17%EDTA+5.25% NaClO+0.9%NaCl combined with ultrasonic irrigation.
