Effect of different adhesion strategies on fiber post cementation: Push-out test and scanning electron microscopy analysis

AIM: The aim of this study was to investigate the effect of phosphoric acid etching and the dentin pre-treatment with sodium hypochlorite (NaOCl) on the push-out bond strength between fiber post and root canal dentin. MATERIALS AND METHODS: Root canals of 48 human incisors were selected, post spaces were prepared and assigned to four groups: G1-37% phosphoric acid (15 s); G2-5.25% NaOCl (2 min) +37% phosphoric acid (15 s); G3-37% phosphoric acid (60 s); and G4-5.25% NaOCl (2 min) +37% phosphoric acid (60 s). Fiber post cementation was performed with two-step etch-and-rinse adhesive system/dual-cured resin cement according to the manufacturer's recommendation. After 24 h, each root was sectioned transversally into three slices (cervical, middle and apical) and the bond strength of each section was determined using a push-out bond strength test. Morphology analysis of the bonded interface was evaluated using a scanning electron microscopy. Push-out strength data (MPa) were analyzed by Analysis of Variance and Tukey-Kramer (α = 0.05). RESULTS: Considering the NaOCl pre-treatment, no statistically significant differences were observed among groups; however, when the phosphoric acid was applied during 60 s in the apical portion without NaOCl pre-treatment, the bond strength was statistically significant increased. CONCLUSION: The NaOCl pre-treatment did not improve the bond strength of adhesive luting cement to root canal dentin. The findings suggest that the use of 37% phosphoric acid for 60 s may have a beneficial effect on bond strength in the apical root third.