Effect of 2% chlorhexidine digluconate on bond strength of a glass-fibre post to root dentine

Aim To assess the immediate influence of dentine bonding systems (DBS) associated with 2% chlorhexidine digluconate (CHX) on glass-fibre post-bond strength to root dentine, in terms of coronal, middle and apical thirds. Methodology Sixty bovine roots were root filled and randomly assigned to 1 of 6 groups (n=10): SBMP (3-step etch-and-rinse system, Scotchbond Multi-Purpose), SB (2-step etch-and-rinse system, Single Bond 2), SE (2-step self-etching system, Clearfil SE Bond) and SBMP-CHX, SB-CHX and SE-CHX, respectively, associated with CHX. For all groups, a glass-fibre post was luted with a dual-cure resin cement, RelyX ARC. After 7-day storage, specimens were subjected to the push-out test. Failure modes were analysed under optical microscopy (40x). Bond strength values were statistically analysed by two-way anova and Bonferroni tests (P<0.05). Results The effect of DBS was significant (P<0.05), and SE reached higher bond strength in comparison with the other DBS tested. CHX association did not show improvement with any DBS (P>0.05); rather, it negatively affected SE, which was detected for all thirds. There was no difference between thirds (P>0.05), except for the SE-CHX, which presented lower values for the apical third (P<0.05). Adhesive cement/dentine adhesive failure was predominant for all groups. CHX did not influence the failure mode for any DBS (P>0.05). Conclusions The performance of the dentine bonding systems was material dependent. CHX did not improve immediate bond strength; however, CHX negatively affected the bond strength of the self-etching system, especially in the third apical.