Effect of chlorhexidine and isopropyl alcohol on immediate and delayed bond strength of glass fiber posts

Aim: To investigate the effects of dentinal treatment with chlorhexidine and isopropyl alcohol, alone or associated, on the bond strength and bond stability of glass fiber posts cemented with a self-adhesive resin cement. Materials and Methods: Forty bovine teeth were endodontically treated and randomly distributed into four groups, according to the dentinal treatment after post space preparation: distilled water (Control); 2% chlorhexidine (CHX); isopropyl alcohol (ISO); 2% chlorhexidine + isopropyl alcohol (CHX+ISO). Glass fiber posts were cemented with a self-adhesive resin cement and after 24 h specimens were cut into six 1.5 mm-thick slices. One slice of each root third (i.e. apical, middle and coronal) was subjected to immediate push-out test and the other was stored in distilled water at 37 degrees C for six months for delayed pushout test. Bond strength was registered in megapascal (MPa). Failure mode was evaluated by a stereomicroscope, with 40x magnification. Data analysis was performed using Kruskal-Wallis and Friedman tests, with 5% significance level. Results: No significant differences were detected between experimental groups or between root thirds in the same group in the immediate evaluation. After six months of aging, all groups showed a significant decrease in bond strength values, but ISO group presented higher bond strength than Control and CHX groups (p=0.0001). The most common type of failure for all groups was adhesive between resin cement and root dentine. Conclusions: Dentinal treatment with CHX and ISO, isolated or combined, did not affect the immediate bond strength of glass fiber posts, but the ISO group presented better bond stability after six-month aging.