In vitro study of endodontic post cementation protocols that use resin cements

Sodium hypochlorite (NaOCl) may alter resin bond strength by deproteination of demineralized dentin collagen.

To analyze the effect of NaOCl treatment on bond adhesion and tensile strength of different post cementation protocols in vitro.

The periconductual dentin of 120 single-rooted, caries-free, unrestored human teeth was etched with 37% orthophosphoric acid. The teeth in Group I (60) were left untreated, and the teeth in Group II (60) were treated with 10% NaOCl. Four post-cementation protocols were examined (15 teeth in each) for Groups I and II: ED Primer dentin adhesive + Panavia 21 Ex; ED Primer dentin adhesive + Dual Cement; Panavia 21 Ex; and Dual Cement. For each condition, resin tags, hybrid layers over the periconductual dentin and post surface, were analyzed by scanning electron microscopy (SEM). Specimens were loaded with a uniaxial tensile force using an electromechanical testing machine until cement failure. Bond adhesion and tensile strength with different protocols were examined statistically using multiple analysis of variance at a significance level of alpha<.05.

SEM revealed morphologic differences; Group II exhibited cylindrical, solid tags and Group I, tapered, hollow tags. Uniaxial tensile strength tests showed that in Group I, Panavia 21 Ex cement was strongest, whereas in Group II, this protocol was the weakest and Dual Cement with adhesive was the strongest. In Group II, Panavia 21 Ex diminished the tensile bond strength; however, combination with dentin adhesive increased it.

Within the limitations of this study, NaOCl treatment did not significantly alter tensile bond strength, but when combined with the dentin adhesive ED Primer, a significant rise in strength resulted. A positive relationship existed between increased tag numbers and higher tensile bond strength.