Effect of Dentin Pretreatment on Bond Strength Stability of Self-etching and Etch-and-Rinse Adhesives to Intracoronally Bleached Dentin

Purpose: To evaluate the effect of chlorhexidine or glutaraldehyde pretreatment on the bonding stability of selfetching and etch-and-rinse adhesives to bleached dentin. Materials and Methods: The occlusal surface of 80 third molars was abraded to expose a flat mid-dentin surface, which was then subjected to a bleaching procedure using 20% hydrogen peroxide and sodium perborate for 14 days. Afterwards, the specimens were kept in distilled water, followed by application of either a three-step etchand- rinse (Adper Scotchbond Multi-Purpose Plus, SBMP) or a two-step self-etching (Clearfil SE Bond, CSE) adhesive system. For each approach, the bleached dentin was treated with chlorhexidine or glutaraldehyde, or left untreated, prior to the adhesive procedure. Unbleached dentin was used as a control. Composite cylinders were built up over the adhesive-covered dentin followed by parallel sectioning of specimens to obtain 1-mm slices. The slices were trimmed to obtain hourglass-shaped specimens with approximately 1.0 mm2 of bonding interface. Half of the specimens were subjected to microtensile bond strength (μTBS) testing after 24 h, while the other half were stored in distilled water for 3 months prior to the μTBS test. The mode of failure was analyzed using optical microscopy. Results: For the SBMP protocol, the highest μTBS was achieved with glutaraldehyde-treated dentin, and the same μTBS values were maintained after 3 months of storage. For the CSE protocol, the highest μTBS was obtained with chlorhexidine-treated dentin. Conclusion: Glutaraldehyde and chlorhexidine pretreatment should be considered to improve the μTBS of adhesives to bleached dentin, while the pretreatment effect was adhesive dependent.