Effect of phytic acid etchant on resin-dentin bonding: Monomer penetration and stability of dentin collagen

Purpose: Phytic acid (IP6) works well as an etchant in dentin bonding to remove the smear layer due to its acidity and chelating effect. This study compared the etching effect of IP6 with phosphoric acid (PA) and ethylenediaminetetraacetic acid (EDTA) on resin-dentin bond strength, micromorphology of the etched dentin surface and nanoleakage formation along resin-dentin interfaces and compared the protecting effect against collagen degradation. Methods: Dentin disks and flat dentin surfaces were obtained from extracted human teeth. Specimens were etched with 35% PA (15s), 0.5M EDTA (30s) or 1% IP6 (30s). The surfaces and longitudinal sections of the etched dentin disks were observed using field emission scanning electron microscope (FE-SEM). An etch-and-rinse adhesive was used to create composite build up-specimens for microtensile bond strength (mu TBS) testing and nanoleakage observation. To evaluate the effect on collagen degradation, demineralized bovine root dentin blocks were challenged with bacterial collagenase and then observed under light microscope. Results: PA-and EDTA-treated groups showed significantly lower mTBS when compared to IP6-treated group. PA showed distinct nanoleakage and severe collagen degradation. Only slight nanoleakage was detected in IP6 group. IP6 showed better effect than EDTA in preventing collagen degradation induced by bacterial collagenase. Conclusions: IP6 effectively removed the smear layer and etched dentin, providing high bond strength values and causing minimal nanoleakage and slight collagen degradation. (C) 2016 Japan Prosthodontic Society. Published by Elsevier Ltd. All rights reserved.