In vitro evaluation of the effect of experimental primers on dentin-adhesive bonding and dentin matrix matalloproteinase inhibition

Abstract

This study will evaluate the effects of experimental primers based on Naringin and Kaempferol used in different concentrations and application times on the dentin bond strength, and on the morphology and enzymatic activity of the dentin-adhesive interface. Primers based on natural compounds (Naringin and Kaempferol) will be used in two concentrations (10 mM and 20 mM), and applied on dentin for different times (30 s and 60 s). Besides the experimental primers, 0.2% chlorhexidine digluconate will be used as positive control at both application times. Dentin acid-etching with 37% phosphoric acid without primer application will serve as negative control. In all groups, dentin will be etched with 37% phosphoric acid (Condicionador Dental Gel, Dentsply Sirona) for 15 s, followed by the application of 300 µL of each primer during the aforementioned times in the experimental groups. Primers will be volatized by a slight air stream, and an ethanol-based, etch-and-rinse adhesive will be applied following manufacturer's recommendations. Two layers of a hybrid resin composite will then be placed over dentin and light-cured separately. The microtensile bond strength test (n=8) and the failure mode analysis will be performed at 24 hours and after one year of water storage. For the analyses of the dentin-adhesive interface morphology (n=5) and enzymatic activity (n=3), a flowable bulk-fill composite will be used after adhesive resin light-curing. Dentin-adhesive interface morphology will be assessed by applying the rhodamine B dye into the adhesive resin bottle, while proteolytic activity at the bonding interface will be analyzed using a fluorescein-conjugated gelatin. Both methodologies will be assessed by a multiphoton confocal microscope. Bond strength data will be analyzed by 3-way ANOVA, followed by Tukey's test, and compared to the positive and negative control groups by the Dunnett's test (significance level of 5%). Data from the remaining methodologies will be analyzed descriptively. (AU)