The purpose of this study was to investigate the dentin/adhesive interfacial characteristics of three current commercial adhesives with different relative hydrophilic/hydrophobic composition, using a nondestructive staining technique. Dentin surfaces of 18 unerupted human third molars were randomly selected for treatment with one of three commercial dentin bonding agents according to manufacturers instructions for the wet bonding technique. The adhesives were ranked based on hydrophilic/hydrophobic component ratios (ie, ability to dissolve in water), highest to lowest, as follows: Uno (Pulpdent) > Prime&Bond NT (PBNT, Dentsply Caulk) > Single Bond (SB, 3M ESPE). Dentin/adhesive (d/a) interface sections were stained with Goldners trichrome, a classical bone stain, and examined using light microscopy. The extent and degree to which the adhesive encapsulates the demineralized dentin matrix is reflected in the color differences in the stained sections. The depth of demineralization appeared comparable among these bonding systems, but adhesive infiltration varied from highest to lowest as follows: Uno > PBNT > SB. The differential staining technique provided a clear representation of the depth of dentin demineralization and extent/degree of adhesive encapsulation of the exposed collagen at the d/a interface. This technique provides a mechanism for readily identifying vulnerable sites at the d/a interface. The composition of the one-bottle adhesive systems has a substantial effect on the interfacial structure of the d/a bond.
Keywords: collagen, encapsulation, dentin, adhesive