Enamel tensile bond strength and morphology of resin-enamel interface created by acid etching system with or without moisture and self-etching priming system

The purpose of this study was to estimate the effect of three types of different adhesive systems on enamel adhesion. Scotchbond Multi-Purpose (MP) as a traditional system, Single Bond (SB) as a wet-bonding system and Clearfil SE Bond (SE) and Unifil Bond (UB) as self-etching priming systems were used. Bovine enamel was treated with each system and tensile bond strength (TBS) of resin to the enamel was measured. The conditioned enamel surfaces and resin-enamel interfaces were also morphologically observed with scanning electron microscope (SEM). The mean TBS for MP, SB, SE and UB were 15.3, 13.7, 14.3 and 11.6 MPa, respectively. There was no significant difference in mean TBS among all products but the traditional system showed the most stable TBS. In SEM observations, self-etching primer created a weaker etched pattern on the enamel surface than phosphoric acid. At the resin-enamel interfaces, thick tag-like extensions penetrated into the enamel etched with phosphoric acid regardless of using the wet-bonding technique, while self-etching primer created thin lamina-like resin penetrations. These results indicate that the traditional system with phosphoric acid etching exhibits the most stable enamel adhesion although the enamel-bonding promoting abilities of these adhesive systems are equivalent to each other.