Interfacial and surface characterization of two self-etching adhesive systems and a total-etch adhesive after bonding to ground and unground bovine enamel—a qualitative study

The purpose of the study was to evaluate the enamel surface and interface morphology of two self-etching adhesive systems (SAS) vs a total-etch control, after bonding to ground and unground enamel using field emission scanning electron microscopy (FESEM). Thirty bovine incisors were used in this study. The buccal enamel surface of 15 teeth was ground flat to resemble freshly cut enamel. The rest of the teeth were left intact. Two SAS, Clearfil SE Bond (CSE, Kuraray) and Prompt L-Pop (3M-ESPE), and a conventional adhesive system, Scotchbond Multipurpose (3M-ESPE, control), were used to condition the surface of unground and ground enamel on 12 teeth. A composite button was bonded to the remaining 18 teeth; a cross-section (1 mm thick) was obtained from each and the bonded interface was polished. All specimens were dehydrated in ascending grades of ethanol, gold-sputter-coated, and observed under FESEM (Hitachi S-4000) to evaluate the ultrastructural morphology of the enamel surface and the enamel–dentin interface. The etching patterns and adhesive penetration varied according to the aggressiveness of the SAS, with CSE being the mildest and H₃PO₄ being the most aggressive. There were no significant differences on the ultrastructural morphology of the enamel surface between unground and ground specimens. It appears that microporosities within enamel prisms provide sufficient enamel–resin hybridization in unground enamel. The enamel dissolution pattern and depth of infiltration depend on the type of SAS used, with no significant differences in unground and ground enamel.