Effect of phosphoric acid etching and blasting with aluminum oxide on the enamel topography and adhesion of resin composite to intact or abraded enamel

Objectives

To evaluate the effects of the phosphoric acid (PA) etching, self-etching technique (SE) and blasting with Al₂O₃ particles (BL) on the bonding of a dental adhesive to intact (INT) or abraded (ABR) enamel.

Methods

Enamel surfaces were treated as follows: 1- ABR-PA: INT was abraded with SiC paper and etched with PA (20 s) before Clearfil Universal Bond Quick adhesive application; 2- ABR-SE: ABR was SiC and adhesive applied in SE mode; 3- INT-PA: INT was etched with PA and adhesive applied; 4- INT-SE: the adhesive (SE mode) was applied to INT; 5- INT-BL: INT was BL and the adhesive was applied (SE mode), and 6- INT-BA: INT was BL, etched with PA and adhesive applied (SE mode). The enamel surface treated was examined with scanning electron microscopy (SEM) (n = 3) and Al₂O₃ particles were characterized using SEM and EDX. The enamel bond strength was measured by microtensile test (24 h and 1 year) (n = 8) and the morphology of enamel-adhesive interfaces were analyzed by SEM (n = 3). Bond strength data were analyzed by two-way ANOVA and Tukey’s test (α = 0.05).

Results

Al₂O₃ particles had an irregular shape, their length varied (50–20 µm) and the perimeter mean was 38.8 µm. The enamel morphology significantly influenced the enamel bond strength. ABR-PA, INT-BL, and INT-BA provided greater and stable enamel-dentin interaction and bond strength.

Significance

The enamel morphology significantly influenced the enamel bond strength. Using the adhesive in etch-and-rinse mode, enamel must be abraded before etching and must be Al₂O₃-blasted when used in SE mode.