Selective Acid Etching Improves the Bond Strength of Universal Adhesive to Sound and Demineralized Enamel of Primary Teeth

Purpose: To evaluate the influence of enamel condition and etching strategy on bond strength of a universal adhesive in primary teeth. Materials and Methods: Thirty-six primary molars were randomly assigned to six groups (n = 6) according to the enamel condition (sound [S] and demineralized [DEM]/cariogenic challenge by pH cycling prior to restorative procedures) and adhesive system (Scotchbond Universal Adhesive [SBU]) used in either etch-and-rinse (ER) or selfetching (SE) mode, with Clearfil SE Bond as the self-etching control. The adhesives were applied to flat enamel surfaces and composite cylinders (0.72 mm2) were built up. After 24-h storage in water, specimens were subjected to the microshear test. Bond strength (MPa) data were analyzed using two-way ANOVA and Tukey's post-hoc tests (α = 0.05). Results: Significant differences were found considering the factors adhesive system (p = 0.003) and enamel condition (p = 0.001). Demineralized enamel negatively affected the bond strength, with μSBS values approximately 50% lower than those obtained for sound enamel. SBU performed better in etch-and-rinse mode, and the bond strength found for SBU applied in self-etching mode was similar to that of CSE. Conclusions: Enamel etching with phosphoric acid improves the bond strength of a universal adhesive system to primary enamel. Demineralized primary enamel results in lower bond strength. Keywords: multimode adhesive, microshear bond strength, enamel, etching strategy