Purpose: To investigate whether application of three all-in-one self-etching adhesives in a phase-separated stage has an adverse effect on bonding to enamel and dentin. Materials and Methods: The shear bond strengths (SBSs) on ground enamel and dentin of the adhesives G-Bond, Hybrid Bond, and iBond, combined with Venus composite, were determined. The adhesives were dispensed in a dish and applied either 1) immediately, 2) after 2 min, or 3) after 5 min dark storage under ambient conditions. The adhesives were shortly stirred with a microbrush and applied. Prior to light activation, the adhesives were air dried for 10 s with a strong air blast. Composite cylinders were produced in a cylindrical mold clamped on the treated surface. SBSs (n = 8) were determined in a universal testing machine at 1 mm/min crosshead speed after 24 h storage in 37°C water. Data were statistically analyzed with Kruskal-Wallis ANOVA and the Mann-Whitney U-Test (p < 0.05). The qualitative compositions of the separated phases were determined by FTIR spectroscopy. Results: In the separated stage, the adhesives showed acidic monomer-rich phases, containing all components of the original adhesive composition, and water-rich phases with minor amounts of mainly functional monomers dissolved. The SBSs of the individual adhesives applied on enamel or dentin at the different times after dispensing were not significantly different. Conclusion: Application of the adhesives tested either as homogeneous solution or in a phase-separated stage has no adverse effect on bonding strength to enamel or dentin when applied under the present study conditions.
Keywords: self-etching adhesives, enamel-dentin bonding, phase separation