Purpose: To evaluate the effect of the hydrophilicity of adhesives on the compatibility between one-bottle simplified adhesives and a dual-curing resin cement.
Materials and Methods: Three experimental and two commercial adhesives (All-Bond Universal, OptiBond Allin- One) with the same or similar pH and various degrees of hydrophilicity were tested in this study. Extracted human dentin was treated with each adhesive and bonded with a dual-curing resin cement (Duolink), which was either light cured or chemically (self) cured (n = 10). Shear bond strength was tested using the Ultradent jig method, and failure modes were determined using a stereomicroscope. Water contact angle (as a measure of hydrophilicity/-phobicity) was measured on a fully cured adhesive (n = 10). The data were analyzed statistically by ANOVA and Tukeys test. The quantitative relationship between the hydrophilicity and bond strength differences was analyzed (confidence level 95%).
Results: Among the experimental adhesives, differences in bond strengths between light-curing and self-curing modes were larger for the more hydrophilic adhesives. For the commercial adhesives, Optibond All-in-One had a lower contact angle than All-bond Universal (p < 0.05). Bond strength (MPa) values for Optibond All-in-One and All-bond Universal were 29.6 and 31.5, respectively (light cured), and 1.9 and 30.0, respectively (self-cured). Adhesive failure was a predominant mode for all adhesives except for All-Bond Universal. Regression analysis indicated a linear correlation between adhesives hydrophilicity and bond strength differences (p < 0.05).
Conclusion: The more hydrophilic adhesives were less compatible (larger bond strength differences between different curing modes) with this dual-curing resin cement. All-bond Universal is more hydrophobic than Optibond All-in-One and it is compatible with this self-/dual-curing resin cement.
Keywords: dentin, shear bond strength, adhesive, dual curing, contact angle, hydrophilicity, compatibility