Objectives. This study evaluated the kinetics of water uptake and percent conversion in neat
versus ethanol-solvated resins that were formulated to be used as dental bonding agents.
Methods. Five methacrylate-based resins of known and increasing hydrophilicities (R1, R2,
R3, R4 and R5) were used as reference materials. Resins were evaluated as neat bonding
agents (100% resin) or they were solvated with absolute ethanol (95% resin/5% ethanol or
85% resin/15% ethanol). Specimens were prepared by dispensing the uncured resin into a
circular mold (5.8mm×0.8 mm). Photo-activation was performed for 80 s. The water sorption/
diffusion/solubility was gravimetrically evaluated, while the degree of conversion (DC)
was calculated by Fourier-transform infrared spectroscopy.
Results. Water sorption increased with the hydrophilicity of the resin blends. In general,
the solvated resins exhibited significantly higher water sorption, solubility and water diffusion
coefficients when compared to their corresponding neat versions (p < 0.05). The only
exception was resin R1, the least hydrophilic resin, in which neat and solvated versions
exhibited similar water sorption (p > 0.05). Addition of ethanol increased the DC of all resins
tested, especially of the least hydrophilic, R1 and R2 (p < 0.05). Despite the increased DC of
ethanol–solvated methacrylate-based resins, it occurs at the expense of an increase in their
water sorption/diffusion and solubility values.
Significance. Negative effects of residual ethanol on water sorption/solubility appeared to be
greater as the hydrophilicity of the resin blends increased. That is, the use of less hydrophilic
resins in dental adhesives may create more reliable and durable bonds to dentin.
