Water Sorption, Water Solubility, and Rheological Properties of Resin-Based Dental Composites Incorporating Immobilizable Eugenol-Derivative Monomer

The present study aimed to evaluate the properties of new dental formulations incorporating a new polymerizable-derivative of eugenol (EgGMA). The experimental composites were prepared (by weight) with 35% resin-based matrix (1:1, bisphenol A-glycidyl methacrylate/triethylene glycol dimethacrylate) and 65% reinforcing materials (4:3, hydroxyapatite/zirconium oxide). A portion of 0.0, 2.5, and 5.0% of the resins with respect to the total composite was replaced by EgGMA monomer to obtain TBEg0, TBEg2.5, and TBEg5, respectively. The complex viscosity (at 25 and 37 °C), degree of conversion (DC), and water sorption (W_SP) and water solubility (W_SL) (3 cycles of sorption-desorption process) were investigated. Data were statistically analyzed using one-way and Tukey post-hoc tests. The results revealed a viscosity reduction with shear-thinning behavior as the EgGMA amount and temperature increased. The average complex viscosities at a lower frequency (ω = 1.0 rad/s) and at 25 °C were 234.7 ± 13.4, 86.4 ± 16.5, and 57.3 ± 17.1 (kPa·s) for TBEg0, TBEg2.5, and TBEg5, respectively. The inclusion of EgGMA led to a lower DC and W_SP but higher W_SL, compared to those of the reference (TBEg0). However, no significant differences between TBEg2.5 and control were detected (p > 0.05). Therefore, the incorporation of EgGMA in a low quantity, e.g., up to 8.45 mol% of resins, within the matrix may enhance the composite’s performance, including handling and solubility properties without any apparent effect on DC and water sorption, making it a promising monomeric biomaterial for various applications including restorative dentistry.