Methods: The experimental resin blend used in this study composed of 40 wt% bisphenol A diglycidyl ether dimethacrylate (Bis-GMA), 30 wt% Bis[2-(methacryloyloxy)ethyl] phosphate (Bis-MP), 28.8 wt% 2-hydroxylethyl methacrylate (HEMA), 0.26 wt% camphorquinone and 1 wt% ethyl N, N-dimethyl-4-aminobenzoate. Resin specimens were prepared from the experimental adhesive resin, containing 0.5 wt%, 1.0 wt%, 1.5 wt% and 2.0 wt% of PA. The neat resin without PA was used as the control group. Flexural strength (FS) and the modulus of elasticity (E) of the neat and PA-incorporated resin specimens (n=6) were measured using three-point bending tests after 24 h dry storage. The microhardness (H) of the neat and PA-incorporated resin specimens (n=10) were determined using Vickers hardness indentation. Degree of monomer conversion (DC) of the neat and PA-incorporated resins was determined by FTIR analysis (n=3). One-way ANOVA was used to examine the effect of PA concentrations on FS, E, H and DC. Multiple comparisons were carried out using Tukey’s test with statistical significance set at α= 0.05.
Results: Incorporation of 1.5 wt% and 2.0 wt% PA significantly reduced FS, E and H of resin specimens (P<0.001). The DC of the experimental adhesive resin was not affected by the different concentrations of PA (P>0.05).
Conclusions: Up to 1.0 wt % of proanthocyanidin can be incorporated into an experimental adhesive resin without interfering its mechanical properties or degree of conversion.