Bond strength of Gradia veneering composite to fibre-reinforced composite

This study investigated the shear bond strength of light-curing veneering composite resin to glass fibre-reinforced composite (FRC). Polymer pre-impregnated FRC reinforcement was further impregnated with dimethacrylate monomer resin. The light polymerized FRC substrate was ground and dimethacrylate intermediate resin was applied on the surface before the light-curing veneering composite. Adhesional behaviour of veneering composite to the initially light polymerized FRC substrate was compared with well-polymerized FRC substrate. The treatment time of FRC substrate by the intermediate resin for 5 s and 5 min were also compared. Shear bond strength of veneering composite to FRC was determined for dry and thermocycled specimens (n = 6). The analysis of variance (anova) revealed significant differences (P = 0.042) between the shear bond strengths when 5 s and 5 min intermediate resin treatment times were compared. The highest shear bond strength (21.0 MPa) for FRC substrates was achieved when the well-polymerized FRC substrate was treated for 5 min with the intermediate resin and stored dry before tests. Thermocycling reduced the shear bond strengths. The results of this study suggest that applying the intermediate resin increased the shear bond strength values of veneering composite to FRC with multiphase polymer matrix. It was also concluded, that the use of multiphase polymer matrix FRC can be polymerized to high degree of conversion without deferiorating the shear bond strength of veneering composite to the FRC.