Physicochemical properties and interfacial morphology of a universal adhesive doped with a collagen cross-linker and a remineralizing agent

This study aimed to evaluate the incorporation of epigallocatechin-3-gallate (EGCG) and beta-tricalcium phosphate (βTCP) into a universal adhesive system and their effects on the physicochemical properties of the adhesive and the stability of dentin bonding. The experimental groups included: Single Bond Universal (SBU) applied in the self-etch mode, SBU + EGCG, SBU+βTCP, and SBU + EGCG+βTCP. Demineralized middle dentin bars (n = 4) were treated with biomodifying/remineralizing solutions and analyzed by FTIR spectroscopy. The modulus of elasticity (n = 10), the flexural strength (n = 10), and the degree of conversion (n = 5) were evaluated to determine the impact of these additives on the physicochemical properties of the adhesive. Dentin bonding was evaluated using microtensile bond strength, nanoleakage, and micropermeability tests after 24 h and six months of storage. Infrared spectroscopy analysis revealed an increase of amide II and III peaks in the group modified with EGCG + βTCP. Physicochemical properties were not affected by the incorporation of the additive, except for an increased of degree of conversion in SBU + EGCG + βTCP group. Bond strength values showed a significant reduction in all experimental groups compared to the control at 24 h; however, no differences were observed among groups after six months. Only the EGCG-contained groups preserved bond strength after six months. Nanoleakage and micropermeability analyses demonstrated silver nitrate uptake and fluorescein infiltration, respectively, after aging in all groups. Incorporation of EGCG, alone or combined with βTCP did not adversely affect the physicochemical properties of the universal adhesive; however, the present results did not demonstrate an actual improvement in long-term bond strength.