In situ formation of amorphous cupric phosphate for improved dentin bonding

Objective Insufficient penetration of bonding agents into the demineralized dentin matrix (DDM) leads to a poor-quality hybrid layer and reduced bonding durability. We designed a pretreatment agent consisting of copper sulfate and dipotassium hydrogen phosphate to form amorphous copper phosphate nanoparticles (Nano-ACuP) in situ for improved dentin bonding. Methods The effect of different concentrations of the pretreatment agent on the release of confined water was investigated. Moreover, the deposition and binding sites, hydrophilicity, surface charge, and mechanical properties were characterized. The effect of Nano-ACuP pretreatment on bonding durability was evaluated using microtensile strength tests and nano-permeability experiments. The collagenase inhibitory and antibacterial properties of Nano-ACuP were evaluated with a series of inhibition experiments and in situ enzyme profiling, respectively. Results Nano-ACuP generated in situ formed chemical bonds with the polar and anionic groups of collagen and non-collagenous proteins in the DDM. Moreover, Nano-ACuP pretreatment reduced dentin interfacial hydration, decreased the dentin surface potential, increased the dentin mechanical properties, and increased the Young's modulus and hardness of the dentin matrix. Nano-ACuP pretreatment promoted the penetration of bonding monomers into the hybrid layer. When Nano-ACuP was used in combination with Single Bond 2 or Single Bond Universal, it improved the bonding strength and durability, which was minimally reduced over 1 year of water aging. Nano-ACuP inhibited collagenase activity and possessed antimicrobial properties. Significance Nano-ACuP pretreatment significantly improved the effectiveness and durability of dentin bonding by reconfiguring the interfacial microenvironment of DDM. This study provides new ideas and strategies for further improving dentin bonding.