Refactoring phosphorylated hydrogel-like interface of demineralized dentin matrix via actively induced formation of nano-ACPs forms a defect-low hybrid layer promoting adhesive dentistry

Durability problem of dentin bonding originated from defective bonding interfaces caused by inadequate infiltration of adhesives into demineralized dentin matrix (DDM) is one of the biggest chanllenges in clinical dentistry, while the scientific mechanism remains unclear. We propose that due to poor physical compatibility, the DDM hydrogel-like interface formed by phosphorylated non-collagenous-proteins can be the primary cause of inadequate infiltration of adhesive containing high-content hydrophobic marcromonomers and the formation of numerous defects in the DDM-cured adhesive interface phase. To test this assumption, we develop a novel bonding strategy based on the hydrogel-like interface dehydrogelation refactoring via actively inducing in situ formation of numerous amorphous calcium phosphate nanoparticles within 30 s. The easy-to-collapse DDM is remolded into a robust porous hybrid structure of low polarity. Irrespective of using a wet or dry DDM, the improved physical compatibility between the DDM interface and adhesives greatly promotes infiltration of various adhesives and the integration of the DDM-cured adhesive interface phase. The resulting defect-low bonding interface greatly improves bonding strength and stability indicating the central role of this long-neglected hydrogel-like DDM interface in the problems associated with dentin bonding, which enriches the theory of adhesive dentistry. Free from hard-to-get advanced adhesive materials and sophisticated operations, accessibility and homogeneity of high-quality dentin bonding may benefit clinical dentistry.