A Novel Dual Cross-linking Reagent for Dentin Bonding Interface Stability

The cross-linking reagent has been proposed as a means of modifying dentin collagen, inhibiting matrix metalloproteinase activities, and enhancing bond durability during dentin bonding procedures. This study aimed to synthesize an operation-friendly dual cross-linking reagent—3-(4-formyphenoxy)-2-hydroxypropyl methacrylate (FPA)—to assess its ability to cross-link dentin collagen and reduce enzymatic activity at the bonding interface. Cytotoxicity was evaluated by a cell counting kit–8 test and calcein AM/propidium iodide assay. Attenuated total reflection–Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, and molecular docking of FPA-collagen showed that FPA can mediate covalent bonding and hydrogen bonding. The hydroxyproline release test and thermogravimetric analysis demonstrated that FPA-collagen can resist exogenous proteases and thermolysis. The gelatin zymography and in situ zymography indicated that FPA can reduce enzymatic activity at the bonding interface. The bonded samples were subjected to microtensile bond strength analysis after 24 h and thermocycling. The bonding interface quality was evaluated by the water contact angle, confocal laser scanning microscope, field emission scanning electron microscopy, and nanoleakage assessment. This study demonstrated the effectiveness and significant clinical potential of the dual cross-linking reagent FPA in that it increases the longevity of resin-dentin bonds and reduces dentin matrix metalloproteinase activities at the bonding interface.