Dentin bonding is a dynamic process that involves the penetration of adhesive resin monomers into the extrafibrillar and intrafibrillar demineralized collagen matrix using a wet-bonding technique. However, adhesive resin monomers lack the capacity to infiltrate the intrafibrillar space, and the excess water that is introduced by the wet-bonding technique remains at the bonding interface. This imperfectly bonded interface is inclined to hydrolytic degradation, severely jeopardizing the longevity of bonded clinical restorations. The present study introduces a dentin bonding scheme based on a dry-bonding technique, combined with the use of extrafibrillar demineralization and a collagen-reactive monomer (CRM)-based adhesive (CBA). Selective extrafibrillar demineralization was achieved using 1-wt% high-molecular weight (MW) carboxymethyl chitosan (CMCS) within a clinically acceptable timeframe to create a less aggressive bonding substance for dentin bonding due to its selectively extrafibrillar demineralization capacity. CMCS demineralization decreased the activation of in situ collagenase, improved the shrinking resistance of demineralized collagen, and thus provided stronger and more durable bonding than traditional phosphoric acid etching. The new dentin bonding scheme that contained CMCS and CBA and used a dry-bonding technique achieved an encouraging dentin bonding strength and durability with low technical sensitivity. This bonding scheme can be used to improve the stability of the resin-dentin interface and foster the longevity of bonded clinical restorations.

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This study evaluated the use of a new collagen-reactive monomer (CRM), isocyanate-terminated urethane methacrylate precursor, which has covalent affinity to dental collagen, in the formation of dentin-resin bonds and compared it with 2 other dental adhesives. Dentin specimens were bonded with either the CRM-based adhesive (CBA), One-Step (OS; Bisco, Inc.), or a negative adhesive (NA) control and subjected to 24-h storage in water, thermocycling to simulate 1-y clinical function, or a matrix metalloproteinase–mediated aging process. We tested the microtensile bond strength (µTBS), characterized the bonding interface with an atomic force microscope, conducted micro-Raman analysis, and performed leakage tests and in situ zymography. CBA and OS exhibited comparable bonding strength after 24 h ( P > 0.05); however, there was a sharp decrease in µTBS after aging for all except CBA ( P < 0.001). Raman spectra results indicated increased collagen crosslinking and chemical reaction between the adhesive and collagen in the CBA group. CBA achieved high-quality hybridization with collagen, improving mechanical properties and integrity, and decreased the enzyme-mediated degradation of the bonding interface by inhibiting collagenolytic activity. With the promising bonding durability of coapplied CBA, CRM may be the first dental adhesive to provide strong and long-lasting resin-dental collagen bonding without the additional conditioning step. The use of CBA results in high-quality hybrid layers that protect the resin-dentin interface from harmful biological and chemical activities commonly occurring in the oral environment.

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