The integrity of a dental adhesive is a significant contributor to establishing a long-lasting dental restoration. However, commercially available methacrylate-based dental adhesives do not effectively bind the collagen matrix and adhesive layer present at the adhesion interface. This leads to a high risk of water, bacteria, and enzyme infiltration into the adhesive interface. Furthermore, phase separation into hydrophilic/hydrophobic domains is a common feature during the photopolymerization of dental adhesives. The low-crosslinked hydrophilic domain promotes polymer network swelling and subsequent methacrylate hydrolysis. All these factors compromise the long-term adhesive performance of these materials.<br/><br/>To address these challenges, new interfacial bonds should be introduced into the adhesive resin. The catechol moiety can effectively bond with collagen fibrils by forming bidentate hydrogen bonds or covalent bonds with amine and thiol functionalities present on the collagen surface. Moreover, the dynamic hydrogen bonds between two catechol moieties might strengthen the compromised domain of the adhesive resins. These potential advantages associated with incorporating catechol functionalities might address the elevated susceptibility of degradation at the resin-dentin interface.<br/><br/>In this study, methacrylate-based polymer networks incorporating catechol moieties were synthesized via photopolymerization. The effects of incorporating catechol into the network structure were assessed via kinetic, thermomechanical, water swelling, adhesion, and cytotoxicity characterization. The results show that incorporating catechol-based monomers will not significantly affect the kinetics of polymerization. The final conversion only decreases by 4% when 25% of the traditional monomer HEMA was replaced by the novel catechol-based monomer CMA (25% CMA). In addition, adhesive formulations 25% CMA have lower water sorption (decrease of 30%) and significantly higher lap-shear adhesion strength (4x greater) compared with the conventional formulation with 0% CMA. Overall, introducing catechol into dental adhesive formulations provides a promising way to enhance the long-term performance of dental adhesive materials.

Methacrylate-based polymer network incorporating catechol moieties for dental adhesive application

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ACS Fall 2022

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