Addition of a Reverse Amide to Methacrylate-Based Dental Materials to Inhibit Microbial Biofilm Formation. - Secondary caries (SC), the leading reason for the repair or replacement of bonded resin composite fillings worldwide across both pediatric and adult populations, mirrors the etiopathogenesis of primary caries, originating from stagnant Streptococcus mutans biofilms on filling surfaces. For many decades, research efforts on SC prevention have predominantly concentrated on integrating antimicrobial agents into methacrylate-based dental materials (MBM), employing synthetic or natural molecules as well as heavy metal elements. The therapeutic mode of action of these agents, rooted in bacteria-killing mechanisms via surface contact with dental materials and/or drug release, has the potential to disrupt the delicate ecological balance (eubiosis) between commensal (beneficial) and pathogenic (harmful) bacteria within stagnant biofilms, potentially exacerbating dental plaque activity instead of preventing it. Consequently, dentistry faces a shortfall in materials capable of inhibiting disease-associated biofilms while preserving commensal species. Our overarching objective is to leverage the antibacterial properties inherent in the reverse amide 2-aminoimidazole (RA/2-AI) family of small molecules to engineer innovative dental materials. Research findings results have indicated that they covalently interacted with methacrylate and inhibited S. mutans biofilm formation while promoting commensal species when used in water-based solutions. The overall objectives of this NIH grant application are to (i) synthetize a derivative of the RA/2AI family, i.e. 2-amino-N-undecyl-H-imidazole-5-butanamide, hereafter H10, as well as use click chemistry to generate a new methacrylate-based antimicrobial agent containing covalently conjugated H10-HEMA monomer, (ii) formulate MBM self-etch adhesive (SEA) containing both forms of H10, and evaluate their biostability, mechanical characteristics, tooth-material bond strength, and (iii) assess their effectiveness against dysbiotic dental biofilm. The central hypothesis is that MBM-SEA containing H10 sustain mechanical and tooth adhesive properties while inhibiting dysbiotic Streptococcus mutans biofilm formation. The rationale for this project lies in the comprehensive assessment of the biostability, mechanical robustness, tooth-adhesive characteristics, and biofilm inhibition capabilities inherent in SEA containing H10 synthetized forms. The following specific aims are proposed: 1) Evaluate the biostability, mechanical and tooth-material bond strength properties for H10 SEA forms; and 2) Determine in vitro effectiveness SEA against dysbiotic dental biofilm. Under the first aim, HPLC will evaluate H10 release, three-point bending the flexural strength, microtensile bond strength will examine the materials' short- and long-term dentin-enamel adhesion. The research proposed in this application is innovative because 1) it focuses on 2-AI small molecules that inhibits and/or disperse S mutans biofilm, and 2) is amendable to covalent conjugation via click-chemistry with methacrylate-based monomers. The significance of this work lies in its potential to advance dental materials that effectively combat biofilm dysbiosis associated with cavities at the margins of MBM fillings.
