Synthesis and Characterization of New Hydrolytic Resistant Antibacterial Pyridinium and N‐Alkyl Ammonium‐Containing Methacrylamides for Dental Resin Adhesives

Abstract Resin‐based composites have relatively short lifetime mainly attributed to hydrolytic and enzymatic degradation of easily hydrolyzed methacrylates in the dental resin adhesive. To address these problems, a series of antibacterial and hydrolytic resistant methacrylamide monomers containing quaternary ammonium salts and long alkyl chains, MAPs , MADAs, and BMADPB were synthesized. Synthesized methacrylamides exhibited antibacterial activities against S. mutans and E. faecalis . Factors that affect the antibacterial activities are intermolecular hydrogen bonding and alkyl chain length. Some synthesized methacrylamides expressed equal or lower cytotoxic activities against mouse dental papilla cell lines than those of bis‐GMA and MDPB , common methacylates used in dental resin adhesives. Degree of conversion at 30 s, the clinically relevant exposure time for tooth restoration, of methacrylamides (51%–83%) were lower than that of the reference antibacterial methacrylate, MDPB (98%) due to lower reactivity of methacrylamide compared with methacrylate. Addition of selected methacrylamides in the resins remarkably improved flexural modulus after water storage. Hydrolysis experiment in acidic condition of the synthesized monomers and their corresponding polymers proved their hydrolytic stability. Antibacterial activities, cell viability, mechanical strength, and hydrolytic stability of new methacrylamides represent alternative antibacterial and durable monomers for resin adhesives.