Contact-killing of adhering streptococci by a quaternary ammonium compound incorporated in an acrylic resin

Purpose: Acrylates for bonding of joint prostheses and stainless-steel brackets in orthopedics and orthodontics are prone to bacterial adhesion and biofilm formation, respectively, leading to serious infectious complications. Here we describe the preparation of a contact-killing acrylic resin by incorporation of [3-(methacryloylamino)propyl] trimethylammonium chloride (MAPTAC). Methods: Physicochemical properties of the acrylates with and without MAPTAC incorporated were determined with X-ray photoelectron spectroscopy and water contact angles. The bond-strength of the acrylate with different percentages of MAPTAC was determined in a shear mode. The efficacy in contact-killing of the acrylate with MAPTAC incorporated with and without an adsorbed salivary coating was evaluated for various oral streptococcal strains. Cytotoxicity was tested against human skin fibroblasts. Results: Actylates with 16 wt% and 20 wt% incorporated MAPTAC showed strong contact-killing of various oral streptococcal strains up to challenge concentrations of 10(9) mL(-1) within 15 min, with no elution of antimicrobial polymers. Contact-killing reduced after coating with a salivary conditioning film, but still remained significant up to a challenge concentration of 10(5) mL(-1). No cytotoxicity of acrylate with incorporated MAPTAC was observed toward human skin fibroblasts. The bond strengths of stainless-steel brackets fixed to etched enamel through the resin (12 +/- 3 MPa) decreased with increasing amounts MAPTAC to half of the original value when 20 wt% of MAPTAC was incorporated, which remained within a clinically acceptable range. Conclusions: These results suggest that MAPTAC can be effectively incorporated in orthodontic resin to provide long-term bactericidal activity against oral bacteria, with potential application in orthopedics.