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

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). 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. Acrylates with 16 wt% and 20 wt% incorporated MAPTAC showed strong contact-killing of various oral streptococcal strains up to challenge concentrations of 109 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 105 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. 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.