Protein-repellent and antibacterial effects of a novel polymethyl methacrylate resin

Objectives: Heat-cured resins are commonly used in orthodontics; however, there is a high incidence of caries, periodontal diseases and denture-induced stomatitis. The objectives of this study were to: (1) develop a new bioactive polymethyl methacrylate (PMMA) resin containing 2-methacryloyloxyethyl phosphorylcholine (MPC) and quaternary ammonium dimethylaminohexadecyl methacrylate (DMAHDM), and (2) investigate the effects on mechanical properties, protein-repellency and antibacterial properties. Methods: MPC and DMAHDM were mixed into a commercial acrylic resin (Nature Cryl (TM) MC). Mechanical properties were measured in three-point flexure. Surface roughness was assessed using atomic force microscopy (AFM). Protein adsorption onto the PMMA resin was measured using a micro bicinchoninic acid (BCA) method. A human saliva microcosm model was used to investigate the live/dead staining and metabolic activity of the biofilms. Results: Incorporation of 3% MPC and 1.5% DMAHDM into PMMA resin achieved protein repellent and antibacterial capabilities, without compromising the mechanical properties. PMMA resin with 3% MPC + 1.5% DMAHDM had protein adsorption that was 1/6 that of a commercial control (p < 0.05). The PMMA resin with 3% MPC + 1.5% DMAHDM had much greater reduction in biofilm growth than using MPC or DMAHDM alone (p < 0.05). Conclusions: A bioactive PMMA resin with a combination of strong protein-repellent and antibacterial capabilities was developed for the first time. The new resin greatly reduced the biofilm growth and metabolic activity, without compromising its mechanical properties. Significance: Novel PMMA resin is promising for applications in orthodontic retainers and orthodontic appliances to reduce biofilm activity and protein adsorption around the resin.