Method: A series of QAMs with different CL was synthesized. Five different alkyl organo-halides were chosen to react with dimethylamino methacrylate, resulting in new antibacterial monomers DMAPM (CL=3), DMAHM (CL=6), DMADDM (CL=12), DMAHDM (CL=16) and AMAODM (CL=18). Each QAM was incorporated into a nanocomposite containing 20% of nanoparticles of amorphous calcium phosphate (NACP) for remineralization. This yielded five nanocomposites with the five new QAMs. Two composites without QAM served as control. A flexural test was used to measure the mechanical properties. A dental plaque microcosm biofilm model was used to evaluate antibacterial activity.
Result: Flexural strength (mean±sd; n=6) of nanocmposites with QAMs was (68±7)MPa, similar to (70±6)MPa of control composites (p>0.1). Composites with QAMs were strongly-antibacterial. Increasing CL from 3 to 16 enhanced the antibacterial activity (p<0.05), and decreased the CFU by 2 orders of magnitude. Further increasing the CL to 18 decreased the antibacterial potency. At CL=16, the metabolic activity and lactic acid production of adherent biofilms were 10-fold lower than those on control composites.
Conclusion: New antibacterial monomers were synthesized and incorporated into NACP nanocomposites to combine antibacterial and remineralization capabilities. Increasing CL from 3 to 16 decreased the CFU by 2 orders of magnitude. The new QAM-NACP nanocomposite possessed potent anti-biofilm activity without compromising load-bearing properties, and is promising for antibacterial and remineralizing restorations to inhibit caries.