An innovative quaternary ammonium methacrylate polymer can provide improved antimicrobial properties for a dental adhesive system

A quaternary ammonium methacrylate polymer (QAMP) with antimicrobial potential was synthesized. The resulting product (QAMP) was characterized by FTIR spectroscopy, NMR spectroscopy, visible spectrophotometry, XRPD and TGA. The in vitro susceptibility tests against Streptococcus mutans of QAMP were investigated prior and after incorporation into a commercial adhesive system (Clearfil SE Bond). The release of quaternary ammonium compounds from the experimental adhesive system (Clearfil SE Bond+5% QAMP) was performed during 1, 7, 14, 21 and 30 days. Spectroscopic data confirmed that QAMP was successfully obtained. Thermogravimetric analysis indicated that QAMP was heat stable. Prior incorporation into the adhesive system, QAMP revealed an inhibition halo of 18.33 +/- 0.6mm. By agar disk diffusion test, Clearfil SE Bond containing 5% QAMP presented an inhibition halo (16.67 +/- 1.5mm) similar to Clearfil Protect Bond (positive control, 17.00 +/- 1.7, p=0.815) and significantly higher than Clearfil SE Bond (negative control, 11.00 +/- 1.0, p=0.006). The minimum inhibitory/bactericidal concentrations for Clearfil SE Bond containing 5% QAMP were 20LmL(-1). The release of quaternary ammonium compounds from the experimental adhesive containing QAMP was very low (5.1%) when compared to Clearfil Protect Bond that released 47.2% of its quaternary ammonium monomer (MDPB) after 30 days. The QAMP can offer enhanced antimicrobial properties for self-etching adhesive systems.