Biocompatibility and bactericidal study of antibacterial dental monomers

Objective: To study the cytotoxicity and bactericidal effect of three synthesized antibacterial monomers. Methods: Three long-chain methacrylate and methacrylamide monomers (AM-1, AM-2, AM-3) containing quaternary ammonium fluoride moieties were synthesized (Polymer Preprint 2008, 49(1):885-6). Their cytotoxicity to L-929 mouse fibroblast cells was tested using agar overlay method according to the ISO standard 10993-5. Triplicate wells were dosed with 0.1ml of the test article (10^-4M of each monomer in 0.5%DMSO/medium solution) on a filter. High density polyethylene and latex were as negative and positive controls, respectively. After incubating at 37^oC in 5%CO₂ for 24hrs, the cell culture was examined macroscopically and microscopically (100X) for cell decolorization to determine the zone of cell lysis and the cell morphology.

Bactericidal (Kill-time) study of the three monomers against Streptococcus mutans ATCC 35668 was conducted as follows. 10 ml solution of each test tube containing a serial dilution (10^-3M through10^-6M in 0.5%DMSO/medium) of each antibacterial monomer and BisGMA (control) and Streptococcus mutans with starting population of 1.14x10⁵ was incubated for 24 hour at 37^oC; the bacteria cells were counted microscopically.

 Results: cytotoxicity: AM-1 and AM-2 have grade 0 (no reactivity) while AM-3 has grade 1 (slight reactivity). The bactericidal results were expressed as: Log Reduction = LogB - LogA, where A = CFU/ml of the test tube containing the test article after incubation, B = CFU/ml of the starting population.

Conclusion: all three antibacterial monomers are biocompatible and have bactericidal effects against S. mutans at 10^-3M concentration. AM-2 has higher bactericidal effect than AM-1 and AM-3 at 10^-4M concentration. Sponsored by NIH/NCRR COBRE grant (P20RR020160).