title: Time-kill behaviour against eight bacterial species and cytotoxicity of antibacterial monomers.
abstract: OBJECTIVE
  The objectives of this study were to investigate: (1) the antibacterial activity of two antibacterial monomers, dimethylaminododecyl methacrylate (DMADDM) and dimethylammoniumethyl dimethacrylate (DMAEDM), against eight different species of oral pathogens for the first time; (2) the cytotoxicity of DMAEDM and DMADDM.
  
  
  METHODS
  DMAEDM and DMADDM were synthesized by reacting a tertiary amine group with an organo-halide. Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against eight species of bacteria were tested. Time-kill determinations were performed to examine the bactericidal kinetics. Cytotoxicity of monomers on human gingival fibroblasts (HGF) was assessed using a methyl thiazolyltetrazolium assay and live/dead viability assay.
  
  
  RESULTS
  DMADDM showed strong bactericidal activity against all bacteria, with MIC of 1.2-9.8μg/mL. DMAEDM had MIC of 20-80mg/mL. Time-kill determinations indicated that DMADDM and DMAEDM had rapid killing effects against eight species of bacteria, and eliminated all bacteria in 30min at the concentration of 4-fold MBC. Median lethal concentration for DMADDM and DMAEDM was between 20 and 40μg/mL, which was 20-fold higher than 1-2μg/mL for BisGMA control.
  
  
  CONCLUSIONS
  DMAEDM and DMADDM were tested in time-kill assay against eight species of oral bacteria for the first time. Both were effective in bacteria-inhibition, but DMADDM had a higher potency than DMAEDM. Different killing efficacy was found against different bacteria species. DMAEDM and DMADDM had much lower cytotoxicity than BisGMA. Therefore, DMADDM and DMAEDM are promising for use in bonding agents and other restorative/preventive materials to combat a variety of oral pathogens.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Fourth Military Medical University, Xi'an, China; Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Fang
authors.initials: F
authors.lastname: Li
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weir
authors.forename: Ashraf F
authors.initials: AF
authors.lastname: Fouad
authors.forename: Hockin H K
authors.initials: HH
authors.lastname: Xu
mesh_terms: D000190:Actinomyces / Q000187:drug effects; D000900:Anti-Bacterial Agents / Q000138:chemical synthesis / Q000494:pharmacology* / Q000633:toxicity; D001419:Bacteria / Q000187:drug effects*; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D013293:Enterococcus faecalis / Q000187:drug effects; D005347:Fibroblasts / Q000187:drug effects; D005881:Gingiva / Q000166:cytology / Q000187:drug effects; D006801:Humans; D007779:Lactobacillus acidophilus / Q000187:drug effects; D008689:Methacrylates / Q000138:chemical synthesis / Q000494:pharmacology* / Q000633:toxicity; D050296:Microbial Viability / Q000187:drug effects; D009055:Mouth / Q000382:microbiology; D016966:Porphyromonas gingivalis / Q000187:drug effects; D001443:Prevotella melaninogenica / Q000187:drug effects; D000644:Quaternary Ammonium Compounds / Q000138:chemical synthesis / Q000494:pharmacology* / Q000633:toxicity; D013211:Staphylococcus aureus / Q000187:drug effects; D013295:Streptococcus mutans / Q000187:drug effects; D013298:Streptococcus sanguis / Q000187:drug effects; D013997:Time Factors
chemical_list: D000900:Anti-Bacterial Agents; D008689:Methacrylates; D000644:Quaternary Ammonium Compounds; C586974:dimethylaminododecyl methacrylate; C000602049:dimethylammoniumethyl dimethacrylate
keywords: Antibacterial activity; Cytotoxicity; Human fibroblasts; Oral bacteria; Quaternary ammonium methacrylate; Time-kill