title: Dental plaque microcosm biofilm behavior on calcium phosphate nanocomposite with quaternary ammonium.
abstract: OBJECTIVE
  Half of dental restorations fail in 10 years, with secondary caries as the main reason. Calcium phosphate composites could remineralize tooth lesions. The objectives of this study were to: (1) impart antibacterial activity to a composite with nanoparticles of amorphous calcium phosphate (NACP); and (2) investigate the effect of quaternary ammonium dimethacrylate (QADM) on mechanical and dental plaque microcosm biofilm properties for the first time.
  
  
  METHODS
  The NACP and glass particles were filled into a dental resin that contained bis(2-methacryloyloxy-ethyl) dimethyl-ammonium bromide, the QADM. NACP nanocomposites containing 0%, 7%, 14%, and 17.5% of QADM by mass, respectively, were photo-cured. A commercial composite with no antibacterial activity was used as control. Mechanical properties were measured in three-point flexure. A human saliva microcosm model was used to grow biofilms on composites. Live/dead assay, metabolic activity, colony-forming unit (CFU) counts, and lactic acid production of biofilms on the composites were measured.
  
  
  RESULTS
  Increasing QADM mass fraction monotonically reduced the biofilm viability, CFU and lactic acid. Biofilms on NACP nanocomposite with 17.5% QADM had metabolic activity that was 30% that on a commercial composite control (p<0.05). Total microorganisms, total streptococci, and mutans streptococci CFU counts (mean ± sd; n = 6) on composite control was 6-fold those on NACP +17.5% QADM nanocomposite. Composite control had long strings of bacterial cells with normal short-rod shapes, while some cells on NACP-QADM nanocomposites disintegrated into pieces. Adding QADM to NACP did not decrease the composite strength and elastic modulus, which matched (p>0.1) those of a commercial composite without Ca-PO(4) or antibacterial activity.
  
  
  CONCLUSIONS
  A dental plaque microcosm model was used to evaluate the novel NACP-QADM nanocomposite. The nanocomposite greatly reduced the biofilm viability, metabolic activity and lactic acid, while its mechanical properties matched those of a commercial composite. NACP-QADM nanocomposite with calcium phosphate fillers, good mechanical properties and a strong antibacterial activity may have potential for anti-biofilm and anti-caries restorations.
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Lei
authors.initials: L
authors.lastname: Cheng
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weir
authors.forename: Ke
authors.initials: K
authors.lastname: Zhang
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Wu
authors.forename: Sarah M
authors.initials: SM
authors.lastname: Xu
authors.forename: Xuedong
authors.initials: X
authors.lastname: Zhou
authors.forename: Hockin H K
authors.initials: HH
authors.lastname: Xu
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D018441:Biofilms / Q000187:drug effects*; D001965:Bromides / Q000494:pharmacology*; D002130:Calcium Phosphates / Q000494:pharmacology*; D002327:Cariostatic Agents / Q000737:chemistry*; D015169:Colony Count, Microbial; D003188:Composite Resins / Q000737:chemistry*; D003773:Dental Plaque / Q000378:metabolism / Q000382:microbiology; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D005898:Glass; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D055595:Mechanical Phenomena; D050296:Microbial Viability / Q000187:drug effects; D053761:Nanocomposites / Q000737:chemistry; D018583:Pliability; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D012463:Saliva / Q000382:microbiology; D018709:Statistics, Nonparametric; D013295:Streptococcus mutans / Q000187:drug effects
chemical_list: D000900:Anti-Bacterial Agents; D001965:Bromides; D002130:Calcium Phosphates; D002327:Cariostatic Agents; D003188:Composite Resins; D000644:Quaternary Ammonium Compounds; C519480:amorphous calcium phosphate; D019344:Lactic Acid; C051470:ammonium bromide