title: Effect of dimethylaminohexadecyl methacrylate mass fraction on fracture toughness and antibacterial properties of CaP nanocomposite.
abstract: OBJECTIVE
  Biofilm acids contribute to secondary caries which is a reason for restoration failure. Previous studies synthesized nanoparticles of amorphous calcium phosphate (NACP) and dimethylaminohexadecyl methacrylate (DMAHDM). The objectives of this study were to develop DMAHMD-NACP nanocomposite for double benefits of antibacterial and remineralization capabilities, and investigate the DMAHMD mass fraction effects on fracture toughness and biofilm response of NACP nanocomposite for the first time.
  
  
  METHODS
  DMAHDM was incorporated into NACP nanocomposite at mass fractions of 0% (control), 0.75%, 1.5%, 2.25% and 3%. A single edge V-notched beam method was used to measure fracture toughness K(IC). A dental plaque microcosm biofilm model using human saliva as inoculum was used to measure the antibacterial properties of composites.
  
  
  RESULTS
  K(IC) was about 1 MPa×m(1/2) for all composite (mean±sd; n=6). Adding DMAHDM from 0% to 3% did not affect K(IC) (p>0.1). Lactic acid production by biofilms on composite containing 3% DMAHDM was reduced to less than 1% of that on composite control. Metabolic activity of adherent biofilms on composite containing 3% DMAHDM was reduced to 4% of that on composite control. Biofilm colony-forming unit (CFU) counts were reduced by three orders of magnitude on NACP nanocomposite containing 3% DMAHDM.
  
  
  CONCLUSIONS
  DMAHDM-NACP nanocomposite had good fracture resistance, strong antibacterial potency, and NACP for remineralization (shown in previous studies). The DMAHDM-NACP nanocomposite may be promising for caries-inhibiting dental restorations, and the method of using double agents (DMAHDM and NACP) may have a wide applicability to other dental materials including bonding agents and cements.
authors.affiliation: Department of Prosthodontics, School of Stomatology, Shandong University, Shandong Provincial Key Laboratory of Oral Biomedicine, Jinan 250012, China; Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Junling
authors.initials: J
authors.lastname: Wu
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA; State Key Laboratory of Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Han
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weir
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Mary Anne S
authors.initials: MA
authors.lastname: Melo
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA.
authors.forename: Eric D
authors.initials: ED
authors.lastname: Levine
authors.affiliation: Biomaterials & Tissue Engineering Division, Department of Endodontics, Prosthodontics and Operative Dentistry, University of Maryland Dental School, Baltimore, MD 21201, USA; Center for Stem Cell Biology & Regenerative Medicine, University of Maryland School of Medicine, Baltimore, MD 21201, USA; Marlene and Stewart Greenebaum Cancer Center, University of Maryland School of Medicine, Baltimore, MD 21201, USA. Electronic address: hxu@umaryland.edu.
authors.forename: Hockin H K
authors.initials: HH
authors.lastname: Xu
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry* / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects*; D002130:Calcium Phosphates / Q000737:chemistry / Q000494:pharmacology; D003188:Composite Resins / Q000737:chemistry / Q000494:pharmacology; D003731:Dental Caries / Q000517:prevention & control; D003764:Dental Materials / Q000494:pharmacology; D003773:Dental Plaque / Q000188:drug therapy / Q000382:microbiology; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D008689:Methacrylates / Q000737:chemistry* / Q000494:pharmacology*; D050296:Microbial Viability / Q000187:drug effects; D053761:Nanocomposites / Q000737:chemistry*; D053758:Nanoparticles / Q000737:chemistry; D012463:Saliva / Q000382:microbiology; D013295:Streptococcus mutans / Q000187:drug effects / Q000502:physiology; D014089:Tooth Remineralization / Q000379:methods*
chemical_list: D000900:Anti-Bacterial Agents; D002130:Calcium Phosphates; D003188:Composite Resins; D003764:Dental Materials; D008689:Methacrylates; C519480:amorphous calcium phosphate; D019344:Lactic Acid
keywords: Antibacterial; Calcium phosphate nanocomposite; Caries inhibition; Dental plaque microcosm biofilm; Mechanical properties; Quaternary ammonium monomer