title: Antibacterial and protein-repellent orthodontic cement to combat biofilms and white spot lesions.
abstract: OBJECTIVE
  White spot lesions are the most undesired side-effect of fixed orthodontic treatments. The objectives of this study were to combine nanoparticles of silver (NAg) with 2-methacryloyloxyethyl phosphorylcholine (MPC) to develop a modified resin-modified glass ionomer cement (RMGI) as orthodontic cement with double benefits of antibacterial and protein-repellent capabilities for the first time.
  
  
  METHODS
  NAg and MPC were incorporated into a commercial RMGI. Another commercial orthodontic adhesive also served as control. Enamel shear bond strengths (SBS) were determined. Protein adsorption was measured via a micro bicinchoninic acid method. A dental plaque microcosm biofilm model with human saliva as inoculum was tested. Biofilms adherent on the cement samples and planktonic bacteria in the culture medium away from the cement surfaces were both evaluated for bacterial metabolic activity, colony-forming units (CFU), and lactic acid production.
  
  
  RESULTS
  Adding 0.1% NAg and 3% MPC to RMGI, and water-aging for 30 days, did not adversely affect the SBS, compared to the unmodified RMGI control (p>0.1). The modified RMGI containing 0.1% NAg and 3% MPC achieved the greatest reduction in protein adsorption, bacterial adhesion, CFU, metabolic activity and lactic acid production. The RMGI containing 0.1% NAg and 3% MPC inhibited not only the bacteria on its surface, but also the bacteria away from the surface in the culture medium.
  
  
  CONCLUSIONS
  The incorporation of double agents (antibacterial NAg+protein-repellent MPC) into RMGI achieved much stronger inhibition of biofilms than using each agent alone. The novel antibacterial and protein-repellent RMGI with substantially-reduced biofilm acids is promising as an orthodontic cement to combat white spot lesions in enamel.
authors.affiliation: Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China; Biomaterials & Tissue Engineering Division, School of Dentistry, University of Maryland, Baltimore, MD 21201, USA.
authors.forename: Ning
authors.initials: N
authors.lastname: Zhang
authors.affiliation: Biomaterials & Tissue Engineering Division, School of Dentistry, University of Maryland, Baltimore, MD 21201, USA; State Key Laboratory of Oral Diseases, West China School of Stomatology, Sichuan University, Chengdu, China.
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.affiliation: Biomaterials & Tissue Engineering Division, School of Dentistry, University of Maryland, Baltimore, MD 21201, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Weir
authors.affiliation: Department of Orthodontics, School of Stomatology, Capital Medical University, Beijing, China. Electronic address: byuxing@263.net.
authors.forename: Yuxing
authors.initials: Y
authors.lastname: Bai
authors.affiliation: Biomaterials & Tissue Engineering Division, School of Dentistry, University of Maryland, 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; Department of Mechanical Engineering, University of Maryland, Baltimore County, MD 21250, 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 / Q000378:metabolism; D001422:Bacterial Adhesion / Q000187:drug effects; D018441:Biofilms / Q000187:drug effects*; D001840:Dental Bonding; D003731:Dental Caries / Q000517:prevention & control*; D003738:Dental Cements / Q000737:chemistry* / Q000494:pharmacology*; D003743:Dental Enamel / Q000187:drug effects; D003773:Dental Plaque / Q000382:microbiology; D005899:Glass Ionomer Cements / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D019344:Lactic Acid / Q000378:metabolism; D053768:Metal Nanoparticles / Q000737:chemistry; D008689:Methacrylates / Q000737:chemistry / Q000494:pharmacology; D010767:Phosphorylcholine / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology; D011897:Random Allocation; D012463:Saliva / Q000382:microbiology; D012834:Silver / Q000008:administration & dosage / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D000900:Anti-Bacterial Agents; D003738:Dental Cements; D005899:Glass Ionomer Cements; D008689:Methacrylates; D014867:Water; D010767:Phosphorylcholine; D019344:Lactic Acid; D012834:Silver; C070638:2-methacryloyloxyethyl phosphorylcholine
keywords: Antibacterial property; Human saliva microcosm biofilm; Orthodontic cement; Protein repellent; Shear bond strength; White spot lesions