title: Liquid crystalline epoxy nanocomposite material for dental application.
abstract: OBJECTIVE
  Novel liquid crystalline epoxy nanocomposites, which exhibit reduced polymerization shrinkage and effectively bond to tooth structures, can be applied in esthetic dentistry, including core and post systems, direct and indirect restorations, and dental brackets. The purposes of this study were to investigate the properties of liquid crystalline epoxy nanocomposites including biocompatibility, microhardness, and frictional forces of bracket-like blocks with different filler contents for further clinical applications.
  
  
  METHODS
  In this study, we evaluated liquid crystalline epoxy nanocomposite materials that exhibited various filler contents, by assessing their cell activity performance using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and their microhardness with or without thermocycling. We also evaluated the frictional force between bracket-like duplicates and commercially available esthetic bracket systems using Instron 5566.
  
  
  RESULTS
  The liquid crystalline epoxy nanocomposite materials showed good biocompatibility. The materials having high filler content demonstrated greater microhardness compared with commercially available bracket materials, before and after the thermocycling treatment. Thus, manufacturing processes are important to reduce frictional force experienced by orthodontic brackets.
  
  
  CONCLUSIONS
  The microhardness of the bracket-like blocks made by our new material is superior to the commercially available brackets, even after thermocycling. Our results indicate that the evaluated liquid crystalline epoxy nanocomposite materials are of an appropriate quality for application in dental core and post systems and in various restorations. By applying technology to refine manufacturing processes, these new materials could also be used to fabricate esthetic brackets for orthodontic treatment.
authors.affiliation: Dental Department, National Taiwan University Hospital, Taipei 10002, Taiwan.
authors.forename: Yun-Yuan
authors.initials: YY
authors.lastname: Tai
authors.affiliation: Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10002, Taiwan.
authors.forename: Sheng-Hao
authors.initials: SH
authors.lastname: Hsu
authors.affiliation: Graduate Institute of Clinical Dentistry, School of Dentistry, National Taiwan University, Taipei 10002, Taiwan.
authors.forename: Rung-Shu
authors.initials: RS
authors.lastname: Chen
authors.affiliation: Institute of Polymer Science and Engineering, National Taiwan University, Taipei 10002, Taiwan; Department of Materials Science and Engineering, National Taiwan University, Taipei 10002, Taiwan. Electronic address: suwf@ntu.edu.tw.
authors.forename: Wei-Fang
authors.initials: WF
authors.lastname: Su
authors.affiliation: Research Center of Developmental Biology and Regenerative Medicine, National Taiwan University, Taipei 10002, Taiwan; Graduate Institute, School of Dentistry, National Taiwan University, Taipei 10002, Taiwan; Director, Visiting Staff, Division of Esthetic Restoration, Department of Dentistry, National Taiwan University Hospital, Taipei 10002, Taiwan. Electronic address: minhueychen@ntu.edu.tw.
authors.forename: Min-Huey
authors.initials: MH
authors.lastname: Chen
mesh_terms: D003799:Dental Stress Analysis; D004853:Epoxy Resins / Q000737:chemistry*; D017276:Friction; D008422:Materials Testing; D053761:Nanocomposites / Q000737:chemistry*; D016910:Orthodontic Brackets; D013314:Stress, Mechanical
chemical_list: D004853:Epoxy Resins
keywords: biocompatibility; frictional force of dental brackets; liquid crystalline epoxy nanocomposite; microhardness