title: Characterization of multiwalled carbon nanotube-polymethyl methacrylate composite resins as denture base materials.
abstract: BACKGROUND
  Most fractures of dentures occur during function, primarily because of the flexural fatigue of denture resins.
  
  
  OBJECTIVE
  The purpose of this study was to evaluate a polymethyl methacrylate denture base material modified with multiwalled carbon nanotubes in terms of fatigue resistance, flexural strength, and resilience.
  
  
  METHODS
  Denture resin specimens were fabricated: control, 0.5 wt%, 1 wt%, and 2 wt% of multiwalled carbon nanotubes. Multiwalled carbon nanotubes were dispersed by sonication. Thermogravimetric analysis was used to determine quantitative dispersions of multiwalled carbon nanotubes in polymethyl methacrylate. Raman spectroscopic analyses were used to evaluate interfacial reactions between the multiwalled carbon nanotubes and the polymethyl methacrylate matrix. Groups with and without multiwalled carbon nanotubes were subjected to a 3-point-bending test for flexural strength. Resilience was derived from a stress and/or strain curve. Fatigue resistance was conducted by a 4-point bending test. Fractured surfaces were analyzed by scanning electron microscopy. One-way ANOVA and the Duncan tests were used to identify any statistical differences (α=.05).
  
  
  RESULTS
  Thermogravimetric analysis verified the accurate amounts of multiwalled carbon nanotubes dispersed in the polymethyl methacrylate resin. Raman spectroscopy showed an interfacial reaction between the multiwalled carbon nanotubes and the polymethyl methacrylate matrix. Statistical analyses revealed significant differences in static and dynamic loadings among the groups. The worst mechanical properties were in the 2 wt% multiwalled carbon nanotubes (P<.05), and 0.5 wt% and 1 wt% multiwalled carbon nanotubes significantly improved flexural strength and resilience. All multiwalled carbon nanotubes-polymethyl methacrylate groups showed poor fatigue resistance. The scanning electron microscopy results indicated more agglomerations in the 2% multiwalled carbon nanotubes.
  
  
  CONCLUSIONS
  Multiwalled carbon nanotubes-polymethyl methacrylate groups (0.5% and 1%) performed better than the control group during the static flexural test. The results indicated that 2 wt% multiwalled carbon nanotubes were not beneficial because of the inadequate dispersion of multiwalled carbon nanotubes in the polymethyl methacrylate matrix. Scanning electron microscopy analysis showed agglomerations on the fracture surface of 2 wt% multiwalled carbon nanotubes. The interfacial bonding between multiwalled carbon nanotubes and polymethyl methacrylate was weak based on the Raman data and dynamic loading results.
authors.affiliation: Associate Professor, Department of Comprehensive Care, Case Western Reserve University School of Dental Medicine, Cleveland, Ohio. Electronic address: rxw26@case.edu.
authors.forename: Russell
authors.initials: R
authors.lastname: Wang
authors.affiliation: Postgraduate student, Department of Civil Engineering, Case Western Reserve University School of Engineering, Cleveland, Ohio.
authors.forename: Junliang
authors.initials: J
authors.lastname: Tao
authors.affiliation: Associate Professor, Department of Civil Engineering, Case Western Reserve University School of Engineering, Cleveland, Ohio.
authors.forename: Bill
authors.initials: B
authors.lastname: Yu
authors.affiliation: Professor, Department of Macromolecular Science and Engineering, Case Western Reserve University School of Engineering, Cleveland, Ohio.
authors.forename: Liming
authors.initials: L
authors.lastname: Dai
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D003819:Denture Bases; D004548:Elasticity; D006801:Humans; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D037742:Nanotubes, Carbon / Q000737:chemistry*; D018583:Pliability; D019904:Polymethyl Methacrylate / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D013314:Stress, Mechanical; D013499:Surface Properties; D013696:Temperature; D013818:Thermogravimetry
chemical_list: D000180:Acrylic Resins; D003188:Composite Resins; D003764:Dental Materials; D037742:Nanotubes, Carbon; C040291:Lucitone; D019904:Polymethyl Methacrylate