title: Nanoparticulate fillers improve the mechanical strength of bone cement.
abstract: OBJECTIVE
  Polymethylmethacrylate (PMMA-) based bone cement contains micrometer-size barium sulfate or zirconium oxide particles to radiopacify the cement for radiographic monitoring during follow-up. Considerable effort has been expended to improve the mechanical qualities of cements, largely through substitution of PMMA with new chemical structures. The introduction of these materials into clinical practice has been complicated by concerns over the unknown long-term risk profile of these new structures in vivo. We investigated a new composite with the well characterized chemical composition of current cements, but with nanoparticles instead of the conventional, micrometer-size barium sulfate radiopacifier.
  
  
  METHODS
  In this study, we replaced the barium sulfate microparticles that are usually present in commercial PMMA cements with barium sulfate nanoparticles. The resultant "microcomposite" and "nanocomposite" cements were then characterized through morphological investigations such as ultra-small angle X-ray scattering (USAXS) and scanning electron microscopy (SEM). Mechanical characterization included compression, tensile, compact tension, and fatigue testing.
  
  
  RESULTS
  SEM and USAXS showed excellent dispersion of nanoparticles. Substitution of nanoparticles for microparticles resulted in a 41% increase in tensile strain-to-failure (p = 0.002) and a 70% increase in tensile work-of-fracture (p = 0.005). The nanocomposite cement also showed a two-fold increase in fatigue life compared to the conventional, microcomposite cement.
  
  
  CONCLUSIONS
  In summary, nanoparticulate substitution of radiopacifiers substantially improved the in vitro mechanical properties of PMMA bone cement without changing the known chemical composition.
authors.affiliation: Department of Orthopaedic Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, MA, USA. agomoll@yahoo.com
authors.forename: Andreas H
authors.initials: AH
authors.lastname: Gomoll
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Fitz
authors.forename: Richard D
authors.initials: RD
authors.lastname: Scott
authors.forename: Thomas S
authors.initials: TS
authors.lastname: Thornhill
authors.forename: Anuj
authors.initials: A
authors.lastname: Bellare
mesh_terms: D001466:Barium Sulfate / Q000737:chemistry; D001843:Bone Cements / Q000737:chemistry; D019245:Compressive Strength; D066298:In Vitro Techniques; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D053761:Nanocomposites / Q000737:chemistry; D053758:Nanoparticles / Q000737:chemistry; D019904:Polymethyl Methacrylate / Q000737:chemistry; D013314:Stress, Mechanical; D013718:Tensile Strength
chemical_list: D001843:Bone Cements; D001466:Barium Sulfate; D019904:Polymethyl Methacrylate