title: Correlation of filler content and elastic properties of resin-composites.
abstract: OBJECTIVE
  The aim was to determine the Young's modulus (E), bulk modulus (B), shear modulus (G) and Poisson's ratio (nu) of a series of composite restorative materials and to correlate them with their filler volume-fractions.
  
  
  METHODS
  Twelve model resin-composite formulations, with systematically varied volume-fraction (Tokuyama), a flowable resin-composite (Point 4 flowable, Kerr) and two hybrid resin-composites (Filtek Supreme XT, 3M-Espe & X-tra Fil, Voco) were investigated. Twelve cylindrical specimens (5 mm x 6 mm) were prepared from each material. Six were free to expand radially under axial compressive loading, and were used to calculate the Young's modulus (E). The other six were radially constricted in a rigid stainless steel ring during loading, from which the bulk modulus (B) was calculated. Compression loading was performed at 1mm/min. The Young's and bulk moduli were determined using equations of elasticity. Poisson's ratio from nu=0.5-(E/6B) and shear modulus from G=E/2(1+nu).
  
  
  RESULTS
  Young's moduli ranged from 2.19 to 7.15GPa, bulk moduli from 12.79 to 22.43GPa and shear moduli from 0.74 to 2.47GPa. Poisson's ratio ranged from 0.45 for the stiffer to 0.47 for the more compliant composites. Statistically significant differences (ANOVA and Bonferroni at p=0.05) were found depending on filler volume-fraction.
  
  
  CONCLUSIONS
  Elastic moduli varied significantly and a positive correlation existed between elastic moduli and filler volume-fraction (r2: 0.905-0.992 and 0.940-1.000 for Young's and bulk moduli, respectively).
authors.affiliation: Biomaterials Science Research Group, School of Dentistry, The University of Manchester, Manchester, UK.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Masouras
authors.forename: Nick
authors.initials: N
authors.lastname: Silikas
authors.forename: David C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D004548:Elasticity; D005898:Glass / Q000737:chemistry; D006801:Humans; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry; D011092:Polyethylene Glycols / Q000737:chemistry; D011109:Polymethacrylic Acids / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D015040:Zirconium / Q000737:chemistry
chemical_list: C515802:1,6-bis(methacroyloxy-2-ethoxycarbonylamino)-2,4,4-trimethylhexane; D003188:Composite Resins; D003764:Dental Materials; C515951:Filtek Supreme Plus; D008689:Methacrylates; D011109:Polymethacrylic Acids; C529733:X-tra fil composite resin; C451741:point 4 composite resin; C020946:triethylene glycol dimethacrylate; C009495:titanium dioxide; C041979:2,2-bis-(4-(2-methacryloxyethoxy)phenyl)propane; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide