title: Rheological properties of experimental Bis-GMA/TEGDMA flowable resin composites with various macrofiller/microfiller ratio.
abstract: OBJECTIVE
  The purpose of this study was to investigate the rheological behavior of resin composites and to evaluate the influence of each component, organic as well as inorganic, on their viscoelastic properties by testing model experimental formulations.
  
  
  METHODS
  Several unfilled mixtures of 2,2-bis-[4-(methacryloxy-2-hydroxy-propoxy)-phenyl]-propane (Bis-GMA) and triethylene glycol dimethacrylate (TEGDMA) were prepared as well as experimental flowable resin composites using a Bis-GMA/TEGDMA 50/50 wt% mixture as organic fraction filled at 60% in weight with varying ratios of silanated barium glass (1 microm) and partially hydrophobic fumed silica (0.1 microm). Their rheological properties were investigated using dynamic oscillatory rheometers. Transmission electron microscopy (TEM) was also performed to investigate the spatial organization of the filler particles.
  
  
  RESULTS
  Unfilled Bis-GMA/TEGDMA mixtures all showed a Newtonian behavior. The experimental flowable resin composites were non-Newtonian, shear-thinning fluids. As the quantity of microfiller increased, the viscosity increased and the shear-thinning behavior increased as well. In addition, the experimental composites showed thixotropy, i.e. their viscosity is a function of time after deformation. All these properties were not specifically linked to the creation and destruction of a visible network between inorganic particles, as no difference could be seen between particles' spatial organization at the equilibrium rest state or immediately after deformation.
  
  
  CONCLUSIONS
  The complex viscoelastic properties of resin composites are due to interactions between microfiller and monomer molecules. Modifying the chemical and physical properties of the particles' surface could possibly improve their flow properties and thus their clinical handling performances.
authors.affiliation: School of Dentistry and Stomatology, Université catholique de Louvain, Brussels, Belgium. Sebastien.Beun@patd.ucl.ac.be
authors.forename: Sébastien
authors.initials: S
authors.lastname: Beun
authors.forename: Christian
authors.initials: C
authors.lastname: Bailly
authors.forename: Anne
authors.initials: A
authors.lastname: Dabin
authors.forename: José
authors.initials: J
authors.lastname: Vreven
authors.forename: Jacques
authors.initials: J
authors.lastname: Devaux
authors.forename: Gaëtane
authors.initials: G
authors.lastname: Leloup
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D017609:Barium Compounds / Q000737:chemistry; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D002626:Chemistry, Pharmaceutical; D003188:Composite Resins / Q000737:chemistry*; D003764:Dental Materials / Q000737:chemistry*; D004548:Elasticity; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D009991:Oscillometry / Q000295:instrumentation; D011092:Polyethylene Glycols / Q000737:chemistry*; D011109:Polymethacrylic Acids / Q000737:chemistry*; D012212:Rheology / Q000295:instrumentation; D012821:Silanes / Q000737:chemistry; D017640:Silicates / Q000737:chemistry; D012822:Silicon Dioxide / Q000737:chemistry; D013314:Stress, Mechanical; D014783:Viscosity
chemical_list: D000538:Aluminum Silicates; D017609:Barium Compounds; D003188:Composite Resins; D003764:Dental Materials; D011109:Polymethacrylic Acids; D012821:Silanes; D017640:Silicates; C415406:barium borosilicate; C102738:barium glass filler; C111840:flowable hybrid composite; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; D012822:Silicon Dioxide