title: Synthesis and study of physical properties of dental light-cured nanocomposites using different amounts of a urethane dimethacrylate trialkoxysilane coupling agent.
abstract: OBJECTIVE
  The purpose of this work was the study of the effect of the amount of a urethane dimethacrylate silane (UDMS) coupling agent on physical properties of dental light-cured resin nanocomposites based on Bis-GMA/TEGDMA (50/50 wt/wt) matrix and Aerosil OX50 as filler.
  
  
  METHODS
  Silica nanoparticles (Aerosil OX 50) used as filler were silanized with 5 different amounts of UDMS 1.0, 2.5, 5.0, 7.5 and 10 wt% relative to silica. The silanizated silica nanoparticles were identified by FT-IR spectroscopy and thermogravimetric analysis (TGA). Then the silanized nanoparticles (60 wt%) were mixed with a Bis-GMA/TEGDMA (50/50 wt/wt) matrix. Degree of conversion of light cured composites was determined by FT-IR analysis. The static flexural strength and flexural modulus were measured using a three-point bending set up. The dynamic thermomechanical properties were determined by DMA analyzer. Measurements were taken in samples stored, immediately after curing, in water at 37°C for 24 h. Sorption, solubility and volumetric change were determined after storage of composites in water or ethanol/water of 75 vol% for 30 days. Thermogravimetric analysis of composites was performed in nitrogen atmosphere from 50 to 800°C.
  
  
  RESULTS
  Almost all of used amount of silane remained chemically bounded on the surface of silica particles, forming a layer around them, which have dense accumulation of methacrylate groups. No significant statistic difference was found to exist between the degree of conversion values of composites with different silane contents. The composite with the lowest amount of UDMS (1.0 wt%) showed the lower flexural strength value, the higher static and dynamic elastic modulus values and the higher sorbed liquid value and solubility.
  
  
  CONCLUSIONS
  The optimum concentration of UDMS seems to be that of 2.5 wt%. Higher concentrations of UDMS did not improve the properties of composites.
authors.affiliation: Laboratory of Organic Chemical Technology, Department of Chemistry, Aristotle University of Thessaloniki, Thessaloniki GR-54124, Greece.
authors.forename: Maria M
authors.initials: MM
authors.lastname: Karabela
authors.forename: Irini D
authors.initials: ID
authors.lastname: Sideridou
mesh_terms: D000042:Absorption; D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins / Q000138:chemical synthesis* / Q000737:chemistry*; D003432:Cross-Linking Reagents; D003799:Dental Stress Analysis; D055119:Elastic Modulus; D006244:Hardness; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D008422:Materials Testing; D055595:Mechanical Phenomena; D008689:Methacrylates / Q000737:chemistry; D015394:Molecular Structure; D053761:Nanocomposites / Q000737:chemistry; D018583:Pliability; D011092:Polyethylene Glycols; D058105:Polymerization; D011109:Polymethacrylic Acids; D011140:Polyurethanes / Q000737:chemistry; D012821:Silanes / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013729:Terpenes; D013818:Thermogravimetry
chemical_list: D003188:Composite Resins; D003432:Cross-Linking Reagents; D008689:Methacrylates; D011109:Polymethacrylic Acids; D011140:Polyurethanes; D012821:Silanes; D013729:Terpenes; C029824:urethane dimethacrylate luting resin; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C048339:camphoroquinone; D012822:Silicon Dioxide