title: Organosilicon dental composite restoratives based on 1,3-bis[(p-acryloxymethyl) phenethyl] tetramethyldisiloxane.
abstract: OBJECTIVE
  The major concern associated with the use of polysiloxanes as polymer matrices in dental restorative materials, is the generally modest mechanical properties of the polymers. However, it has long been demonstrated that thermal stability, and mechanical properties of polysiloxanes can be substantially modified by incorporation of bulkier substituents such as phenyl groups or more polar groups in the chains. The purpose of this research was to evaluate visible light activated dental composites based on the high molecular weight siloxane monomer 1,3-bis[(p-acryloxymethyl) phenethyl] tetramethyldisiloxane (BAPD).
  
  
  METHODS
  Hardness, diametral tensile strength (DTS), degree of conversion (DC), water sorption (WS) and polymerization shrinkage of BAPD-based composites and bis-GMA-based composites were determined and compared.
  
  
  RESULTS
  Composites based on BAPD exhibited low WS, high DC, low polymerization shrinkage, and had hardness and DTS values that were not significantly lower than those of dental composites based on bis-GMA.
  
  
  CONCLUSIONS
  BAPD is a high molecular weight monomer (MW = 511) with a low viscosity. It did not require the use of low molecular weight diluent monomers in formulating composite resins. The DC of BAPD was high, ranging from 86 to 94%. Although the DC of BAPD was significantly higher than the conventional difunctional dental monomers, the polymerization shrinkage of the siloxane composites (1.70 - 1.81 vol%) was comparable to several composites based on bis-GMA.
authors.affiliation: LAI Laboratories Inc., 14617 White Oak Drive, Burnsville, MN 55337, USA. jlai@aol.com
authors.forename: J H
authors.initials: JH
authors.lastname: Lai
authors.forename: A E
authors.initials: AE
authors.lastname: Johnson
authors.forename: R B
authors.initials: RB
authors.lastname: Douglas
mesh_terms: D000042:Absorption; D017438:Bisphenol A-Glycidyl Methacrylate; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods*; D003799:Dental Stress Analysis; D006244:Hardness; D008027:Light; D008422:Materials Testing; D015394:Molecular Structure; D044367:Phase Transition; D012833:Siloxanes / Q000737:chemistry* / Q000528:radiation effects; D013718:Tensile Strength; D014867:Water
chemical_list: C490022:1,3-bis((p-acryloxymethyl)phenethyl)tetramethyldisiloxane; D012833:Siloxanes; D014867:Water; D017438:Bisphenol A-Glycidyl Methacrylate