title: Evaluation of dental restorative composites containing polyhedral oligomeric silsesquioxane methacrylate.
abstract: OBJECTIVE
  The aim of this study was to explore novel polymeric dental restorative composites, in which polyhedral oligomeric silsesquioxane methacrylate monomer (POSS-MA) was used to partially (or completely) replace the commonly used base monomer 2,2'-bis-[4-(methacryloxypropoxy)-phenyl]-propane (Bis-GMA).
  
  
  METHODS
  The composites were cured (hardened) by photo-initiated free radical polymerization. Mechanical properties (i.e. flexural strength, Young's modulus and diametral tensile strength) of the composites were tested by a universal mechanical testing machine; photopolymerization induced volumetric shrinkage was measured using a mercury dilatometer; and near infrared (NIR) technique was used to study the degree of methacrylate double bond conversion and photopolymerization rate.
  
  
  RESULTS
  Small percentage POSS-MA substitution of Bis-GMA (i.e. mass fraction of 10% or less) in the resin system improved the mechanical properties of the composites; while large amount substitution led to less desirable mechanical properties, lower methacrylate double bond conversion, and slower photopolymerization rate. Statistical examinations showed the maximum flexural strength of the composites occurred when 10% (mass fraction) of Bis-GMA was replaced by POSS-MA, while the highest modulus occurred when the mass fraction of POSS-MA was 2%.
  
  
  CONCLUSIONS
  Polymeric dental restorative composites with improved mechanical properties may be designed by judicious choice of monomer (POSS-MA, Bis-GMA and TEGDMA) compositions.
authors.affiliation: Department of Chemistry and Chemical Engineering, South Dakota School of Mines and Technology, Rapid City, SD 57701-3995, USA. hao.fong@sdsmt.edu
authors.forename: Hao
authors.initials: H
authors.lastname: Fong
authors.forename: Sabine H
authors.initials: SH
authors.lastname: Dickens
authors.forename: Glenn M
authors.initials: GM
authors.lastname: Flaim
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry; D003188:Composite Resins / Q000737:chemistry*; D018772:Dental Marginal Adaptation; D003793:Dental Restoration, Permanent / Q000379:methods; D003799:Dental Stress Analysis; D004548:Elasticity; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry*; D015394:Molecular Structure; D017646:Organosilicon Compounds / Q000737:chemistry*; D044367:Phase Transition; D018583:Pliability; D019265:Spectroscopy, Near-Infrared; D013718:Tensile Strength; D014961:X-Ray Diffraction
chemical_list: D003188:Composite Resins; D008689:Methacrylates; D017646:Organosilicon Compounds; C503161:polyhedral oligomeric silsesquioxane methacrylate; D017438:Bisphenol A-Glycidyl Methacrylate