title: Effect of liquid rubber additions on physical properties of Bis-GMA based dental resins.
abstract: OBJECTIVE
  The aim of this investigation was to determine the effect of an experimental liquid rubber (LR) toughening agent on fracture toughness, crosslink density and Barcol hardness of polymerized mixtures of 50/50 wt% Bis-GMA and TEGDMA.
  
  
  METHODS
  An experimental LR, was added to a solution of Bis-GMA and TEGDMA containing 1wt% dimethylamino ethyl methacrylate and 0.5 wt% camphoroquinone at concentrations 0-10%. The composites were polymerized by exposure to a visible light curing unit for 60s. Fracture toughness was determined according to ASTM. 399. Crosslink density was evaluated using a swell test in ethanol.
  
  
  RESULTS
  Mean fracture toughness values ranged from 0.39 MPa m(1/2) for samples containing 6% to 1.24 MPa m(1/2) for samples containing 8% LR. Fracture toughness of samples containing 2%, 4%, and 8% LR were significantly higher than controls. The highest degree of cross-linkage was obtained in controls and lowest for samples containing 2% LR. Barcol Hardness values ranged from 36.7 for the control and 4% LR composition to 31.2 for samples containing 10% LR.
  
  
  CONCLUSIONS
  Addition of 2, 4 and 8% LR increases the fracture toughness of Bis-GMA/TEGDMA composites. Addition of LR shows promise as a method of improving the fracture toughness of Bis-GMA based dental composites.
authors.affiliation: Department of Restorative and Preventive Sciences, University of Pennsylvania, 240 South 40th Street, Philadelphia, PA 19104, USA. mantefk@gmail.com
authors.forename: Francis K
authors.initials: FK
authors.lastname: Mante
authors.forename: Rose O
authors.initials: RO
authors.lastname: Wadenya
authors.forename: Daniel A
authors.initials: DA
authors.lastname: Bienstock
authors.forename: Jared
authors.initials: J
authors.lastname: Mendelsohn
authors.forename: Edward E
authors.initials: EE
authors.lastname: LaFleur
mesh_terms: D017438:Bisphenol A-Glycidyl Methacrylate; D003188:Composite Resins / Q000737:chemistry*; D003793:Dental Restoration, Permanent; D003799:Dental Stress Analysis; D006244:Hardness; D055115:Light-Curing of Dental Adhesives; D008422:Materials Testing; D008689:Methacrylates; D015394:Molecular Structure; D011092:Polyethylene Glycols; D011109:Polymethacrylic Acids; D012408:Rubber; D013729:Terpenes
chemical_list: D003188:Composite Resins; D008689:Methacrylates; D011109:Polymethacrylic Acids; D013729:Terpenes; C020946:triethylene glycol dimethacrylate; D011092:Polyethylene Glycols; D017438:Bisphenol A-Glycidyl Methacrylate; C048339:camphoroquinone; D012408:Rubber; C519537:diethylaminoethyl methacrylate