title: The influence of bis-EMA vs bis GMA on the degree of conversion and water susceptibility of experimental composite materials.
abstract: OBJECTIVE
  The aim of this work was to assess the influence of the bis-EMA content on the degree of conversion (DC) and its effect on the water sorption and solubility.
  
  
  METHODS
  In a polytetrafluorethylene (PTFE) mould, 30 samples (Ø = 5 mm, height = 2 mm) of four experimental dental composite resins were cured for 10 s, 20 s and 40 s. The DC was analysed by Fourier Transform (FT)-Raman spectroscopy. To analyse sorption and solubility, six samples (Ø = 15 mm and thickness = 1 mm) of each composite (n = 72) were stored in water at 37°C for different storage periods: 24 h, 7 days and 30 days.
  
  
  RESULTS
  When cured for 20 or 40 s the DC increased with the increasing content of bis-EMA. However, the presence of 15 wt% of bis-GMA did not affect the DC, except when cured with 10 s irradiation time. This study also found a correlation between the content of bis-EMA and the reduced values for sorption and solubility, for all storage times used, when the materials were cured with 20 s.
  
  
  CONCLUSIONS
  The DC of mixtures with higher content of bis-EMA is affected by the presence of bis-GMA at lower energy density delivered from the curing device, suggesting that the restrictions caused by the presence of hydrogen bonds is dependent of the irradiation time used.
authors.affiliation: Department of Clinical Dentistry/Faculty of Health Sciences, The Arctic University of Norway , Tromsø , Norway.
authors.forename: Roberto Belloti
authors.initials: RB
authors.lastname: Cornelio
authors.forename: Aksel
authors.initials: A
authors.lastname: Wikant
authors.forename: Hanne
authors.initials: H
authors.lastname: Mjøsund
authors.forename: Hilde Molvig
authors.initials: HM
authors.lastname: Kopperud
authors.forename: Johan
authors.initials: J
authors.lastname: Haasum
authors.forename: Ulf Wiel
authors.initials: UW
authors.lastname: Gedde
authors.forename: Ulf Thore
authors.initials: UT
authors.lastname: Örtengren
mesh_terms: D001559:Benzhydryl Compounds / Q000737:chemistry*; D017438:Bisphenol A-Glycidyl Methacrylate / Q000737:chemistry*; D003764:Dental Materials; D005583:Fourier Analysis; D008689:Methacrylates / Q000737:chemistry*; D012995:Solubility; D013059:Spectrum Analysis, Raman; D014867:Water / Q000737:chemistry*; D000098826:Bisphenol A Compounds
chemical_list: D001559:Benzhydryl Compounds; D017438:Bisphenol A-Glycidyl Methacrylate; D003764:Dental Materials; D008689:Methacrylates; D014867:Water; C002462:4,4'-isopropylidenediphenol dimethacrylate; D000098826:Bisphenol A Compounds
keywords: FT-Raman spectroscopy; bis-EMA; dental composites; energy density; hydrogen bonds