title: Improved polymerization efficiency of methacrylate-based cements containing an iodonium salt.
abstract: OBJECTIVE
  This study evaluated the effect of adding diphenyliodonium hexafluorphosphate (DPI) as a third component of the free-radical photoinitiator system of model resin cements on their photopolymerization kinetics/stress and fundamental properties.
  
  
  METHODS
  A model resin cement containing a 1:1 mass ratio of 2,2-bis[4-(2-hydroxy-3-methacryloxypropoxy)phenyl]propane and triethyleneglycol dimethacrylate was obtained. Camphorquinone (1 mol%) and 2-(dimethylamino)ethyl methacrylate (2 mol%) were added to monomer blend. Six mixtures were obtained by incorporation of 0 (control), 0.25, 0.5, 1, 2, or 4 mol% of DPI. The cements were loaded with a 60% mass fraction of silanated glass fillers. Polymerization kinetics (using Fourier-transform near-infrared spectroscopy), flexural strength and modulus, water uptake/solubility, and polymerization stress were assessed. Data were statistically analyzed using one-way ANOVA and Student-Newman-Keuls' test (P ≤ 0.05).
  
  
  RESULTS
  In the DPI-modified materials, the onset of autodeceleration occurred earlier and at higher conversion compared with the control cement. The addition of DPI also led to a more active early-stage polymerization. The flexural modulus was generally higher for DPI-containing materials. Water uptake and solubility were generally lower for materials with DPI fractions ≥ 0.5%. Significant increase of polymerization stress was observed only in the group with 1 mol% of DPI compared with the control cement.
  
  
  CONCLUSIONS
  The effect of DPI on the photopolymerization reactivity of the cement is concentration-dependent; the use of DPI could result in better polymerization efficiency of resin-based cements.
authors.affiliation: Piracicaba Dental School, State University of Campinas, Brazil; School of Dentistry, University of Uberaba, Brazil. Electronic address: goncalves1976@yahoo.com.br.
authors.forename: Luciano S
authors.initials: LS
authors.lastname: Gonçalves
authors.forename: Rafael R
authors.initials: RR
authors.lastname: Moraes
authors.forename: Fabrício A
authors.initials: FA
authors.lastname: Ogliari
authors.forename: Letícia
authors.initials: L
authors.lastname: Boaro
authors.forename: Roberto R
authors.initials: RR
authors.lastname: Braga
authors.forename: Simonides
authors.initials: S
authors.lastname: Consani
mesh_terms: D003738:Dental Cements / Q000737:chemistry*; D007455:Iodine / Q000737:chemistry*; D007700:Kinetics; D008689:Methacrylates / Q000737:chemistry*; D058105:Polymerization; D012492:Salts / Q000737:chemistry*
chemical_list: D003738:Dental Cements; D008689:Methacrylates; D012492:Salts; D007455:Iodine
keywords: Dental materials; Free-radical polymerization; Light curing; Onium salt; Resin cements