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    STUDIA CHEMIA - Issue no. 3 / 2011  
         
  Article:   EVALUATION OF FREE RADICAL CONCENTRATION IN SOME NEW DENTAL COMPOSITE MATERIALS BY ESR SPECTROSCOPY.

Authors:  DOINA PRODAN, LAURA SILAGHI-DUMITRESCU, CRISTINA PREJMEREAN, RADU SILAGHI-DUMITRESCU, LAURA BOLOJAN, G. DAMIAN. 		 
       
         
  Abstract:  During polymerization of dimethacrylate monomers employed in dental materials, the gel effect leads to entrapment of radicals and unreacted monomers in the crosslinked network, affecting physico-mechanical properties and the biocompatibility. Reported here is a study of the effect of the resin composition, irradiation time and storage time of some new light-cured dental composites upon the free propagating radical concentration, using Electron Spin Resonance (ESR). Six new experimental dental light-cured composites based on the Bis-GMA monomer - 2,2-bis[4-(2-hydroxy-3-methacryloyloxy-propoxy)phenyl]-propane, on the corresponding Bis-GMA dimer, 2-hydroxyethyl methacrylate (HEMA) and on 1,6-Bis-[2-methacryloyloxyethoxycarbonyl-amino]-2,4,4-trmethylhexane (UDMA) have been employed, with three different photoinitiator systems. The hybrid filler consisted of quartz, strontium/zirconium glass and fluoro-hydroxyapatite. ESR signals developed under visible light irradiation during polymerization were measured, with intensities dependent on the time of irradiation. These signals decay very slowly in time – on the scale of days or longer.

Keywords: Resin composites; ESR ; Free radicals 		 
         
     
         
         
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