title: Effect of modulated irradiation time on the degree of conversion and the amount of elutable substances from nano-hybrid resin-based composites.
abstract: OBJECTIVE
  The aim of our study was to analyse whether the irradiation time and/or the modulation of irradiation time influence the degree of conversion (DC) and the amount of elutable substances from modern nano-hybrid resin-based composites (RBCs).
  
  
  METHODS
  The DC was recorded in real time for 5 min by means of attenuated total reflectance-Fourier transform infrared spectroscopy (n = 5) on the lower surface of 2-mm-thick samples irradiated with continuous and modulated irradiation times for 20 s and 40 s. The modulated times comprise a short polymerisation (2 s or 5 s) followed by a rest period of 1 min and an additional polymerisation to complete 20 s and 40 s of polymerisation (2 s + 18 s, 5 s + 15 s, 2 s + 38 s and 5 s + 35 s). After storing the specimens in ethanol/water for 7 days at 37 °C, the eluates were analysed by gas chromatography-mass spectrometry. Results were statistically analyzed using a one-way ANOVA analysis (α = 0.05).
  
  
  RESULTS
  The effect of irradiation time on DC is similar in all three analyzed materials, showing a significant increase in DC by increasing irradiation time from 20 s to 40 s, while the DC is not influenced within one irradiation time (20 s or 40 s) by the modulation of time.
  
  
  CONCLUSIONS
  The type and amount of eluates are strongly dependent from the material and the irradiation protocol.
  
  
  CONCLUSIONS
  An interrupt irradiation of RBCs is clinically feasible, reducing in general the amount of elutable substances at similar DC as the corresponding continuous polymerisation.
authors: Department of Operative/Restorative Dentistry, Periodontology and Pedodontics, Ludwig-Maximilians-University of Munich, Goethestr. 70, 80336, Munich, Germany, nilie@dent.med.uni-muenchen.de.
authors: Nicoleta
authors: N
authors: Ilie
authors: Julia
authors: J
authors: Obermaier
authors: Jürgen
authors: J
authors: Durner
mesh_terms: D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D008401:Gas Chromatography-Mass Spectrometry; D006245:Hardness Tests; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D053761:Nanocomposites; D058105:Polymerization; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins