title: Degree of conversion and hardness of a silorane-based composite resin: effect of light-curing unit and depth.
abstract: OBJECTIVE
  To investigate the effect of different light-curing units and depths on the degree of conversion (DC) through Fourier transform infrared spectroscopy (FTIR) and Knoop Hardness Number (KHN) of a silorane-based composite resin (Filtek LS, 3M ESPE, St Paul, MN, USA) (LS).
  
  
  METHODS
  LS specimens mounted in a particular designed matrix were photoactivated by three light-cure units (LCUs) at depths of 2, 3, 4, and 5 mm. The DC was determined in a FTIR spectrometer with an attenuated total reflectance accessory. The KHN was measured in an automatic microhardness tester. The results were analyzed using the Friedman and Spearman statistical tests (α=0.05).
  
  
  RESULTS
  There was no effect of LCUs on the DC (p=0.472) or KHN (p=0.174) for all of the studied depths. The highest DC and KHN means were found at 2-mm depth, which were not statistically different from 3-mm depth, but were higher than 4-mm and 5-mm depths (p=0.007). Spearman analysis found a positive linear correlation between the variables KHN and DC (r=0.858, p<0.000).
  
  
  CONCLUSIONS
  The LCUs' effect was not verified. Values of DC and KHN for LS decreased with increasing depth. The highest values for both DC and KHN were obtained at depths of 2-3 mm.
authors.forename: S A S
authors.initials: SA
authors.lastname: Torres
authors.forename: G C
authors.initials: GC
authors.lastname: Silva
authors.forename: D A
authors.initials: DA
authors.lastname: Maria
authors.forename: W R C
authors.initials: WR
authors.lastname: Campos
authors.forename: C S
authors.initials: CS
authors.lastname: Magalhães
authors.forename: A N
authors.initials: AN
authors.lastname: Moreira
mesh_terms: D003188:Composite Resins / Q000627:therapeutic use*; D003793:Dental Restoration, Permanent / Q000379:methods; D003799:Dental Stress Analysis; D006244:Hardness; D006801:Humans; D055115:Light-Curing of Dental Adhesives / Q000379:methods*; D017550:Spectroscopy, Fourier Transform Infrared
chemical_list: D003188:Composite Resins; C543062:Filtek LS Low Shrink resin