title: Robust spectrometer-based methods for characterizing radiant exitance of dental LED light curing units.
abstract: OBJECTIVE
  Firstly, to assess light output, from a representative range of dental light curing units (LCUs), using a new portable spectrometer based instrument (checkMARC™) compared with a "gold standard" method. Secondly, to assess possible inconsistency between light output measurements using three different laboratory-grade thermopile instruments.
  
  
  METHODS
  The output of four blue-dental LCUs and four polywave blue-and-violet-LCUs was measured with two spectrometer-based systems: a portable spectrometer instrument and a benchtop Integrating Sphere fiber-coupled spectrometer system. Power output was also recorded with three thermopiles according to ISO 10650-2. Beam profile images were recorded of LCU output to assess for spatial and spectral beam uniformity.
  
  
  RESULTS
  Power recorded with the portable spectrometer instrument closely matched the 'gold standard' Integrating Sphere apparatus calibrated according to International Standards. Radiant exitance for the eight LCUs differed significantly between the three thermopiles. Light source to thermopile sensor distance influenced recorded power significantly (p<0.05), indicating the severe limitations of thermopiles for absolute measurements. Polywave LCU beam profiles demonstrated output spectral heterogeneity.
  
  
  CONCLUSIONS
  Spectrometer-based methods are capable of overcoming the limitations inherent with thermopile-based measurement techniques. Spectrometer based measurements can fulfill the intention of ISO 10650.
authors.affiliation: The Dental School, St. Chad's Queensway, Birmingham B4 6NN, UK.
authors.forename: Adrian C
authors.initials: AC
authors.lastname: Shortall
authors.affiliation: Bluelight Analytics Inc., 24-2625 Joseph Howe Dr, Halifax, NS B3L 4G4, Canada.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Felix
authors.affiliation: The University of Manchester: School of Dentistry and Photon Science Institute, Manchester M13 9PL, UK. Electronic address: David.Watts@manchester.ac.uk.
authors.forename: David C
authors.initials: DC
authors.lastname: Watts
mesh_terms: D002138:Calibration; D055117:Curing Lights, Dental; D008422:Materials Testing; D013053:Spectrophotometry / Q000295:instrumentation*
keywords: Dental Light curing unit; ISO 10650-2; Irradiance; Radiant exitance; Spectral radiant power; Spectrometer; Thermopile