title: Effect of distance on irradiance and beam homogeneity from 4 light-emitting diode curing units.
abstract: OBJECTIVE
  To quantify the effect of distance on the irradiance and beam homogeneity from 4 curing lights.
  
  
  METHODS
  Four light-emitting diode curing lights were evaluated: Fusion, Bluephase 16i, Demi and FlashLite Magna. The irradiance at the centre of the light beam (ICB) was measured at 1.0 to 9.0 mm from the emitting tip using a 3.9-mm diameter probe connected to a spectrometer. The uniformity of the beam from each curing light was characterized by means of the "top hat factor" at 2.0, 4.0, 6.0 and 8.0 mm from the emitting tip. The useful beam diameter, within which irradiance values were greater than 400 mW/cm2, was calculated. The ICB, top hat factor and useful beam diameter were compared by analysis of variance and Fisher's protected least significant difference test at α = 0.01.
  
  
  RESULTS
  At all distances, the ICB was lowest for the FlashLite Magna and highest for the Fusion. Only the Fusion maintained an ICB above 1000 mW/cm2 at the 8.0 mm distance. For distances between 2.0 and 8.0 mm, the top hat factors were similar for the Fusion and the Demi, lower for the Bluephase 16i and lowest for the FlashLite Magna.
  
  
  CONCLUSIONS
  Beam homogeneity, top hat factors and ICB varied significantly among the curing lights. These results indicate that deep restorations may not be adequately cured if the curing time is based on data obtained when the curing light is positioned close to the radiometer or resin. In addition, a single irradiance value cannot be used to describe the light output from a curing light.
authors.affiliation: Dalhousie University, Halifax, NS. rbprice@dal.ca
authors.forename: Richard B
authors.initials: RB
authors.lastname: Price
authors.forename: Daniel
authors.initials: D
authors.lastname: Labrie
authors.forename: J Marc
authors.initials: JM
authors.lastname: Whalen
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Felix
mesh_terms: D003188:Composite Resins / Q000528:radiation effects; D055117:Curing Lights, Dental / Q000592:standards*; D003737:Dental Cavity Preparation / Q000145:classification; D003764:Dental Materials / Q000528:radiation effects; D004867:Equipment Design; D006801:Humans; D021621:Imaging, Three-Dimensional; D011874:Radiometry; D012984:Software; D013056:Spectrophotometry, Ultraviolet; D013499:Surface Properties; D013997:Time Factors
chemical_list: D003188:Composite Resins; D003764:Dental Materials