title: Evaluation of a second-generation LED curing light.
abstract: BACKGROUND
  Light-emitting diode (LED) curing lights offer advantages over quartz-tungsten-halogen (QTH) lights, but the first-generation LED lights had some disadvantages.
  
  
  OBJECTIVE
  This study compared a second-generation LED light with a QTH light to determine which was better at photopolymerizing a variety of resin composites.
  
  
  METHODS
  The ability of a LED light used for 20 and 40 seconds to cure 10 resin composites was compared with that of a QTH light used for 40 seconds. The composites were 1.6 mm thick and were irradiated at distances of 2 and 9 mm from the light guide. The Knoop hardness at the top and the bottom of each composite was measured at 15 minutes and 24 hours after irradiation.
  
  
  RESULTS
  The different curing lights and irradiation times did not have the same effect on all of the composites (p < 0.01). For specimens analyzed 24 hours after irradiation, the LED light used for 20 seconds cured 5 of the composites as well as when the QTH light was used for 40 seconds (p > 0.01). When used for 40 seconds, the LED light cured 6 of the composites as well as when the QTH light was used (p > 0.01), and all 10 composites achieved more than 80% of the hardness produced with the QTH light.
  
  
  CONCLUSIONS
  This LED light could not polymerize all of the composites as well as the QTH light. However, when used for 40 seconds, it cured more than half of the composites as well as when the QTH light was used, and all of the composites achieved a hardness comparable to that produced with the QTH light.
authors: Department of Dental Clinical Sciences, Dalhousie University, Halifax, Nova Scotia. rbprice@dal.ca
authors: Richard B T
authors: RB
authors: Price
authors: Corey A
authors: CA
authors: Felix
authors: Pantelis
authors: P
authors: Andreou
mesh_terms: D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D003748:Dental Equipment; D003793:Dental Restoration, Permanent / Q000295:instrumentation*; D006219:Halogens; D006244:Hardness; D006801:Humans; D008027:Light; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry; D012666:Semiconductors; D013997:Time Factors
chemical_list: D003188:Composite Resins; D006219:Halogens; D011108:Polymers