title: Effectiveness of second-generation light-emitting diode (LED) light curing units.
abstract: OBJECTIVE
  The purpose of this study was to evaluate the effectiveness of three commercially available light emitting diode (LED) light curing units (LCU) (Elipar FreeLight--3M ESPE; UltraLume LED2--Ultradent; and Single V--BioArt) for polymerizing Z250-A3 composite (3M ESPE) using Knoop hardness, polymerization depth, and flexural strength properties.
  
  
  METHODS
  The XL 2500 (3M ESPE) LCU, which is a conventional halogen unit, was used as a control. In all cases the curing time was 20 seconds. Hardness was determined 24 hours after composite cure for 10 samples of 8 mm diameter and 2 mm height for each LCU tested. Samples were stored dry in a light-proof container prior to testing. The depth of cure of the composite was measured immediately after composite polymerization for each LCU using three samples 4 mm in diameter and 6 mm in height. Flexural strength was determined for five samples 24 hours after immersion in distilled water at 37 degrees C. Each sample measured 25 mm in length, 2 mm in width, and 2 mm in height for each LCU tested.
  
  
  CONCLUSIONS
  The results were treated statistically for comparison of the LCUs. In all cases the results obtained by LED LCUs were not different or were higher than a conventional halogen LCU.
  
  
  CONCLUSIONS
  Second generation LED LCUs were as effective as/or more effective than a halogen LCU for polymerization of the used composite. The present study shows second generation LEDs have the potential to replace halogen LCUs.
authors.affiliation: Department of Conservative Dentistry, Federal University of Rio Grande do Sul, Porto Algere, Rio Grande do Sul, Brazil. ubcampre@ufrgs.br
authors.forename: Ulisses Bastos
authors.initials: UB
authors.lastname: Campregher
authors.forename: Susana Maria Werner
authors.initials: SM
authors.lastname: Samuel
authors.forename: Carmen Beatriz Borges
authors.initials: CB
authors.lastname: Fortes
authors.forename: Alberth David Correa
authors.initials: AD
authors.lastname: Medina
authors.forename: Fabricio Mezzomo
authors.initials: FM
authors.lastname: Collares
authors.forename: Fabricio Aulo
authors.initials: FA
authors.lastname: Ogliari
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000528:radiation effects*; D003748:Dental Equipment; D003799:Dental Stress Analysis; D006219:Halogens; D006244:Hardness; D008027:Light; D044367:Phase Transition; D018583:Pliability; D019279:Resin Cements / Q000528:radiation effects*; D012666:Semiconductors
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; D006219:Halogens; D019279:Resin Cements