title: Halogen light versus LED for bracket bonding: shear bond strength.
abstract: BACKGROUND
  LED light-curing devices seek to provide a cold light activator which allows protocols of material polymerization with shorter duration.
  
  
  OBJECTIVE
  The present study aimed to evaluate the shear bond strength of bracket bonding using three types of light-curing devices: One with halogen light (Optilight Plus - Gnatus) and two with LEDs (Optilight CL - Gnatus and Elipar Freelight - 3M/ESPE).
  
  
  RESULTS
  Comparing the results by analysis of variance, the Gnatus LED device showed an inferior statistical behavior in relation to other light sources, when activated by a short time. But, when it was used for 40 seconds, the polymerization results were consistent with the other evaluated sources. The device with the best average performance was the halogen light, followed by the 3M/ESPE LED.
  
  
  CONCLUSIONS
  It was concluded that the LEDs may be indicated in orthodontic practice, as long as a protocol is used for the application of light with the activation time of 40 seconds.
authors.affiliation: University of São Paulo City, Brazil. paulo@carvalho-ortodontia.com.br
authors.forename: Paulo Eduardo Guedes
authors.initials: PE
authors.lastname: Carvalho
authors.forename: Valdemir Muzulon
authors.initials: VM
authors.lastname: dos Santos
authors.forename: Hassan
authors.initials: H
authors.lastname: Isber
authors.forename: Flávio Augusto
authors.initials: FA
authors.lastname: Cotrim-Ferreira
mesh_terms: D000704:Analysis of Variance; D001641:Bicuspid; D055117:Curing Lights, Dental; D001840:Dental Bonding / Q000295:instrumentation*; D003743:Dental Enamel / Q000737:chemistry*; D006801:Humans; D008422:Materials Testing / Q000379:methods; D016910:Orthodontic Brackets; D058105:Polymerization; D019279:Resin Cements / Q000737:chemistry*; D033081:Shear Strength; D013193:Stainless Steel / Q000737:chemistry*; D013718:Tensile Strength
chemical_list: D019279:Resin Cements; D013193:Stainless Steel
keywords: Dental bonding; Orthodontic brackets; Orthodontics; Shear bond strength