title: Depth of cure and surface microhardness of composite resin cured with blue LED curing lights.
abstract: OBJECTIVE
  This study examined the depth of cure and surface microhardness of Filtek Z250 composite resin (3M-Espe) (shades B1, A3, and C4) when cured with three commercially available light emitting diode (LED) curing lights [E-light (GC), Elipar Freelight (3M-ESPE), 475H (RF Lab Systems)], compared with a high intensity quartz tungsten halogen (HQTH) light (Kerr Demetron Optilux 501) and a conventional quartz tungsten halogen (QTH) lamp (Sirona S1 dental unit).
  
  
  METHODS
  The effects of light source and resin shade were evaluated as independent variables. Depth of cure after 40 s of exposure was determined using the ISO 4049:2000 method, and Vickers hardness determined at 1.0 mm intervals.
  
  
  RESULTS
  HQTH and QTH lamps gave the greatest depth of cure. The three LED lights showed similar performances across all parameters, and each unit exceeded the ISO standard for depth of cure except GC ELight for shade B1. In terms of shade, LED lights gave greater curing depths with A3 shade, while QTH and HQTH lights gave greater curing depths with C4 shade. Hardness at the resin surface was not significantly different between LED and conventional curing lights, however, below the surface, hardness reduced more rapidly for the LED lights, especially at depths beyond 3 mm.
  
  
  CONCLUSIONS
  Since the performance of the three LED lights meets the ISO standard for depth of cure, these systems appear suitable for routine clinical application for resin curing.
authors.affiliation: School of Dentistry, The University of Queensland, 200 Turbot Street, Brisbane, Qld 4000, Australia.
authors.forename: Paul C L
authors.initials: PC
authors.lastname: Tsai
authors.forename: Ian A
authors.initials: IA
authors.lastname: Meyers
authors.forename: Laurence J
authors.initials: LJ
authors.lastname: Walsh
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000528:radiation effects*; D003748:Dental Equipment; D006244:Hardness; D008027:Light; D015394:Molecular Structure; D044367:Phase Transition; D011108:Polymers / Q000737:chemistry; D012666:Semiconductors
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; D011108:Polymers