title: A comparison of polymerization by light-emitting diode and halogen-based light-curing units.
abstract: BACKGROUND
  Light-emitting diode, or LED, technology provides certain advantages over halogen-based light polymerization of resin-based composites. The authors investigated the adequacy of cure of LED light-curing units, or LCUs.
  
  
  METHODS
  The authors used two halogen-based light-curing units (Optilux 400 and 501, Demetron Research Corp., Danbury, Conn.) and two commercially available LED LCUs (LumaCure, LumaLite, Spring Valley, Calif., and VersaLux, Centrix, Shelton, Conn.) to polymerize top surfaces of hybrid (Filtek Z-250, 3M, St. Paul, Minn.) and microfilled (Renamel, Cosmedent, Chicago) resin-based composite specimens. Specimens were indented on their top and bottom surfaces with a Knoop hardness tester and measured for hardness. Bottom:top hardness ratios determined the percentage of cure. The authors separated the data into eight groups (two composites cured with four different lights) with 15 observations per group, for a total sample size of 120.
  
  
  RESULTS
  The authors compared composites and curing lights by a two-way analysis of variance, and results indicated significant main effects. The main effect of composite was statistically significant (P < .0001) when microfilled composite was compared with hybrid composite, regardless of curing light, for all top and bottom hardness measurements, with the hybrid producing much higher hardness measurements overall. The main effect of light was significant as well (P < .0001), regardless of composite type, with the two halogen-based lights producing harder top and bottom composite surfaces than the two LED LCUs.
  
  
  CONCLUSIONS
  The light output of commercially available diodes for resin-based composite polymerization still requires improvement to rival the adequacy of cure of halogen-based LCUs. Additional studies are necessary.
  
  
  CONCLUSIONS
  Commercially available LED LCUs were introduced just in the past year. However, they may not adequately polymerize resin-based composites, which can lead to restoration failures and adverse pulpal responses to unpolymerized monomers.
authors.affiliation: Department of General Dentistry, Lackland Air Force Base, Texas 78236-5551, USA. william.dunn@lackland.af.mil
authors.forename: William J
authors.initials: WJ
authors.lastname: Dunn
authors.forename: Anneke C
authors.initials: AC
authors.lastname: Bush
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects; D004581:Electronics; D004867:Equipment Design; D006219:Halogens; D006244:Hardness; D006801:Humans; D008029:Lighting / Q000295:instrumentation*; D016555:Matched-Pair Analysis; D008422:Materials Testing; D011108:Polymers / Q000737:chemistry* / Q000528:radiation effects; D011109:Polymethacrylic Acids / Q000737:chemistry / Q000528:radiation effects; D011874:Radiometry; D012666:Semiconductors; D013223:Statistics as Topic; D013499:Surface Properties
chemical_list: D003188:Composite Resins; C444701:Filtek Z250; D006219:Halogens; D011108:Polymers; D011109:Polymethacrylic Acids; C444445:renamel microfill