title: Second generation LEDs for the polymerization of oral biomaterials.
abstract: OBJECTIVE
  New blue, so called second generation light emitting diodes (LEDs) are now available with a high optical power output. These LEDs will potentially find widespread application in commercially available light curing units (LCUs). This study, therefore, investigated the curing performance of a prototype LCU containing one high power LED and a conventional halogen LCU (Polofil).
  
  
  METHODS
  The performances of the LCUs were evaluated by measuring the Knoop hardness and depth of cure of the composites. Three dental composites were selected (Z100, Admira and Revolcin Flow) in a light (A2) and a dark shade (A3.5 or A4), respectively, and were polymerized for 40 s each.
  
  
  RESULTS
  The LED prototype (irradiance=901 mW/cm2) achieved a statistically significantly greater (p<0.05) depth of cure than the halogen LCU (irradiance=860 mW/cm2) for all composites. Generally, there was no statistically significant difference in Knoop hardness on the top and bottom of a 2 mm thick disk for the composites Z100 and Admira if polymerized with the LED prototype or halogen LCU. The composite Revolcin Flow, however, showed in general a statistically significant lower Knoop hardness if polymerized with the LED LCU.
  
  
  CONCLUSIONS
  The present study shows that second generation LEDs have the potential to replace halogen LCUs if the composites are selected carefully. Furthermore, this study confirmed that the depth of cure test does not discriminate between LCU's performance for composites containing co-initiators, but the Knoop hardness test does.
authors.affiliation: Institute of Materials Science and Technology (IMT), Friedrich-Schiller-University Jena, Löbdergraben 32, Jena D-07743, Germany.
authors.forename: Alexander
authors.initials: A
authors.lastname: Uhl
authors.forename: Bernd W
authors.initials: BW
authors.lastname: Sigusch
authors.forename: Klaus D
authors.initials: KD
authors.lastname: Jandt
mesh_terms: D000704:Analysis of Variance; D003188:Composite Resins / Q000737:chemistry / Q000528:radiation effects*; D003748:Dental Equipment; D011211:Electric Power Supplies; D006219:Halogens; D006244:Hardness; D006245:Hardness Tests; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D011108:Polymers / Q000737:chemistry; D011874:Radiometry; D012666:Semiconductors; D012822:Silicon Dioxide / Q000737:chemistry / Q000528:radiation effects; D012833:Siloxanes / Q000737:chemistry / Q000528:radiation effects; D013674:Technology, Dental / Q000295:instrumentation; D013729:Terpenes; D015040:Zirconium / Q000737:chemistry / Q000528:radiation effects
chemical_list: D003188:Composite Resins; D006219:Halogens; D008689:Methacrylates; D011108:Polymers; D012833:Siloxanes; D013729:Terpenes; C083568:Z100 composite resin; C479084:admira; C483028:revolcin; C048339:camphoroquinone; D012822:Silicon Dioxide; D015040:Zirconium