title: In vitro effect of light-emitting diode light polymerization on the color stability of three resin-based restorative materials.
abstract: OBJECTIVE
  To investigate the color stability of resin-based restorative materials when polymerized with light-emitting diode (LED) curing light in the constant or exponential mode.
  
  
  METHODS
  Eight specimens of Admira (AD), Compoglass F (CO), and Tetric EvoCeram (TE) constantly cured or exponentially cured with a high-powered LED curing light for 10, 20, or 60 s. The CIE-Lab values (L*, a*, b*) were measured prior to and after performing the water storage or color stability test according to EN ISO 7491 (Suntest).
  
  
  RESULTS
  Statistical analysis showed significant changes in the color values after each of the aging processes, as well as between DeltaL, Deltaa, Deltab, and DeltaE of the materials, which were dependent on curing time, mode, and aging condition (p<0.05). CO performed very well during water storage, but AD and TE exceeded the clinically relevant limit DeltaE=1. After the Suntest and 180 d additional water storage, TE showed the highest mean (SD) DeltaE=4.4 (1.1) to 5.4 (1.9). Although AD and CO performed best in the constant mode, they exceeded DeltaE=1. All materials shifted to more red.
  
  
  CONCLUSIONS
  The extent of discoloration depended on (a) the curing mode, (b) the curing time, and (c) the aging condition. Not all materials performed clinically acceptably in all tests; TE even showed unacceptable DeltaE>3.3. The optimal curing time was 20 s for both curing modes and all tested materials.
authors.affiliation: Heinrich-Heine-University, Medical Faculty, Centre of Dentistry, Department of Operative and Preventive Dentistry and Endodontics, Düsseldorf, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Rüttermann
authors.forename: Andrea
authors.initials: A
authors.lastname: Servos
authors.forename: Wolfgang H-M
authors.initials: WH
authors.lastname: Raab
authors.forename: Ralf
authors.initials: R
authors.lastname: Janda
mesh_terms: D000704:Analysis of Variance; D003116:Color; D003124:Colorimetry; D003188:Composite Resins / Q000737:chemistry* / Q000528:radiation effects*; D003748:Dental Equipment; D003793:Dental Restoration, Permanent; D008027:Light; D008422:Materials Testing; D008689:Methacrylates / Q000737:chemistry / Q000528:radiation effects; D044367:Phase Transition; D012666:Semiconductors; D012833:Siloxanes / Q000737:chemistry / Q000528:radiation effects; D013997:Time Factors
chemical_list: D003188:Composite Resins; D008689:Methacrylates; D012833:Siloxanes; C501891:Tetric EvoCeram; C479084:admira; C476992:compoglass flow