title: Colour stability of veneering composites after accelerated aging.
abstract: OBJECTIVE
  To investigate the colour stability of four indirect composite restorative materials after accelerated aging.
  
  
  METHODS
  Four indirect composites (Gradia, Signum+, HFO and Adoro) were used. For each material, six specimens were prepared and subjected to accelerated aging (Suntest CPS+, Atlas, Chicago, IL, USA) according to ISO 7491. A Dr. Lange Microcolor Data Station colorimeter (Braive Instruments, Liege, Belgium) was used to measure specimen colour before and after aging. Measurements were performed according to the CIE L*a*b* system, and the mean L*, a* and b* values for each material were calculated. The equation DeltaE = [(DeltaL*)2 + (Deltaa*)2 + (Deltab*)2](1/2) was used to measure the total colour change (DeltaE), where DeltaL*, Deltaa* and Deltab* are the differences in the respective values before and after aging. One-way ANOVA were used to determine statistically significant differences in DeltaL*, Deltaa*, Deltab* and DeltaE.
  
  
  RESULTS
  No statistically significant differences were found in DeltaL*, Deltaa*, Deltab* and DeltaE among the materials tested (PDeltaL*=.063; PDeltaa*=.521; PDeltab*=.984 and PDeltaE=.408). After aging, Gradia specimens showed an increase in lightness (DeltaL*=0.36) and a green-yellow shift (Deltaa*=-1.18, Deltab*=0.6), while Signum+ specimens exhibited an increase in lightness (DeltaL*=0.5) and a green-blue shift (Deltaa*=-0.9, Deltab*=-0.45). HFO specimens exhibited an increase in lightness (DeltaL*=0.75) and a green-yellow shift (Deltaa*=-1.3, Deltab*=0.06), and Adoro specimens exhibited an increase in lightness (DeltaL*=2.07) and a green-yellow shift (Deltaa*=-1.3, Deltab*=0.68).
  
  
  CONCLUSIONS
  Colour changes were found to be within accepted values of perceptibility and clinical acceptance after accelerated aging, and no statistically significant differences were found in DeltaL*, Deltaa*, Deltab* and DeltaE among the materials tested.
authors.affiliation: Associate Professor, Department of Biomaterials, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece.
authors.forename: Triantafillos
authors.initials: T
authors.lastname: Papadopoulos
authors.forename: Aspasia
authors.initials: A
authors.lastname: Sarafianou
authors.forename: Andreas
authors.initials: A
authors.lastname: Hatzikyriakos
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