title: Accelerated aging effects on color and translucency of bleaching-shade composites.
abstract: OBJECTIVE
  This study was performed to evaluate the influence of accelerated aging on the color and translucency parameter (TP) of bleaching-shade resin composites.
  
  
  METHODS
  Thirty-three bleaching shades and two control conventional shades of microhybrid (MH) and microfill (MF) resin composite specimens (n = 5) were aged in an accelerated aging chamber set to standard CAM 180 cycles. One side of each specimen was evaluated for surface color and TP changes compared with baseline in increments of 150 kJ/m2 for intervals up to 450 kJ/m2 using a spectrophotometer. A deltaE* > or = 3.7 was considered to be a poor match, and the total TP range was divided into three equal parts representing low, medium, and high translucency. Data were analyzed with analysis of variance.
  
  
  RESULTS
  Compared to the baseline, deltaL*, deltaa*, deltab*, and deltaE* ranges at 450 kJ/m2 were -0.8 to 5.0, -0.6 to 1.2, -8.3 to 0.0, and 0.7 to 8.6 for MH and 0.2 to 1.3, 0.1 to 1.3, -2.5 to 1.1, and 1.7 to 2.7 for MF composites. Scheffé's S intervals (p = .05) for comparisons of deltaL*, deltaa*, deltab*, and deltaE* values of MH composites between baseline and 450 kJ/m2 were 1.6, 0.6, 1.7, and 1.5, respectively. Corresponding Tukey-Kramer intervals for MF composites were 0.7, 0.3, 0.6, and 0.6, respectively. TP values at baseline ranged from 0.9 to 4.3 for MH and from 1.4 to 2.2 for MF composites, whereas deltaTP for baseline minus 450 kJ/m2 ranged from -1.1 to 1.7 for MH and from -0.1 to 0.3 for MF composites. Scheffé's S interval (p = .05) for comparisons of deltaTP values of MH composites for baseline minus 450 kJ/m2 was 1.0. Corresponding Tukey-Kramer interval for MF composites was 0.4.
  
  
  CONCLUSIONS
  Aging-dependent color changes at 450 kJ/m2 were above the limit that indicated a poor match for 18/26 MH, while corresponding values for microfills were within acceptable range. Accelerated aging generally caused decreases in L* (specimens became darker) and a* values (specimens became redder), while b* values increased (specimens became more chromatic) for both MH and MF composites. TP was relatively stable during aging for both MH and MF composites.
authors.affiliation: Houston Biomaterials Research Center, Department of Restorative Dentistry and Biomaterials, The University of Texas Dental Branch at Houston, Houston, TX 77030-3402, USA. rparavina@uth.tmc.edu
authors.forename: Rade D
authors.initials: RD
authors.lastname: Paravina
authors.forename: Joe C
authors.initials: JC
authors.lastname: Ontiveros
authors.forename: John M
authors.initials: JM
authors.lastname: Powers
mesh_terms: D003116:Color; D003124:Colorimetry; D003188:Composite Resins / Q000737:chemistry*; D019554:Dental Restoration Wear / Q000706:statistics & numerical data*; D003793:Dental Restoration, Permanent / Q000706:statistics & numerical data*; D008422:Materials Testing / Q000706:statistics & numerical data; D017797:Prosthesis Coloring / Q000706:statistics & numerical data*; D013997:Time Factors; D014073:Tooth Bleaching / Q000706:statistics & numerical data
chemical_list: D003188:Composite Resins