title: Correlations between color differences based on three color-difference formulas using dental shade guide tabs.
abstract: OBJECTIVE
  The purpose of this study was to determine the correlation among color-difference values based on three formulas between shade tab pairs from two shade guides [Vita Lumin (VITA) and Chromascop (CHRO)].
  
  
  METHODS
  The color of shade tabs was measured relative to the standard illuminant D(65) under the 8 degrees standard observer function, and distributions for CIE L*, a*, and b* values were compared. One hundred and twenty shade pairs from VITA and 190 shade pairs from CHRO were used to calculate color differences using CIELAB, DIN99, and CIEDE2000 formulas (DeltaE*(ab), DeltaE(99), and DeltaE(00), respectively). A paired t-test was used to determine the difference between each pair of the three color-difference values (alpha= 0.01). Regression analysis was used to determine the correlations between the color differences (alpha= 0.01).
  
  
  RESULTS
  For both shade guides, there were significant differences between DeltaE*(ab) and DeltaE(00), DeltaE*(ab) and DeltaE(99), and DeltaE(99) and DeltaE(00) (p < 0.01). DeltaE*(ab) and DeltaE(00), and DeltaE*(ab) and DeltaE(99) were strongly correlated (r(2)= 0.90 to 0.94, p < 0.05). Although a simplified a* rescaling function of the CIE a* axis has been added in the CIEDE2000 formula, the influence of the opposite signs in the a* value were found to be irrelevant to the DeltaE(00) value.
  
  
  CONCLUSIONS
  DeltaE*(ab),DeltaE(99), and DeltaE(00) can be used interchangeably for the evaluation of color difference of shade tabs.
authors.affiliation: Department of Dental Biomaterials Science, School of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Jong-Gil
authors.initials: JG
authors.lastname: Kim
authors.forename: Bin
authors.initials: B
authors.lastname: Yu
authors.forename: Yong-Keun
authors.initials: YK
authors.lastname: Lee
mesh_terms: D000465:Algorithms; D017554:Carbon Compounds, Inorganic / Q000737:chemistry; D003116:Color; D003124:Colorimetry / Q000295:instrumentation; D003775:Dental Polishing / Q000295:instrumentation; D017267:Dental Prosthesis Design / Q000295:instrumentation*; D003779:Denture Design / Q000295:instrumentation*; D004867:Equipment Design; D006801:Humans; D008029:Lighting / Q000295:instrumentation; D008422:Materials Testing; D010783:Photometry; D017797:Prosthesis Coloring / Q000295:instrumentation*; D017655:Silicon Compounds / Q000737:chemistry; D013499:Surface Properties
chemical_list: D017554:Carbon Compounds, Inorganic; D017655:Silicon Compounds; C022088:silicon carbide