title: Acceptability of shade differences in metal ceramic crowns.
abstract: BACKGROUND
  Application of technology that quantify color and color differences is currently used in esthetic restorative materials research. However, parameters for the size of perceptible and acceptable color differences in metal ceramic crowns have not been determined.
  
  
  OBJECTIVE
  The CIELAB colorimetric system was used to study the relationship between instrumentally measured color differences (delta E) and human observer assessment of color differences in metal ceramic crowns.
  
  
  METHODS
  Subjects were shown pairs of metal ceramic crowns whose color difference varied from indistinguishable to obvious. The subjects attempted to discern a difference in each pair's color and indicated the clinical acceptability of the shade difference between the crown pairs.
  
  
  RESULTS
  Correlations between instrumental and visual assessment of color differences in these crown pairs did not agree in all dimensions of color space. Thresholds acceptability of color differences were 1.1 delta E units for red-varying crowns and 2.1 delta E units for yellow-varying crowns. Thresholds for perceptibility judgments were significantly lower than thresholds for acceptability judgments.
  
  
  CONCLUSIONS
  Acceptability thresholds were found to be dependent on chromaticity. Observers were more sensitive and critical of crowns whose color differed in redness as opposed to crowns whose color differed to the same extent in yellowness.
authors.affiliation: Division of Fixed Prosthodontics, Faculty of Dentistry, University of Manitoba, Winnipeg, Canada.
authors.forename: R D
authors.initials: RD
authors.lastname: Douglas
authors.forename: J D
authors.initials: JD
authors.lastname: Brewer
mesh_terms: D016009:Chi-Square Distribution; D003116:Color / Q000592:standards*; D003118:Color Perception; D003258:Consumer Behavior; D003442:Crowns; D004056:Differential Threshold; D005260:Female; D006801:Humans; D016014:Linear Models; D008297:Male; D016876:Metal Ceramic Alloys; D015588:Observer Variation; D017797:Prosthesis Coloring / Q000592:standards*
chemical_list: D016876:Metal Ceramic Alloys