Color difference thresholds in dental ceramics

Abstract

Objectives: The objective of the study was to determine the perceptibility and acceptability thresholds for dental ceramics using CIEDE2000 (ΔE 00) and CIELAB (ΔEab) color difference formulas and a novel TSK Fuzzy Approximation. Methods: A 13-observer panel performed independent observations of perceptibility and acceptability judgments on 105 pairs of ceramic discs (14 mm in diameter and 3 mm thick). Color differences of the disc pairs were calculated using both color difference formulas (ΔE 00 ranged from 0.10 to 9.91). Two fitting procedures were used: S-shaped curve and TSK Fuzzy Approximation. For both procedures, from the resultant fitting curves, the 95% confidence intervals were estimated and the 50:50% thresholds were calculated (50% positive and 50% negative answers). Results: With the S-shaped fitting procedure, a 50:50% acceptability threshold was found to be ΔE00 = 2.25 (r2 = 0.88) and ΔEab=3.46 (r2 = 0.85). Corresponding values with a TSK Fuzzy Approximation were ΔE00 = 2.23 (r2 = 0.89) and ΔEab=3.48 (r2 = 0.86). The perceptibility thresholds for fitted S-shape curves were ΔE00 = 1.30 (r2 = 0.74) and ΔEab=1.80 (r2 = 0.70) and ΔE00 = 1.25 (r 2 = 0.75), and ΔEab=1.74 (r2 = 0.71) for the TSK Fuzzy Approximation. The ΔL′, ΔC′, ΔH′ values corresponding to a 50% acceptability threshold were ΔL′ = 2.44, ΔC′ = 3.15 and ΔH′ = 3.24 respectively. Conclusions: The CIEDE2000 color difference formula provided a better fit than CIELAB formula in the evaluation of color difference thresholds of dental ceramics. There was a statistically significant difference between perceptibility and acceptability thresholds for dental ceramics. The TSK Fuzzy Approximation has been proved to be a reliable alternative approach for the color threshold calculation procedure. © 2010 Elsevier Ltd.