Exploring the CIEDE2000 thresholds for lightness, chroma, and hue differences in dentistry

Abstract

Objective: To evaluate the perceptibility and acceptability CIEDE2000 (KL:KC:KH) thresholds for lightness, chroma and hue differences in dentistry.

Method: A Python-based program was developed to conduct a psychophysical experiment based on visual assessments of computer simulated images of human teeth. The experiment was performed on a calibrated display. A 40-observer panel: dentists and laypersons (male and female; n=10), evalu- ated three subsets of simulated human teeth: the lightness subset (%ΔL00 ≥ 98 %), the chroma subset (%ΔC00 ≥ 98 %) and the hue subset (%ΔH00 ≥ 98 %), using ΔE00 ≥ 5 units. A Takagi-Sugeno-Kang Fuzzy Approximation model was used as fitting procedure, and 50:50 % lightness, chroma and hue CIEDE2000 (1:1:1) and CIEDE2000 (2:1:1) perceptibility (PT00) and accept- ability (AT00) thresholds were calculated. Data was statistically analyzed using t-test (p < 0.05).

Results: The 50:50 % PT00 for KL=1 were ΔL00=1.04, ΔC00=1.58 and ΔE00=1.01; and for KL=2 were ΔL00=0.51, ΔC00=1.58 and ΔE00=0.71. The 50:50 % AT00 for KL=1 were ΔL00=2.82, ΔC00=3.04 and ΔE00=2.66; and for KL=2 were ΔL00=1.40, ΔC00=3.04 and ΔE00=1.78. PT00 and AT00 ΔH00 may be considered no computable. A significant difference was found between CIEDE2000(1:1:1) and CIEDE2000(2:1:1), between lightness and chroma metrics, and between observer groups. No differences for lightness and chroma PT00 were found between male and female groups.

Conclusions: It is important to use PT00 and AT00 for lightness, chroma and hue specific to evaluate perceptual sensitivity for color changes in the tooth color space. AT00 for lightness and chroma are influenced by the observer’s experience and gender. Males and laypersons show more tolerance for changes in chroma (ΔC00) and in lightness (ΔL00).

Significance: Hue and chroma mismatch are more difficult to be accepted in dental color space.