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

OBJECTIVE

To evaluate the perceptibility and acceptability CIEDE2000 (K:K:K) 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 (%∆L ≥ 98 %), the chroma subset (%∆C ≥ 98 %) and the hue subset (%∆H ≥ 98 %), using ∆E ≥ 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 (PT) and accept- ability (AT) thresholds were calculated. Data was statistically analyzed using t-test (p < 0.05).

RESULTS

The 50:50 % PT for K=1 were ∆L=1.04, ∆C=1.58 and ∆E=1.01; and for K=2 were ∆L=0.51, ∆C=1.58 and ∆E=0.71. The 50:50 % AT for K=1 were ∆L=2.82, ∆C=3.04 and ∆E=2.66; and for K=2 were ∆L=1.40, ∆C=3.04 and ∆E=1.78. PT and AT ∆H 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 PT were found between male and female groups.

CONCLUSIONS

It is important to use PT and AT for lightness, chroma and hue specific to evaluate perceptual sensitivity for color changes in the tooth color space. AT for lightness and chroma are influenced by the observer's experience and gender. Males and laypersons show more tolerance for changes in chroma (∆C) and in lightness (∆L).

SIGNIFICANCE

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