Investigation of hue effects in tooth whiteness perception

Objective: To identify the hue angles that provide the optimal perception of tooth whitening.

Methods: Thirty-three male/female adult observers with normal color vision were recruited to assess teeth images on a color calibrated display. Images of teeth were generated which simulated color changes in each of eight hue directions in the CIE a*b* plane, each equi-distant from a baseline tooth color. Using a paired comparison study design, observers were asked to indicate which of two images had whiter teeth. The data were converted into an interval scale using Thurstone's Law of Comparative Judgment. The relationship between the hue angles and the scores was modeled by curve fitting.

Results: The optimal hues were found in a region between green and blue in the CIE a*b chart. When the tooth color travels in an optimal hue direction, the same amount of color change will result in a greater change in whiteness perception than when traveling in other hue directions.

Conclusions: The optimal hues for tooth whitening were identified from the visual perception study. The most effective tooth whitening direction is to change tooth color towards the greenish-blue hue direction.

Clinical significance: This study gives clinicians and researchers a better understanding of tooth color hue effects in tooth whiteness perception.