Calculation of whiteness and yellowness indexes using colorimetric and photographic methods for tooth shade evaluation

Abstract

Accurate color assessment is still a challenge for food-industrial applications and dental aesthetics. Even though current tooth color determination relies mostly on visual shade matching with shade guides, the technological advancements move towards objective tooth color assessment by using instruments such as colorimeters, spectrophotometers and digital cameras. Objective assessment of tooth color improves the communication between the professionals including clinicians, dentists, laboratory technicians and equipment designers. Tooth color can be evaluated by calculation of whiteness and yellowness indexes. Precise determination of these indexes is particularly important in dentistry, where monitoring the quality of dental restoration and the tooth appearance during whitening treatments is essential for improving the patient outcome. In this study, we evaluated the effect of tooth staining and a whitening treatment using violet illumination alone on yellowness and whiteness indexes. These indexes were quantified by colorimetry and digital photography, which were compared in terms of absolute values of the indexes and variation due to staining and whitening procedures. The violet illumination was capable of generating (36 ± 2) % of W* whiteness index recovery and (41 ± 2) % decrease on the YIE313 yellowness index. Even though the absolute W* and YIE313 values are relatively close for photographic and colorimetric methods, the indexes contrast were (37.3 ± 0.01) % and (12.8 ± 0.1) % lower for digital photography compared to colorimetry. We believe our study can be used as a guide for the evaluation of the color contrast generated on whitening monitoring devices in future studies.