Impact of Ambient Light on Tooth Shade Determination by Spectrophotometry

Modern spectrophotometers emit an illuminant mimicking the ideal light source and are expected to provide more accurate dental shade readouts than human visual assessment. The illuminant is thought to prevent contamination from external light, commonly present in a clinical setting. However, preliminary tests showed that positioning of the spectrophotometer device is critical for precise color determination, possibly due to the influence of ambient light. Objective: Evaluate the impact of different ambient light conditions on the measurement of human tooth color by a hand-held spectrophotometer under controlled positioning. Methods: Twenty color measurements of the right maxillary central incisor using a spectrophotometer (VITA Easyshade, Vident USA) were performed under 4 different controlled light conditions: fluorescent, incandescent, halogen and dark (control). Color space coordinates L (value), C (chroma), H (hue), on a and b color-opponent dimensions were recorded and analyzed with the Kruskal-Wallis test. Vita3D shades were also recorded with the spectrophotometer. Results: Significant differences (p≤0.05) of the measured parameters were found between incandescent and dark light conditions for H, a and b. All color coordinates except L differed significantly between incandescent and halogen illuminants. H and a coordinates were significantly different between dark and fluorescent light conditions, while b varied when fluorescent and incandescent condition were compared. Vita3D shade readings were constant in the dark environment only. Furthermore, agreement of the L, C and H coordinates of Vita3D shades to the control condition were 95%, 45% and 55% in fluorescent, incandescent and halogen light condition respectively. Conclusion: These results suggest that ambient light conditions significantly impact on specific tooth color coordinates and Vita3D shades obtained by the evaluated spectrophotometer, despite the system's independent illuminant. Interestingly, value was the only coordinate unaffected by external light conditions. Further investigation would be valuable to determine how individual changes in color coordinates affect clinical shade selection.