Evaluation of the accuracy and limitations of three tooth-color measuring machines

Abstract

Background/purpose: To use dental shade guides as the standard to evaluate the accuracy of tooth-color matching devices and how they are affected by the limitation of uneven distribution and insufficient color space coverage of the dental shade guide. The aim of this study was to develop a systemic method to enhance the accuracy of using tooth-color matching devices. Materials and methods: The tabs of the Munsell Book of Color were tested with three tooth-color measuring instruments (ShadeEye NCC, VITA Easyshade, and DeguDent Shadepilot). The results of each instrument were analyzed by an Analysis of Variance (ANOVA) test and a Tukey's post-hoc test to find out the limit of each instrument. Hue, chroma, and value were identified as factors that affect the results of the measurements. Results: The accuracy of the DeguDent Shadepilot did not vary significantly with changes in the parameters hue, chroma, and value. The ShadeEye NCC had a ΔE value above the acceptable limit (ΔE = 4.2) when value was lower than 4 and chroma was higher than 6. The VITA Easyshade had a large ΔE when hue ranged from 7.5YR and to 10YR, value was higher than 7, and chroma was higher than 6. Conclusion: By knowing the limits of each machine after being analyzed with the Munsell Book of Color, we can use the color measuring instrument in the specific color space range that the devices measuring accuracy performs the best in to achieve objective and accurate tooth-color measuring results in routine dental practice.

Keywords

• CIELAB color system
• colorimeter
• color matching
• spectrophotometer
• the Munsell Book of Color