Instrumental colorimetric evaluation of rose bengal shade guides

PURPOSE: Our preliminary study had indicated rose bengal (RB) staining might have the potency as a diagnostic aid of oral malignant lesions, however, RB shade guides had not been quantitatively measured. In the present study, we adjusted our 5-graded shade guide into a 4-graded one, and evaluated color difference of adjacent grades and within the same grade. METHODS: Instrumental colorimetry of the shade guides were conducted in the 1976 CIEL*a*b* space. Five sets of 4-graded shade guides of the same size were sent for instrumental colorimetry, for each shade tab, 3 measurements were performed, and averages of reflectance values were recorded ranged from 380 to 800 nm at 10 nm intervals. CIELAB color coordinates, L*, a*, b* were provided. RESULTS: The mean ΔE_grade (ΔE between adjacent grades) were 8.948~16.131 CIELAB units, and mean ΔE_tab (ΔE between every 2 shade tabs in the same grade) of the 4 grades were 1.932~2.311 CIELAB units. Color differences of the adjacent grades of the 4-graded shade guides were more than 6.254 CIELAB units, while color differences of the same grade were no more than 3.747 CIELAB units. CONCLUSION: Color differences of the adjusted RB shade tabs were easy to identify, the uniformity was also considerably good.