Influence of Ultraviolet Component on Detecting Differences Using Colorimetric Spectrophotometer

Objectives: Spectrophotometers are widely applied in laboratory studies for precise color evaluation. The inclusion of the UV component (radiation with wavelengths below 400nm) in the illuminant is an adjustable parameter that may affect the analysis since natural teeth and some restorative materials exhibit fluorescence. Therefore, this study aimed to evaluate the influence of including/excluding the UV component on the spectrophotometer's ability to detect statistically significant color differences among the tab shades (T) of the Vita Bleachedguide shade guide (VB), which provides distinct and well-known colors organized based on lightness (L*) values.
Methods: The VB tab shades were numbered according to L* values (T1=highest L* and T15= lowest L*) and fixed in a custom-made holder to standardize the position for color reading. The L*, a*, and b* coordinates of each tab shade were obtained with a colorimetric spectrophotometer (CM-2600d - Konica Minolta) under D65 illuminant. Five readings were performed with the UV component included and five with its exclusion. The color difference values (△Eab) were calculated by comparing each tab of the shade guide with the darkest one (T15/5M3). The color difference data (UV included/excluded) were separately subjected to one-way ANOVA and Tukey's test, with a significance level of 5%.
Results: Significant differences between the tab shades were found when the UV was included (p=0.001) and when it was excluded (p=0.001). The Tukey's test results for △Eab means and standard deviations without UV were: T14-2.58(0.12)a; T13-4.35(0.14)b; T12-5.08(0.07)c; T11-5.75(0.17)d; T10-6.48(0.08)e; T9-7.44(0.13)f; T8-8.72 (0.14)g; T7-9.33(0.08)h; T6-9.86(0.06)i; T5-10.31(0.07)j; T4-11.29(0.14)k; T3-12.07(0.21)l; T2-13.74(0.16)m; T1-17.01(0.12)n.
And for △Eab with UV were: T14-2.45(0.13)a; T13-4.21(0.15)b; T12-5.06(0.11)bc; T11-5,70(0.19)c; T10-6.40(0.26)d; T9-7.67(0.26)e; T8-8.45(0.29)f; T7-9.90(0.29)g; T6-9.89(0.26)g; T5-10.49(0.26)h; T4-11.30(0.32)h; T3-12.46(0.24)ij; T2-13.87(0.38)j; T1-17.21(0.43)k.
Conclusions: It can be concluded that color readings with UV excluded showed a higher ability to detect statistically significant differences among the shades. The absolute values of color difference were smaller when UV was included.