For many years, the comparative and the subjective way of determining the shade of the teeth, dental color guides, have been used. Later were invented spectrophotometers that were able to detect the color change more accurately than a human eye [1] Spectrophotometer data are in the form of quantitative values.

Clark was the first to try to objectify and measure tooth color using the Munsell color scale [2]. 

The CIE, the Commission International de l’Eclairage, an international organization authorized for light, lighting, and color, presented the CIELab system, a uniform color scale, where L represents brightness, and a and b are chromatic characteristics [3].

In this study, the CIE L * c * h coordinate system was used. In Lch coordinate space, L represents brightness, c represents color and h is the hue. The values of c and h are calculated from the a and b coordinates in L * a * b * system. The difference in color is represented by delta values: ΔL *, ΔC *, and Δh *, compared under standard conditions. The total color difference (ΔE * ch) shows the difference between the L *, c *, and h * of the sample and the control measurement. This difference is calculated by the following formula (https://sensing.konica minolta.us):

ΔE ∗ ch = [(ΔL ∗) 2 + (Δc ∗) 2 + (Δh ∗) 2] ½

Delta values for L, c and h can be positive or negative. From the aspect of clinical assessment, if ΔE is less than  3.3, changes in the color of the restoration are acceptable by the human eye [4]. Perceptiveness is a difference in tooth color that can be detected, and acceptability is a tolerable difference in color [5-9].

Many researchers investigated color changes of the artificial or natural teeth, under the influence of different conditions and solutions [10-14].

Fifteen upper left second acrylic molars, color shade 2B, size 84, type Gnathostar, produced by Ivoclar Vivadent, were  divided into 5 groups, 3 in  each series. Samples were immersed in Bosnian coffee, carbonated dark drink, red wine, sage tea, and distilled water, each tooth separately (Figure 1).

Figure 1: Artificial Teeth Immersed in Five Different Solutions

Figure 2: Apparatus On Which the Measurement was Performed (Spectroshade, Handy Dental, Mht S. P. A. Verona, Italy)

Figure 3: Tooth Scan

Figure 4: Tooth Color Data Obtained Using the Device

Figure 5: Teeth Cleaned and Air Dried Before Measuring

For each sample, L, c and h values were measured (Table 1).

ΔL, Δc and Δh were obtained by calculating the differences between L, c or h of the sample, and mean values of L, c and h from the control group of distilled water (Table 2).

Afterwards, ΔL, Δc and Δh were used in the formula ΔE ∗ ch  =  [(ΔL ∗) 2 + (Δc ∗) 2 + (Δh ∗) 2] ½, in order to calculate ΔE for each sample (Table 3).

Statistical analysis was performed by using the SPSS software version 26.0. 

The absolute mean values of color change, ΔE, in each series, were much above the lower limit of human eye perception, which is 3.3 (5). 

Carbonated dark drink caused the highest color change (ΔE = 22.1). Coffee and tea stained the teeth with similar intensity (ΔE 13.1, and 11.0, respectively, Table 4). The   medians and standard deviations of ΔE are also presented (Table 4).

The Kruskal-Wallis H test was used to compare different solutions (Table 5).

Table 1: Measured Values For L, C and H.

Table 2. Values Δ L, Δ C and Δ H For Each Sample

Table 3. Δe Values for Every Sample

Table 4. Mean Value for ΔE for Each Fluid

Table 5. ΔE Analysis Using Kruskal Wallis Test

a. Kruskal Wallis Test, b. Grouping Variable: Fluid

p value less than 0.05 was considered as significant. There was no statistically significant difference in tooth color change between different fluids (χ² (3) = 4.385, p = 0.223, Table 5).

Goiato MC examined the coloring effect of coffee, wine, carbonated dark drink, two mouthwashes, and concluded that color changes occurred on acrylic dentures in all cases [10]. In a study by Indian authors Gupta R et al., it was shown that the composite is most discolored by coffee, tea and carbonated drink [11]. In another study, the discoloring effect of chlorhexidine, tannic acid and iron on plaque formed on acrylate was monitored. None of the solutions individually caused a statistically significant discoloration, but did cause it under the influence of iron after the use of chlorhexidine and tannic acid [12]. Guler AU et al.  found that red wine and coffee and tea with sugar have the greatest coloring effect on acrylic provisional prosthetic material [13]. The color stability of acrylic and composite temporary materials was examined in a study conducted by Turker SB, et al., where coffee, tea, carbonated dark drink and orange juice led to discoloration of the material [14].

The study showed that the coloring ability of four different liquids, Bosnian coffee, tea, wine and carbonated drink  is greatest in the case of carbonated dark drink and sage tea (acrylic Gnathostar Ivoclar Vivadent artificial teeth were used). There was no statistically significant difference in the coloring effect between four solutions.

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2. Clark, E.B. "Tooth color selection." Journal of the American Dental Association, vol. 20, 1933, pp. 1065-1073.

3. CIE 15: Technical Report. Colorimetry, 3rd edition. 2004, www.cdvplus.cz/file/3-publikace-cie15. Accessed September 2020.

4. Vichi, A., M. Ferrari and C.L. Davidson. "Color and opacity variations in three different resin-based composite products after water aging." Dental Materials, vol. 20, no. 6, 2004, pp. 530-534.

5. Wee, A.G. et al. "Use of a porcelain color discrimination test to evaluate color difference formulas." The Journal of Prosthetic Dentistry, vol. 98, no. 2, 2007, pp. 101-109.

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9. Douglas, R.D. and J.D. Brewer. "Acceptability of shade differences in metal ceramic crowns." The Journal of Prosthetic Dentistry, vol. 79, no. 3, 1998, pp. 254-260.

10. Goiato, M.C. et al. "Effect of different solutions on color stability of acrylic resin-based dentures." Brazilian Oral Research, vol. 28, no. 1, 2014, pp. 1-7.

11. Gupta, R. et al. "A spectrophotometric evaluation of color changes of various tooth colored veneering materials after exposure to commonly consumed beverages." The Journal of Indian Prosthodontic Society, vol. 5, no. 2, 2005, pp. 72-78.

12. Nordbo, H., A. Attramadal and H.M. Eriksen. "Iron discoloration of acrylic resin exposed to chlorhexidine or tannic acid: a model study." The Journal of Prosthetic Dentistry, vol. 49, no. 1, 1983, pp. 126-129.

13. Guler, A.U. et al. "Effects of different drinks on stainability of resin composite provisional restorative materials." The Journal of Prosthetic Dentistry, vol. 94, no. 2, 2005, pp. 118-124.

14. Türker, S.B., A. Kocak and E. Aktepe. "Effect of five staining solutions on the colour stability of two acrylics and three composite resins based provisional restorations." The European Journal of Prosthodontics and Restorative Dentistry, vol. 14, no. 3, 2006, pp. 121-125.