## 4 Discussion
The ranges found are similar to those reported in a previous work [22] for color inconstancy in human teeth (1.4-8.2 CIEDE2000 units). In addition, CIEDE2000 color inconstancy in teeth [22] under the LED RGB1 showed the highest values, and B3, B4, and B5 the lowest, similar to what was found for dental ceramics in this study. Furthermore, as reported in CIEDE2000 regarding color inconstancy in teeth [22], color changes were mainly due to hue changes in LEDs RGB1, B4, and B5, and chroma changes in LED B3. Thus, our results showed similar trends of color inconstancy (when changing from D65 to CIE white LEDilluminants) in human teeth and dental ceramics. Nevertheless, it should be noted that in the case of the studied dental ceramics, the size of color inconstancy produced by the CIE white LEDs is lower than in human teeth (0.8-7.0 versus 1.4-8.2 CIEDE2000 units). Therefore, the effect of LED illuminants on dental ceramic has a lower magnitude than on natural teeth. According to the literature, the 50:50% perceptibility/acceptability color difference thresholds for dental ceramics can be considered as 1.25/2.23 CIEDE2000 units, respectively [14]. Therefore, it can be stated that, in general, for all shades and dental ceramics studied, the color produced perceptible color change from D65 to a white LED ill illuminant in most cases and unacceptable color change in some cases (e.g., LED RGB1). Consequently, it can be considered that the evaluated shade may have a high color inconstancy in comparison with the perceptible threshold value of a shade under two different illuminants. In particular, RGB1, V1, and BH1 LED illuminants produced the highest color inconstancy with respect to the recommended illuminant in dentistry (CIE D65). This result was also reported in natural teeth, although in this study [22] other values of 50:50% visual thresholds (0.8/1.8) [9] were used to evaluate the effect of the white LED illuminants on color of teeth. On the other hand, the results found in the present study (Figure 5) also show that if a proper selection of the LED illuminants is made (e.g., LED B3, B4 and B5), a visually acceptable color inconstancy (with respect to the recommend illuminant CIE D65) can be achieved. In summary, these findings imply that when a change in illumination from D65 to white LEDs is produced, the color shift of the materials analyzed will be perceptible to an average human observer with normal color vision. In some cases (e.g., change from D65 to LED RGB1), such color changes will be clearly unacceptable to an average human observer. Lastly, our results show that, by using LED illuminants in dental ceramics, different color shifts, mainly for C* and h (Figure 5), may be achieved. These results prove that the use of the CIE-proposed white LEDs [2] have the potential to affect the color appearance of a dental ceramic material in various ways. Given that different LED sources are generally available on the market, our presented results using different prototypes of white LEDs are consistent with what is currently available [18]. With respect to aesthetic dentistry, choosing LEDs that generate maximum or minimum color shifts in relation to outdoor equivalent illumination (D65) is plausible.