# Color Differences of Polimerized Resin-Based Composites and Corresponding Shade Guides
## 4 Discussion
For this reason, the study design employed polymerized RBCs. Nevertheless, we standardized the size of each sample, which measured 6 mm in diameter and had a thickness of 2 mm. The 6 mm diameter coincided with the external diameter of the spectrophotometer head, thus reducing the likelihood of measurement errors [9; 35]. By using this thickness, we concurred with [PERSON] et al. (2011) in considering that a reproducible thickness in clinical practice is important, although there is no consensus on this matter and some articles have used samples of 2 mm [41; 42], 1.5 mm [38], 1 mm [16; 43] or 1.2 mm [44]. However, there _is_ consensus regarding D65 lighting conditions, and as with some previously mentioned authors [16; 43; 45], we decided to use these standards in our study. In addition, there was evidence that the background used to record color could influence the color of the samples [44]; the white background was standardized (L: 94.6, a: 0.2, b: \(-\)0.8) for this reason, so that it would not interfere with the registering process and would meet the previously mentioned D65 conditions. Furthermore, the composites used in this study were \"body\" type, which resulted in low translucency. Most of the articles that were revised prepared composite samples with an even surface [43; 44; 45; 46; 47]. In our study, flat surfaces without any defects were achieved by pressing down the samples with flat objects such as a microscope slide, as researchers of other papers also described doing in their Material and Methods sections [2; 43; 44], and by using another polytetrafluoroethylene sheet [45]. Obtaining a flat surface is fundamental to reducing errors in spectrophotometer recording and reproducing similar conditions to clinical results. Of course, it would be ideal if the specific color from the VITAPAN Classical(r) shade guide of a composite did not differ from one's own perception of it [31]. Nonetheless, various papers have shown differences between commercially available composites and the corresponding colors from the VITAPAN Classical(r) shade guide [48; 49]. Such differences may be due to different values in L*a*b* parameters. In our body of research, the actual difference between all of the composites studied and their respective colors from the VITAPAN Classical(r) shade guide could be seen. These differences vary between composites, the lowest color difference being registered in the Vocco(r) composite for the color A3.5 (\(\Delta\)E\({}_{00}\) = 3.5) and the highest in the Empress(r) composite for the color A3 (\(\Delta\)E\({}_{00}\) = 13.1). The Empress(r) and Harmonize(r) composites showed higher \(\Delta\)E\({}_{00}\) values than Filtek(r) or Vocco(r), which might indicate that they were closer to the corresponding color from the VITAPAN Classical(r) shade guide. For the color A2, the Filtek(r) composite displayed less color difference from the guide (\(\Delta\)E\(00\) = 4.0) than Vocco(r) (\(\Delta\)E\(00\) = 6.4); however, for the colors A3 and A3.5, the Vocco(r) composite (\(\Delta\)E\(00\) = 5.3; \(\Delta\)E\(00\) = 3.5) demonstrated closer proximity to the VITAPAN Classical(r) shade guide. [PERSON] et al. (2019), with a 50:50% perceptibility threshold (PT) and a 50:50% acceptability threshold (AT), determined that \(\Delta\)E\(00\) values > 1.8 and \(\leq\)3.6 should be considered \"moderately unacceptable\" color differences; those >3.6 and \(\leq\)5.4 should be deemed \"clearly unacceptable\"; finally, if they are greater than 5.4, they should be regarded as \"extremely unacceptable\" [50]. The results obtained by analyzing the color difference between composite samples and the VITAPAN Classical(r) shade guide showed that only the Vocco(r) composite for the color A3.5 exhibited \"moderately unacceptable\" results with \(\Delta\)E\(00\) = 3.5. Results falling within the \"clearly unacceptable\" range included Filtek(r) for the colors A2 and A3.5 with \(\Delta\)E\(00\) values of 4.0 and 4.1, respectively, and Vocco(r) for the color A3 with \(\Delta\)E00 = 5.3.