# Color Differences of Polimerized Resin-Based Composites and Corresponding Shade Guides
## 2 Materials and Methods  
### Fabrication and Color Measurement of the RBC Specimens  
Four RBC brands (Harmonize(r), Empress(r) Direct(r), Grandio(r) and Filtek(r) 500) were compared to the color standards established for the three VITAPAN Classical shade guides (A2, A3 and A3.5) and corresponding RBC shade tabs. For each of the shades noted above, three specimens of each brand were fabricated. The name, manufacturer, composition, filler size and filler information of the composites are presented in Table 1.  
In this study, color measurement was performed with a Vita EasyShade Compact IV(r) dental spectrophotometer ([PERSON], Bad Sackingen, Germany) by placing the device sensor in direct contact with the resin composite surface by three measurements per sample per VITAPAN Classical tabs (\(n\) = 108). We used a 2 mm-thick polytetrafluoroethylene (Teflon) sheet, into which we made holes with an external 6 mm diameter trephine, so that it matched the diameter of the spectrophotometer sensor. We then proceeded to place three samples per composite brand and color into it. Therefore, nine discs (6 mm in diameter and 2 mm thick) from each resin material were fabricated by placing the material into a polytetrafluoroethylene sheet mold and light-curing them for 20 s after placing a mylar strip on either side of the mold and pressing it gently to remove excess material using microscopic slides. The RBCs were cured with a light polymerization unit (Smart Lite Pro, Dentsply Sirona, York, PA, USA) following the manufacturer's instructions and irradiance values were frequently checked by using a digital radiometer (Bluephase Meter II, Ivocalr Vivadent Inc., Amherst, NY, USA) so that they were above 1000 mW/cm\({}^{2}\). After polymerization, the specimen was measured with a digital caliper (500-181, Mitutoyo, Tokyo, Japan) with a precision of 0.05 mm. The surface was examined by visual inspection, and the specimen  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Product Name** & **Manufacturer** & **Composition Type** & **Filler Size** & **Filler (Weight \%)** \\ \hline Harmonize(r) (LOT number 8609456) & Kerr (Brea, CA, USA) & Nanohybrid composite & 5–400 nm & 81\% \\ Empress Direct® (LOT number Y42709) & Ivocalr-Vivadent (Schaan, Liechtenstein) & Nanohybrid composite & 0.04–3 μm & 79\% \\ Grandio® (LOT number 1924504) & Vocco (Cuxhaven, Germany) & Nanohybrid composite & 0.01–0.1 μm & 84\% \\ Filtek 500(r) (LOT number N898020) & 3M (Saint Paul, MN, USA) & Nanohybrid composite & 0.6–1.4 μm & 78.5\% \\ \hline \hline \end{tabular}
\end{table}
Table 1: Characteristics of the RBCs used.  
was rejected if there were any defects or irregularities. All color measurements were made post-curing, and between fabrication and color measurement, specimens were stored in a darkened area and protected from damage. CIELAB values were recorded using the spectrophotometer in tooth measurement mode as described above with the probe positioned in the hole.  
The color was evaluated according to the CIE L*a*b* color notation system, recording the parameters L* (lightness), a* (reddish-green) and b* (yellowish-blue) per sample and the mean values were calculated. All color measurements were performed according to the CIEDE2000 color coordinates for the standard D65 illumination against a white background (L: 94.6, a: 0.2, b: \(-\)0.8), at a stable ambient temperature of 23 \({}^{\circ}\)C (73.4 \({}^{\circ}\)F) and by the same operator (D.F.M.).