## 2 Materials and Methods  
### Specim Preparation  
Four commercially available dental porcelain powders (Creation CC (Creation Willi Geller International GmbH, Meininge, Austria), IPS InLine (Ivoclar Vivadent, Schaan, Liechtenstein), Noritake EX-3 (Kuraray Noritake Dental Inc., Tokyo, Japan), and Vita VM 13 (VITA Zahnfabrik H. Rauter GmbH & Co. KG, Bad Sackingen, Germany) were tested in this study (Table 1). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Brand** & **Manufacturer** & **Ceramic Chemical Composition** & **Ceramic Modeling Liquid** \\  & & & **Chemical Composition** \\  & & & **(Weight \%)** \\ \hline \hline \multirow{7}{*}{Creation CC} & \multicolumn{3}{c}{Leucite-containing feldspathic porcelain} \\  & & & SiO\({}_{2}\) (55–65\%); Al\({}_{2}\)O\({}_{3}\) (12–18\%); & \\  & & & K\({}_{2}\)O (12–16\%); Na\({}_{2}\)O (3–5\%); & \\ \cline{1-1}  & & & TiO\({}_{2}\) (<1\%); ZrO\({}_{2}\) (<1\%); CaO (1–3\%); & \\ \cline{1-1}  & & & LiO (<1\%) MgO (<1\%); B\({}_{2}\)O\({}_{3}\)(1–2\%); & \\ \cline{1-1}  & & & BaO (1–2\%); SnO\({}_{2}\) (<1\%); P\({}_{2}\)O\({}_{5}\) (<1\%) & \\ \cline{1-1}  & & & CeO\({}_{2}\) CeF\({}_{3}\) oxides (<0.1\%); Pigments & \\ \cline{1-1}  & & & (0.1–0.3\%) & \\ \hline \hline \end{tabular}
\begin{tabular}{c c c} \hline \hline \multirow{2}{*}{IV IPS InLine (IV)} & \multirow{2}{*}{Ivoclar Vivadent, Schaan, Liechtenstein} & \multicolumn{1}{c}{Leucite-containing feldspathic porcelain} \\  & & SiO\({}_{2}\) (59.5–65.5\%); Al\({}_{2}\)O\({}_{3}\) (13.0–18.0\%); & \\ \cline{1-1}  & & K\({}_{2}\)O (10.0–14.0\%); Na\({}_{2}\)O (4.0–8.0\%); & \\ \cline{1-1}  & & other oxides (<4.0\%); pigment (<2.0\%) & \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical compositions of different ceramics and related modeling liquids, according to manufacturers. Sources: [[https://www.ivocalervivalent.com](https://www.ivocalervivalent.com)]([https://www.ivocalervivalent.com](https://www.ivocalervivalent.com)) (accessed on: 31 July 2019); [[https://www.creation-willigeller.com](https://www.creation-willigeller.com)]([https://www.creation-willigeller.com](https://www.creation-willigeller.com)) (accessed on: 31 July 2019); [[https://apollonia-indent.net](https://apollonia-indent.net)]([https://apollonia-indent.net](https://apollonia-indent.net)) (accessed on: 31 July 2019); [[https://www.kuraraynoritake.e](https://www.kuraraynoritake.e)]([https://www.kuraraynoritake.e](https://www.kuraraynoritake.e)) (accessed on: 31 July 2019) and [[https://www.vita-zahnfabrik.com](https://www.vita-zahnfabrik.com)]([https://www.vita-zahnfabrik.com](https://www.vita-zahnfabrik.com)) (accessed on: 31 July 2019). The porcelain powders used were composed of dentin-feldspathic porcelain containing leucite crystals. In preparation for firing, 0.7 g of each porcelain powder was mixed once with distilled water (15 specimens/porcelain type), and once with their corresponding porcelain's modeling liquid (15 specimens/porcelain type). A homogeneous slurry was obtained according to manufacturer's recommendations and inserted, in one increment, into a metallic matrix. The mold was overfilled with slurry, and condensed by one dental technician ([PERSON]) on a vibrating table for 90 s. The slurry was then transferred into standardized cylindrical metallic pistons (25 mm length, 4 mm width, and 1.2 mm thickness), and absorbent paper was used to remove excess liquid. The disc-shaped specimens were thereafter removed from the matrix and placed in specific furnaces (Vacumat 40, VITA Zahnfabrik) for firing cycles, according to the manufacturer's recommendations (Table 2). After the sintering process, the surface of each specimen was manually polished sequentially, using up to #600-grit silicon-carbide paper (Struers, Willich, Germany) under water-cooling, until a flat surface was obtained. Dimensions were verified using a digital micrometer (Mitutoyo, Kanagawa, Japan). The three dimensions (length, width, and height) of each specimen were measured. Specimens were inspected for cracks and replaced if needed.