## 2 Materials and Methods
Subsequently, the final crystallization process for the samples was conducted using the same dental furnace (Programat CS, Ivoclar Vivadent), adhering to the manufacture's specifications for each material type. After crystallization, surface roughness values were recorded for Group 2, which served as the positive control group (baseline after crystallization). The remaining ninety-six (96) samples were distributed among into the final four groups (Groups 3, 4, 5, and 6). The allocation was based on the polishing system used and the timing of the procedure, whether polishing was performed before or after the final crystallization. All groups and their respective treatment protocols are detailed in Table 2.  
All samples were polished by the same calibrated operator following standard protocols and the respective manufacturer's recommendations. The polishing procedures incorporated the progressive use of two-step extra-oral polishers--one for pre-polishing and another for achieving a high shine (see Figure 2). These steps were conducted with a straight handpiece attached to a low-speed electric motor (Forza ELM, Brasseler, Savannah, GA, USA) to ensure a consistent rotational speed. Speeds varied from 6000 to 12,000 rpm, with each step lasting exactly 40 s under moderate pressure, without the use of diamond polishing paste or water cooling, culminating in a precise 80 s polishing protocol for each sample, as detailed in Table 3.  
Figure 1: Sample design using CEREC SW 5.2 (Dentsply Sirona). Before conducting surface roughness measurements, all specimens were subjected to ultrasonic cleaning in distilled water for 5 min to eliminate any residual debris that could potentially affect the readings. Post-cleaning, samples were air-dried for 10 s. Surface roughness was then quantified using a three-dimensional (3D) confocal laser microscope (OLS4000 LEXT, Olympus, Center Valley, PA, USA). \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{\begin{tabular}{c} **Groups** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Blocks** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Polishing System** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Electric Handpiece** \\ **Finishing/Polishing Protocol** \\ \end{tabular} } \\ \hline \multirow{4}{*}{3} & IPS E.MAX CAD & \multirow{2}{*}{[PERSON]—Dialite LD} & Pre-polishing: 40 s 10,000 rpm \\  & (\(n=12\)) & & High-shine: 40 s 10,000 rpm \\ \cline{2-6}  & VITA SUPRINITY PC & \multirow{2}{*}{[PERSON]—Dialite LD} & Pre-polishing: 40 s 10,000 rpm \\  & (\(n=12\)) & & High-shine: 40 s 10,000 rpm \\ \hline \multirow{4}{*}{4} & IPS E.MAX CAD & \multirow{2}{*}{[PERSON]—Dialite LD} & Pre-polishing: 40 s 10,000 rpm \\  & (\(n=12\)) & & High-shine: 40 s 10,000 rpm \\ \cline{2-6}  & VITA SUPRINITY PC & \multirow{2}{*}{[PERSON]—Dialite LD} & Pre-polishing: 40 s 10,000 rpm \\  & (\(n=12\)) & & High-shine: 40 s 10,000 rpm \\ \cline{2-6}  & IPS E.MAX CAD & \multirow{2}{*}{Meisinger—Lithium Silicate} & Pre-polishing: 40 s 10,000 rpm \\  & (\(n=12\)) & & High-shine: 40 s 6000 rpm \\ \cline{2-6}  & VITA SUPRINITY PC & Vita Suprinity Wheels & Pre-polishing: 40 s 12,000 rpm \\  & (\(n=12\)) & & High-shine Set Technical & High-gloss: 40 s 12,000 rpm \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Polishing protocols per group. Figure 2: Silicate wheel polishers, from left to right: Brasseeler Dialite LD, pre-polishing and high gloss; Meisinger polishing wheels for silicate ceramics, pre-polishing and high shine; and Vita Suprinity polishing set technical, pre-polishing and high gloss. The unevenness of the ceramic surface was assessed by using the expansion of the well-known two-dimensional (2D) parameters (Ra and Rq) to three-dimensional (3D) parameters: The Sa parameter (arithmetic mean height) represents the 3D surface roughness, defined by the average deviation from the mean plane in the Z (x,y) coordinate system.