## 2 Materials and Methods  
Two high-strength CAD/CAM ceramics, lithium disilicate (LDS) (IPS e.max CAD, Ivoclar Vivadent, Schaan, Liechtenstein! ;) and zirconia-reinforced lithium silicate (ZLS) (Vita Suprinity, VITA Zahnfabrik, Bad Sackingen, Germany), were used in this study. The ceramic groups of each material were polished by same calibrated operator using 2 different polishing systems before and after crystallization. For the LDS group, Dialite LD (Brasseler, Savannah, GA, USA) and lithium silicate polishers (Meisinger, Centennial, CO, USA) were used, and for the ZLS, Dialite LD (Brasseler) and Suprinity Polishing Set Technical (VITA Zahnfabrik, Bad Sackingen, Germany) were used (Table 1). The evaluation of surface roughness for both ceramic groups utilized the (Sq) parameter, which is based on the square root average. These measurements were taken after polishing procedures, both when polished before and after the final crystallization of all sample groups. To ensure consistency across all samples, an Ivovine molar along with the adjacent teeth was altered to achieve a flat and broad horizontal surface. The modified preparation was digitalized using a CEREC Omniciam SW 5.2 (Dentsply Sirona, Charlotte, NC, USA). Subsequently, the sample design was finalized using the biogenic copy mode, as depicted in Figure 1. The sample was dimensionally verified with a digital caliper, measuring 12 \(\times\) 14 \(\times\) 5 mm\({}^{3}\). The occlusal area provided a flat surface that accurately simulated the outermost layer of milled restorations. This surface was then selected as the focal point for the investigation. \begin{table}
\begin{tabular}{c c c c} \hline
**Trademark—Polishers** & **Details** & **Product No** & **rpm** \\ \hline \multicolumn{4}{c}{Two-step diamond-impregnated} \\ BRASSELER & polishers (red & R17 MLD.HP & 7000–10,000 \\ Dialite LD & medium-grit and yellow & R17 FLD.HP & 7000–10,000 \\  & fine-grit wheels for & & \\  & straight handpiece) & & \\ \hline \multicolumn{4}{c}{Two-step diamond-impregnated} \\ MEISINGER & polishing system & DPO09-170-HP & 10,000 \\ Lithium Silicate Polishing & (pre-polish and & DPO10-170 HP & 6000 \\ Wheels & high-shine wheels for & & \\  & straight handpiece) & & \\ \hline \multicolumn{4}{c}{Two-step diamond-coated} \\ VITA SUPRINITY & polishing system (pre- & ERHR15M6 & 12,000 \\ Polishing Set Technical & and high-gloss wheel & ERHR15F6 & 12,000 \\  & polishers for straight & & \\  & handpiece) & & \\ \hline \end{tabular}
\end{table} 
Table 1: Contouring and polishing materials used in the study. Prior to the study, a power analysis was carried out to determine the appropriate sample size. Drawing from previous studies in the literature, an anticipated mean difference of 0.2 with an expected standard deviation of \(\pm\)0.18 was assumed. The significance level was set to 5%. To achieve a statistical power of 80%, the calculation yielded a sample size of 10 per group. However, to allow for any potential errors, a total of twelve (12) samples were randomly allocated into six groups for each material type. A total of sixty (60) samples were prepared for each of the two monolithic CAD/CAM materials: lithium disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS). The machining of these samples was performed using a Sirona MCXL milling machine (Dentsply Sirona, Bensheim, Germany). To ensure consistency, the diamond cylinder pointed bur 12S and step bur 12S used to mill the samples were replaced before the commencement of the machining process and subsequently every 15 milling cycles. Immediately following the milling procedure, which was performed at standard speed in fine mode, the baseline surface roughness values (Sa and Sq) for both materials, LDS and ZLS, were recorded, and Group 1 was designed as the negative control group, wherein they had their surface roughness values noted at this stage.