## 4 Discussion  
Surface roughness in ceramics is known to significantly influence stress concentration, fracture strength, plaque/bacterial adhesion, optics, and the final aesthetics of the mate \begin{table}
\begin{tabular}{c c c} \hline
**BASELINE (Control) Groups (\(n=12\))** & **Values (Subset for Alpha = 0.05)** \\ \hline VITA Suprinity PC after crystallization & 0.630 \({}^{\text{a}}\) & \\ \hline VITA Suprinity PC before crystallization & 0.967 \({}^{\text{b}}\) & \\ \hline IPS e.max CAD after crystallization & & 1.107 \({}^{\text{c}}\) \\ \hline IPS e.max CAD before crystallization & & 1.225 \({}^{\text{d}}\) \\ \hline Significance level (\(p\)-value) & 1.000 & 1.000 & 0.009 \\ \hline \end{tabular}
\end{table} 
Table 5: One-way ANOVA. Values with different letters were significantly different from each other (\(p<0.05\)). rial [17; 18; 19; 20; 36]. For CAD/CAM materials, roughness is affected by the geometry and grain size of the milling tools used in the subtractive milling process. In this study, samples were milled with a MC XL milling machine, utilizing two 64-micron grit diamonds burs operating simultaneously. The resulting surfaces were not as smooth as required for optimal clinical applications. It was observed that both lithium disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS) displayed significant roughness values after milling (baseline) and after final crystallization. This indicates the necessity for post-milling procedures to achieve the desired clinical smoothness [37]. At the baseline, before and after crystallization, LDS did not exhibit significant differences in Sa roughness values (\(p\) = 0.009), implying that the material's surface roughness remained relatively consistent throughout the crystallization process. On the other hand, ZLS showed significantly lower roughness values compared to LDS, both before and after crystallization (\(p\) < 0.001). The discovery of statistically significant differences in baseline roughness between the two materials leads to the rejection of the first null hypothesis (refer to Figure 3). The observed differences in mean surface roughness between the materials can be attributed to their distinct microstructures and individual characteristics, such as the type and size of the crystalline phase [35]. Furthermore, the crystallization process itself significantly contributed to the reduction of surface roughness in ZLS. Previous studies by [PERSON] et al. (2016) [29] and [PERSON] et al. (2018) [38] have previously reported that the flow of the vitreous component during the crystallization heat treatment could \"heal\" potential cracks or minute defects incurred during milling, which would explain the smoother surface observed in ZLS post-crystallization. However, despite the improvements noted, the roughness values obtained from the confocal laser microscopy (referenced in Table 4) and SEM micrographs evaluation (Figures 4 and 5) still indicate that the surface smoothness does not meet the ideal standards for clinical performance. Figure 3: The Y axis represents surface roughness values (Sa) in microns, and the X axis represents baseline groups for both materials, IPS e.max CAD and Vita Suprinity PC, before and after the final crystallization of the samples. Figure 4: IPS e.max CAD—two-dimensional (2D) and three-dimensional (3D) micrographs produced by Olympus LEXT OLS4100 Confocal Laser Scanning Microscope. **(A)** IPS e.max CAD after milling (baseline) with surface roughness more apparent, **(B)** LDS polished using Brasseler pre-crystallization, **(C)** LDS polished using Brasseler post-crystallization, **(D)** LDS polished using Meisinger pre-crystallization, and **(E)** LDS polished using Meisinger post-crystallization. While there are extensive reports on various techniques, systems, and high-strength ceramic materials, much of the literature on surface roughness has relied on either contact or non-contact (2D) profilometers.