## 4 Discussion
In this study, roughness was measured using a cutting-edge technique with a 3D measuring confocal laser microscope (OLS4000 LEXT by Olympus). Figure 5: VITA Suprinity PC—two-dimensional (2D) and three-dimensional (3D) micrographs produced by Olympus LEXT OLS4100 Confocal Laser Scanning Microscope. (**A**) Suprinity PC after milling (baseline), (**B**) ZLS polished using Brasseler pre-crystallization, (**C**) ZLS polished using Brasseler post-crystallization, (**D**) ZLS polished using VITA Suprinity set pre-crystallization, (**E**) ZLS polished using VITA Suprinity set post-crystallization. This 3D microscope allows for a comprehensive evaluation within the defined area by expanding upon the traditional 2D roughness parameters (Ra and Rq), represented by Sa (arithmetic mean height) and Sq (root mean square height), calculated from the average values of Z (x,y) within the measured area. The advantage of using the 3D laser microscope lies in its ability to measure a larger area with high-resolution imagery, offering a more representative assessment compared to linear roughness evaluations. Therefore, the second objective of this study was to assess and compare the effectiveness of different extra-oral polishing systems (Brasseler, Meisinger, and Vita Polishers) in terms of 3D roughness, both before and after the final crystallization of two high-strength silicate ceramics, lithium disilicate (LDS) and zirconia-reinforced lithium silicate (ZLS). For the LDS groups (3, 4, 5, and 6), a one-way ANOVA revealed that the differences in polished roughness values of LDS, both pre- and post-crystallization, as well as between the Brasseler and Meisinger polishing systems, were not statistically significant (\(p=0.129\)). Consequently, the second null hypothesis was not rejected, indicating that no additional data comparison was warranted for LDS. The polishing effectiveness for LDS, evaluated with the surface roughness parameters Sa and Sq, showed no significant variance, neither before nor after crystallization, nor between the two different polishing systems used. This outcome aligns with the manufacturer's claim that post-milling procedures for lithium disilicate (IPS e.max CAD) are equally effective at any stage of crystallization. This provides clinical and technical reassurance that post-milling procedures for IPS e.max CAD can be performed at whichever stage is most convenient, without compromising efficiency or performance. In contrast, for the ZLS groups (3, 4, 5, and 6), the one-way ANOVA indicated significant differences among the four groups. Subsequent analysis using the Tukey multiple comparisons test revealed significant disparities when polishing was conducted before versus after crystallization within the same polishing system, as illustrated in Figure 6.  
ZLS groups displayed significantly lower values of surface roughness (Sa) when polishing was performed after the final crystallization of the material (\(p<0.001\)). Both polishers, Brasseler and Vita polishers, provided a significantly smoother surface when they polished after final crystallization of the samples, without a significant difference  
Figure 6: The Y axis represents the surface roughness value (Sq) in microns, and the X axis represents the polished groups of Vita Suprinity PC, either by Brasseler or Vita Polishers, before and after final crystallization of the samples. among the two. Therefore, for ZLS (Vita Suprinity PC), the recommendation is that the polishing procedure should be performed post-crystallization to achieve significantly better performance in the means of surface roughness. This difference in surface roughness of ZLS, polished before and after crystallization, can be attributed to its pre-crystallized composition. This composition includes a porous glassy matrix with embedded round and submicrometric elongated grains of lithium metasilicates and lithium orthophosphates, alongside tetragonal zirconia fillers [39]. As described by [PERSON] et al. (2013) [40] and [PERSON] et al.