## 4 Discussion
[46] conducted a study to investigate the relationship between surface roughness and gloss in various dental materials. The study revealed that surface roughness is a contributing factor to gloss, but it is not the sole determinant. In other words, high surface roughness does not always mean low gloss, and vice versa [46]. [PERSON] et al. [40] investigated the impact of prophylactic polishing pastes on leucite-reinforced glass ceramics, lithium disilicate glass ceramics, and zirconia, focusing on roughness and gloss [40]. They observed a negative relationship between surface roughness and gloss. Similar findings have been reported in other studies concerning the mechanical polishing of feldspathic and hybrid CAD-CAM ceramics; [PERSON] et al. [40] found that the relationship between 2D roughness and gloss was statistically significant and negatively correlated: roughness increased as surface gloss decreased. The correlation between 2D roughness and translucency was weak for e.max. Further, as a novel study we also found a negative correlation between gloss and roughness in our own study [89; 90]. If the restoration was subjected to furnace glazing, the procedure would require a considerable delay of cementation or, more likely, a second appointment. This could save operator time but cannot be considered an effective chairside procedure. [85]. However, there is no \"gold standard\" finishing and polishing material and/or technique patterned in the literature. In order to improve the comparison of data concerning the efficacy of finishing and polishing systems, it would be useful to standardize methodologies among studies [91]. The difference in gloss values observed between mechanically polished and glazed ceramics can be attributed to both the mechanism of surface modification and inherent material properties. Mechanical polishing involves gradual abrasion using finer-grit abrasives, resulting in a uniform and microscopically smoother surface. This process effectively removes surface irregularities and flattens the microstructure, enhancing specular light reflection, which directly correlates with higher gloss levels [90]. In contrast, glazing relies on applying and firing a thin glassy layer over the ceramic. While it improves esthetics and seals porosities, the glaze layer may exhibit microcracks, uneven thickness, or surface waviness--especially after clinical adjustments--which can diffuse reflected light and reduce gloss [92; 93]. Moreover, the ceramic material itself plays a crucial role. Lithium disilicate ceramics (e.g., EC, LS) consist of a fine crystalline phase embedded in a glassy matrix, allowing for more effective polishing due to their relatively homogeneous and softer microstructure). In contrast, zirconia ceramics (e.g., KAT) are fully crystalline, harder, and denser, making them more resistant to mechanical abrasion and more difficult to polish to the same degree of smoothness [37]. These differences impact the surface topography after finishing, and consequently, the gloss outcome. This study has some limitations. The main limitation of this study is that it was conducted in vitro. While linear roughness parameters such as Ra have been widely used to characterize surfaces, it is also true that these alone are insufficient to fully understand most of the features present in the topography of a material. Therefore, 3D profilometry could be used in future investigations. The specimens were not milled using CAD-CAM but prepared with a low-speed sectioning device. In contrast to our study, the majority of surfaces on crowns or bridges are anatomically curved. For forthcoming investigations, a specialized apparatus capable of enabling standardized pressure during polishing could be employed. This study was performed purely in vitro. While the roughness values (\(<\)0.2 \(\upmu\)m) and gloss (\(>\)60 GU) met clinically acceptable thresholds, the absence of biological testing (e.g., bacterial adhesion, wear resistance) limits direct clinical applicability [92; 93]. Future work should consider these factors.