###### Abstract  
The purpose of this in vitro study is to compare the roughness and gloss of four resin-modified CAD/CAM ceramics after different surface treatments. Forty-eight specimens (1.20 \(\times\) 12 mm\({}^{2}\)) were prepared from Lava Ultimate (LU), Vita Enamic (VE), Cerasmart (CS), and Crystal Ultra (CU) CAD/CAM ceramics. The prepared specimens were polished with silicon carbide paper before being roughened with a 30 \(\upmu\)m grit diamond bur. Each material was allocated into four groups: control (no treatment), Luster Meisinger polishing (MP), Optiglaze (OG), or Meisinger polishing, followed by a final polishing with Shoftu Direct Dia Paste (MP+PP). The roughness and gloss were measured after the surface treatment using a profilometer and gloss meter, respectively. Scanning electron microscopy micrographs were obtained to analyze the surface characteristics. Statistical analysis was performed using a multivariate analysis of variance (MANOVA), one-way ANOVA, and [PERSON]'s post hoc test (\(\alpha\) = 0.05). The surface treatments significantly affected the surface roughness and gloss of the tested materials (\(p<\) 0.05). All the tested resin-modified CAD/CAM ceramics demonstrated a lower surface roughness and higher gloss after glazing using OG, followed by MP+PP and MP. The highest and lowest Ra were presented by the control VE (0.63 \(\pm\) 0.23 \(\upmu\)m) and glazed LU specimens (0.04 \(\pm\) 0.01 \(\upmu\)m), respectively. The highest and lowest GU were presented by the glazed LU (90.48 \(\pm\) 4.69 GU) and the control VE specimens (23.32 \(\pm\) 2.41 GU), respectively. After clinical adjustment, finishing and polishing, the restoration is essential to obtain a restorative surface with lower roughness and the highest gloss. Surface glazing using Optiglaze exhibited the smoothest and glossiest surface of all the tested resin-modified ceramics. C 2022 2022 2022 223 2022 223 2022 223 2022 223 2022 223 2022 223 2022 223 2022 23 202  
A wide range of CAD-CAM resin-modified ceramic materials have been introduced after the technological innovation and material revolution [5; 6; 7]. The combination of an organic resin matrix and various proportions of inorganic ceramic fillers has led to materials exhibiting different physical, mechanical, and optical properties [8; 9]. Lava Ultimate (LU) and Cerasmart (CS) are resin composites that contain glass particles embedded in a polymer matrix. Vita Enamic (VE) is an example of a porous, interconnected, feldspathic porcelain infiltrated by a polymer [10; 11]. A recently developed resin-modified ceramic, Crystal Ultra (CU), comprises 30% cross-linked polymer blends and 70% ceramic-like inorganic silicate glass fillers [4]. Comparatively, CU has a higher polymer content than other resin-modified ceramics, such as Vita Enamic, which only contains about 50% of CU's polymer content [4; 12; 13]. In clinical situations, after the try-in of the prosthetic crown, the occlusal or inter-proximal necessary corrections are mostly performed with a diamond bur. This affects the properties of the restoration by increasing its surface roughness [14; 15], and thereby negatively affecting the optical properties of the restoration [16; 17]. The clinical adjustments result in micro-irregularities that promote microbial bio-film adhesion [18]. The roughened surface must be re-smoothed and re-polished using the best method currently available for each material class to ensure clinical success [19; 20]. The manufacturer of resin-modified ceramic materials recommends using diamond-impregnated rubber points for finishing, followed by polishing with a #9 soft Robinson bristle brush and a polishing agent. Another option is to apply a light-polymerized glazing agent over the modified surfaces to regain the surface gloss [21]. It is crucial to provide the patient with a smooth restoration for the health of the tooth and the periodontium, in addition to the esthetics of the restoration [22].