###### Abstract
On the other hand, rough surfaces provide a suitable environment for plaque accumulation and discoloration, and this might lead to plaque-induced gingivitis and secondary caries, and can negatively affect translucency [23; 24]. Surface roughness should be minimized to achieve a healthy oral cavity with pleasant esthetics. It is recommended to have the surface roughness below 0.2 um and a minimal plaque-retentive restoration [25]. The surface roughness of dental materials has been assessed using profilometry, scanning electron microscopy, and atomic force microscopy [20; 26; 27]. Nevertheless, the profilometer is frequently used because it provides a quantitative measurement of surface characteristics [28]. The most frequently used roughness parameter is the average arithmetic height (Ra), which is easy to define and calculate and provides a good profile of height variations [23; 29]. Since voids and irregularities complicate the measurements, it is well-known that studying surface roughness is challenging [30]. Gloss is defined as \"a specific light intensity reflectance on a surface with the incident angle equal and opposite to the reflectance angle\" [31]. After the adjustment of the final restoration and re-polishing it in clinical conditions, the gloss of the crown is affected. The gloss of conventional resin composite materials deteriorates faster than ceramics [29]. In a study by [PERSON] et al. [32], the gloss of resin-modified ceramics (VE and LU) was compared with lithium disilicate ceramic. They concluded that these materials have a gloss slightly lower than that of lithium disilicate ceramic but higher than a composite. Another study conducted by [PERSON] et al. [30] demonstrated that lithium disilicate maintained its gloss, while the gloss of the resin-ceramic (VE and LU) decreased after toothbrush abrasion. Surface gloss is highly dependent on surface roughness, and both depend on the material itself, its particles' size, and the polishing technique applied [32; 33]. In addition, using a polishing paste can also affect surface gloss [34; 35]. The gloss of restorative materials is measured using a gloss meter, and the results are expressed in gloss units (GU). The maximally refractive surface has 100 GU, while the non-reflective surface has zero GU [36]. The gloss of natural tooth enamel ranges between 40 and 53 GU [37]. According to the American Dental Association (ADA), the gloss of dental restoration should be in the acceptable range of 40-60 [37; 38]. The gloss of resin-modified ceramic restorations is between 56 and 57 GU, which is within the acceptable range [30]. The surface treatment of conventional ceramics in dental practice has been studied extensively. In recent years, the use of resin-modified ceramics for the fabrication of dental restorations has increased enormously. However, there is a research gap in the literature regarding the application of the best chair-side surface treatment for these ceramics, especially with new materials being introduced to the dental market on a regular basis. Therefore, this in vitro study aims to assess the surface roughness and gloss of four resin-modified CAD/CAM ceramic materials after different surface treatment protocols. The null hypothesis states no significant difference in roughness and gloss of resin-modified CAD/CAM ceramics following different surface treatments.