## 4 Discussion  
This in vitro investigation evaluated the effects of surface treatment protocols on the roughness and gloss of resin-modified CAD/CAM ceramics. Based on the study's outcome, the surface treatment protocols led to a significant difference (\(p<0.001\)) in the roughness and gloss of the resin-modified ceramics, thereby rejecting the null hypothesis. Glazing with OG was the most effective protocol among the surface treatment protocols applied, with the lowest roughness and the highest gloss among all the studied materials. Two surface treatment protocols (OG and MP+PP) resulted in surface roughness within the acceptable range (0.2 \(\upmu\)m) [25]. It is evident that applying a polishing paste after MP has a positive effect on all of the materials' surface roughness and gloss, and this is also supported by previous research [26, 28]. The composition of the polishing paste and the particle size of the abrasive grains affect its efficiency in polishing the surface [26]. In this study, Direct Dia Paste, which is composed of a 20% diamond polishing paste and a 2-4 \(\upmu\)m particle-sized synthetic diamond powder that acts as abrasive grains, demonstrated its effectiveness in polishing resin-modified ceramics. On the other hand, using MP alone resulted in a borderline or slightly higher Ra. For example, the Ra after treatment with MP for VE (0.39 \(\upmu\)m) and CU (0.34 \(\upmu\)m) might contribute to plaque-induced gingivitis and an increased risk of dental caries [25]. The surface treatment protocol is not the only controlling factor, because the composition of the material has a great impact on surface roughness. It is challenging to choose the best surface treatment protocol for resin-modified ceramic materials because of their heterogeneous and complex nature, which includes both a soft resin matrix and very hard filler particles. According to [PERSON] et al. [45], materials with weak micromechanical characteristics have better polishability. In particular, the organic matrix, the size, distribution, ratio, and nature of the inorganic fillers in the resin-modified ceramics play a vital role in determining the material's surface roughness [46, 47]. Nevertheless, comparing different materials based on their constituent parts is challenging since the organic content percentages within the tested ceramics are not explicitly defined because they are considered confidential business information [47]. This study showed that LU has the lowest surface roughness value (0.16 \(\pm\) 0.04). This result is consistent with a prior investigation comparing the roughness of five CAD-CAM ceramics after surface treatment, in which LU also had the lowest surface roughness [45]. According to [PERSON] et al. [45], polishability and hardness have an inverse relationship, which partially explains the surface roughness value of LU. The study demonstrates that Optiglaze, which primarily works by sealing microcracks and surface flaws, is the most efficient method to obtain lower surface roughness. The findings of this study are corroborated by earlier research that established Optiglaze's efficacy [48]. A study conducted by [PERSON] et al. supported that OG is efficient in providing a smooth surface for the LU, CS, and VE materials they tested [48]. In addition, they concluded that 5000 thermocycling for the glazed surfaces resulted in a negligible difference in surface roughness [48]. However, there are limited studies assessing the performance of glazing materials, particularly with resin-modified ceramic materials. [PERSON] et al. [49] found