## 4 Discussion  
The surface roughness is the variable used to describe the quality of a surface [22]. Surface roughness is directly related to plaque accumulation, discoloration, material degradation and increased patient dissatisfaction [9, 23]. Polishing protocols have a significant impact on the surface roughness of denture base materials with the intention of a gradual removal of rough layers from the surface [14]. The aim of these procedures is to achieve a sufficient smooth and glossy surface to prevent bacterial plaque formation [11, 14, 24]. A problem related to the polishing protocols resides in their reliance on operator-dependent variables that directly influence the resulting surface roughness outcomes. In 2008, [PERSON] et al. [12] addressed the first standardized method of polishing acrylic resins that would effectively ensure operational repeatability, facilitating the comparative assessment of various resins on a more homogeneous basis. The efficacy of a mechanized polishing protocol was established [12, 13], revealing significant differences between the control group and the corresponding study samples, similar to the results obtained by the present authors (\(p=0.003\)). Nevertheless, in comparison to the conventional protocol, the Pa values of the mechanized protocol exhibited higher values. Hence, while its efficacy has been substantiated, conventional polishing emerges as noteworthy. The abrasion process involves traversing a series of abrasive particles (varying in fineness) over the surface. The hardness of the abrasive particles must be higher than the polymeric matrix being abraded. The pressure exerted by the abrasives, as well as the shape, size, rate and duration of the movement, may influence the efficacy of the polishing system [22, 25, 26]. To minimize the impact of the vari \begin{table}
\begin{tabular}{c c c c} \hline
**Group** & **Resin Type** & **Skewness** & **Kurtosis** \\ \hline \multirow{4}{*}{Mechanized} & Self cured & 0.51 & 0.07 \\  & 3D printed & 0.52 & \(-1.04\) \\  & Milled & 1.49 & 0.83 \\  & Injected molded & 1.04 & 0.13 \\  & Heat cured & 0.75 & \(-0.62\) \\ \hline \multirow{4}{*}{Conventional} & Self cured & 1.54 & 2.16 \\  & 3D printed & 0.84 & \(-0.24\) \\  & Milled & 2.75 & 8.71 \\  & Injected molded & 0.44 & \(-1.08\) \\  & Heat cured & 0.41 & \(-1.46\) \\ \hline \multirow{4}{*}{Control} & Self cured & \(-0.28\) & \(-0.03\) \\  & 3D printed & \(-0.10\) & 2.23 \\ \cline{1-1}  & Milled & \(-0.85\) & 2.04 \\ \cline{1-1}  & Injected molded & 3.17 & 18.92 \\ \cline{1-1}  & Heat cured & 0.66 & 2.10 \\ \hline \end{tabular}
\end{table} 
Table 5: Skewness and kurtosis for polishing techniques and resin types. ables, a single operator executed all polishing procedures, and the rate (rotation per minute) and duration of treatment were standardized. The only difference presented between the two polishing techniques was the pressure exerted by the handpiece on the samples. The fact that the mechanized protocol presupposes the movement of the handpiece on the platform where the test piece is inserted may not exert sufficient pressure to produce the same polishing level in comparison to the conventional technique [3]. Milled resins present significant differences because of the higher degree of PMMA polymerization. As a result, their surface pressure resistance increases, leading to the appearance of secondary roughness (3.32 \(\pm\) 2.47 \(\upmu\)m vs. 1.44 \(\pm\) 1.08 \(\upmu\)m; \(p\) = 0.001) [27; 28]. Furthermore, when a single operator applies the same polishing protocol, variations in the Pa values are directly influenced by the processing techniques of acrylic resins. The polymerization temperature and time affect the content of the resins [28; 29]. In the polymerization reaction of self-cured resin, the degree of conversion to a polymethyl methacrylate polymer is reduced; in consequence, higher values are associated with it.