## 4 Discussion
Height distribution is indicated by height probability density, which compares the probability of having a given surface height relative to the centerline for each group, and is shown in Figure 4. Beyond the average roughness values, skewness (Rsk/Psk) and kurtosis (Rku/Pku) should be considered to provide information about the distribution of irregular heights on the surface [14,17]. Previous studies [4,21] showed a quasi-normal Gaussian distribution for mechanically polished specimens and a clearly asymmetric distribution for manually polished specimens. By contrast, after the polishing procedure (manual or mechanized), the present authors verified that the height distribution displayed an increase in kurtosis and a leftward skewness tendency, signifying asymmetry in height data and extreme values associated with valleys (Tables 8 and 9). Negative skewness describes a significant number of local maxima below the mean, as compared to a Gaussian distribution [10,14,24], which corresponds to areas with deep valleys and a lack of high peaks. A parameter Sku >3 (leptokurtic) describes surfaces with high peaks and deep valleys. By combining both parameters, a plateau-like smooth surface with deep valleys is observed, similar to the mechanized samples (Figure 4, 1A and 2A). In terms of CV, the control group registered the lowest CV value of 0.067 compared to the polishing techniques, exhibiting a height distribution with lower kurtosis (Table 9) and a skewness near zero (Table 8). This finding implies that the control group, directly resulting from the processing technique, produces a more uniform surface finish for Ra than the other two techniques, which increases the dispersion of surface roughness values. The literature also describes that surface height distribution features are contingent on the processing method used [6]. The ultimate shape of surfaces generated through cumulative processes, such as 3D printed resin, results from the aggregation of numerous random local events, displaying a cumulative effect that follows a Gaussian form (Rsk = 0 and Rku = 3) (Figure 4) [10, 14]. Similar values were obtained for Pa, and a distinctive pattern was seen for Ra. Surface roughness parameters revealed an increased CV value for mechanically polished specimens (Table 7). Measurements of Pa and Ra for manual polished resins reflect not only the intrinsic roughness characteristics of the surface, but also the influence of the operator's factors, such as the technician's skill, wrist stability, attention level, and other relevant considerations associated with the manual polishing process. In contrast to the results obtained by [PERSON] [21], mechanized polishing exhibited significantly higher Ra dispersion values. The efficiency of mechanized over manual protocols is questionable since it did not have the most reliable process for value dispersion or the Ra and Pa values obtained in relation to the control group. Notably, surface polishing influences the features of height data distribution [7, 24]. Improvements to the polishing device and the present protocol should be implemented. As previously mentioned [4, 21], a protocol not dependent on the operator is more reliable. Obstacles to clinical usage of the proposed mechanical polishing system include the curvature exhibited on a denture base surface and the shape irregularity of removable prostheses [21]. This is a preliminary and analytical study. Studies analyzing this specific approach are not described in the literature for prosthetic acrylic resins. However, the integration of skewness and kurtosis has already been studied in other dental materials. For example, the authors performed a functional analysis on the shear bond strength of prosthetic rehabilitations in zirconia ceramics and resorted to these parameters [22]. Table 10 summarizes the differences between both approaches and clarifies the importance of analyzing additional parameters.