## 3 Results  
All participants completed the study with good compliance, and no adverse effects were reported. The descriptive data for the entire sample (Mean, Median, SD) are presented in Table 3. As shown, the normality of the data distribution was analyzed using the Shapiro-Wilk test, and it revealed that values obtained for pH had a normal distribution, while the oxygen and carbon dioxide values deviated significantly from the normal distribution (\(p<0.05\)). Consequently, all data analyses regarding salivary pH values were analyzed using parametric statistical tests, while the oxygen and carbon dioxide content were analyzed using non-parametric analyses. Obtained data were in line with the initial drop of salivary pH values one minute after starting gum chewing, followed by additional decrease during five minutes that remained stable 10 min after baseline, with slight pH recovery 30 min from the beginning of the experiment. Paired T-test was employed for intergroup analysis and revealed that the drop of salivary pH in the period between the first and fifth minutes from the beginning of the experiment was statistically significant (\(p=0.025\), Table 4). Since the values for oxygen and carbon dioxide content revealed non normal distribution, the Wilcoxon signed-rank test was applied for intergroup comparisons. Regarding the oxygen content, a statistically significant drop (\(p=0.025\), Table 5) was observed between \begin{table}
\begin{tabular}{c c c} \hline \hline  & **Phase** [\({}^{\circ}\)] & **T** [\({}^{\circ}\)**C] \\ \hline
**Oxygen-free** & 54.88 & 27.33 \\ \hline
**Air-saturated** & 21.98 & 17.3 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Calibration values of phase for oxygen-free and air-saturated water. the 5 th and 10 th minutes, which was followed by a significant increase (\(p\) = 0.025, Table 4) in the period from 10 to 30 min. No significant differences between evaluated groups were observed with respect to CO\({}_{2}\). The measured results of pH, O\({}_{2}\), and CO\({}_{2}\) for all volunteers, presented in Figures 3-5, were classified according to gender. The measured results are shown for each volunteer (divided with vertical lines) by mean value and standard deviation (SD). One way ANOVA, followed by Tukey post hoc test, revealed no statistically significant differences in obtained data in relation to gender. The pH values for male and female volunteers are presented in Figure 3a,b, respectively. The horizontal line in the graphs presents the pH = 7 and it corresponds to a neutral environment. It can be seen that 10/12 male and 15/18 female volunteers had the acidic initial pH value, and a small number of volunteers had alkaline saliva before chewing xylitol gum. In most cases, we observed that volunteers with alkaline pH and pH values higher than 6.6 had a reduced pH value after chewing gum, while volun \begin{table}
\begin{tabular}{c c c c c} \multicolumn{5}{c}{**Paired Samples \(t\)-test**} \\ \hline  & & **Statistic** & **df** & \(p\) \\ \hline pH/bg & pH/1 & Student’s t & 0.8206 & 29.0 & 0.419 \\  & pH/5 & Student’s t & 1.7136 & 29.0 & 0.097 \\  & pH/10 & Student’s t & 1.9109 & 29.0 & 0.066 \\ pH/30 & Student’s t & 1.5139 & 29.0 & 0.141 \\ pH/1 & pH/5 & Student’s t & 2.3654 & 29.0 & 0.025 \\  & pH/10 & Student’s t & 1.5282 & 29.0 & 0.137 \\ pH/30 & Student’s t & 1.0842 & 29.0 & 0.287 \\ pH/10 & Student’s t & 0.0588 & 29.0 & 0.953 \\ pH/30 & Student’s t & \(-\)0.9580 & 29.0 & 0.346 \\ \hline \end{tabular}
\end{table} 
Table 4: Within-the-group comparison of pH at different time intervals.