Statistical analysis

The mean pH of the pH readings for each individual site was calculated. The mean for the two sites at each of the different time points was calculated, as well as the minimum pH and maximum pH fall. The area under the curve (AUC_7.0) was calculated using Prism software. The mean ± SD and 95% confidence interval for the salivary S. mutans and lactobacilli concentrations were calculated for each group.

The data analysis was processed and analysed with GraphPad Prism software (version 8.2.0 (272)). Two-way analysis of variance (ANOVA) followed by Tukey’s multiple comparisons test was used for the changes in the pH value within the test and placebo groups. Comparisons of changes in the plaque pH between the two groups were made using Sidak’s multiple comparisons test. Detailed information regarding the pH readings was reported using paired t-test. Salivary cariogenic bacteria between the test and control groups were assessed using a two-way ANOVA test. Changes in the buffer capacity between the two groups was tested using paired t-test. The relative quantification of investigated probiotic bacteria species in plaque was carried out using qPCR gene expression analysis (Bio Molecular Systems, Australia), a statistical analysis was carried out using one-way ANOVA followed by Tukey’s comparison test. A difference with a value of p < 0.05 was considered to be statistically significant.