Fig. 2

α-and β-diversity of salivary microbial communities in HC Group and pPN Group. A Ace index of salivary microbiota in both groups. B Sobs index of salivary microbiota in both groups. C Shannon index of salivary microbiota in both groups. D Intergroup differences in β-diversity of salivary microbiota. E, F Comparison of salivary microbial communities between HC Group and pPN Group using PCoA and NMDS based on Bray–Curtis distance (E, ANOSIM R² = 0.2139, P = 0.001, F, ANOSIM R² = 0.3139, P = 0.001). PCoA principal coordinate analysis, NMDS non-metric multidimensional scaling. P < 0.05 (*), P < 0.01 (**), P < 0.001 (***)