Figure 3.

The oral cavity as the origin of the internal microbiome in humans. The microbiome in the oral cavity can disseminate to the remote sites of the body, such as the brain, stomach, intestines, and heart, via hematogenous and enteric pathways. The PP, a pathologically deepened GS due to microbial infection and colonization, gradually allows detachment of the connective tissues of the JE from the tooth surface. The epithelial layer of the apical JE is thin enough for bacterial virulence factors as well as pathogenic bacteria, such as P. gingivalis, to infiltrate into the bloodstream, resulting in a leaky gum syndrome. The microbiome of the oral cavity also affects gut microbiome profiles by moving through the gastrointestinal tract, causing a variety of gut-related diseases, such as IBD, IBS, and colon cancer.