Figure 1.

Scheme for presumed mechanisms by which periodontitis causes neuroinflammation. These consist of three possibilities as follows: (1) Peripheral pro-inflammatory cytokines associated with periodontitis communicate with the brain via the neural pathway, humoral pathway, and cellular pathway. (2) Periodontal bacteria/bacterial molecules can directly invade the brain either through the blood stream or via cranial nerves. (3) Communication between periodontal bacteria/bacterial molecules and brain-resident microglia could occur through the leptomeninges.