Rheumatoid arthritis and periodontal disease: What are the similarities and differences?

Rheumatoid arthritis (RA) and periodontal disease (PD) are chronic inflammatory diseases that share similar osteoclasia, human leukocyte antigen-DR4 allelic genes and immunological profile, and characteristic cytokines. Smoking can contribute to more severe RA and PD; secretion of pro-inflammatory mediators destroys the soft synovial membrane and periodontium, respectively. Anti-citrullinated protein antibodies and anti-α-enolase antibody are characteristic of these two diseases. Some studies suggest that PD may be associated with RA. Anti-Porphyromonas gingivalis (P. gingivalis) antibody, but no P. gingivalis bacterium can be detected in RA patients' joint fluid. Anti-P. gingivalis antibody has been seen as a biomarker of RA. Both diseases share some nosogenesis and common pathological pathways. However, there are differing views on the connection between the two diseases. Interferon-inducible-16 (IFI16) is a genic marker of RA; moreover, the association between IFI16 and PD is rare. Some studies suggest PD is related to periodontal parameters and patient's pathological status rather than RA. Disease frequency in men and women differ between these two diseases. The expression of interleukin-17 (IL-17) receptor only associates with different genders in PD (PD of different sexes have different IL-17 expressions). Periodontal local treatment only affects clinical periodontal status, and it does not alter circulating levels of IL-6, tumor necrosis factor-alpha or C-reactive protein which are associated with RA. This review examines the similarities and differences between these two diseases and explores possible interactions. Importantly, we will discuss whether PD is a feature of RA and whether this knowledge provides helpful information in future treatment of both diseases.