Introduction: Several epidemiological studies have suggested that a link between periodontal disease and rheumatoid arthritis. In cohorts, the risk of development of rheumatoid arthritis is increased in subjects with periodontal disease. The main bacterium implicated in chronic periodontal disease is Porphyromas gingivalis, a commensal microorganism of the mouth. P. gingivalis is the only microorganism with a deiminase capable of transforming arginine into citrulline, and is suspected of to play a major role in the production of anti-citrulline antibodies, the principal diagnostic marker of rheumatoid arthritis.