Rheumatoid arthritis and periodontitis are chronic inflammatory diseases defined respectively by the destruction of the articular cartilage and tooth-supporting periodontal tissues. Although the epidemiologic evidence for an association between these two diseases is still scarce, there is emerging scientific information linking specific bacterial periodontal pathogens, such as Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, in the citrullination process, leading to autoantibody formation and compromised immunotolerance of the susceptible patient to rheumatoid arthritis. In this review, we update the existing information on the evidence, not only regarding the epidemiologic association, but also the biologic mechanisms linking these two diseases. Finally, we review information emerging from intervention studies evaluating whether periodontal treatment could influence the initiation and progression of rheumatoid arthritis.