The oral cavity is home to vast populations of commensal microbial organisms which constitute the 'healthy oral microbiome.' Periodontitis is a destructive, infectious, inflammatory condition affecting the gums. Initially, a biofilm structure develops, causing localized inflammation. This biofilm is then colonized by certain anaerobic bacteria, including the 'red complex' organisms. There is an increasing interest in the communication between these organisms and host immune surveillance, a dialog which may plays an important role in the development of autoimmune diseases. Studies have shown an association between periodontitis and other inflammatory conditions including rheumatoid arthritis, psoriatic arthritis, ankylosing spondylitis and systemic lupus. The advent of accessible 16S ribosomal sequencing has led to exciting developments in the characterization of the human microbiome and the ability to study this interaction in more detail. The transmucosal communication between periodontitis and host immunity may provide avenues of discovery regarding the etiology and progression of rheumatic diseases.