Previous studies have reported the co-existence of periodontitis and rheumatoid arthritis, with the two diseases bearing similarities in etiology and pathogenesis, and sharing common risk factors. Elisabeth Brouwer, from the University Medical Center in Groningen (The Netherlands), and colleagues reviewed records of 95 patients with rheumatoid arthritis, and found that 18% of the patients had severe periodontal disease and 32% had moderate periodontal disease.  As well, in among the milder cases of periodontal disease, the rheumatoid arthritis patients in that group had lower C-reactive protein levels than patients with worsening periodontal disease.  Submitting that infective periodontitis, which destroys the supporting soft tissue and hard tissue of the teeth, shares risk factors with rheumatoid arthritis, the researchers comment that: “"We believe these findings indicate that periodontal disease might contribute to arthritis severity.”