As per a case-control study in 'Arthritis Research & Therapy', there is a significant association between periodontitis and RA, not considering the other confounders.

Many studies have reported the prevalence of periodontitis in RA patients. But, the strength of this association, its temporal link and possible relationship between the severity of periodontitis and RA disease activity is still not fully understood. This case-control study was performed with an objective to estimate whether periodontitis is concerned with RA and whether periodontitis severity is connected to RA disease activity.

A total of 187 patients diagnosed with RA and 157 control patients without inflammatory joint disease were included in this study. The RA disease activity and severity were examined with the help of Disease Activity Score 28, Simplified Disease Activity Index, Clinical Disease Activity Index, anti-citrullinated protein antibody titers, rheumatoid factor, erythrocyte sedimentation rate, the C-reactive protein, the presence of extra-articular manifestations and the type of RA therapy. The exposure severity was investigated considering the periodontal parameters, i.e. plaque index, bleeding on probing, probing pocket depth and clinical attachment levels. Sociodemographic variables and comorbidities were regarded as the confounding variables. Using the nonparametric and parametric tests, the outcome and exposure variables were distinguished. The possible connected were examined using the regression analysis with a calculation for the adjusted odds ratio (OR).A significant association was portrayed between periodontitis and RA with an adjusted OR of 20.57. All the parameters associated with periodontal status (plaque index, bleeding on probing, probing pocket depth and the clinical attachment levels) were significantly worse in RA patients as compared to the controls.

An ordinal logistic regression model predicted a connection between periodontal severity and disease activity.  "This connection was more evident in patients suffering from pronounced periodontal disease and higher RA disease activity, "concluded Beatriz Rodríguez-Lozano et al. (study authors).