OBJECTIVES: To assess the effect of periodontal treatment on clinical and biochemical parameters of rheumatoid arthritis (RA) and quality of life (QoL) in patients with moderately active RA who were diagnosed with periodontitis. METHODS: In this open-label randomised controlled trial, RA subjects (n = 22) were allocated to "immediate" or "delayed" periodontal treatment (full-mouth non-surgical scaling and root planing, systemic antibiotics, and oral hygiene instructions). The main outcome was the 3-month change on the Disease Activity Score 28 based on the Erythrocyte Sedimentation Rate (DAS28-ESR). The Health Assessment Questionnaire and the General Oral Health Assessment Index were used to assess general and oral health QoL, respectively. RESULTS: Periodontal health significantly improved after periodontal treatment (P = 0.03). Periodontal treatment appeared to be safe but led to no significant effects on the DAS28-ESR (adjusted mean difference with 95% confidence interval (aMD) of -0.03 [-0.98; 0.92]). There was no evidence of improvement in the general QoL after periodontal treatment and no significant effect was found for the oral health QoL, despite a positive trend in the "psychological impacts" domain (aMD of 0.13 [-0.07; 0.33], P = 0.20). CONCLUSIONS: Although no clinical effect of periodontal treatment on RA was identified, this trial provides important data to support periodontal care in RA patients. Periodontal treatment is safe and reduces oral inflammation with a possible effect on oral health QoL. Since both periodontitis and RA are complex and multifactorial chronic diseases, it is likely that patient-centred approaches involving both oral health professionals and rheumatologists will contribute to optimal patient care. ISRCTN79186420.< Réduire