The Impact of Periodontal Therapy on Disease Activity in Patients with Rheumatoid Arthritis and Concomitant Periodontitis: A Systematic Review and Meta-Analysis

Background/Objectives: The interplay between oral and systemic diseases is highlighted by the shared inflammatory mechanisms and epidemiological associations between periodontitis and rheumatoid arthritis (RA). Building on previous syntheses of the effect of periodontal therapy on RA disease activity, we sought to refine the evidence base through strict restriction to randomized controlled trials (RCTs), separate analysis of the two non-interchangeable formulations of the Disease Activity Score on 28 joints (DAS28-CRP and DAS28-ESR, based on either C-reactive protein or erythrocyte sedimentation rate, respectively), and inclusion of recent randomized trials. We aimed to determine whether the first two steps of periodontal therapy (steps 1 and 2 of the 2020 EFP S3-level clinical practice guideline), delivered through supragingival professional mechanical plaque removal and subgingival instrumentation, reduce DAS28 in adults with concurrent RA and periodontitis. Methods: The review protocol was registered in PROSPERO (CRD420261400735). Five databases were searched in accordance with PRISMA 2020. Only RCTs were eligible. Risk of bias was assessed with RoB-2. DAS28-CRP and DAS28-ESR were analyzed in separate random-effects forest plots. Sensitivity analyses addressed adjunctive antibiotics and high baseline disease activity. Results: Ten trials (n = 430 randomized patients) were included. At 3 months, DAS28-CRP was significantly reduced (between-group MD = −0.84, 95% CI −1.38 to −0.29; change-from-baseline MD = −0.55, −0.92 to −0.19). On DAS28-ESR at 3 months, the change-from-baseline estimate was significant (MD = −1.27, −2.22 to −0.31) and the follow-up estimate concordant in direction but not significant (MD = −0.89, −1.85 to 0.07), with substantial heterogeneity. Conclusions: Periodontal therapy may be associated with short-term reductions in RA disease activity, particularly DAS28-CRP at 3 months, with directionally concordant but less certain effects on DAS28-ESR. The evidence remains limited by small sample sizes, risk of bias, substantial heterogeneity of the DAS28-ESR estimates, and sparse follow-up beyond 3 months. As no trial reported individual responder categories, these group-level findings support periodontal therapy as a possible adjunctive measure in RA rather than a predictable, clinically meaningful benefit at the individual patient level.