A self-sustaining inflammatory loop between rheumatoid arthritis (RA) and periodontitis (PD) has been uncovered by recent research, providing evidence that periodontal therapy may partially reverse both oral and systemic inflammation.

People with RA are known to experience more severe PD than the general population, but the causal relationship and underlying biological mechanisms remain unclear.

Recent research, published in the Journal of Clinical Periodontology, investigated these links by examining dysbiosis-mediated inflammation in the subgingival microbiome, drawing on data from the OPERA (Outcomes of PEriodontal therapy in Rheumatoid Arthritis) and INSPIRED (INfluence of Successful Periodontal Intervention on REnal and Vascular Systems in patients with chronic kidney Disease) randomised controlled trials.

Conducted across centres in the UK and the US, the researchers used microbiome sequencing, immunological profiling and network-based modelling to characterise host–microbe interactions.

Rheumatoid arthritis and periodontitis cohorts

A total of 159 participants were included across four groups: 100 patients with both RA and PD, 22 with RA but no PD, 18 with PD alone, and 19 healthy controls.

Participants with RA were significantly older than those without the condition, and women predominated across all cohorts.

Within the RA and PD group, patients were randomised to receive either intensive non-surgical periodontal treatment comprising full-mouth professional plaque removal or oral hygiene instruction alone, with follow-up at three and six months.

Subgingival plaque samples were analysed with 16S rRNA gene sequencing, while gingival crevicular fluid cytokines and serum antibodies to periodontal pathogens were quantified using multiplex- and enzyme-linked immunoassays.

A ‘vicious cycle’ of inflammation

Subgingival dysbiosis was evident in patients with RA, regardless of periodontal status, and RA emerged as the dominant factor in microbial composition and organisation.

Machine-learning models predicted RA status with an out-of-box error rate of just 4.05%, compared with 38.6% for PD, underscoring the dominant influence of systemic autoimmunity on the oral microbiome.

Several bacteria, including Cryptobacterium curtum, Leptotrichia, Prevotella and Actinomyces species, were strongly linked to RA and correlated with elevated local levels of inflammatory mediators such as tumour necrosis factor-α, interleukin-6 and interleukin-1β.

Circulating antibodies to periodontal pathogens, including Porphyromonas gingivalis, were significantly higher in RA patients with and without PD (P≤0.003).

Clinical measures of periodontal disease severity correlated with RA disease activity, including Disease Activity Score 28, erythrocyte sedimentation rate and swollen joint counts (all P<0.05). Following intensive periodontal therapy, patients experienced significant reductions in gingival levels of inflammatory cytokines and in systemic antibody responses to oral bacteria.

Notably, antibodies to Fusobacterium nucleatum fell by a mean of 14.92 units (P=0.026), alongside improvements in RA clinical parameters compared with control treatment.

Clinical implications and future directions

The authors highlighted imbalances in group size and age, the lack of a formal sample size calculation, and the potential influence of unmeasured confounders, including comorbidities and non-RA medications, as limitations of the research. Additionally, low smoking prevalence in RA cohorts limited the assessment of its contribution to dysbiosis.

Nevertheless, Professor Iain Chapple, co-lead for the oral, intestinal and systemic health theme of Birmingham’s NIHR Biomedical Research Centre, and one of the lead investigators, noted that the findings are extremely significant.

‘It’s the first time that RA and PD have been shown to be linked in a circular relationship, creating a vicious cycle of inflammation,’ he said.

‘We found that treating gum disease through intensive periodontal therapy broke this cycle: it improved RA activity scores, reduced antibodies to oral pathogens, and re-established a balanced interaction between oral microbes and the immune system within three months.’

As such, the findings suggest that routine periodontal assessment and treatment could form part of integrated RA care to help reduce the systemic inflammatory burden.

Now, larger, long-term studies using multiomics are needed to clarify causality and guide combined therapeutic strategies, the authors concluded.

Reference
Lopez-Silva O et al. Dysbiosis-Mediated Inflammation: A Pathophysiological Link Between Rheumatoid Arthritis and Periodontitis. J Clin Periodontol 2026;53(3):466–77.