Joint and oral health: The overlooked connection between rheumatoid arthritis and periodontitis (Review)

Rheumatoid arthritis (RA) and periodontitis are chronic, progressive inflammatory disorders that exhibit a notable bidirectional association, increasingly recognized in both rheumatology and periodontology. Epidemiological research has revealed a higher prevalence and severity of periodontitis in individuals with RA, indicating an association that may reflect shared immunological mechanisms. Both conditions are characterized by immune dysregulation, involving the overproduction of pro‑inflammatory cytokines, such as tumor necrosis factor‑&alpha; (TNF‑&alpha;), interleukin (IL)‑6 and IL‑17, which mediate tissue destruction in joints and periodontal tissues alike. A significant microbiological connection has been identified in periodontal pathogens, particularly <em>Porphyromonas gingivalis</em>, which produces peptidyl arginine deiminase and induces protein citrullination. Notably, other microbes, such as <em>Aggregatibacter actinomycetemcomitans</em>, which can induce neutrophil hypercitrullination, have also been implicated in this association. These microbial mechanisms are considered to contribute to the formation of anti‑citrullinated protein antibodies, although causality has not been definitively established. Immunologically, the overlapping inflammatory cascades and shared genetic predispositions underscore the systemic link between the two diseases. Therapeutically, anti‑rheumatic treatments, particularly biologics targeting TNF‑&alpha; and IL‑6, may provide benefits in periodontal health; however, the currently available evidence remains inconsistent and not universally accepted. This inter‑association emphasizes the need for integrated medical‑dental approaches, promoting early diagnosis and collaborative management to improve overall patient outcomes and quality of life. The present review synthesizes evidence published since 2020, prioritizes testable salivary and microbial biomarker candidates (e.g., citrullinated vimentin, citrullinated &alpha;‑enolase/CEP‑1, neutrophil proteases and oral microbiome signatures), and translates these findings into practical screening and co‑management steps for rheumatologists and periodontists.