Background
Numerous studies support a bidirectional association between rheumatoid arthritis (RA), a chronic autoimmune degenerative inflammatory joint disease, and periodontitis, a chronic inflammatory disease caused by the immune reaction to bacteria organized in biofilms. RA and periodontitis are both multifactorial chronic inflammatory diseases that share common modifiable and non-modifiable risk factors. There is no cure for RA; treatment is based on lifestyle modifications and a variety of medications: nonsteroidal anti-inflammatory drugs (NSAID), glucocorticoids, and disease-modifying antirheumatic drugs (DMARDs, e.g., conventional synthetic DMARDs [csDMARDs]; biological DMARDs [bDMARD] and targeted synthetic DMARDs). There are molecular pathways of inflammation that are common to both RA and periodontitis. Thus, there is a potential effect of RA treatments on periodontitis. This systematic review aims to assess the impact of antirheumatic agents on periodontal conditions of patients suffering from both RA and periodontitis.

Methods
PubMed/MEDLINE, Cochrane Library, and Embase online databases were systematically explored, and a manual search was performed to identify relevant studies published until January 2023. This review is registered in the PROSPERO database (CRD42023409006).

Results
A total of 2827 articles were identified, and 35 fulfilled the inclusion criteria. The included studies generally show a consensus that, at normal dosage, NSAID and corticosteroids have negligible impact on periodontium. Similarly, csDMARD alone or in combination with other csDMARD demonstrated no adverse effect on periodontium. Monotherapy with bDMARD had a positive effect on periodontal pocket depths and gingival inflammation in the longitudinal studies up to 6 months but showed negligible effect on the periodontium in interventional studies with a longer follow-up (9 months and 15.1 months). However, the combination of tumor necrosis factor (TNF)-α inhibitors + methotrexate (MTX) was associated with a rise in gingival inflammation. Due to the considerable heterogeneity of the study designs, a meta-analysis could not reasonably be performed.

Conclusion
Within the limitations of the available studies, there is evidence to suggest that bDMARD monotherapy may improve the periodontal condition of RA patients with periodontal disease to a certain extent; the concomitant medication of TNF inhibitor + MTX could worsen gingival inflammation. More data are required to understand the impact of RA therapies on periodontal health.