SUMMARY TITLE: Effect of endodontic treatment on inflammatory markers, disease activity and periapical healing in rheumatoid arthritis patients with apical periodontitis RATIONALE: Chronic inflammation plays a pivotal role in rheumatoid arthritis as subjects present with elevated serum levels of numerous cytokines such as IL-1, IL-6, 1L-12, IL-17, tumour necrosis factor-alpha, RANK and RANK Ligand. Periodontal and pulpal inflammation are two major low grade chronic inflammatory diseases of the oral cavity. Apical periodontitis extends from the chronic inflammatory process that originated in the dental pulp to surround the apex of the tooth. Thus Rheumatoid arthritis and apical periodontitis converge upon common pathway of inflammation. The scientific literature has also shown to provide potential link between endodontic infection and rheumatoid arthritis. The evidence of increased prevalence of apical periodontitis in subjects of rheumatoid arthritis is provided mainly by cross-sectional and case control studies. Interventional studies have been performed in subjects with rheumatoid arthritis and periodontal disease, with results depicting beneficial effect of periodontal therapy in patients of rheumatoid arthritis. To best of our knowledge no interventional study has been performed to assess the healing pattern of apical periodontitis in subjects of rheumatoid arthritis and subsequently effect of endodontic intervention on inflammatory profile and disease burden in the same.