Does a biological link exist between periodontitis and rheumatoid arthritis?

Table 1 Similarities between periodontal structures and articular joint

Supporting periodontal structures	Articular joint
Periodontal structures comprise of cementum, alveolar bone, periodontal ligament, gingival crevicular fluid and gingiva	Articular joints comprise of articular cartilage, bone, ligaments, synovial cavity, synovial fluid, and synovial capsule
Cementum is an avascular tissue	Articular cartilage is an avascular tissue
Periodontal ligament is a thin connective tissue that surrounds the root connecting it to the alveolar bone	Synovial tissue is a thin layer of connective tissue. It consists primarily of two cell types- type A synoviocytes (macrophage derived) and type B synoviocyte (fibroblast derived)
Periodontal ligament is collagenous and consists of epithelial rests of malassez, fibroblasts, osteoblasts and ground substances (hyaluronic acid and proteoglycans-fibronectin and laminin)	Synovial fibroblasts are the most abundant and produce the structural components of the joints including collagen, fibronectin and laminin
Gingival crevicular fluid is an infiltrate of blood	Synovial fluid is an infiltrate of blood