Biology of Receptor Activator of Nuclear Factor Kappa-B Ligand (RANKL) and Osteoprotegerin (OPG) in Periodontal Health and Disease - A Review

Periodontitis is a destructive disease that targets tooth-supporting structures through complex and multifactorial pathogenic processes. Alveolar bone destruction, a hallmark of periodontitis progression and one of the major causes of tooth loss in human, is mediated by the host immune and inflammatory response to microbial challenge. The discovery of the receptor activator of nuclear factor-kappa B (RANK)/ RANK ligand (RANKL)/osteoprotegerin (OPG) axis has improved the knowledge of bone metabolism regulation. The RANKL/RANK interaction is needed for differentiation and maturation of osteoclast precursor cells to activate osteoclasts and for the survival of mature osteoclasts. Osteoprotegerin is the naturally occurring inhibitor of osteoclast differentiation. It binds to RANKL with high affinity and blocks RANKL from interacting with RANK. The RANKL/OPG ratio is increased in periodontitis compared to healthy individuals, suggesting that this molecular interaction may be important in modulating local bone loss. In recent decades, studies on cellular and molecular mechanisms of bone loss in periodontitis have suggested that the use of host modulation agents is an important adjunctive therapy to scaling and root planning. This line of investigation is expected to help in the development of new therapeutic approaches to stop progressive bone resorption induced by oral bacterial challenge