The RANK/RANKL/OPG System: A Genetic Jigsaw in Bone Remodelling

Orthodontic tooth movement is facilitated by remodelling of the dental and paradental tissues which, when exposed to varying degrees of magnitude, frequency and duration of mechanical loading, express extensive physical and chemical changes that differ from the processes of physiological dental drift or tooth eruption. These force-induced strains alter the periodontal ligament's vascularity resulting in the release of cytokines, tumour necrosis factor α (TNFα), prostaglandins, growth factors and others which can evoke many cellular responses in and around teeth providing a favourable microenvironment for tissue resorption and deposition-bone remodelling. Receptor activator nuclear factor kappa B ligand (RANKL) and osteoprotegerin (OPG) belonging to the TNFα superfamily play a significant role in regulation of bone homeostasis. This RANK/RANKL/OPG system produced by the bone microenvironment represents important and final cytokine of osteoclast biology in which the ratio of RANKL to OPG regulates the orientation of bone formation or resorption.