TNFSF11 and periodontal disorder: Many studies have raised an important association between cytokines, originated from neutrophils and other defense cells, and different stages of periodontal disease, especially interleukin 1-β, IL-6, tumor necrosis factor-α (TNF-α), and receptor activator of nuclear factor kappa-B ligand (RANKL), that seem to have the most substantial role as central key elements in the cytokine networks of the development of periodontal diseases [13, 14].