Its expression is elevated in gingival crevicular fluid at sites of recent bone and attachment loss in patients with periodontal disease.3 An incubation of PDL fibroblasts with IL-1β resulted in an upregulation of receptor activator of nuclear factor kappa-B ligand (RANKL) expression.4 RANKL is essential for the formation of osteoclasts, and several studies have shown that these cells are indeed generated in the presence of PDL fibroblasts.5-6 It is not clear, however, whether cementoblasts also have the capacity to induce the formation of osteoclasts. This evidence concerns the gene TNFSF11 and periodontal disorder.