TNF and diabetes mellitus: In this sense, it has been reported not only that elevated systemic levels of IL-6 and TNF-α in the simultaneous presence of diabetes and periodontitis than in periodontitis alone, as well as the increased levels of these well-known pro-inflammatory cytokines in GCF can activate osteoclasts, which promote bone resorption, destruction of alveolar bone, tissue inflammation, and periodontitis progression (17–19).