TNF and periodontitis: Nowadays is well established the relationship between the progression of periodontitis and several factors, such as the presence of the periodontal pathogens, high levels of proinflammatory cytokines (IFN-γ and TNF-α), matrix metalloproteinases (MMP) and prostaglandin E2 (PGE2), and low levels of inflammation's inhibitory cytokines (IL-10), transforming growth factor beta (TGF-β), and tissue inhibitors of MMP (TIMP) [6, 8].