TNF and chronic periodontitis: The rs1800629 consists of a G→A substitution at position 308 in the promoter region of TNF -α and is related to higher frequency of gene expression and higher levels of circulating cytokine, being previously associated with susceptibility to chronic periodontitis and diabetes mellitus type II.24 According to a review by El-Tahan, Ghoneim, and El-Mashad43 (2016) TNF -α has several reported SNPs in its promoter region that are mostly studied in the context of autoimmune diseases and act in either up or downregulation of gene expression.