Studies of salivary TNF-α levels have failed to provide evidence of association with periodontitis often because the levels of TNF-α in saliva are very low or nonexistent [75, 76, 78, 79, 81, 82, 84]; although one study did report significantly elevated levels of TNF-α in periodontitis patients as compared to healthy controls, the actual levels of TNF-α were very low (<4.3 pg/mL) [85]. The gene discussed is TNF; the disease is periodontitis.