In our ligature-induced experimental periodontitis model, the levels of TNF-α and IL-1 were elevated, which is in line with the findings in patients with periodontal diseases.5 In patients with chronic periodontitis, aggressive periodontitis, and peri-implantitis, the levels of TNF-α and IL-1 were elevated and contributed to patients’ susceptibility to the disease.16 – 18 Graves’ study showed that, when TNF-α and IL-1 were antagonized with antibodies, a cause-and-effect relationship between inflammation degree and periodontitis severity was verified.5 The gene discussed is TNF; the disease is chronic periodontitis.