Oxidative stress is an important factor in developing periodontal disease and DM.5 The findings of the Thomas et al study indicate that serum TAC was greater in the systemically healthy group without periodontitis and lower in the systemically healthy with chronic periodontitis.6 In the Canakci et al. study,7 higher salivary MDA levels and lower salivary SOD and GPx activities were detected in periodontitis patients compared with the healthy controls. The gene discussed is SOD1; the disease is periodontitis.