In addition, TNF-α and IL-1 β also induce reactive oxygen species (ROS) generation in periodontal tissue (Wang et al., 2014), where oxidative stress has been shown to be involved in periodontitis (Tomofuji et al., 2006; Maruyama et al., 2011).These pro-inflammatory mediators are required for the immune defense against bacteria, yet their uncontrolled activity leads the accumulation of ROS (superoxide radicals, hydrogen peroxide, hydroxyl radicals and singlet oxygen) (Gölz et al., 2014). This evidence concerns the gene TNF and periodontitis.