HGF and periodontitis: Moreover, the (co) monomers triethylene glycol dimethacrylate (TEGDMA) and 2-hydroxyethyl methacrylate (HEMA) induce reactive oxygen species (ROS) production and HGF apoptosis [12, 13] Considering that oxidative DNA damage in fibroblasts is closely related to periodontitis [14, 15], a recent study indicated that the pathogeneses of peri-implantitis and periodontitis are similar [16]; hence, ROS production, cell apoptosis, and oxidative DNA damage may play a vital role in peri-implantitis.