Periodontal disease occurs due to the reaction between the bacteria in the dental plaque and the host immune system, resulting in the immune–inflammatory response that manifests as infiltration of periodontal tissues by neutrophils, macrophages, and lymphocytes, and the generation of cytokines (IL-1β, TNF-α, and IL-6), prostaglandin E2, destructive enzymes (matrix metalloproteinases), and ROS in high concentrations [99,100]. The gene discussed is IL6; the disease is periodontal disorder.