Periodontal disease pathogenesis is a complex subject, requiring a thorough understanding of the macroscopic and microscopic features of the periodontium (i.e., the supporting structures of the tooth), as well as the role that the immune system plays in the host response to bacterial biofilms.
The human body is continually working to keep the internal environment in a condition of homeostasis. The system that wards off disease and provides resistance to foreign organisms is the immune system. In the oral cavity, plaque consists of a community of microorganisms called the biofilm. The bacteria within the biofilm are capable of initiating the gingival
lesion by triggering a localized inflammatory reaction. The host immune system responds to this bacterial challenge through an array of coordinated but complex processes that are designed to eliminate the initiating agent(s) and return the site to a state of homeostasis. The severity and extent of destruction of the periodontium is often related to a combination of factors such as the virulence of the biofilm bacteria, the robustness of the immune response and the chronicity of the inflammatory lesion.