This document discusses the microflora associated with periodontal disease. It begins with an introduction to bacteria's role in periodontal diseases and provides a history of research in this area from the 17th century to present. It then describes the normal oral microflora and microflora associated with periodontal disease. Key pathogens implicated in periodontal disease include Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola. The document also discusses virulence factors of periodontal bacteria and their role in colonization, evading host defenses, and tissue destruction. Microbial diagnosis of periodontal disease is also covered.