Periodontal disease is the most prevalent disease affecting the human dentition. Periodontal disease is a chronic bacterial infection characterized by persistent inflammation, connective tissue breakdown and alveolar bone destruction.The term periodontal disease includes to gingivitis, chronic periodontitis, aggressive periodontitis, necrotising ulcerative gingivitis, necrotising periodontal disease,etc which may or may not have accompanying risk factors such as smoking, systemic conditions and viral infections such as Herpes and HIV.In known research, 800-1,000 species that colonize the oral cavity were identified, nevertheless only about 50 species are strongly related to periodontal disease. The quest to identify specific periodontal pathogens has led to significant progress, including the identification of a number of micro-organisms, mostly gram-negative anaerobic bacteria that colonize subgingival tooth sites. Foremost amongst this group are three species which comprise the so-called ¿red complex¿, are frequently isolated together, and are strongly associated with diseased sites in the mouth.