Methods: This cross-sectional study included 352 diabetic patients with periodontitis who were registered at Riyadh Armed Forces Hospital, King Faisal Specialist Hospital and Research Centre, King Abdul Aziz Medical City, Naval Base Hospital, and Sultan Bin Adulaziz Humanitarian City, Riyadh, Kingdom of Saudi Arabia from July 2004 to August 2008. Microbiological analysis comprised the detection of Bacteroides forsythus (BO, Awegatibacter actinomycetemcomitans (Aa), Porphyromonas gingivalis (Pg), and Prevotella intermedia (Pi) by polymerase
chain reaction method.