The Bacteriological Studies Section has been determining the cultivable flora of various forms of periodontal disease and periodontal health, and is currently examining the flora of sites that have been documented to have lost periodontal attachment. Subgingival bacterial samples are taken at sites that have been determined via clinical examination to have lost periodontal attachment since the previous examination. Additionally, samples are collected from control teeth that are selected based on the similarity of their clinical characteristics to the sample site. Further samples are taken from progressive sites following conservative periodontal therapy. Samples are collected, dispersed, and cultured anaerobically, and randomly selected colonies are characterized to species- or subspecies-level using polyacrylamide gel electrophoresis of cellular proteins, biochemical tests, gas chromatography, and serologic tests. Data to date indicate that there is no statistical difference between the flora of progressive sites and control sites that have experienced no attachment loss, but that treated sites are significantly different from both. This project is currently in progress.