Use of metronidazole as a probe in the study of human periodontal disease

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Abstract
The present investigation was performed to test the hypothesis that the persistence of inflammatory periodontal disease in human subjects is incompatible with the elimination of the anaerobic segments of the subgingival microbiota.16 human subjects participated in the trial. They were selected on the basis of advanced periodontal disease which had produced at least 4 pairs of contra lateral teeth with advanced disease. At the Baseline examination the diseased sites were characterized by assessment of plaque, gingivitis, probing depth and attachment level. In addition, the composition of the subgingival microbiota was determined. One pair of sites was subjected to biopsy. In the tissue samples the size of the inflammatory cell infiltrate was assessed.Following the Baseline examination the patients were randomly distributed into 2 treatment groups, test and control. The patients of the test group received metronidazole for 3 periods of 2 weeks each, separated by intervals of 8 weeks. In addition, all patients received detailed oral hygiene instruction and a series of subgingival scalings involving 2 quadrants of the dentition, either the right or the left jaw quadrants, Reexaminations were performed 2, 10, 20, 30 and 50 weeks after the Baseline examination. Biopsies from the predetermined sites were obtained at the reexaminations performed 2,20 and 50 weeks after the initiation of the therapy.The results demonstrated that the elimination of metronidazole sensitive bacteria from the subgingival microbiota resulted in the disappearance of clinical and histopathological signs of periodontal disease. Metronidazole has a unique bactericidal range against anaerobic bacteria. The present findings, therefore, emphasize the central role played by the anaerobic segments of the subgingival plaque for the maintenance of the inflammatory component of periodontal disease.