Role of anaerobic bacteria in periodontal disease

Microscopic examination and cultural studies of subgingival dental plaque have indicated that a complex, predominantly anaerobic flora is associated with periodontal disease. About 10 to 15 bacterial species, all of them anaerobic with the exception of A actinomycetemcomitans, have been suggested to be periodontal pathogens. These data indicate that most forms of periodontal disease are chronic anaerobic infections. This possibility has been evaluated by the systemic use of metronidazole, an antimicrobial whose spectrum of activity is limited to anaerobes. These six metronidazole double-blind studies demonstrate that metronidazole, given for periods of time as short as 1 week, can lead to a significant improvement in periodontal health. Maximal benefits are obtained when the metronidazole is given after the tooth surfaces are debrided of plaque and calculus. The best response is often noted in the more advanced cases, in which an anaerobic flora including spirochetes and black-pigmented Bacteroides usually predominates in the subgingival plaque. The success of short-term metronidazole treatment in these investigations indicates that the overgrowth of certain anaerobes in the plaque is responsible for most forms of periodontal disease.