[The etiopathogenesis of periodontal diseases: the role of microorganisms. A review].

The microbiology of periodontal diseases as well as associations between certain microorganisms and types/stages of periodontal diseases are discussed and the ecology and the composition of the subgingival plaque are included in this discussion, too. Furthermore, the possible role of microorganisms associated with periodontal diseases, their pathogenic mechanisms and their virulence factors are treated in the present article. Periodic upsets of the host-parasite equilibrium seem to be responsible for the bursts of disease progression. Several plaque hypotheses (specific, non-specific, opportunistic) have been proposed as likely models to explain the nature of periodontal infections and diseases. However, none of these theories is widely accepted at the moment. Therefore, we suggest that further investigations concerning the complex bacterial interactions and the manner in which the host responds to the mass and the composition of the dental plaque must be carried out in the future.