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[Periodontology yesterday and tomorrow. Epidemiology, aetiology and classification of periodontal diseases].

Modern periodontology is pervaded by a host of problems, and their solving may bring a considerable progress in this field. Views are verified on the incidence of parodontal diseases and their course. It is thought that the incidence of parodontal diseases is generally decreasing, and their course is more varied than it has been assumed as yet. An ever greater role is ascribed to bacteria in the aetiology of these diseases, this role is thought even to be a specific one. In connection with the advances in microbiological and histological examination new trends appear in the classification of parodontal diseases.