Difficulties encountered in the search for the etiologic agents of destructive periodontal diseases.

The present paper outlines some of the difficulties encountered in the search for the etiologic agents of destructive periodontal diseases. These include technical problems such as acquiring an appropriate microbial sample, as well as difficulties in the dispersion, cultivation and identification of isolates in that sample. Many of these difficulties are currently being successfully addressed. A second set of problems is more conceptual in nature. These include difficulties in distinguishing between periodontal diseases and determining the state of activity of periodontal lesions. In addition, complexes of organisms and/or sequences of species may be involved in the progress of lesions. A further problem is encountered in attempting to distinguish overgrowths of opportunistic species from increases in proportions of true pathogens. Finally, it appears likely that different infections occur at the same time in a single oral cavity. The technical and conceptual difficulties eventually filter down to the data analytical step and present numerous problems to the analyst. With all of these difficulties in mind, it is not surprising that the etiologic agents of destructive periodontal diseases are not clearly defined. However, improvement in technological assessments of the microbiota and clinical evaluation of the disease should permit reasoned approaches to be taken. The delineation of the etiologic agents of destructive periodontal diseases will be, of necessity, a multistage iterative process. Etiologic agents will be suggested by predominant cultivable studies and hypotheses concerning subsets of these agents tested using more specific procedures such as selective media, immunofluorescent techniques or DNA probes.(ABSTRACT TRUNCATED AT 250 WORDS)