The long-term objective of this proposal is to study the changes in microbial composition of dental plaque during its longitudinal development and to determine some of the principles which may govern these changes. The purpose of the present investigation is to study the nature of the changes in microbial populations from the predominantly Gram positive supragingival and sulcular plaques associated with health to the strikingly different Gram negative apical plaques associated with periodontal pockets in destructive disease. Sites at different depths within the pockets will be sampled in different stages of disease. One sample will be taken from the healthy sulcus, two samples from a mild periodontitis pocket and three samples from each of the deep pockets associated with advanced disease, one of which will be disease active. The microbial composition, both proportions and absolute numbers, in each of the sample will be determined by the predominant cultivable technique supplemented by darkfield microscopy for spirochetes and other morphologically distinct forms. The same sites will be resampled following successful periodontal therapy. Differences in the composition of the plaque microbiotas between comparable sites will be analyzed by non parametric statistics. Relationships between individual species in different zones on single teeth and between microbial species and clinical measurement of disease will be sought with correlation and regression techniques. Up to 20-50 percent of the organisms recovered from subgingival samples grow poorly or not at all in broth. Attempts will be made to formulate broth media for such organisms. Agar surface and resting cell tests for characterizing organisms especially those which continue to fail to grow in liquid media will be developed. Lack of classification schemes for the numerically dominant but poorly described subgingival organisms hampers periodontal microbiology. One such group of organisms, the "fusiform" Bacteroides, will be characterized and classified.