The objectives of this project are 1) to assess methods that can improve the diagnosis of pathogenic bacterial populations on surfaces of the teeth and 2) to evaluate the potential of various therapeutic measures to control such populations. Samples of bacterial plaques removed from surfaces of the teeth are studied to determine the prevalence of Streptococcus mutans, various actinomyces, spirochetes, and various motile rods. The prevalence of these forms and the appearance of either carious or periodontal lesions are followed as patients apply various therapeutic measures directed to reduce or eliminate the above mentioned populations. Standard microscopic and cultural methods are used to detect the presence of the microbes under consideration. Antibacterial agents and fluoride preparations are prescribed as adjuvants to oral-hygience measures and to recommendations on eating habits.