1) To study bacterial interrelationships in an in vivo gnotobiotic animal model of the bacteria Streptococcus mutans, Lactobacillus casei and Actinomyces viscosus. 2) To determine the effects of sequential inoculation of the colonization of bacteria and subsequent production of caries. 3) To determine the effect on the production of caries of mono- and of multiple inoculation. 4) To determine the effects of modulation of the host response to one or more of the bacteria on the colonization and production of caries. 5) To compare the results obtained in the in vivo model with those obtained in the in vitro experiment (Clarkson, R01 Root caries study in vitro).