Changes in Streptococcus mutans and lactobacilli in plaque in relation to the initiation of dental caries in Negro children

Over a period of 18 months, a study was made of dental plaques and caries on three selected tooth surfaces in 12 Negro children, ages 7–9. Although the mean number of Streptococcus mutans increased with time on each of the three surfaces, it remained much higher in the pits and fissures than on the buccal and approximal surfaces. The initiation of caries tended to be preceded by elevated numbers of both Strep. mutans and lactobacilli. However, the lactobacilli became a sizeable proportion of the plaque microbiota only after the appearance of caries. Caries frequently occurred in the absence of lactobacilli, but not in the absence of Strep. mutans.