Selection of Streptococcus mutans and lactobacilli in an intra-oral human caries model.

Microbiologic changes during caries development underneath a plaque-retaining band were investigated by the use of selective media for streptococci, Streptococcus mutans, and lactobacilli. The final four-week plaque samples on 16 experimental teeth in six young subjects were assessed. Seven experimental teeth in three other subjects were sampled at baseline and after one, two, and four weeks. All 23 experimental teeth developed a white spot lesion. In the final four-week plaque samples on the lesions, S. mutans accounted for 8% and lactobacilli 0.1% of the total CFU, both being significantly higher than in plaque from unbanded control surfaces. All experimental teeth sampled during lesion formation showed consistently elevated plaque levels of S. mutans and lactobacilli in comparison with baseline and control values at weeks one, two, and four. The results demonstrated a cariogenic environment in the human mouth associated with rapid selection of aciduric bacterial species such as S. mutans and lactobacilli.