Sucrose-induced ecological response of experimental dental plaques from caries-free and caries-susceptible Human volunteers.

Microbial succession, experimental cariogenicity, and sucrose metabolism were examined in dental plaques which developed on sterile bovine enamel inserts in acrylic palatal appliances. The appliances were worn for a period of 14 days by 10 caries-free and 10 caries-susceptible human volunteers. Three of six enamel inserts on each appliance were exposed extraorally to 10% sucrose in 0.85% saline six times a day, and three were exposed simultaneously to 0.85% saline as a control environment. The responses of the plaques to the high-sucrose environment in both caries status populations were compared. In all plaques, exposure to 10% sucrose stimulated the succession of Veillonella spp., Lactobacillus spp., Streptococcus salivarius, and, to a lesser extent, Streptococcus mutans and a decline in levels of Streptococcus sanguis, Neisseria spp., and gram-negative anaerobic rods. Plaques from caries-free mouths, in contrast to those from caries-susceptible mouths, harbored higher levels of Veillonella spp., gram-negative anaerobic rods, and Neisseria spp. and lower levels of Lactobacillus spp. Sucrose-exposed plaques from caries-free mouths also induced less enamel microhardness changes and formed less lactic acid from [14C]sucrose during a 60-min incubation at 37 degrees C than did comparable plaques from caries-susceptible mouths. The experiments revealed consistent differences in the ecological response to a cariogenic substrate environment in plaques from the two populations, with plaques from caries-free subjects exhibiting less cariogenic potential than those from caries-susceptible subjects.