The relationship between the number of the bacterium Streptococcus mutans at discrete sites on the dentition of macaque monkeys (Macaca fascicularis) and the subsequent development of dental caries.

Sixteen consecutively-born monkeys were used in a longitudinal study to determine the changes occurring in the total number of bacteria in the palatal grooves of the upper left first deciduous molar teeth, following the introduction of a sucrose-based diet. The total number of bacteria recovered from the grooves increased significantly following the diet change. Twenty-nine days after the diet change, the number of Streptococcus mutans had increased from a median value of less than 10(2) to approx. 10(7) per groove, and the number of Streptococcus sanguis decreased. These changes in the number of Strep. mutans occurred prior to the detection of dental caries. Grooves that became carious harboured significantly more bacteria and more Strep. mutans than did grooves remaining caries-free six months after the diet change.