Comparison of the Initial Streptococcal Microflora on Dental Enamel in Caries-active and in Caries-inactive Individuals

This study compared the initial (4 h) microflora on enamel in 7 caries-active and in 7 caries-inactive adolescents. In both groups the microflora was dominated by streptococci which comprised 61 and 78% (median values) of the total viable counts in caries-active and caries-inactive individuals, respectively (p less than 0.01). Identification of a total of 700 streptococcal isolates according to a recently revised classification showed that the predominant streptococci belonged to the species Streptococcus oralis, Streptococcus mitis biovar 1, and Streptococcus sanguis. Early plaque from caries-inactive individuals differed from that of caries-active individuals by significantly higher proportions of S. sanguis (p less than 0.05) and IgA1 protease producing streptococci (p less than 0.05). In caries-active individuals, there was a tendency to elevated levels of S. mitis biovar 1 (p less than 0.10). In addition, caries-active individuals were colonized by significantly higher numbers of mutans streptococci on the enamel surfaces (p less than 0.01). However, in both groups Streptococcus mutans (serotype c) comprised less than or equal to 2% of the early streptococcal flora. Streptococcus gordonii, S. mitis biovar 2, and Streptococcus salivarius were present in low proportions and did not show differences in distribution that could be related to caries activity. The observed differences in the composition of the early streptococcal microflora may be a factor that governs the eventual cariogenic potential of dental plaque.