The salivary concentration of Streptococci mutans and Streptococci sanguis and their colonization of artificial tooth fissures in man.

Artificial fissures were inserted in 3 subjects for 1-21 days. At a salivary concentration of lo3 colony-forming units (CFU) Strep. mutans@, fissures were colonized by this organism. The proportional distribution of Strep. mutans increased with time and comprised up to 6 per cent of the total number of organisms in the fissure at day 21. The total number of organisms in the fissure did not increase with time after 1 day. The salivary concentration of Strep. sanguis was about lo6 CFU/ml in all subjects. The proportional distribution of this organism in the fissure varied both between different individuals and with time in the same individual. When the artificial fissures were inserted during a regimen which reduced the salivary concentrations of Strep. mutuns, the organism did not colonize the artificial fissures, even though the salivary concentration of Strep. mutans after cessation of the regimen increased to levels generally associated with colonization. If the fissures had been inserted 2 weeks before the Strep. mutans reducing regimen was started, the reduction of the number of Strep. mutans in the saliva to levels generally not associated with colonization did not influence the proportional distribution of Strep. mutans in the artificial fissure. These observations indicate that the initial inoculum is a main determinant for the colonization of the artificial fissures by Strep. mutans.