THE DISSOLUTION OF MINERAL SUBSTRATES IN THE DETERMINATION OF THE CARIOGENIC POTENTIAL OF STREPTOCOCCUS-MUTANS

Whilst the limited usefulness of caries activity tests based solely on counts of mutans streptococci is becoming increasingly apparent, to date, little attention has been paid to potential differences in the virulence of strains isolated from patients with varying disease experience. Recently an in vitro test was described involving the dissolution of bovine enamel, as a means of determining the cariogenic potential of S. mutans strains. The current study aimed to investigate this test further and to compare the dissolution of bovine enamel and different hydroxyapatite preparations as a possible means of differentiating strains of S. mutans with regard to cariogenicity. In the presence of a 5 per cent sucrose solution, six strains were incubated with either bovine enamel, solid hydroxyapatite, or powdered hydroxyapatite for 5, 24 or 48 h, following which acid anion production, calcium release and change in pH were measured. The results showed that incubation with the powdered hydroxyapatite for 5 h resulted in significant differences between strains which correlated with clinical disease experience. It is suggested that this improved assay could be used to investigate further the clinical significance of the relationship between in vitro cariogenic potential and caries experience.