[The role of Streptococcus mutans in human caries].

Definite proof has been found that S. mutans, and probably S. sobrinus and lactobacilli, are responsible for caries in man. The aciduria of S. mutans encourages the selection inside the plaque and is directly responsible for its cariogenicity. Other aciduric species, as S. sobrinus, cause caries on the smooth surface of the tooth, where the principal causes of the rampant caries reside. If during the eruption of the tooth the fissures become colonized in depth by S. mutans, the development of caries becomes a highly probable event. Instead, if the colonization of the tooth by S. mutans takes place after the fissure depth have been occupied by other microbic species not cariogenic, it is probable that the caries will not manifest or will appear in a less severe form. In conclusion, the knowledge already acquired on the ecology of S. mutans and the mechanism of cariogenesis clearly indicate that all factors that interfere with the colonization of the tooth by S. mutans can greatly reduce the incidence of caries in man.