Essential dependence of smooth surface caries on, and augmentation of fissure caries by, sucrose and Streptococcus mutans infection.

Streptococcus mutans-free Osborne-Mendel rats were used to study the ability of well-characterized S. mutans strains of Bratthall serotypes c, d, and E to form plaque and cause caries when the animals consumed either sucrose- or glucose-containing diets. All of the serotype representatives successfully infected, colonized, and emerged in the oral ecology of animals, independent of the carbohydrate supplementation of the diet. However, the sucrose-containing diet supported higher percentages of S. mutans of all the serotypes in the plaque and greater amounts of plaque on the teeth. Smooth surface caries was essentially S. mutans dependent and sucrose dependent; fissure caries, although it was neither dependent on S. mutans infection nor sucrose consumption, was augmented by both. This sucrose-associated emergence of all three serotype representatives in the plaque flora and their virulence in the production of caries can be ascribed to their production of alkali-solible alpha-(1 yields 3)-rich glucans from sucrose.