What substance is responsible for the cariogenicity of Streptococcus mutans?

The substance responsible for the cariogenicity of Streptococcus mutans is glucans. Glucans are a type of polysaccharide that Streptococcus mutans synthesizes from sucrose through the action of enzymes known as glucosyltransferases. These glucans contribute to the formation of dental biofilm and plaque, providing a sticky matrix that helps bacteria adhere to tooth surfaces.

The presence of glucans in the oral environment enhances the ability of Streptococcus mutans to colonize and establish itself on teeth, leading to the development of dental caries. The sticky nature of glucans not only promotes bacterial accumulation but also creates a microenvironment conducive to acid production from fermentable carbohydrates, which is detrimental to tooth enamel and promotes decay.

Other substances mentioned, such as levans and fructans, do not play the same pivotal role in the cariogenicity of Streptococcus mutans as glucans do. While sucrose serves as a substrate for glucan synthesis, it is the glucans themselves that are primarily responsible for the pathogenicity associated with this bacterium.