Mutans streptococci play an important role in the initiation and progression of dental caries. This bacterium thrives in the plaque that forms on the surface of teeth. It uses sugars to produce acids capable of dissolving the tooth enamel, which will eventually develop cavities.

Mutans streptococci are usually transmitted from adults to children, and then settle on and attack the emerging teeth. The earlier the colonisation of teeth occurs, the higher the prevalence of dental caries is.