Dental caries is a true infectious disease which fulfils Koch’s postulates. The transmission of mutans streptococci from mother to child via salivary transfer has been demonstrated in numerous studies. Behaviour patterns include kissing, sampling of food, and sharing spoons or feeding utensils. The child’s own saliva provides a level of protection from early childhood caries but this is limited
to the mandibular incisor teeth. The higher the salivary levels of mutans streptococci in the mother, the greater the number of organisms transmitted. Analysis of the strains present in families has shown that strains are highly conserved within mother to child pairs and also between siblings.
The presence of either or both S. mutans and S. sobrinus in approximal plaque is strongly correlated with early carious lesions in children. S. mutans is normally acquired much earlier in life than S. sobrinus, however some adults and elderly patients harbour S. mutans alone and not S. sobrinus. It is rare to find a patient with coronal or root surface caries who does not harbour S. mutans in high numbers. For many years, S. mutans were thought to lack a suitable ecological niche in the pre-dentate oral cavity so that pre-dentate inoculation was unlikely to lead to colonization. However, it has been shown that inoculation with S. mutans can occur early in life through repeated exposure from the mother and siblings. This raises the possibility of interrupting transmission by selective decontamination of both mother and infant using intermittent home application of suitable anti-bacterial mouthwashes.