For an infectious disease to occur, it must have a source or reservoir (person, animal, soil).  In dental caries the source may be the mother who transfers the infection to the infant.

Potential microorganisms may be transferred directly (by people, insects) or indirectly (through water, air or soil).  In dental caries the transfer agent is through saliva of the mother to the infant.

Pathogens must survive the transfer and successfully establish within the host. In dental caries, this will take several attempts and only at specified time periods.

Colonization (multiplication of the organism) may occur without evoking a tissue or immune response. In dental caries this occurs.  Additionally, colonization and bacterial multiplication in dental caries is dependent upon sugar intake and other local factors.

Infection indicates that colonization has occurred and the disease process has begun as indicated by damage to the tissue.  In dental caries, there is demineralization of the tooth surface.

The host response will determine if there is a manifestation of the disease (demineralization). If the host response is adequate, the individual may have the infection without the clinical manifestations of the disease.  He/she may thus be a carrier, harboring the infectious agent which can be spread to others.  In dental caries, the carrier would usually be the mother. (Greenstein, G & Lamster, I. Bactrerial transmission in periodontal disease: A critical review. J. Periodontol. 68:421-431, 1997. )