It should also be understood that caries is an infectious disease that may be transmitted from one person to antother. this is exemplified by the fact that mothers with a high caries risk or experience harbor substantial numbers of mutan streptococci and lactobacilli in oral cavities and saliva. Within a short time after eruption of the primary teeth in their infants, these caries-prone mothers transmit cariogenic bacteria to their young children, leading to increased caries susceptibility.