Acquisition of Oral Bacteria

Objectives: Participants will...

• Recognize that caries is a preventable infectious disease.
• Learn the specific bacteria associated with tooth decay.
• Know the source and timing of bacterial acquisition by children.

Dental decay in infants and young children is referred to as early childhood caries (ECC). The initiation and progress of ECC are somewhat different from adult caries. The bacteria flora in infants is still in the process of organization and the child’s immune and other defense systems are still immature. It is generally accepted today that caries is an infectious, transmissible disease that can be prevented.

The major group of carigenic bacteria is mutans streptococci. Stable colonization of Streptococcus mutans requires a non-shedding hard surface; therefore it is not found in the mouth before tooth emergence. The bacteria adhere to the salivary pellicle on the tooth surface and together with a variety of other microorganisms form a biofilm, the dental plaque. Specific members of the plaque biofilm are capable metabolizing sucrose or refined sugar to form a sticky, extracellular capsule, which in turn, allows carigenic bacteria to form "critical mass" and concentrate acid. The production of acid as a by-product of bacterial metabolism of sugars creates cavities.

According to a longitudinal study by Caufield et al, infants become stably colonized by Streptococcus mutans during a period which they called the "window of infectivity". The period is around 2 year of age, on average, but can vary among individuals. The same window period was found for other populations, both within the US and in other countries, including Sweden, Italy, Japan and China. Other investigators report even earlier ages. The source of infection was primarily the mother, as was shown by DNA fingerprinting. Infants who had hypoplastic enamel became colonized by S. mutans at an earlier age. Mother’s nutritional and health status influenced the development of hypoplasia in the infant‘s teeth.

Overall, many studies suggest that the perinatal period of child development and the interaction with mother, such as breast feeding and administration of antibiotics, influence time of acquisition. Kohler et al demonstrated that early colonization of S. mutans manifested as greater severity of caries. Efforts to interfere with the transmission of cariogenic bacteria from affected mothers to their infants are being explored and their effectiveness evaluated as a viable means of reducing caries in young children.