Serum antibodies against oral Streptococcus mutans in young children in relation to dental caries and maternal close-contacts.

Thirty-six children aged 2.6-4.9 years were studied with respect to dental caries, Streptococcus mutans counts in dental plaque, and the estimates of total amount and avidity of serum IgG, IgM and IgA antibodies against Strep. mutans 10449, serotype c. A significant positive correlation (r = 0.49, p less than 0.01) was found between the number of Strep. mutans and caries-index in children. Two children with dental caries had no oral Strep. mutans. In median tests, high antibody titre and avidity of serum IgG antibodies against Strep. mutans were associated (p less than 0.05) with low counts of Strep. mutans. No such relationship was found with IgM or IgA antibodies. Children who had had frequent maternal close-contacts in their first year had significantly more (p less than 0.05) IgG antibodies against Strep. mutans than children with rare close-contacts.