Increased dental caries activity in pre-school children with low baseline levels of serum IgG antibodies against the bacterial species Streptococcus mutans.

The caries increment was followed for two years in 33 children, aged 2.6-4.9 years at the start of the investigation. This was analysed in relation to Streptococcus mutans counts in dental plaque and serum IgG, IgM and IgA antibodies against Strep. mutans 10449 (serotype c). Furthermore, related factors, sugar, fluoride consumption and oral hygiene, were analysed. Large numbers of Strep. mutans in dental plaque were significantly associated with high caries incidence. Children with dental caries at the first examination and an increasing incidence of caries throughout the study period had significantly lower serum IgG antibodies against Strep. mutans (p = 0.006) than those whose caries activity was decreasing or who were caries-free at the beginning of the follow-up. The protective effect of specific serum IgG antibodies was most pronounced on the approximal surfaces of deciduous molars. Specific IgA or IgM antibodies were not associated with the development of caries.