COLONIZATION WITH MUTANS STREPTOCOCCI AND LACTOBACILLI AND THE CARIESEXPERIENCE OF CHILDREN AFTER THE AGE OF 5

Some authors suggest that there is a ''window of infectivity'' for mut ans streptococci (MS) at an early age, after which colonization is not likely to occur. Moreover, children with low or non-detectable levels of MS at an early age are at lower risk for caries. It was our aim to study caries experience and colonization with MS and lactobacilli in a group of children at 11 years of age who had been documented to have been MS-free until 5 years of age. For this group, the mfs and MFS va lues at 11 years of age were found to be 1.12 +/- 2.81 and 0.44 +/- 0. 88, respectively. These values are much lower than those of a control group of 11-year-old children who had always been MS-positive since th e age of 2, being 3.10 +/- 3.43 and 1.20 +/- 1.91, respectively. Of th e 30 children without detectable MS up to the age of 5, 22 had acquire d MS at 11 years of age, but their MS counts were significantly lower than those of the control group. No correlation was observed between t he levels of MS of the children and the mothers. In children at 11 yea rs of age, no differences were found in the numbers of lactobacilli an d sugar intakes per week between the children MS-free and the children MS-colonized at 5 years of age. The present study indicates that the acquisition of MS is still possible after the so-called ''window of in fectivity'' and that a delayed acquisition of MS may reduce the caries experience in the primary and permanent dentition at a later age.