Effects of chlorhexidine-fluoride gel treatments in mothers on the establishment of mutans streptococci in primary teeth and the development of dental caries in children.

In a longitudinal 3-year study, 151 children were followed for the colonization of the primary dentition by mutans streptococci (MS) and for the development of dental caries. At the age of 1 year, the child-mother pairs were divided into three groups on the basis of the levels of MS in maternal saliva. In the experimental group, the mothers had MS levels higher than 10(5) CFU/ml, and they were given chlorhexidine (1%)-sodium fluoride (0.2%) gel treatments twice a year for 3 years. Two control groups were formed. In control group 1, the mothers also had high levels of MS, but no gel was given. In control group 2, the mothers had low (< 10(5) CFU/ml) baseline levels of salivary MS, and no chlorhexidine-fluoride gel was used. In the total study population, 16, 42, and 54% of the children were colonized by MS by the age of 2, 3, and 4 years, respectively. Most children harbored only Streptococcus mutans, but 2 had both S. mutans and Streptococcus sobrinus, and 2 had only S. sobrinus. Twenty-eight percent of the MS-positive children developed caries by the age of 4 years, whereas 4 out of 27 children with dental caries did not have any detectable MS in their plaque samples. Both the colonization by MS and the caries incidence were highest in control group 1 and lower in the experimental group and in control group 2. These observations suggest that the reduction of maternal salivary MS at the time of tooth emergence may delay, or perhaps even prevent, the colonization of MS in the children's primary dentition with a concomitant decline in caries incidence, even in a population with an already low prevalence of dental caries.