An indicator to assess caries risk of infants is very important. One conventional risk indicator is the number and/or proportions of Streptococcus mutans, but this method reflects the existing situation and is not suitable for assessing caries risk of infants that have not yet been infected with S mutans. Researchers searched for an indicator for the establishment of S mutans. To evaluate the changes caused by the establishment of S mutans in the microbiota of the infant oral cavity, the authors monitored changes in the oral microbiota of 2 predentate infants over a 3-year period and in a cross-sectional study of 40 nursery school-aged children. Saliva was cultivated on nonselective blood agar, Mitis-Salivarius agar, and Mitis-Salivarius agar supplemented with bacitracin combined with identification of selected isolates. Two longitudinal observations suggested that S mutans establishment would induce a decrease in α-haemolytic bacteria in the microbial population of the oral cavity. This suggestion was compensated with the results of the study, and it was revealed that the establishment of 103 CFU/mL of S mutans in saliva might be predicted by a microbiota comprising less than approximately 55% of α-haemolytic bacteria. The authors conclude that a decrease in the proportion of α-haemolytic bacteria in the saliva of infants is applicable as an indicator to predict the establishment of S mutans and to assess dental caries risk. This information can serve as a background for planning dental care and treatment in the infants before infection with S mutans occurs.
