Salivary mutans streptococci and caries prevalence in 8-year-old Swedish schoolchildren

The aim of this study was to obtain cross-sectional information about the quantitative distribution of salivary mutants streptococci assessed with a clinically applicable microbiological method and the relation to dental caries in young schoolchildren. A total of 355 8-year-old children were examined for the presence and number of mutants streptococci in saliva by a specially prepared strip, the "Strip-mutans" method, cultivated in a selective broth. The strips were first visually examined and grouped by aid of a templet provided by the manufacturer and thereafter transferred to a laboratory for enumeration of colony forming units (CFU) with aid of a stereomicroscope. Caries scores were obtained from the dental records. Mutans streptococci were identified in 70% of all children. 46% were free from the bacterium or harboured low levels (0-10 CFU) while high levels (greater than or equal to 500 CFU) were found only in 6% of the material. Strong positive correlations (p less than 0.001) were found between different levels of mutans streptococci infection and the caries experience in both the primary (dmfs) and the permanent (DMFS) dentition. A statistically significant correlation between the direct examination and the microscopic enumeration was disclosed (r = 0.84). The bacterial culturing technique used in this study proved to be practical and reliable and thus useful in clinical routines of pediatric dentistry.