Streptococcus sobrinus and Streptococcus mutans in a Longitudinal Study of Dental Caries

Abstract

Mutans streptococci have been correlated with human dental caries. Much is known about the role of Streptococcus mutans in the caries process, but the role of S. sobrinus is less clear. This bacterium has been reported to be very acidogenic and aciduric in vitro and cariogenic in rats and should, therefore, have at least some cariogenic potential in humans. This study was aimed at determining the possible relationship between S. sobrinus, S. mutans and dental caries in a longitudinal study by using a non-selective culturing method and species-specific monoclonal antibodies. At the beginning of this study, 158 children aged 4 yr were examined clinically and salivary mutans streptococci were counted on MSB agar. At 5 and 6 yr of age, the children were examined and mutans streptococci were detected by using species-specific monoclonal antibodies and MSB agar. The carriage rate of S. sobrinus increased between 5 and 6 yr from 25 to 48 per cent. The presence of this microorganism was significantly associated with caries incidence (P=0-03). Relationships between the presence of S. sobrinus and salivary pH, buffer capacity or flow rate were not found. The presence of S. sobrinus or S. mutans was not significantly correlated with dmft when using the species-specific monoclonal antibodies. However, this correlation was highly significant (P< 0-001) when the mutans streptococci were detected by using the selective medium MSB. This suggests that differences in cariogenic potential occur within the species S. mutans or S. sobrinus. The present longitudinal study indicates that S. sobrinus is correlated with caries incidence, but its role in the initiation of caries could not be ascertained.