STREPTOCOCCUS-SOBRINUS AND STREPTOCOCCUS-MUTANS IN A LONGITUDINAL-STUDY OF DENTAL-CARIES

Mutans streptococci have been correlated with human dental caries. Muc h is known about the role of Streptococcus mutans in the caries proces s, 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 i n humans. This study was aimed at determining the possible relationshi p between S. sobrinus, S. mutans and dental caries in a longitudinal s tudy by using a non-selective culturing method and species-specific mo noclonal antibodies. At the beginning of this study, 158 children aged 4 yr were examined clinically and salivary mutans streptococci were c ounted on MSB agar. At 5 and 6 yr of age, the children were examined a nd mutans streptococci were detected by using species-specific monoclo nal antibodies and MSB agar. The carriage rate of S. sobrinus increase d between 5 and 6 yr from 25 to 48 per cent. The presence of this micr oorganism was significantly associated with caries incidence (P=0.03). Relationships between the presence of S. sobrinus and salivary pH, bu ffer capacity or flow rate were not found. The presence of S. sobrinus or S. mutans was not significantly correlated with dmft when using th e species-specific monoclonal antibodies. However, this cor-relation w as highly significant (P<0.001) when the mutans streptococci were dete cted by using the selective medium MSB. This suggests that differences in cariogenic potential occur within the species S. mutans or S. sobr inus. The present longitudinal study indicates that S. sobrinus is cor related with caries incidence, but its role in the initiation of carie s could not be ascertained.