PCR Detection of Streptococcus mutans and S. sobrinus in Schoolchildren

Objectives: Streptococcus mutans and S. sobrinus are associated with the development of dental caries. These bacteria were detected by PCR and then their presence was compared with the incidence of dental caries in Japanese schoolchildren.

Methods: Plaque samples were collected from all erupted tooth sites in the 128 subjects, aged 11-12 years old and each with mixed and permanent dentition, with a sterile toothbrush. A dental examination was performed for dft (decayed, filled, total) for primary tooth and DFT for permanent tooth with the WHO caries diagnostic criteria. A Mann-Whitney U-test was employed to compare the caries scores between combinations of the bacteria.

Results: In all subjects, the presence of S. mutans and S. sobrinus was 38.3% and 68.0%, respectively; 14.8% were positive for S. mutans alone, 44.5% were positive for S. sobrinus alone, 23.4% were positive for both S. mutans and S. sobrinus, and 17.2% were negative for both S. mutans and S. sobrinus. The total score (dft+DFT) of schoolchildren positive for both S. mutans and S. sobrinus was significantly higher than those positive for S. mutans alone (P<0.01). Conclusions: These results indicate that schoolchildren harboring both S. mutans and S. sobrinus have a significantly higher incidence of dental caries than those with S. mutans alone.