title: Quantitative real-time polymerase chain reaction for Streptococcus mutans and Streptococcus sobrinus in dental plaque samples and its association with early childhood caries.
abstract: BACKGROUND
  Streptococcus mutans and Streptococcus sobrinus are closely associated with the development of early childhood caries (ECC). Recently, quantitative real-time polymerase chain reaction (qRT-PCR) has been used for rapid and accurate quantification of these bacterial species.
  
  
  OBJECTIVE
  This study aims to detect quantitatively the levels of S. mutans and S. sobrinus in plaque samples by qRT-PCR, and to assess their association with the prevalence of ECC in Korean preschool children.
  
  
  METHODS
  One hundred and five children (71 months old or younger) were examined and classified into three groups (caries-free, ECC, severe ECC). Dental plaque samples were collected and qRT-PCR was conducted using oligonucleotide primers specific for glucosyltransferase gene (S. mutans-gtfB, S. sobrinus-gtfU) and universal primer. Pearson's correlation test was conducted to evaluate the relationship between the dmfs (decayed, missing, or filled surfaces primary teeth) scores and the microbiological findings.
  
  
  RESULTS
  There was a significant difference between the levels of S. mutans and S. sobrinus in the plaque samples of the three groups (P < 0.05). The proportion of S. sobrinus to S. mutans showed strong correlation to the dmfs scores (r = 0.748, P < 0.05).
  
  
  CONCLUSIONS
  The qRT-PCR results of this study showed that children with ECC had higher level of S. mutans and S. sobrinus in their dental plaque samples. The children with higher ratio of S. sobrinus to S. mutans in their dental plaque showed higher incidence of ECC.
authors.affiliation: Department of Pediatric Dentistry, School of Dentistry, Seoul National University, Seoul, South Korea.
authors.forename: Eun-Jung
authors.initials: EJ
authors.lastname: Choi
authors.forename: Sung-Hoon
authors.initials: SH
authors.lastname: Lee
authors.forename: Young-Jae
authors.initials: YJ
authors.lastname: Kim
mesh_terms: D000704:Analysis of Variance; D002648:Child; D002675:Child, Preschool; D015169:Colony Count, Microbial; D003731:Dental Caries / Q000453:epidemiology / Q000382:microbiology*; D003733:Dental Caries Susceptibility; D003773:Dental Plaque / Q000378:metabolism*; D006801:Humans; D007723:Korea / Q000453:epidemiology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018709:Statistics, Nonparametric; D013295:Streptococcus mutans / Q000302:isolation & purification*; D016986:Streptococcus sobrinus / Q000302:isolation & purification*