Quantitative detection of Streptococcus mutans and bacteria of dental caries and no caries groups in permanent teeth from a north China population

Background Streptococcus mutans （S. mutans） is the prime pathogen of dental caries. There are few reports that studied the relationship between S. mutans, bacteria and dental caries in permanent teeth when compared to those in primary teeth. This study aimed to detect S. mutans and bacteria of dental caries and non-caries groups in permanent teeth from a north China population by real-time polymerase chain reaction （PCR） and compare the relationship between the number of these bacteria and the prevalence of dental caries in permanent teeth.