Measuring the Relationship between S. mutans Levels and Dental Caries Severity in Patients

Bacteria living in the oral cavity, such as Streptococcus mutans, can ferment sugars to produce acids, which can damage teeth. Dental caries currently affects more than two billion people worldwide. Consensus has not yet been reached regarding how strongly S. mutans contributes to dental caries: some researchers reason that S. mutans is the primary contributor to dental caries, while others claim that other species may also be significant contributors. The purpose of this study was to determine if there was a correlation between the S. mutans UA159 concentration and the plaque index in 24 patients at the Missouri Southern Dental Hygiene Clinic. S. mutans DNA was extracted from each dental plaque sample. A qPCR assay was used to quantify levels of dexA, a gene coding for dextranase, which hydrolyses glucans in plaque. The concentration of dexA correlated with the concentration of S. mutans in each sample. We hypothesized that there would be a strong correlation between the S. mutans level and dental caries severity. Linear regression analysis indicated that there was no correlation between the S. mutans concentration and plaque index (R² = 0.0248). There was no correlation between the threshold cycle value and plaque index (R² = 0.0039). Our results suggest that other S. mutans strains or bacterial species contributed more strongly to dental caries than did S. mutans UA159.