Dental plaque as a refuge for caries

Researchers from the Clinic for Preventive and Oral Dentistry and the Department of Biomedical Engineering at the University of Basel have produced a study on the preservation of caries-causing bacteria and how they can survive due to dental plaque. The study has been published in the journal PLOS ONE. According to it, extracellular polysaccharides would play a key role in the preservation of these bacteria.

When sugar and starch are converted into acids that wear down the enamel, cariogenic bacteria, which reside in the biofilm, have the ability to damage our oral health. This process can also lead to tooth decay. On the other hand, the dissolution of calcium increases the concentration of calcium locally and creates an environment that is hostile to bacterial life.


EPS are substances that form extracellular cariogenic bacteria by means of sugar residues. They create the biofilm scaffold and ensure that bacteria can attach themselves to the dental plaque. EPS integrate calcium into the biofilm.

Research has shown that calcium tolerance and preservation capacity in the biofilm increase the more cariogenic bacteria are dissolved. The scientists thus prove that the cariogenic bacteria develop processes to help them survive high calcium concentrations.

Because the extracellular polysaccharides possess a high number of binding sites, they can integrate free calcium into the biofilm. This equalizes the toxic substance and stiffens the EPS structure of the biofilm.

Data of Interest

The use of EPS to integrate calcium also leads to caries. It inhibits enamel remineralization, as there is not enough free calcium present in the plaque. “This discovery is important to gain a better understanding of calcium regulation in caries,” says microbiologist Monika Astašov-Frauenhoffer.