Fluoride Indeed Helps Against Cavities Because Bacteria Lose Traction on Teeth

Cutting-edge technology was used towards solving the 50-year-old mystery why exactly fluoride in drinking water, toothpastes, or other oral-care products prevents tooth decay.

Karin Jacobs and colleagues explain their findings in a paper available in the journal Langmuir. Despite a half-century of scientific research, controversy still exists over exactly how fluoride compounds reduce the risk of tooth decay. That research established long ago that fluoride helps to harden the enamel coating that protects teeth from the acid produced by decay-causing bacteria. But newer studies already found that fluoride penetrates into and hardens a much thinner layer of enamel than previously believed, lending credence to other theories about how fluoride works.

The report describes new evidence that fluoride also works by impacting the adhesion force of bacteria that stick to the teeth and produce the acid that causes cavities. The experiments - performed on artificial teeth (hydroxyapatite pellets) to enable high-precision analysis techniques - revealed that fluoride reduces the ability of decay-causing bacteria to stick, so that also on teeth, it is easier to wash away the bacteria by saliva, brushing and other activity.

In the past decade, atomic force microscopy (AFM) has been established as a powerful tool in bacterial research. By means of AFM force spectroscopy with bacterial probes, it is possible to study the adhesion force between bacteria and surfaces on a single bacterium level. This microscopic approach is direct and quantitative in contrast to the classical macroscopic flow chamber studies.

The researchers used this force spectroscopy to characterize adhesion on a single bacterial level, testing the adhesion of Streptococcus mutans, Streptococcus oralis, and Staphylococcus carnosus on smooth, high-density hydroxyapatite surfaces, pristine and after treatment with fluoride solution. Indeed, all bacteria species exhibit lower adhesion forces after fluoride treatment of the surfaces.

The authors acknowledge funding from the German Science Foundation (DFG) and the Federal State of Saarland.

Reference:

"Reduced Adhesion of Oral Bacteria on Hydroxyapatite by Fluoride Treatment"
Langumir