Does toothpaste affects oral microbiota?
Toothpaste prevents cavities and demineralization of enamel without affecting the composition of the oral microbiota but rather by modifying its production of acid or sugars, or the balance between remineralization and demineralization.
Sodium fluoride has been used in toothpastes and mouthwashes for more than 70 years. It has made a significant contribution to the fight against cavities, without its mode of action being precisely known. To this day, the underlying mechanisms are still the subject of multiple hypotheses: inhibition of microbial carbohydrate metabolism, reduction of acid production, inhibition of the demineralization of enamel, stimulation of the mineralization of enamel… To understand the mechanism of action of this chemical compound, two Swiss researchers examined its effects on the oral microbiota, pH and demineralization.
Creation of biofilms
The experiment was conducted in vitro: biofilms similar to those encountered in the oral microbiota were created and cultured on discs soaked with saliva. After 48 hours and various manipulations, the discs were exposed either to sodium fluoride at different concentrations (doses corresponding approximately to those used for a young child, a child and an adult), or to fluoride-free solutions. To assess demineralization, the impact of sodium fluoride was tested on discs of bovine enamel.
A stable microbiota
After 64 hours, neither the vitality nor the growth of the microbiotas were affected (or only very slightly) by sodium fluoride at concentrations used in everyday life (child and adult brushing). The number of bacteria was not impacted either. No demineralization of enamel was observed, while acidity was controlled, with an increase in pH to 5.5 and 5.0 respectively, compared with 4.5 in the control dishes. Moreover, the volume of sugars in the biofilm decreased significantly.
The authors conclude that these results show that sodium fluoride prevents demineralization of dental enamel without affecting the composition nor the growth of the biofilm. They suggest that its use could lead to a decrease in the production of acid or sugars by biofilm bacteria, or a modification of the demineralization/remineralization balance.
Thomas Thurnheer, Georgios N. Belibasakis, Effect of sodium fluoride on oral biofilm microbiota and enamel demineralization. Archives of Oral Biology 89 (2018) 77-83