Sodium fluoride

The prevention of dental caries by topical fluoride is achieved by various mechanisms. Sodium fluoride kills bacteria that cause caries, such a Streptococcus mutans and lactobacilli by interfering with their metabolic activities that result in the formation of lactic acid. Fluoride ions cause the inhibition of glycolytic and other enzymes involved in bacterial metabolism. It changes the permeability of cell membranes, lowering the pH in the cytoplasm of the cell, leading to a decrease in acidity, which is normally implicated in tooth decay.

When administered at low topical doses, fluoride in both saliva and plaque and saliva prevent the demineralization of healthy tooth enamel while remineralizing teeth that have previously been demineralized. Sodium fluoride is absorbed by the surface of hydroxyapatite crystals on the teeth, which are necessary for mineralization. This renders the teeth more resistant to demineralization by changing the apatite crystal solubility. Sodium fluoride inhibits the demineralization of teeth in a pH-related manner. When used in high doses, in formulations such as the fluoride varnishes or gels, sodium fluoride forms a layer on the surface of tooth enamel. When the pH of the mouth is reduced due to acid production by bacteria such as S.mutans, fluoride is released, interfering with bacterial metabolism, and then acts to remineralize the teeth.