Teeth can be the hardest organ in our body, thanks to a mineral called hydroxyapatite Ca10(PO4)6(OH)2. It is the main component of tooth enamel and dentin, particularly in the outermost layer of enamel, which is the hardest part of the tooth. However, strong teeth have a weakness: they are afraid of acid! After we finish eating, a small amount of food residue sticks to the gaps between our teeth. The carbohydrates in this residue are broken down by certain bacteria in the mouth to produce acidic substances, which can dissolve the hydroxyapatite in our teeth. When the acidity in the mouth reaches a critical value, that is, a pH value lower than 5.5, the dissolution of hydroxyapatite will gradually erode the enamel and dentin, leading to cavities.
Fluoride toothpaste contains a certain amount of fluoride-containing ionic compounds, such as sodium fluoride, stannous fluoride, and sodium monofluorophosphate. When we brush our teeth, the fluoride in the toothpaste comes into contact with the tooth surface. The fluoride in the toothpaste reacts with the hydroxyapatite in the enamel, exchanging ions with the hydroxide anions to form acid-resistant fluorapatite Ca10(PO4)6F2, which effectively enhances the tooth's resistance to acid erosion and helps prevent cavities.
Although fluoride is a trace element needed by the human body, daily intake should not be excessive. Long-term excessive intake of fluoride can cause chronic fluoride poisoning, such as fluorosis or fluoride spots. Therefore, when using fluoride toothpaste to brush our teeth, we should not use too much toothpaste. After brushing, we should rinse our mouth thoroughly to completely remove the residual toothpaste in our mouth and avoid swallowing the toothpaste and mouthwash.