Teeth are composed mainly of hard tissues. The hardest part of the teeth is the enamel.
The enamel itself even though very compact and resistant is being attacked by the acids that foods as sugars mainly produce.
This process leads to demineralization of the hard tissues which can result as a dental caries.
It is well known that fluoride in water even though sometimes when in high concentrations causing discoloration of the teeth leads to dental caries resistance. So, what is the cause? Fluoride connects with the hydroxyapatite crystals of the enamel thus replacing the hydroxide ions and stabilizing the structure of the molecule making it more resistant to acid.
Studies had concluded that treating teeth locally with fluoride toothpastes increase the amount of fluorapatite in the enamel as well as that these toothpastes are completely safe. So, using fluoride toothpastes is safe and leads to a lower risk of tooth decay.