The outer white layer of the tooth, the enamel, is the hardest material in the human body due to its very high mineral content. Tooth enamel is composed primarily of minerals, mostly hydroxyapatite.
There are many views on the subject of fluoride in toothpaste - both among adults and children. Fluoride is considered indispensable in dentistry. If there is enough of it in the toothpaste, it prevents tooth decay and hardens the tooth enamel.