Fluoride and Teeth

Fluoride and Teeth

BY : Rhiannon Nevinczenko

Brushing one's teeth is an automatic habit for most of us. As adults, we have forgotten how strange and uncomfortable it was when we started brushing in childhood. Some children are highly resistant to brushing their teeth. As a parent, convincing a child to stand in front of the mirror doing something repetitive, boring, and perhaps uncomfortable for the longest-two-minutes-ever twice a day can be a hard sell. It can be an even harder sell if you don't fully understand why it is necessary yourself, leaving you to rely on the tried-and-true (but ultimately unsatisfying), "Because I'm your parent and I said so."
So, why do we need to brush our teeth?
Chemistry is part of every day life (as it deals with the properties of matter). Even something as simple as brushing your teeth involves chemistry. You likely know the top layer of your teeth to be made of enamel, the hardest mineral in your body. Unfortunately, this does not make it fully impervious to the general tendency of things to dissolve in strong enough acid. Hydroxyapatite is the mineral material that is the foundation of the vast majority of tooth enamel, and will break down or dissolve if in an environment that is too acidic (i.e., has a pH of 5.5 or lower). You may have noticed, after chewing a few too many pieces of bubble gum perhaps, a nasty film on your teeth. This biofilm is a sign that the normal, natural bacteria in your mouth have been given too much sugar (or other fermentable carbs), allowing them to feast and reproduce very quickly. As the bacteria take advantage of your microscopic leftovers, they ferment the sugar, producing acid as a by-product, decreasing the pH of your mouth, and endangering your enamel. This biofilm constitutes a major part of the plaque you are supposed to brush off daily. If left alone, however, the hydroxyapatite crystals in your enamel will begin to break down, resulting in holes (cavities), cracks, and eventually far worse fates (pain, tooth decay, and tooth loss).
Okay, so brushing your teeth puts a dent in the bacterial population. Why, though, do we use fluoridated toothpaste?
Because the pH of your saliva shifts throughout the day, your teeth go through a normal cycle of mild demineralization and remineralization. In a more acidic environment, the hydroxyapatite crystals disintegrate. As the pH returns to neutral or alkaline, the crystals come back together. Hydroxyapatite is made of calcium ions, phosphate ions, and hydroxyl groups. If fluoride is present during remineralization, it replaces the hydroxyl groups, creating a different crystal: fluorapatite. Fluorapatite is much hardier than hydroxyapatite, and more resistant to demineralization. In other words: You won't lose as much enamel to bacteria and acid if some of it is made of fluorapatite!
It is prudent to note, however, that if too much of your enamel is made of fluorapatite, you will experience a different kind of tooth damage. Likewise, fluoride in water is toxic at high doses. The dose makes the poison, and balance is the key. Products made to protect your teeth are produced at safe doses, so long as instructions are followed.
Image credit: Greta Hoffman via Pexels. Pexels license.

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