What Are Teeth Made Of?

Teeth look simple from the outside. Hard, white, you bite into an apple, done thinking about it. But under that surface there’s actually a few layers, and each one is doing something different.

Mostly it’s mineral. A big chunk of a tooth is calcium and phosphate compounds, which is where the strength comes from. There’s protein and water mixed in too, more so in the softer inner parts.

The Hard Outer Layer

Enamel is what you’re actually looking at on a healthy tooth. It covers the crown, and it happens to be the hardest substance in the human body. Harder than bone, believe it or not.

Enamel is mostly a mineral called hydroxyapatite. Its crystal structure is built from calcium and phosphate, which explains why those two minerals get talked about so much when it comes to strong teeth. There’s a little water and protein in there too, but the mineral’s doing nearly all the work.

Enamel has no living cells in it, which means once it’s seriously damaged, it doesn’t grow back. That’s really the whole reason cavities need attention rather than just hoping they’ll sort themselves out.

Why Enamel Matters

It’s almost entirely mineral, and hydroxyapatite is what gives teeth that tough outer shell. It’s extremely hard, but acid is basically its one weakness, acid from your mouth slowly pulls minerals right out of it over time. And because there are no living cells inside enamel, your body has no way to rebuild a section once it’s gone.

What’s Under the Enamel?

Underneath sits dentin. Still hard, but nowhere near as hard as enamel, and it’s got a slightly yellow tint, which is honestly why natural teeth were never going to be bright white all the way through no matter how much you brush.

Dentin has minerals plus a protein called collagen running through it. It’s also full of these tiny tubes that lead toward the inner part of the tooth, which is exactly why temperature changes or pressure can sometimes reach the nerve and cause that jolt of sensitivity.

What About the Root?

Enamel isn’t what holds a tooth in your jaw. The roots are covered by a thin layer called cementum, and that’s what helps anchor the tooth to the tissue around it.

Below the root you’ve got more dentin, and the pulp continues down through the root canals, carrying tiny blood vessels and nerves along with it.

So Why Do Teeth Get Weaker?

Your mouth’s a busy place. Bacteria feed on sugar and produce acid as a byproduct. That acid strips minerals out of enamel. Saliva helps put some of those minerals back, which is honestly one of the more underrated things saliva does, it’s not just there to keep your mouth wet.

Fluoride helps too, it strengthens enamel against acid and supports remineralisation. Brushing twice a day with fluoride toothpaste is one of those boring habits that genuinely earns its keep.