You might have noticed a bunch of hard things sitting in your mouth. Theses are called teeth. Ring a bell? Good. Teeth are pretty useful, you know, with that whole “make it possible for us to eat anything tougher than a milkshake” thing. From apples to ice cream, fudge to dad’s overcooked meatloaf, teeth are perfect for helping us devour every last morsel we decide to shove down our necks. So teeth are cool to have, no-one’s arguing that, but just how do they do what they do? What makes up a tooth, and just how tough are they?
In order to get through the crust of that meatloaf Dad left in the oven half an hour too long, teeth have to be strong. That strength is all down to their finely tuned design, perfected over the ages, which has the shape and strength to cut, pierce, grind and chew all manner of foods.
We have several types of teeth, all designed for different uses, but they’re all made of the same stuff. On the outside you have enamel. Most of us have heard of this, as it’s what we have to keep in top condition to stop anything nasty getting down into the more sensitive parts of the tooth. Enamel is seriously hard, harder than steel in fact. The Mohs scale is what we use to measure the hardness of a substance, and teeth rate a pretty impressive 5 out of 10 on the scale. That might not sound so amazing, but considering that the substance at the very top of the table is diamond, it’s not half bad. Let’s put this in perspective shall we? Your body is chock full of bones; you’d expect them to be the hardest thing in there wouldn’t you? Wrong! Enamel is the hardest substance in your body: harder than your skull or femur or anything else you'd care to name.
Here’s a few things human teeth are harder than:
Enamel is seriously hard, but it's also very brittle. In fact, enamel is almost as brittle as glass! I can hear you scoffing in derision, but hear me out. Enamel is indeed brittle, but if it were as easily broken as glass we’d all have mouthfulls of shattered teeth within a few days. Obviously, teeth are more resistant than a beer bottle thrown against a brick wall, and it turns out that’s down to the way they’re put together. Tooth enamel has a basketweave-like microstructure. What does this mean? This specialised structure prevents cracks that appear in the enamel from spreading throughout the tooth and shattering it. While the enamel is brittle and is frequently cracked, these cracks are localised. Researchers who examined the teeth of the elderly were surprised by how many cracks were present, yet the teeth remained intact. This is thanks to the basketweave microstructure.
Teeth aren’t just tough in terms of strength, they’re also incredibly resistant to heat. To go down a slightly gruesome path for a minute, there’s a reason dental records are such an important tool of identification when a body has been damaged beyond recognition. Teeth can survive heat of almost 900 degrees celsius, meaning they can survive even the most grievous of disasters.
Underneath the enamel is a substance known as dentin. Okay, so it’s not quite as hard as enamel, rating at just a 3 on the Mohs scale, but it’s still an important structural component of the tooth. Dentin surrounds and protects the pulp of the tooth, where the nerves and blood supply are located. If you let a cavity extend far enough, it will reach these nerves and they'll quickly let you know that something isn’t quite right in your mouth.
Now, human teeth are pretty impressive, but there’s an animal out there with an even more incredible set of gnashers. What is it, you ask? A lion? Walrus? Elephant? Wrong, wrong and wrong. It’s a snail. That’s right, a snail, specifically an aquatic snail. You may know them as limpets, those little shells stuck to rocks at the beach. The limpet's teeth are so strong that as they scrape away at the rock they’re attached to, scouring for food, they actually excavate the rock itself and eat it right down. Limpet teeth are so tough, they’re actually the strongest biological material known to man! Though they only measure 5.0-5.5 on the Mohs scale of hardness, their tensile strength is absolutely unmatched, taking a staggering 6.5 gigapascals of force to snap! Humans, as well as all other animals, are apparently inferior to a snail…
Here’s some things Limpet teeth are stronger than:
A lot of evolution has gone into the development of our teeth, and it shows. The result is a substance that can crush bone, survive the heat of the most intense fire and look good doing it. Though human teeth are usurped in the toughness stakes by some of our animal brethren, they’re still pretty impressive in their own right. Just keep them away from their kryptonite: sugar...