Curious Kids: My tooth fell out. Why is it so spiky on the bottom?

This is an article from Curious Kids, a series for children. The Conversation is asking kids to send in questions they’d like an expert to answer. All questions are welcome – serious, weird or wacky!

I lost my first tooth on Tuesday. I was fiddling with it while I was watching TV. I had a mouthful of blood! It soon stopped bleeding. When I looked at the bottom of my tooth the edge was very spiky! Can you tell me why? – Nicholas, age 6, North Sydney.

Thanks for the great question, Nicholas.

At around six months of age, babies usually start getting teeth. The first to appear are the thin front teeth, called incisors. New teeth keep erupting from the gums until around two or two-and-a-half years of age. The molars - the flat grinding teeth at the back of the mouth - come up last. In total, you end up with 20 baby teeth.

At around six years of age, the bottom incisors start to loosen. When adult teeth start to grow, they cause the roots of the baby teeth (which are hidden under the gum and hold the teeth to the jaw) to be “eaten away” to make space for the adult teeth working their way up into the mouth.

Soon the roots of the baby teeth are eaten away until they start to get wobbly. Soon it gets so wobbly it gets knocked out when you eat something or brush your teeth. Or you might twist it out while you’re watching TV, just like you did.

There often is some blood because the wobbly tooth is still attached to the gum, so that gets torn when the tooth is lost and it bleeds a little. There often seems to be more blood than there really is because it mixes with your spit.

The edges of your tooth were sharp because when the root of the baby tooth is being eaten away by the growing adult teeth, it tends to start from the middle of the root. Something like a rough shell edge is left when most of the root has been absorbed and the tooth is finally lost.

When you look at an X-ray, you can see that the baby teeth still have most of their roots, so they look very different to your fallen tooth. You can also see that the growing adult teeth don’t have complete roots - they still grow for a while after the tooth erupts into the mouth.

Some people lose teeth a bit earlier and some a bit later than the normal time, but this is usually OK. However, if your first set of teeth start to fall out before you turn five, then it is worth seeing a dentist who is good at treating kids.

Soon, Nicholas, you will start to get new teeth at the back of your mouth. They’re called the first permanent molars and there are four of them, one in each corner.

These teeth will erupt without a baby tooth falling out, as they are appearing in spots that are currently empty. After that happens, you will have 24 teeth, until you start losing more baby teeth when you are nine or 10.

Then you’ll get more molars at the back (these guys are called the second permanent molars) when you are around 12, and then third permanent molars when you are around 18 or so. These ones are often called wisdom teeth.

Baby teeth are really important. They allow you to chew food, have a nice smile, and help keep space for adult teeth. So it is good to avoid lots of sugar and brush your teeth twice a day with fluoridated toothpaste.

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David Manton does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond the academic appointment above.