Why do we have two different sets of teeth?

Why do we have two different sets of teeth?

Over the last few weeks, my kid has lost not one, but three of his teeth. I'm beginning to think it's his own personal attempt to bankrupt the tooth fairy.

Baby teeth, deciduous teeth, milk teeth - whatever you want to call them - it's clearly time for them to go.

But why do we even have two different sets of teeth?

Baby teeth are the perfect size for little mouths, allowing kids to start eating solid foods. But they aren't that strong - not strong enough for a lifetime of chewing.

As we grow, those baby teeth need to be replaced by a set that fits a bigger mouth and jaw, and that are strong enough to last us (hopefully) our whole lives.

Have you ever thought about how these baby teeth come out?

The common understanding is that adult teeth start to grow beneath the baby teeth, and simply push them out. Which is kind of true ... but also not the whole story.

The reason those baby teeth become wobbly isn't just because adult teeth are pushing from underneath.

They become wobbly because they're slowly undergoing a process of resorption - where the root of the tooth is basically dissolved and reabsorbed by our bodies. Our own bodies eat away at the roots, until the tooth no longer has a solid foundation.

It becomes loose, and falls out, leaving a nice pathway for the adult tooth to follow to the surface.

A special type of cell, called odontoclasts, are responsible for this process. Odontoclasts are formed from progenitor cells.

As adult teeth grow beneath baby teeth, this sends signals to these progenitor cells to turn into odontoclasts. The newly formed odontoclasts go to work on the root of the baby tooth.

It's completely normal for this resorption to happen to our baby teeth. But it can also sometimes happen to adult teeth - which is a pretty serious problem.

Things like an injury can trigger the formation of odontoclasts, which can start to break down the structure of the adult tooth. Which means a trip to the dentist.

Humans aren't alone in this whole shedding teeth business.

Most mammals are like us. Your dog, your cat, your horse - they all do the same, growing a set of milk teeth and later replacing these with adult teeth.

But I've never yet heard a puppy or kitten trying to negotiate the value of a lost tooth with the tooth fairy.

Dr Mary McMillan is a senior lecturer at the School of Science and Technology, University of New England.

This story Why do we have two different sets of teeth? first appeared on The Canberra Times.