Something exciting is happening in our house. Mr six-years-old has his first wobbly tooth.
While he's been busy planning how he can stay awake long enough to catch the tooth fairy in action, I've been reading up about teeth, so I can answer all his questions about his deciduous dentition.
Just like most kids, mine was born with no teeth. And, just like most kids, when he was around six months old he started the painful process of getting his first teeth. Baby teeth, deciduous teeth, milk teeth - whatever you want to call them, now, at age six, he's ready to start losing 'em.
So why do we have two different sets of teeth? Baby teeth are the perfect size for little mouths, allowing kids to start eating all sorts of solid foods.
The reason those baby teeth become wobbly isn't just because adult teeth are pushing up from underneath.
But these first teeth aren't that strong - not strong enough for a lifetime of chewing. So, as kids get bigger, these baby teeth need to be replaced by a set that matches a bigger mouth and jaw. A set that is strong enough to last us (hopefully) our whole lives. So we lose them.
Have you ever thought about how these baby teeth come out? I've polled a few of my friends, and they've all told me the same thing - that adult teeth start to grow up under 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 up 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 eventually falls out, leaving a lovely little pathway for the adult tooth to follow to the surface.
There are a special type of cells, called odontoclasts, that are responsible for this process. Odontoclasts are formed from progenitor cells. As the new adult tooth grows beneath the baby tooth, this sends signals to these progenitor cells to turn into odontoclasts. And these newly formed odontoclasts go to work on the root of the baby tooth.
It's completely normal for this resorption to happen to the roots of our baby teeth. But it can also sometimes happen to adult teeth - which is a pretty serious problem. Sometimes things like trauma 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 as us, 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.
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