Name: 人間が歯を再生できない理由 (Why Humans Can't Regrow Teeth)
Uploaded: 2021-01-14T08:08:44.000Z
Duration: 3 min 13 s
Description: VoiceTubeの動画で発音を聞きながら英語表現を覚えよう！学べる英語：

- [Narrator] Humans need dentists. It's a fact.

Americans spent $129 billion on dental visits,

and an estimated 90% of adults in the US have fillings.

replacing old damaged ones with brand new pearly whites.

Wouldn't it be great if you could do that?

Well, there's actually an important trade-off

Only a handful of mammals can regrow teeth multiple times

compared to the 50,000 species of reptiles and fish.

They replace all 100 or so teeth every three to four months,

and since geckos can live for six to 10 years,

That's all thanks to a special type of cell in their gums

Stem cells are handy because they can morph into different

like tooth stem cells to build new teeth.

Humans have these stem cells when we're younger,

To understand why, let's take a journey back in time

to about 320 million years ago when mammals

another change that eventually emerged was tooth shape.

Reptiles, for example, are what's called generalists,

meaning they eat the animals they can get their teeth on.

And for that, they needed teeth with the same size and shape

Mammals, on the other hand, developed more specific diets,

like grazers who only eat grass and hunters who rip flesh

As a result, mammals evolved different-shaped teeth

And it's this difference that could also explain

Now, let's say you could regrow your molars multiple times, for example.

It's important that the top and bottom sets match up.

Otherwise, they can't grind food as efficiently.

That sounds good in principle, but with each new set,

there's a risk that the regrown teeth won't line up.

So the leading theory is that adult humans can't regrow

our teeth because it was better for survival

However, if you still wish you could regrow a tooth,

Using lasers and drugs, scientists have helped rats and mice

regrow damaged tissue in cavity-ridden teeth

with the idea that if you could regrow tooth tissue,

you could eventually regrow entire teeth,

though no human testing has been done on that yet.

So keep flossing and keep seeing your dentist.

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人間が歯を再生できない理由 (Why Humans Can't Regrow Teeth)

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