你的牙齿有多坚硬？

高齐云

“Did you brush your teeth？” How many times each week do you hear that question？ Do you take good care of your teeth？ Its important to make sure you take good care of your teeth. They make eating and speaking much easier， and you need them your whole life. So thats why youre probably often being asked about your brushing habits.

“你刷牙了吗？”这个问题你每周听到多少次？你好好护理牙齿了吗？确保你好好护理牙齿，这很重要。它们让你吃饭和说话更加容易，你一辈子都需要它们。这就是为什么你可能经常被问到刷牙的习惯。

Have you ever stopped to think about what your teeth are made of？ Theyre very hard. So whats inside of them？ What is it that makes up these things that enable you to chew your way through apples， pizza， and all sorts of other great foods？

你有没有停下来思考过，牙齿是由什么组成的呢？它们很坚硬，那它们里面有什么？是什么能够让你好好咀嚼苹果、披萨饼和各种其他美味食物呢？

Teeth are a lot more complicated than they appear on the outside. The part you can see—called the crown—is just the tip of the iceberg1 when it comes to your teeth. There are all sorts of things going on below the surface！

牙齒比它们表面看起来要复杂得多。你可以看到的部分——称为牙冠——只是你牙齿的冰山一角，下面还有各种各样的东西！

Unlike many of your other body parts， your teeth develop in stages. When you were really young， you began to develop your baby teeth （also called primary teeth）. These 20 teeth help you chew when youre young， but they begin to fall out starting around age five.

与许多其他身体部位不同，牙齿会分阶段发育。当你很小的时候，你就开始长乳牙（也称为初级牙齿）。这20颗牙齿可以帮助你在年幼时咀嚼，但是从五岁时起，它们开始脱落。

As your baby teeth fall out， theyre replaced by your permanent2 teeth. When you finally lose all of your baby teeth around 12 or 13 years， there will be 28 permanent teeth in their place. At last， four more teeth—called wisdom teeth—will grow to complete your full adult set of 32 teeth.

当你的乳牙脱落时，它们会被恒牙所取代。当你最终在12或13年左右的时间里失去所有的乳牙时，它们的位置上会长出28颗恒牙。最终，还会再增加四颗牙齿——称为智齿——来组成你成年时的32颗牙齿。

Although it looks like you can see a lot of your teeth， all you really see is the hard exterior3 known as the crown. The crown is covered with a super-hard， shiny substance called enamel4. The enamel is like body armor for your teeth， protecting their inner parts from damage.

虽然看起来你可以看到很多牙齿，但你真正看到的是坚硬的外表，称为冠。牙冠上覆盖着一种称为牙釉质的超硬且有光泽的物质。牙釉质就像牙齿的防弹衣，保护内部部件免受伤害。

How hard is enamel？ Very hard！In fact， the enamel on your teeth is the hardest substance in your body！Its even harder than your bones.

牙釉质有多硬呢？很硬！事实上，牙齿上的牙釉质是你身体中最硬的物质！甚至比你的骨头更硬。

Underneath the enamel is another hard substance called dentin5. Most of the tooth is made up of dentin. Dentin isnt quite as hard as enamel， but its still quite hard and does a good job of protecting the innermost part of the tooth， called the pulp6. Dentin is about as hard as your bones.

牙釉质下面是另一种叫做牙本质的硬物质。牙齿的大部分由牙本质组成。牙本质并不像牙釉质那么坚硬，但它仍然非常坚硬，而且能够很好地保护牙齿的最内部，称为牙髓。牙本质和骨头一样硬。

The soft pulp is where the tooths nerve endings can be found. Its also where the bodys blood supply connects to the tooth to deliver necessary nutrients7. If your teeth hurt from biting into something hot （or cold） or a cavity， its the nerve endings in the pulp that sense the pain and send messages to your brain about whats going on with your teeth.

柔软的牙髓是牙齿神经末梢的所在之处。它也是身体血液供应连接到牙齿，以提供所需营养的地方。如果你的牙齿因咬热的（或冷的）或龋洞而受伤，那就是牙髓中的神经末梢感知到疼痛，并向你的大脑传递有关牙齿状况的信息。

The pulp reaches all the way under the gums8 to the root of the tooth. A tooths roots are made up of a substance called cementum9， which anchors10 each tooth to the jawbone.

牙髓一直顺着牙龈下面延伸到牙根。牙齿的根部由称为牙骨质的物质组成，该物质将每颗牙齿固定在颚骨上。

Now that you know a bit more about what makes up your teeth， you might want to know why theyre so important. Not only do they help you chew your food， but they also help you talk. Its true！If you think about the words you speak， youll realize that many sounds you make every day are formed by the way your teeth interact with your lips and tongue.

現在你已经了解了许多关于牙齿构成的信息，你可能想知道为什么它们如此重要。它们不仅可以帮助你咀嚼食物，还可以帮助你说话。这是真的！你想想自己说的话，会发现每天发出的许多声音都是由牙齿与嘴唇和舌头相互作用形成的。

Questions：

[1]Do you think it is important to protect our teeth？ （你觉得保护我们的牙齿重要吗？）

[2]What should we do to protect our teeth？ （我们要怎么做才能保护好牙齿呢？）

欢迎投稿！

同学们对上面的问题有什么想法呢？快快来稿同我们分享你的感想和故事吧！你的稿件将有机会在我们的“寒窗心语”栏目中刊登并向大家展示！

[投稿须知]

1. 英文60～150词左右;

2. 电子稿件内请附上你的中文简介，包括：就读学校、年级、班级、姓名、兴趣等，以及生活照一张;

3. 电子稿件内请留下你的联系方式，以便我们在采用稿件后和你联系并寄送样刊;

4. 电子稿件请发至邮箱：814951191@qq.com，邮件名注明“七年级寒窗心语”。