高齊云

“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.

“你刷牙了嗎？”這個(gè)問題你每周聽到多少次？你好好護(hù)理牙齒了嗎？確保你好好護(hù)理牙齒，這很重要。它們讓你吃飯和說話更加容易，你一輩子都需要它們。這就是為什么你可能經(jīng)常被問到刷牙的習(xí)慣。

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？

你有沒有停下來思考過，牙齒是由什么組成的呢？它們很堅(jiān)硬，那它們里面有什么？是什么能夠讓你好好咀嚼蘋果、披薩餅和各種其他美味食物呢？

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！

牙齒比它們表面看起來要復(fù)雜得多。你可以看到的部分——稱為牙冠——只是你牙齒的冰山一角，下面還有各種各樣的東西！

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.

與許多其他身體部位不同，牙齒會(huì)分階段發(fā)育。當(dāng)你很小的時(shí)候，你就開始長(zhǎng)乳牙（也稱為初級(jí)牙齒）。這20顆牙齒可以幫助你在年幼時(shí)咀嚼，但是從五歲時(shí)起，它們開始脫落。

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.

當(dāng)你的乳牙脫落時(shí)，它們會(huì)被恒牙所取代。當(dāng)你最終在12或13年左右的時(shí)間里失去所有的乳牙時(shí)，它們的位置上會(huì)長(zhǎng)出28顆恒牙。最終，還會(huì)再增加四顆牙齒——稱為智齒——來組成你成年時(shí)的32顆牙齒。

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.

雖然看起來你可以看到很多牙齒，但你真正看到的是堅(jiān)硬的外表，稱為冠。牙冠上覆蓋著一種稱為牙釉質(zhì)的超硬且有光澤的物質(zhì)。牙釉質(zhì)就像牙齒的防彈衣，保護(hù)內(nèi)部部件免受傷害。

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.

牙釉質(zhì)有多硬呢？很硬！事實(shí)上，牙齒上的牙釉質(zhì)是你身體中最硬的物質(zhì)！甚至比你的骨頭更硬。

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.

牙釉質(zhì)下面是另一種叫做牙本質(zhì)的硬物質(zhì)。牙齒的大部分由牙本質(zhì)組成。牙本質(zhì)并不像牙釉質(zhì)那么堅(jiān)硬，但它仍然非常堅(jiān)硬，而且能夠很好地保護(hù)牙齒的最內(nèi)部，稱為牙髓。牙本質(zhì)和骨頭一樣硬。

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.

柔軟的牙髓是牙齒神經(jīng)末梢的所在之處。它也是身體血液供應(yīng)連接到牙齒，以提供所需營(yíng)養(yǎng)的地方。如果你的牙齒因咬熱的（或冷的）或齲洞而受傷，那就是牙髓中的神經(jīng)末梢感知到疼痛，并向你的大腦傳遞有關(guān)牙齒狀況的信息。

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.

牙髓一直順著牙齦下面延伸到牙根。牙齒的根部由稱為牙骨質(zhì)的物質(zhì)組成，該物質(zhì)將每顆牙齒固定在顎骨上。

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(xiàn)在你已經(jīng)了解了許多關(guān)于牙齒構(gòu)成的信息，你可能想知道為什么它們?nèi)绱酥匾?。它們不僅可以幫助你咀嚼食物，還可以幫助你說話。這是真的！你想想自己說的話，會(huì)發(fā)現(xiàn)每天發(fā)出的許多聲音都是由牙齒與嘴唇和舌頭相互作用形成的。

Questions：

[1]Do you think it is important to protect our teeth？ （你覺得保護(hù)我們的牙齒重要嗎？）

[2]What should we do to protect our teeth？ （我們要怎么做才能保護(hù)好牙齒呢？）

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