You sleep at night with your milk tooth beside your bed or under your pillow forthe tooth fairy to come and take it and give you a gift in return. Ever wondered whydo you have these brittle1 milk teeth， which we lose as we grow up？

晚上睡覺時，你把乳牙放在床邊或枕頭下，讓牙仙來取走它，并給你一份禮物作為回報。你有沒有想過為什么你會有這些隨著年齡的增長而換掉的易碎的乳牙？

Why are they called Milk Teeth？

為什么叫乳牙？

We all have milk teeth during the process of growing up. They are the first set ofteeth that come out. When a baby is born， it is born without any teeth， since the skull2and the jaws3 of the baby are not yet developed. As the baby grows， the skull and jawbegins to develop. Thus， the first set of teeth or the milk teeth start to come out. Buteven then， the skull and jaw of a child is still developing. It is not yet developed as inthe case of adults. Thus， the milk teeth start falling at the age of 6 or 7.

我們成長的過程中都有乳牙。它們是長出來的第一副牙齒。一個嬰兒出生時并沒有牙齒，因為嬰兒的頭骨和下頜還沒有發(fā)育。隨著嬰兒的成長，嬰兒的頭骨和下頜開始發(fā)育。因此，第一副牙齒或乳牙開始長出來。但即便如此，兒童的頭骨和頜骨仍在發(fā)育中。它還沒有像成年人那樣發(fā)育成熟。因此，乳牙在6、7 歲時開始脫落。

Milk teeth， when they fall， provide the space and guide the permanent4 teeth toerupt5. The milk teeth shape the jaw bones and muscles. Thus when they fall off，they leave that space for the permanent teeth to grow in and give the jaw bones andmuscles the correct structure6. Therefore， milk teeth help in developing the oralcavity7 of a child. Milk teeth also help in the development of a child’s speech andin chewing food. The roots of these milk teeth provide a solid8 space and structurefor the permanent teeth to grow.

乳牙脫落時，為恒牙提供空間，引導(dǎo)恒牙長出。乳牙塑造了頜骨和肌肉的形狀。因此，當(dāng)它們脫落時，它們會為恒牙的生長留下空間，并賦予頜骨和肌肉正確的結(jié)構(gòu)。因此，乳牙有助于兒童口腔的發(fā)育。乳牙還有助于兒童的言語發(fā)育和咀嚼食物。乳牙的根部為恒牙的生長提供了堅實的空間和結(jié)構(gòu)。

The skull of a baby is very small to hold the 32 permanent teeth which adultshave. Thus， a child till the age of 6 will have 20 primary teeth. As they keepdeveloping the jaw， the milk teeth start becoming loose9. Then they eventually fall ofone by one， making way for the permanent teeth to come out. The roots of the milkteeth provide an opening for the permanent teeth to come up， with proper spacingbetween each tooth. Thus at the age of 6 or 7， the jaw of the child is developed andthus the milk teeth start to fall off.

嬰兒的頭骨很小，容納不下成年人的32 顆恒牙。因此，一個6 歲的孩子將會有20 顆乳牙。隨著頜骨的不斷發(fā)育，乳牙開始松動。然后它們最終會一個接一個地脫落，為恒牙的長出騰出位置。乳牙的根部為恒牙的生長提供了一個開口，每顆牙齒之間有適當(dāng)?shù)拈g距。因此，在6、7 歲時，孩子的頜骨發(fā)育成熟，乳牙開始脫落。

What happens after the milk tooth has fallen？

乳牙脫落后會發(fā)生什么？

A permanent tooth starts taking the place of the fallen milk tooth. This toothbegins to push its way up through the gums10. This happens after the age of 6 whenthe child starts developing the first set of incisor11 and molar12 teeth. The two centralincisors or the two teeth on the upper jaw and two on the lower jaw are the first onesto drop and the first set of permanent teeth to come out.

一顆恒牙開始代替脫落的乳牙。這顆牙齒開始從牙齦往上擠。這發(fā)生在6 歲以后，那時孩子開始發(fā)育第一組門牙和臼齒。中間的兩顆門牙，也就是上頜的兩顆和下頜的兩顆，是最先脫落的牙齒，也是最先長出恒牙的位置。

What to do with the fallen milk tooth？

脫落的乳牙怎么辦？

Many countries have many traditions about the fallen milk tooth. The falling offof the primary tooth and gaining the permanent set of teeth is seen as a veryimportant sign of entering into adulthood. In some countries people believe that themilk tooth should be thrown in a specific13 place and a wish should be made. In theWestern countries people believe in leaving the tooth under their pillows at night orbury them in the ground， and the tooth fairy will come and collect it， giving some giftin return.

關(guān)于脫落的乳牙，許多國家有不同的傳統(tǒng)。乳牙的脫落和恒牙的長出被認(rèn)為是進(jìn)入成年的一個非常重要的標(biāo)志。在一些國家，人們認(rèn)為應(yīng)該直接把乳牙扔在一個特定的地方，然后許愿。在西方國家，人們相信晚上把乳牙放在枕頭下或埋在地下，牙仙會來收集它，并給一些禮物作為回報。

Fun Facts about Milk Teeth

關(guān)于乳牙的有趣事實

On an average， we lose 14 milk teeth from the age of 6 to 13—seven from the upper and seven from the lower jaws.

If your milk tooth is loose， never try to pull it out. Let it take its own time to come out and leave the roots undamaged.

Humans have 20 milk teeth and 28 to 32 permanent teeth. Mammals14 likedogs and cats have two sets of teeth—one is their entire set of baby teeth which theylose in a few months， and next is their entire new set of permanent teeth.

Dolphins and other whales have only one set of teeth.

平均而言，我們在 6 歲到 13 歲之間會掉 14 顆乳牙———上頜和下頜各 7顆。

如果你的乳牙松動了，千萬不要試圖把它拔出來。讓它自己慢慢脫落，從而讓它的根不受傷害。

人類有20 顆乳牙和28 到32 顆恒牙。像狗和貓這樣的哺乳動物有兩副牙齒———一副是它們在幾個月內(nèi)會脫落的全部乳牙，另一副是它們?nèi)碌暮阊馈?/p>

海豚和其他鯨魚只有一副牙齒。