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Humans may be no less a part of the animal kingdom than lions,tigers and bears, but certain things set us apart.
或許人類的動物屬性一點也不比獅子、老虎和熊少，但某些特征卻將我們與它們區別開來。
For instance,although like our mammalian cousins we use teeth to bite and chew food,we're the only animals that brush after every meal.
舉例來說，雖然我們與其他哺乳動物一樣用牙齒撕咬和咀嚼食物，但我們是唯一餐后刷牙的動物。
And as four out of five dentists have reminded us on countless television commercials, using one or another variety of toothpaste is crucial for keeping our teeth healthy.
正如五個牙醫中會有四個在數不勝數的電視商業廣告中一直提醒我們的那樣，使用不同種類的牙膏對保持牙齒健康至關重要。
Like that fifth dentist who never seemed to know what was going on, you might have wondered what toothpaste actually is, and how it helps ward off tooth decay.
像永不情知的的第五個牙醫一樣，你可能會疑惑，牙膏到底是什么，它又如何幫助我們避免齲齒。
Toothpaste consists of several ingredients, some of which you'd never think to put in your mouth.
牙膏含有多種成分，有一些你可能從未想過要把它們放進嘴里。
For example, almost all toothpaste contains detergent, or soap.
比方說，幾乎所有的牙膏都含有清潔劑或肥皂。
Getting your mouth washed outwith soap is supposed to be punishment, so what is it doing in toothpaste?
直接用肥皂清潔嘴巴是一種懲罰，那么牙膏中含有的肥皂是如何清潔牙齒的呢？
Although it has a slight antibacterial effect, it's there mainly to make foam, which serves little purpose other than to provide a visual sign to the brusher that the toothpaste is hard at work fighting cavities.
盡管肥皂有輕微的抗菌作用，但它主要是制造泡沫，這些泡沫除了向刷牙的人傳遞牙膏能有效抗擊齲齒的視覺信號外毫無作用。
Of course some ingredients play a more active role, the most famous of which is fluoride, a mineral compound derived from the element fluorine.
當然牙膏里有一些成分在發揮著更為積極的作用，當其中最廣為人知的還是氟化物，這是一種從氟元素中提取出來的無機化合物。
Fluoride protects teeth in two ways: it kills acid-producing bacteria which are mainly responsible for tooth decay, and it strengthens and repairs tooth enamel that has been softened by the acid.
氟化物以兩種方式保護牙齒：首先，它能夠殺死齲齒元兇-造酸細菌；另外，它還可以固化、修復被酸軟化的牙釉質。
So far as we know, the only drawback to using toothpaste is that it makes drinking orange juice after brushing a pretty unpleasant taste experience.
據我們所知，使用牙膏的唯一缺點在于：它使人們刷牙后飲用橙汁成為一種相當不悅的味覺體驗。
But that's a small price to pay for healthy teeth.
但這只是為牙齒健康付出的一點小小代價。
