時(shí)差N小時(shí):我們?yōu)槭裁匆⒀? Why Do We Need To Brush Our Teeth?
或許人類的動(dòng)物屬性一點(diǎn)也不比獅子、老虎和熊少，但某些特征卻將我們與它們區(qū)別開(kāi)來(lái)。
For instance,although like our mammalian cousins weuse teeth to bite and chew food, we're the onlyanimalsthat brush after every meal.
舉例來(lái)說(shuō)，雖然我們與其他哺乳動(dòng)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(dòng)物。
And as four out of five dentists have reminded us oncountless television commercials, using oneor another variety of toothpaste is crucial forkeeping our teeth healthy.
正如五個(gè)牙醫(yī)中會(huì)有四個(gè)在數(shù)不勝數(shù)的電視商業(yè)廣告中一直提醒我們的那樣，使用不同種類的牙膏對(duì)保持牙齒健康至關(guān)重要。
Like that fifth dentist who never seemed to know what was going on, you might havewonderedwhat toothpaste actually is, and how it helps ward off tooth decay.
像永不情知的的第五個(gè)牙醫(yī)一樣，你可能會(huì)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 yourmouth.
牙膏含有多種成分，有一些你可能從未想過(guò)要把它們放進(jìn)嘴里。
For example, almost all toothpaste contains detergent, or soap.
比方說(shuō)，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 intoothpaste?
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 serveslittlepurpose other than to provide a visual sign to the brusher that the toothpaste is hard atworkfighting 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(jué)信號(hào)外毫無(wú)作用。
Of course some ingredients play a more active role, the most famous of which is fluoride, amineralcompound derived from the element fluorine.
當(dāng)然牙膏里有一些成分在發(fā)揮著更為積極的作用，當(dāng)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(lái)的無(wú)機(jī)化合物。
Fluoride protects teeth in two ways: it kills acid-producing bacteria which are mainlyresponsible for tooth decay, and it strengthens and repairstooth enamel that has been softenedby the acid.
氟化物以兩種方式保護(hù)牙齒：首先，它能夠殺死齲齒元兇-造酸細(xì)菌;另外，它還可以固化、修復(fù)被酸軟化的牙釉質(zhì)。
So far as we know, the only drawback to using toothpaste is that it makes drinking orangejuiceafter brushing a pretty unpleasant taste experience.
據(jù)我們所知，使用牙膏的唯一缺點(diǎn)在于：它使人們刷牙后飲用橙汁成為一種相當(dāng)不悅的味覺(jué)體驗(yàn)。
But that's a small price to pay for healthyteeth.
但這只是為牙齒健康付出的一點(diǎn)小小代價(jià)。
