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Did you know that there could be more bacteria living in your mouth than there are people on earth?
你知道吗，寄居于你口中的细菌有可能比全世界的人口数还多？

Bacteria love our mouths because the livin’ is easy–there’s plenty of food and water, and a fairly constant temperature of 95 degrees. The vast majority of these bacteria don’t cause any problems. Some even do community service, cleaning out the food between our teeth without harming the teeth at all!
细菌钟爱我们的嘴是因为口腔中的环境很舒适，不仅有充足的食物及水，其温度也稳定在95华氏度。口腔内绝大多数的细菌不会产生什么问题。有一部分甚至是有益的，义务清理牙缝中的食物残渣，保护我们的牙齿！

But there is one type of bacteria that wreaks¹ havoc² in the mouth by causing cavities. Like most people, the bacterium³ streptococcus mutans loves to eat sugar. In the process, it converts sugar to an acid that corrodes⁴ teeth and causes cavities. Saliva⁵ can neutralize⁶ some of that acid and prevent it from damaging teeth.
但是有一种细菌会对口腔形成危害，造成蛀牙。细菌中的变形链球菌与许多人一样喜爱吃糖，通过将糖转化为酸，进而腐蚀牙齿，形成蛀洞。唾液能够中和部分酸以防牙齿被损害。

But these days, most of us eat so much sugar that our saliva can’t neutralize all the acid that streptococcus mutans produces.
然而现在大部分人摄入的糖分过多，以至于唾液无法中和所有的酸，变形链球菌随即而生。
 
What’s a sugar addict⁷ to do?
那么爱吃糖的人该怎么办呢？

If you brush and floss every day, that physically⁸ disrupts the colonies of bacteria enough to keep the populations under control, somewhere between one thousand and one hundred thousand per tooth. The fluoride in toothpaste and tap water hardens tooth enamel⁹, making it more resistant¹⁰ to the acid produced by streptococcus mutans.
如果你每天刷牙并使用牙线清理牙齿，可有效阻断细菌繁殖，将每颗牙的细菌数控制在一千至十万。牙膏中的氟化物及自来水也能够坚固牙釉质，使牙齿更好的抵御变形链球菌所产生的酸。

Fluoride also helps saliva repair parts of the tooth that have already been damaged by the acid. And, last but not least, it helps not to feed the critters too much of their favorite food: sugar!
氟化物还能够帮助唾液修复被酸损害的部分牙齿。最重要的一点就是不要给细菌它们的最爱——糖。