英语听力文摘 长蛀牙,怎么办？
Don: Sorry, I'm late. I was brushing my teeth.
Yaël: Brushing your teeth! Right before A Moment of Science? Why?
D: I'm trying to get rid of a cavity.
Y: Get rid of a cavity? Are you stuck with a cavity once you have it?
D: It depends on how deep it is. Acid from bacteria in your mouth can cause your tooth to decay. First, the acid eats away the very hard outer layer of your tooth, called the enamel. Inside the enamel is the dentin. It’s spongy and has nerve endings, so your tooth might be sensitive to sweets or cold if the decay reaches there.
But the cavity doesn’t really start to hurt until it gets through the dentin to the soft pulp. That’s when you get a toothache.
Y: Ow!
D: Dentists sometimes will fill a cavity by putting in a filling while the decay is still in the enamel. But decay is reversible until it reaches the dentin. If it’s properly treated, the decay will stop, and the enamel will harden, although the tooth will never be perfect again.
Y: So, that's why you're brushing. Can you do anything else to help get rid of a cavity?
D: Dentists can help by giving you a fluoride treatment, but you have to brush and floss regularly. You might have to give up soda and sweets. So it’s not easy–and dentists know that. That’s why they sometimes fill a cavity in its early stages, before it starts to hurt.
Y: So, you’re not stuck with tooth decay once it happens.
D: Nope. But it’s better not to let it happen in the first place.
摆脱蛀牙的烦恼
D: 对不起，我迟到了。我刚刚刷牙去了!
Y: 刷牙!就在节目开始前!为什么啊?
D: 防止蛀牙啊!
Y: 防止蛀牙?你长过蛀牙吗?
D: 这就得看牙被蛀得有多深了。口腔中的细菌会产生一些腐蚀牙齿的酸性物质。酸性物质会先腐蚀掉牙冠表层的珐琅质(也就是我们所熟知的釉质)。珐琅质所包覆的便是牙本质。牙本质不如珐琅质坚硬，其中还含有很多的神经末梢。因而，如果牙本质也受到了腐蚀，牙齿对甜食或是过冷的东西就会很敏感。
但是，要等到酸性物质通过牙本质，开始腐蚀牙髓了才会对牙齿造成本质的伤害。这个时候牙齿也就开始疼起来了。
Y: 肯定会很疼!
D: 当珐琅质遭到腐蚀时，医生有的时候会采取补牙的方式进行治疗。可是，在牙本质遭到腐蚀之前，腐蚀随时都会发生。如果治疗得当，腐蚀将会停止，珐琅质也会重新变硬，美中不足的是，牙齿不会像受腐蚀前那么完美了。
Y: 这就是你刚刚刷牙的原因!你还有其他防蛀牙的办法吗?
D: 医生还可以为你做氟化物治疗(在蛀牙部位涂上高浓度的氟化物，令初期蛀坏的部分还原)，但是，你必须定期洗牙，还要经常使用牙线清洁牙齿。另外，什么汽水啊，甜食啊，都必须戒掉。所以说，做这个治疗并不容易——当然，医生们也是很清楚的。这也是为什么医生会在蛀牙初期的时候为病人补牙，防止酸性物质的继续腐蚀。
Y: 这么说，你从来都没有长过蛀牙。
D: 当然。但是，“防患于未然”总是好的啊!
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