Why do back teeth decay so easily?

为何后磨牙如此容易被侵蚀？

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To understand what happens when your teeth decay, it's helpful to know what's in your mouth naturally. Here are a few of the elements.

为了理解当你的牙齿龋坏时都发生了什么，了解你口腔的自然状况是有益的。以下是几个基本组成要素。

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Cavities in teeth are caused by decay.

牙齿上的空洞是由龋蚀造成的。

《新英汉大辞典》

This acid attacks the enamel on the teeth and leaves them vulnerable to decay.

BBC: Dental threat of snacking

The report says scientific evidence suggests "almost every proven method to prevent decay includes delivery of fluoride to teeth surfaces".

BBC: Tooth decay in children too high, says chief dental officer

Left untreated, what's termed "early dental caries" -- the first stage of tooth decay -- can destroy tiny teeth and lead to infection, pain, and lifelong consequences.

CNN: Baby's teeth: What you should know