Fluorosis can cause tooth discoloration or surface irregularities.

氟中毒会导致牙齿变色或表面缺陷。

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There's another reason to watch what you eat - some common foods can cause tooth discoloration.

由于一些常见的食物可能会导致牙齿变色，所以你得注意你所吃的东西。

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Over-whitening can also cause teeth to become thin and brittle and can lead to high sensitivity and discoloration as tooth enamel becomes translucent.

美白牙齿过度，会使牙齿变得薄弱。同时，由于牙釉质变为半透明状，会导致牙齿高度敏感、变色。

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If you notice a white spot or discoloration on a baby tooth, "that means there could be a problem developing, " says Dr. Warren Brill, newly elected AAPD president, and the child should see a dentist right away.

CNN: Baby's teeth: What you should know