牙医解释说，他的牙齿变色是由于咖啡引起的。

The dentist explained that the discoloration of his teeth was due to coffee.

氟中毒会导致牙齿变色或表面缺陷。

Fluorosis can cause tooth discoloration or surface irregularities.

人们还可通过电脑远程控制该装置，使得牙齿变色甚至不断闪烁。

People can even get a computer by which to control the contraption making the teeth change colors or even blink.