" Tartar" is a hard yellow layer on your teeth.

“牙垢”是牙齿上一层坚硬的黄色层。

When you do not remove the plaque regularly, then you can get this yellow layer, and that's why some people have yellow teeth, because the plaque has built up so much that it has now become tartar.

如果你不定期去除牙菌斑， 就会形成黄色层，这就是为什么有些人的牙齿是黄色的， 因为牙菌斑已经累积太多， 现在已经变成了牙垢。