Everybody has two sets of teeth.

我认为应该是：每个人都有两排牙齿.
你可以拿镜子照一下是不是有上下两排~
这句话的重点在于怎么理解two sets of ,
我查了一下牛津高阶英语词典,它里面说"set" has the meaning of GROUD.
That means,when refers to a set of sth,you can understand it as a group of similar things that belong together in some way.Using Chinese you can transfer it to"一套,一副,一组（类似的东西）".But the transition is very flexible,and it rests on you to understand it.
(不好意思,觉得用英文解释可能会更易于明白,翻译如下：set 在牛津中有组的意思,即当提到a set of sth,你可以理解为一组相似的、配套的东西,用中文来说可以是一套,一副,一组（类似的东西）,但由于翻译是很灵活的,这要靠你自己多去读、多去想,然后就会慢慢有自己的更贴切的理解了~

每个人有两排牙齿。

每个人都有两排牙齿。

每个人都有两套牙齿。