Do you often have a toothache?

你经常牙痛吗？

I have a toothache. I need to see a dentist.

我牙痛，我得去看牙医。

I ate too much candy and then I have a toothache.

我吃了太多的糖果，结果牙痛了。

If you have a toothache, you have to go to the dentist.

如果你牙痛，你应该去看牙医。

I have a toothache, and have to go to the dentist's every other day.

我牙痛，必须每隔一天去看一次牙医。