刷牙用英语怎么说

"How to say 'brush teeth' in English" is how you ask the question "What is the English translation for '刷牙用英语怎么说'".

The phrase "brush teeth" is already an English expression for this action. So, if you want to say it in a sentence, it would be: "I always brush my teeth before going to bed."

If you want to ask someone how to say "brush teeth" in their language, you can say "What do you call this action in your language?", or "could you tell me how to say 'brush teeth' in your language?".