Learn German: Putzt du dir die Zähne? - Are you brushing your teeth?

We use the dative reflexive pronoun dir because there is already a direct object in the sentence: die Zähne (the teeth). When you do an action to a specific part of your body, the body part is the direct object (accusative), so the reflexive pronoun has to be in the dative case.

Why does the German sentence say die Zähne (the teeth) instead of deine Zähne (your teeth)?

In German, when you talk about actions done to body parts or clothing, you usually use the definite article (die, der, das) instead of a possessive word like deine. The reflexive pronoun dir already makes it perfectly clear whose teeth are being brushed!

Does the verb putzen always need a reflexive pronoun?

Not always! You can use putzen (to clean) for other things without a reflexive pronoun, like Ich putze das Fenster (I am cleaning the window). But when you are cleaning a part of your own body, you use the reflexive form to show who is affected by the action.

What is the word order rule for this type of question?

Because this is a yes/no question, the conjugated verb Putzt comes first. Then comes the subject du, followed immediately by the reflexive pronoun dir, and finally the direct object die Zähne at the end.