Informal:
* "Y'a quelqu'un qui a des dents ?" (Literally: "There's someone who has teeth?")
* "Quelqu'un a des dents ?" (Literally: "Someone has teeth?")
Formal:
* "Est-ce que quelqu'un a des dents ?" (Literally: "Does someone have teeth?")
You could also be more specific by asking:
* "Est-ce que quelqu'un a des dents de lait ?" (Does anyone have baby teeth?)
* "Est-ce que quelqu'un a perdu ses dents ?" (Has anyone lost their teeth?)
Remember that in French, the word order changes depending on the type of question. In general, for yes/no questions, the verb "est-ce que" is used at the beginning.