Crossbows can kill Buffy's type of vampires. Dean's own vampires have different rules, and so do the other kinds, like Godric's kind and Levi's kind, so he's not even sure about that much. If Piper asks, he'll explain it; the more people aware, the better.

"Not as far as I know," Dean replies. He'd usually ask Castiel, but... "But types of demons are different from place to place. I'm guessing you got demons back home?"