Oh man, just saw this one, campy and in poor, I mean
poor taste, it's sort of a hoot. A high school girl suspects she may be a manifestation of the 'vagina dentata' myth, wherein the vagina contains teeth with which to, er, uh, defend said lady. Hilarious hijinx ensue.
Teeth (2007) - IMDb
They've had in on Ifc, where I saw it, a few times. Just found on their website that the next showing is May 29th:
Teeth – IFC
Don't read up on it too much before you see it (says the world famous movie reviewer).