I don’t know about in the vagina, but dermoid tumors or teratomas are fairly common, which have been known to include teeth. Those form on the ovaries, not in the vagina, though. I had one that included two teeth, sweat glands, and hair which claimed my right ovary when I was 22. They are very rarely cancerous. As my doctor explained it to me, being in that area, the tumors have the blueprints to do just about anything. They are not babies gone wrong, do not resemble babies at all as they are just kind of a lump like any other tumor, and have been discussed several times on this board. You can also google either of those terms I gave you for pictures and such.
When I added the word ‘dermoid’ to my Google search, per Thinks2Much’s suggestion, I was able to find confirmation of vaginal teeth from Dr. Dean Edell
“I’ll tell you a funny story. People think I’m making this up. There is a case in a medical journal, I have it in my files, of a gynecologist who actually was doing a Pap-smear on a woman and he saw teeth looking back at him. That’s not a place in the body you expect to see teeth, despite all the jokes. This woman had a dermoid, which can also occur in the pelvic region. It had teeth in it and it had erupted next to her cervix.”
You need to hang out with some more medical students or doctors, then. It’s absolutely amazing what bizarre and utterly disgusting stuff the body is capable of. I got a full run-down on tumors and the body parts and organs they can generate. Teeth in the vagina is utterly plausible. I’m actually surprised that there’s aren’t many more documented cases.
The Master speaketh. He doesn’t address teratoma-induced vagina dentata specifically, but what he does say about it doesn’t leaves the conclusion close enough to jump to.