It's self-evident that humans can grow teeth, since we almost all have them, and many women grow extra sets in their uteruses. The devil is in the details of growing them on demand where desired.
The kind interpretation is that you are thinking of Teratoma (mentioned above). The less kind is that you are thinking of that cheesy black-comedy horror movie from the 2000s.
What.
> [Māui] proposes to kill Hine-nui-te-pō by entering her vagina and exiting through her mouth whilst she is sleeping