This animation explains what hyperdontia is. This rare condition can cause teeth to grow in excess outside of their typical places on the gums, including on the roof of one's mouth.
In extreme cases, the entire roof of the mouth will sprout teeth. It happens when the tissue that produces teeth becomes overactive, and can appear anywhere in the mouth.
Watching the teeth grow from the roof of someone's mouth in this animation was a truly visceral experience. Luckily, these excess teeth can be surgically removed and aren't a serious danger to the person with hyperdontia.
See also: Kitty has a perfect snaggle-tooth
