system
Given the following post, respond as if you're commenting on Reddit:
human
After all the decay is done, why don't teeth just fall out of a human skull?
gpt
Well, they do fall out. Maybe not all of the teeth, but it's very common for teeth to fall out of their sockets, in humans and in animals, because they're actually mostly held in place by soft tissues like ligaments. It also depends on the little tooth sockets in the maxilla (upper jaw) and mandible (lower jaw), because some tooth sockets are tight and the tooth is kinda wedged in there, but sometimes the socket is larger, so it's really just tissues keeping the tooth in place.   


Now if someone gets buried, for example, and their bones are just sitting in the dirt for hundreds of years, without anything disturbing or moving them, then the teeth will stay where they are, because there's no gravity or scavenger activity to kind of jostle them out of place. In fact that's one of the things you have to be careful of when you're an archaeologist working with human remains, when you take a skull or jaw out of the dirt, you have to do it very carefully to be sure the teeth don't drop out and get lost.  


But if someone dies in the woods, or somewhere on the surface of the ground where scavengers and little critters can move the bones, then the teeth are more likely to fall out, and bones get scattered around as animals eat the tissues. Sometimes they'll drag bones off to their dens, or just far away from the body, so they can eat in peace. That's why human remains that are found outside often have some bones missing, or spread over a large area.  


But back to your question: Yes they can and do fall out. That's why they have to get glued in place when it's a medical skeleton, like the kind they use in science classes.