Please help! what happens to human jaws when all teeth are lost?

Atrophy: For the most part, the bone in the jaws atrophies over time without teeth. The lack of internal stimulation results in this loss. That's why older denture patients have so much difficulty with their removable teeth.. There's no bone to support the denture.

Bone loss: When all the teeth are missing, the bone which once surrounded the teeth will shrink.