Missing teeth causes bone loss in both, but especially the lower jaw. The loss of bone over time affects more than just the mouth. Facial sagging, premature aging and loss of function are all results of atrophy in the upper and lower jaws. This is one of the biggest problems denture patients face. Because the dentures sit overtheir gums, the jaw continues to shrink, as the bone is not stimulated by the presence of teeth. This leads to perpetually ill-fitting and/or loose dentures, due to the continued shrinkage over time, even after the denture is refitted.