Here is a representation of the lower jaw from a profile view. Note the height of the bone.

The loss of teeth could be due to trauma or other dental problems. Once the teeth have been lost, the bone will no longer be stimulated by the teeth roots and will begin to resorb due to disuse.

This is similar to the loss of muscle due to diminished use. As much as 40% of the bone mass could be lost in the first 6 months.

Placement of the traditional complete denture restores the tissue lost and replaces the teeth. However, the loss of bone continues, as there is no bone stimulation. The use of the denture can actually increase the loss of bone with the added factor of traumatic atrophy from the denture pounding the tissue and bone.

Over time, more bone will be lost.

In order to maintain the same facial features, the denture tissue base must be increased in size.

With more time, there will be even more bone loss.

Once more, the denture base needs to be increased to compensate for the additional loss.

The bone loss continues.

The denture needs to be continually increased in size in order to compensate for the loss of bone. The denture becomes more and more loose (even with this compensation) as the bone continues to resorb.