When we maintain our teeth, we also maintain the integrity of our facial structure. This middle aged gentleman has all his teeth and we can see how the muscles in his face are properly supported and his facial height (distance from chin to nose) appears normal.
When the teeth are lost, we can immediately see the effects on the facial structures. The muscles in the face are not supported and as such, they sag and droop, creating deep facial lines. The jaws move closer together, causing the chin to protrude, since there are no teeth present to maintain facial height. All these facial changes speed up the aging process, making the individual appear much older. In this computer generated demonstration, although this gentleman is the same age in both pictures, he appears much older with the loss of his teeth, due to the changes in his facial structure.