Regardless of what part of the body we talk about, bone has evolved to perform a very specific task. It must function under pressure or in a weight-bearing capacity. We lose bone mass and bone density if our bones are not allowed to function the way they were intended.

While astronauts are in space and experience “zero gravity”, bone mass decreases simply by not having weight to bear upon their bones and muscles. Despite their efforts to augment this problem by using techniques such as resistance training while in orbit, they return to earth with significantly depleted densities to their bone. Those confined to wheelchairs, having lost the ability to walk, lose incredible volumes of both muscle and bone. You do not see people in wheelchairs with strong muscular legs, with healthy dense bones. We are familiar with the advice given to the more mature element of our population (especially those with osteoporosis): “You must exercise, especially weight bearing exercise”. If you are forced to support your own weight as with walking, the bone cells responsible for building will keep bones strong and healthy. Hip fractures in the elderly are common, especially those who are sedentary. What does this have to do with your mouth? Simply extractions of teeth are the mouth’s equivalent of being placed in a wheelchair. Remember bone cells everywhere in your body require pressure to build stronger bone. Natural teeth when present transmit biting forces from the cutting surface down the roots of the teeth to the jawbone. The bone cells (osteoblasts) are stimulated only when there is pressure from biting on natural teeth. The bone ‘realizes’ it is needed to hold the teeth in place.  In the absence of teeth, bone no longer has a job, and as such it falls into the old cliché: “If you don’t use it you lose it”. Conventional dentures do nothing to stimulate this biting pressure; they sit on the surface of the tissues. The force a denture exerts on bone is of a traumatic type. It actually causes the bone to shrink excessively.

Bone Loss: Resorption and Atrophy

The term resorption describes the process of shrinking that occurs in the jaw bone once the teeth have been removed. This applies to both the upper arch (maxilla) and lower jaw (mandible). After the extraction of one, several or all of your teeth, the bone that once supported the teeth, resorbs, shrinking quite substantially. This shrinking is a process that can go on for the rest of your life.

There are several factors which affect the amount of bone loss:

1. The trauma of the procedure to remove the teeth – excessive trauma or fracture of a root before or during extraction may lead to excessive bone shrinkage. Facial trauma such as an accident usually causes excessive bone loss in the area after trauma.
2. The number of teeth being removed at one time – the greater the number, the greater the trauma to the bone.
3. The amount of disease process that is present at the time, and the likely the original cause for the teeth to be extracted.
4. The wearing of ill fitted dentures causes excessive bone loss including dentures that have been relined or are in excess of five years old.
5. Diet and nutrition.
6. The length of time you have been without natural teeth (the longer you have worn a full denture, the more bone shrinkage you will experience).
7. For partial denture wearers, if you lost the back teeth first but kept the front, on either the upper or lower arch.