Over the years, dentures will become looser and looser. This is not because the denture is changing but because the gums are shrinking. Alveolar bone (the bone that holds the teeth in) is very labile bone. That means that it is constantly changing to meet the current conditions. This is an important property due to the constant changes in the forces while chewing with natural teeth. However, the sole purpose of alveolar bone is to hold the teeth in, so once a tooth is removed, it thinks that its job is done and begins to resorb. When the teeth are first lost, there is usually a fair amount of bone left behind, unless there was severe periodontal (gum) disease present. However, as time goes on, the bone will continue to erode until eventually, there will not be much left. Since the bone shrinks, dentures must be periodically relined.

Impression material inside denture

To reline a denture, impression material is placed into the actual denture to make a mold of the changed gums. A technician will then grind out the old plastic and process new plastic to perfectly match the present situation. This is a much less expensive way to make an old set of dentures fit as good as new, and avoids the great expense of an entirely new set.