If the teeth on your dentures are worn flat, then it is vital they are replaced. In fact, having reached that point you can be certain that you have lost bone structure because of the existing set of dentures.
Remember, bone loss is silent, with no symptoms and no pain. It’s a microscopic process that has no hints of the underlying damage being done. Observe your dentures everyday when you clean them. Over the years, they will get flat. But don’t wait for your gums to get flat, replace your dentures before the bone is lost forever.