All the books agree that a root canaled tooth is a permantly dead tooth, it is like a dead/rotten stump in a woods that attracts termites until it is disolved back to dust.
The laser dentist can remove the metals used in root canals and re-fill it with a magnesium/calcium type material, the tooth is still dead, but at least it is not supplying deadly metals to the body. The jaw bone is reabsorbing the dead teeth 24/7.
Most of my root canaled teeth were stuck to the jaw bone because the jaw was absorbing the dead tooth.