Carol, radiation to the jaw severely reduces the blood supply in that bone, so if there is trauma to it, such as extraction, it may not heal. What is to be avoided at all costs is the dreaded Osteoradionecrosis -- bone death due to radiation. The is where HBO comes in. The increased oxygen causes new capillaries to form, which allows the bone to heal from extractions or other trauma. It is only my opinion, but I think it would be great if everyone could have HBO post rad, but as it is very expensive and time consuming, I doubt that will happen anytime soon. This is just a simple overview. You can search the net for more extensive information.