Doug,
Hi, a little uncertainty and a minor setback has seemed to come your way. Lets forget about the fact that you weren't told about the possibility of bone deterioration and be thankful that the cancer is gone!!
Osteoradionecrosis is a condition caused by radiation therapy. Basically the cells responsible for producing and strengthening bone die and an area of bone void of nutrition becomes necrotic. Left alone the enzymes produced by the dead bone will cause more bone to die. Stimulating factors such as wearing a denture can put pressure on the bone and potentially worsen the problem.
Solution: remove the necrotic bone this is usually preceeded by hyberbaric oxygen treatment (dives) then surgery and the on occasion during healing more dives are needed. Toronto has good facilities for this type of treatment but the wait as you post is a little long. Having not evaluated you and or your x-rays by the sounds of things your doc's got it right.
Your decision is whether to seek quicker treatment in the US. I am unable to advise you on this because that is soley a decision you need to make and then discuss with your docs.
I hope all goes well and pray for a quick recovery for you no matter where you choose to have this looked after.
Cheers,
Mike