It's more the injury to the jaw like from surgery, dental implants, extractions, dentures rubbing than anything spontaneous after radiation, and that it also depends on where radiated, amount, usually above 60Gy, to cause ORN, and the use of HBOT is controversial, and use depends on each individual. I understand malwicker's point that Avaston may have reduced the vasculature, angiogenesis, to the jaw, which has something to do wih ORN, which HBOT may counter.
