Littlerosie, to answer your question from before. and also it may answer your question Suefew. I was diagnosed as having ORN in January 2013 and had several weeks of antibiotics. My consultant wanted to take a back tooth out, but I wouldn't have this done without the HBOT. I ended up taking myself off for oxygen treatment at an MS therapy centre as the hospital did not refer me despite telling me they would. From this the ORN "settled" - I think this means that it has halted/is not active at the moments. But it could start up at any time. The funding for HBOT on the NHS has finally come through (some 16 months later!)although I still haven't got dates to actually start the dives. My hospital consultant now does not want to take the tooth out as he said it would make a bigger hole than if my tooth was left to fall out on its own. But he says that I should still have the HBOT as a preventative.
So Suefew, from my understanding it seems that ORN can spontaneously start and stop, but it seems that the risk that it will start (again) will always be there. If HBOT improves the state of the bone then that would presumably make the risk smaller.
Hope that helps.