Hi @ganna54 I too had osteoradionecrosis and trismus, loss of teeth and regular infections of the gum. My research of hyperbaric treatment all pointed to the fact that dead bone will not come back to life.
Botox is a bandage, not a cure but perhaps some momentary relief. However, with MS, is your neurologist on board with this? Doubtful.
That remains the only option: to rid yourself of the dead bone and tissue. Fortunately there is a procedure. It’s called (in my case anyway) a mandiblectomy with fibula free flap replacement followed by insertion of a teeth prosthetic.
Basically the dead bone is removed and replaced with living bone and blood supply and tissue, which allows it to heal and live in your jaw, able to support a teeth prosthetic. The bone comes from either your fibula, shoulder bone, or pelvic bone. The surgery, when done by an experienced team, is quality of life saving. If you are interested or have questions, there is help out there, I among the group. Have you looked into this?