You can attempt to file a claim with your medical or dental insurance to see if they will pre-approve any necessary treatment but I would imagine that it probably will not be approved. But I would recommend at least trying to see what can be done.
Unfortunately , I do not have good news for you. We routinely send this type of claims to insurances and I have yet to see one get re-imbursed. It seems though that you have done all the right things for your son, and you are to be commended for that. I hope things work out for this part too.