Alpaca, I'll throw in a bit of personal experience with implants here as well. I am extremely fortunate in that I have a close relative who is an oral surgeon. He has played an important role in my treatment from the first surgery forward.

We began talking about implants about three years out. it was not advised at that point, but for the following five years we revisited the possibility every few months. Finally, 8 1/2 years out, he felt it worth trying. Initially, he'd planned on doing a complete run of implants top & bottom ( I should add I lost 50% of my mandible, which was successfully replaced witha fibular graft) After a great many scans, x-rays, exams & consultations, we decided instead to do a full implant field on the upper, and only four on the mandible, with three in healthy, unradiated bone , and the fourth into bone on the edge of the radiation field. The idea being that the bone there would be adequate to serve as a positioning anchor without taking too much loading from bite forces. Instead of individual crowns, he constructed a full denture, without any of the normal ridgeline support. Instead, at four places along the length of the appliance, the implant pegs snap connect with the plate, allowing me to remove it for cleaning.

The procedures were completed a year ago and I have been completely trouble free. I do have to pay close attention to cleanliness around the implant pegs, however I have had no infections of any kind. The lower is stable enough that I am able to eat EVERYTHING once again, including steak & even previously impossible things to masticate, like lettuce & spinach.

That said, I don't think I would risk an implant into radiated bone...there are simply too many potential problems. I hope you can reach a point where you're comfortable with the choices you have. For me, it's worked out brilliantly