I have had 4 molars removed post radiation so far. The first 2 (top) were not at the "epicenter" of the radiation. The last 2 were on the bottom and one of them broke off at the gum line. All of these were removed without HBO, although I had that too. The last 2 were taken out just this year in one sitting. My dentist knows my medical history and HBO was discussed. We felt that the gum condition and blood supply was adequate�. and you are extra careful re infection (antibiotics) and make sure a nice blood clot forms.

I just wished there was a reliable test to figure out if you actually need HBO or not!? Does anybody have any input on this.

With 5 teeth I would go for HBO as well, unless they are out of the radiation field. Your RO should be able to advise you. Also, you want a dentist who is experienced to treat OC patients.
Hope this helps a little.