Michele, first off, to answer what I believe was your primary question, here is a link to some diagrams showing that in fact there are two separate blood supplies for the upper and lower teeth.
http://www.sadanet.co.za/dhw/owners_manual/anatomy3.html Following that, it is possible that there was/is no need to remove any upper teeth as they likely will not be in the beam of radiation. In my case that was what happened, as I only had one upper tooth removed but three lower teeth. Also, my regular dentist too exception to the oral surgeon's plan and in talking with him saved one of my lower teeth. Do not just accept their plan as a cast in stone, ask why.
Bill
