On this issue, I can only speak from personal experience. If there are studies, I would love to read them. I did read one study that compared bite-wing x-rays to panoramic, relative to brain tumors (don't remember what kind) but the results didn't make sense to me.
My experience is that my tumor was stable, and then, after having dental x-rays, it was 50% larger on the next MRI. This could very well be coincidence, but it has happened to others on the list. I read an article that said that, while average growth is 1 to 2 mm per year, for a given tumor, that may actually translate into no growth some years and 2 to 4 mm in other years. My tumor went from 8mm to 12+ in 14 months, after not growing at all for the first 6 months.
I think the jury is still out on this issue. I probably won't have dental x-rays again unless my dentist can make a very good case for it. Never mind that I've had two CT scans since my surgery on July 3rd. There were very good reasons for those and I hope I don't ever need another one.
Life seems to be all about taking calculated risks...
Liz