Hi, Yep, that was something that certainly popped up in my mind when I was diagnosed with an extra large nodule being Hurthle Cell Adenoma (it was pre-cancerous) I had a ton of dental x-rays over the years, not to mention upper chest x-rays for pneumonia etc. Back in the bad old days, mid 1970's they never put a lead apron on and the collar before taking x-rays, so does make me wonder. I was often asked if I had been exposed to radiation as it seems my type of cancer was only triggered by radiation.
The newer digital x-ray machines are 95% less radiation. We may well see in the next 20 years a drop in the rates of cancers in people aged in the younger generation. MY advice to anyone is to shop around and find a dentist who uses the newer machines. Yes, it costs more but it is worth it in the long run.
As a science teacher, the rule is that x-rays, which yields among the highest level of ionized radiation that nature can muster (the lowest level of xray is multiple times the level of energy that the most intense ultra violet can yield) are always dangerous. Having said that, there are times (very few that I can think of) when the benefit might outweigh the fairly high long term risk of xrays. Also, the body can cope with and repair some of the damage caused by xrays. The question is does finding a cavity or gum infection that does not present itself to a trained dentist warrant the long term risk of thyroid or other damage. also, with the advent of x-rays, I wonder if dentists are trained to rely too easily on the x-ray routine. I, as you might guess by now, have decided to (almost) never take an xray again since I broke out with a lip mole I can't get rid of. Also, the dentists seem fine with my decision. Finally, every time I go to a dentist and they get a new x-ray machine, they keep telling me that the new one is 'low dose' or 'safer'. This kind of implies that the one now is dangerous because the next 'new x-ray- machine will also be 'low dose'.