TBH I am far more concerned about treatments - medical and dental - for which there can be no 20 year long, longitudinal studies for - procedures like eye laser surgery or, in dentistry, tooth bleaching. People have been having root canals for a long time, now with no ill effects over long periods, not even according to anecdotal evidence - but what about new, irreversible stuff that gets wheeled out when no longitudinal studies on its efficacy/safety can possibly exist?
I did a postgrad course in the 1990s with an element of statistics and research - looking at mainly medical research, and it was shocking to see that governments will livence drugs going by studies paid for by the drugs company developing the drug (albeit using different names) and with something trialled on as few as - wait for it - 6 subjects. So there are NO guarantees that any medical procedure you ever have done, or any medication you take, is truly 'safe'.