In the 1950s, it was decided, absent data, that low dose radiation was as bad as high dose and so no dose would be tolerated. This was called the Linear No-Threshold (LNT) dose hypothesis. Today this is being overturned in medicine and eventually in dentistry. https://www.forbes.com/sites/jamescon… https://www.nytimes.com/2020/01/14/we… https://www.sciencedirect.com/science…