Maybe it's just me, but I get really nervous when I hear the word "forever". I truly don't believe that there is any such thing, especially with this disease.
We all hope that we're cancer free forever, that the treatment we suffered through "cured" us, but that's hope, not always based in fact. I think your Mom is incredibly fortunate to have a Dentist who's on top of their game, and spotting the problems very early; many are not as lucky, and pay a heavy price as a result.
Is your Mom seeing an ENT? Doctors unfamiliar with oral cancers far outnumber those that are.
If she is simply going from recurrance to recurrance with no cohesive cancer care team and treatment plan to avoid or at least minimize the possibility of another round with the demon, she may want to reconsider that approach.
Radiation today is very precise & controllable. That doesn't necessarily mean that it only covers small areas; it can be used very effectively over larger areas. It is often used as a secondary treatment following surgery to ensure that any errant cancer cells, even on a microscopic level, are eliminated.
SCC is agressive, and it's sneaky. Recurrances are all too common, and just as deadly if not discovered and treated....agressively.
I haven't heard anything about the trials you mention. Doing a search on Quackwatch for beta carotene will not leave you with a warm fuzzy feeling.
For every proven, endorsed main stream treatment, there are dozens of alternative treatments, very few if any relieve anything but your pocketbook. Trust your ENT. If you dont have one, change that. Don't do or take ANYTHING without running it by them first.
Wayne