hugh and stamets are both seen brushing their teeth in discovery. i imagine its just not shown very often

We are actually working on that now! There's a sweetener called Xylitol that essentially starves bacteria to death because they can't process it.

Edit: just found out it's poisonous to dogs.

I could've sworn I read something a few years ago about some scientists genetically modifying or identifying this mutant variant of bacteria that was able to outcompete the natural stuff, but don't produce the stuff that harms teeth. Was sometime in the 80s but the FDA completedly blackballed it.