Worse, people exchange mouth bacteria regularly. Provides the perfect rapid evolution landscape to build super bacteria. So even if perhaps a few % start using

Worse, people exchange mouth bacteria regularly. Provides the perfect rapid evolution landscape to build super bacteria. So even if perhaps a few % start using it, it might be enough to set off a situation where people that didn't use it get harmed by people that did by acquiring super bacteria that they then have to treat / fight.