I've never heard of it.
If it's not evidence-based, even at this late date, why worry about it?
Advice communities change by thinking inductively. So has natural hygiene, as evidenced by Joel Fuhrman's change into a holistic vegan MD rather than an advocate of 'natural hygiene' as such.
We ought to be using our chosen theories THAT WORK for us and a community of "sharing vegans" as a BASE from which to compare and contrast with the growing body of health-relevant information that is consistent with the practice of health-seeking ethical veganism, including all the abstentions from alcohol, meat and animal products, and other poisons
I did a lot of it and it seemed to help, but now I think that saliva swishing accomplishes about the same thing.
Try your own saliva for natural toothpaste, or try calcium bentonite clay.