Forget any of the other perceived benefits.
I'll just carry on to receive this one.
After two pulls the accumulated tartar that my dentist persuaded me was normal build-up and had to be cleaned with a metal pick that made my gums bleed and the stains on my bottom teeth (I don't drink coffee or red wine) that he eventually blamed on taking vitamins, broke up and went away.
I can get flossing tape between my teeth that I never ever could before, and my teeth feel like the dentist has cleaned and polished them, every single day, since then.
I'm with you on the rest of the stuff to say the jury's out but why wait for this one benefit.
But then that is your choice. For quicker information on long-term effects try the foreign Ayurvedic and Russian press. Don't wait around for us Guinea Pigs 'cos we're never gonna pay for the scientific studies.