Do you have scientific evidence (or "proof") of this claim, assuming you're referring strictly to dental caries, and perhaps receding gums?

I don't believe it, whatsoever. In fact I challenged some friends (a dentist, an orthopedic surgeon, and a biochemist -- all researchers affiliated with prestigious institutions) to provide that scientific evidence, and after a year they all concluded that standard dental advice is simply wishful thinking. Since it is the recommendation of dental associations, a practicing dentist must give this advice, but that doesn't make it true.