[wikibob]

Our ancestors with good teeth ate zero sugar, zero processed starch. This is so difficult in modern society as to be essentially impossible.

Sadly yes, dentistry has extremely poor, or rather non existant oversight. The answer however is to extremely carefully select your dentist, and get second opinions. Not to ignore dentistry.

[parliament32]

Ignore it, no, but the industry has "fads" which are very questionable. Effectively every single dentist will insist you need to come in for "cleaning" every 6mo-1yr... yet there are plenty of people like me (either by choice, or lack of dental insurance or whatnot) who haven't been to the dentist in a decade or two and don't have any issues.