Check out the thesis of the recent bestseller Breath by James Nestor. Native American and other traditional cultures put serious emphasis on nose breathing, strictly avoiding mouth breathing. Apparently, consistent nose-breathing can affect nasal and upper-palate development, favoring a spacious mouth and straighter teeth. It can also help avoid dry mouth at night, apparently favoring resistance to dental caries. There is a book by a 19th century ethnographer who discovered some of this, titled Shut Your Mouth and Save Your Life.[1]

[1] https://www.consciousbreathing.com/articles/shut-your-mouth-...

Both beets and sugar cane are old world plants, and maize-based corn syrup wasn't used as a sweetener until the 20th century. It's true that refined sugar is terrible for dental health, but it didn't come from the americas.

Getting kind of off-topic here, but my recollection is that teeth in the pre-industrial age were often destroyed over time by grit from flour milling that would wear down teeth.