From what I read and from personal experience it is a diet that has strongest effects on tooth health, not the the way to toothbrush or floss. For example, in Europe tooth health became much bigger problem after crusades when knights brought various dessert recipes from Lebanon and Syria.
This would be my guess too. I've never had a cavity in my life, which I'm sure is partially genetic, but I don't floss and brush only once a day in the morning. I haven't been to a dentist in ~6 years. My diet is very clean though -- no soda, candy, or really anything else high in sugar other than fruit. I eat a lot of raw vegetables too, which I think clean my teeth as I chew.
The few cavities that I have had were all extremely tiny and hardly visible to the eye. You won't really know on your own that you have a cavity until it's much more fully developed. At that point, getting it repaired is much more aggravating and a pain. I'd highly recommend getting to the dentist more than once every 6 years.
Don't you need to avoid unrefined sugar and starch too? Which is not impossibly difficult (lots of folks do keto), but is more difficult than just avoiding refined sugar.
It is not necessary sugar that causes the damage, but combinations. My personal experience is that a combination of meat or cheese and sweet desserts/drinks after that was the real problem.
