tooth brushing is a compensation for eating too much sugar right? if you managed to cut sugar out of your diet somehow then it might be okay to brush your teeth less? idk
I eat a fairly normal American diet and grew up in a place with minimal fluoride in the water, and I have near-perfect teeth
I also occasionally simply forget to brush
I do chew a lot of gum with xylitol but that's a recent development
Imo tooth quality is largely genetic
iirc, your saliva starts breaking down complex carbs into simple carbs (aka sugar) as soon as they enter your mouth, so you'd have to cut carbs to zero, too
eh i eat pretty much no carbs and no sugars but still find brushing useful, i do use novamin toothpaste which is the good shit (idk why novamin's not sold in US lol)
I suspect it's levelling out genes, environment, and diet.
Genes: good tooth and mouth structure, and good overall health.
Environment: altitude, water quality, pollutants.
Diet: Sugars, hydration, saliva pH, mouth microbiome, and eating foods which may cause dental trauma.
I remember visiting a very poor area in Latin America once as a kid. Went to a very poor village in the jungle. Most striking thing I noticed was that everyone had perfect white teeth despite being so poor and presumably not having access to modern dentistry
when I was in Kenya for a volunteer trip in 2009 I was intrigued to see that the folks in the rural area we visited had a particular kind of tree branch that they would break off and use to clean their teeth—I tried it a few times and it seemed to work okay.
just a datapoint
(to be clear, I am not attempting to imply anything in particular with this datapoint! I don't know what it means. these folks didn't eat candy but they probably ate a decent amount of fresh fruit, which is sugary. they mostly had pretty good teeth iirc? could pull up pics lol)