I don't brush and have not brushed for years...even before paleo I had learned how to naturally clean my mouth out by swishing saliva in conjunction with the use of skillful tongue dexterity...haven't had any cavities since I was a teenager when I was foolishly brushing with flouride toothpaste daily.
Such natural forms of oral hygiene can be fairly effective in cleaning the teeth and keeping corrosive plaques from eating away the enamel, even for people who eat those decay promoting foods.
Ive taken notice that the teeth are alive, and not just dead bone used to pulverize and masticate foodstuff. Ive had weak spots in tooth enamel heal overtime. I went to a dentist when I was 16 and was told I had a small cavity that needed filling, it hurt sometimes but usually wasn't very bothersome, so I let it go...and quit going to the dentist for years. I had some pain from time to time around a couple of old fillings (from when I was a child)and was then seen by a dentist for a check up at age 25.... he said I had good teeth, a couple of weak spots but no active cavities.
I noticed around the 2nd year of Raw paleo that the two molars with fillings, which would sometime hurt when cold or if I bit something too hard, had quit hurting altogether and were no longer sensitive to cold. Something interesting would happen on occasion, it would often occur after a short fast, or sometimes out of the blue, my teeth would get a gritty coating, I could feel on the tops of my molars, like sand paper, and the gum lines would become encrusted with a mineral plaque. I never brushed it off or tried to floss and would just continue to practice natural hygiene, sometimes chewing on connective tissue for a while... and eventually the mineral gritt layer would smooth away leaving my teeth feeling very clean and strong.
The roots of the teeth are alive and when awoken into action by vigorous chewing of raw flesh, they are stimulated to increase in their vitality, leading to the excreting of more dentin promoting growth factors that remineralise the teeth from the inside out, while the chewing of the flesh polishes the surface enamel.
Perhaps if not interfered with by constant brushing, and consuming of corrosive bacteria feeding foods, or chewing on harsh abrasive foods, the whole oral cavity can maintain itself quite well, as it undergoes the periodic cycles rejuvenation...much in the same way all the other bones in the body continue to repair themselves through the life cycle.