So within the existing population today there exist individuals who essentially never get cavities. The hypothesis for this has been 1. they don't eat sugar, or only fibrous foods, etc. 2. They have a genetic difference that builds stronger enamel or similar. I have never heard of anyone discussing bacteria in the mouth as a possible difference. Be interested to see if there is a natural strand that some people have…
I'm 40 years old. Never had cavities. I eat plenty of sugar.
Genetics play a role as well. My mom never got cavities despite never brushing her teeth, whereas my dad could brush pretty regularly and still have a cavity or two when he got checked up. Sadly I inherited my dad's genes, not my mom's.