I've never had a cavity or major repair procedure for my teeth, and I don't understand why. I'm not particularly obsessive about my teeth. Are cavity resistant teeth some kind of genetic trait? Does drinking milk regularly maintain healthy teeth?
Likely a large genetic component. Also the bacteria in your mouth could (possibly also due to your own genetics) be different. I've also never had a cavity filled, I'm 32 and have one spot on an x-ray that dentists disagree on so I've left it.
Pretty normal "healthy" american diet, I guess. I eat meat and most other things. try to eat healthy whole foods and less processed stuff. Rarely drink soda but do eat sweets a few times per week