The first time was when I was 6. My brother Roger and I both went. They more or less told Roger his teeth were perfect. Then they said that I grind my teeth, that I didn't take very good care of them, etc, etc.. It didn't really endear me to dentists.
The 2nd time was in 1999, right before I left Alabama. I discovered that 1) I have a baby tooth on the left side, and 2) I had no cavities. 3)They told me that I should really have my wisdom teeth out incase a cavity formed in the space between where the wisdom tooth abutts the next one. But I figured if I didn't have any cavities before, I'd probably not get any in the future.
The 3rd time was an hour ago. In the past 7 years, I've seen a few black/grey spots form on my teeth. I figured they were probably cavities.
But no. I am still cavity free. The mentioned that I clinched my teeth. The dental hygeinist seemed concerned about that, but the dentist didn't seem to care. They're going to put a crown on the baby tooth, clean my teeth thoroughly, and eventually remove my wisdom teeth.
So my theory is that my family's adult teeth are nigh invulnerable. When I went to the dentist at age 6, I still had baby teeth, and my brother had probably grown into his adult teeth.