Thanks, Bob.
When I went to a dentist once, he basically told me that I had lived in Florida (which I had as a kid), because they used a high amount of fluoride in the water and consequently my teeth were yellower than for people from other locations. We never discussed more than that, though.
As for the dentist I follow on Threads, he said there was evidence that hydroxyapatite was better than fluoride, and the studies I saw indicated it was at least as good. He also said it was less toxic than fluoride, but I haven’t seen any studies about that.