That paste used to make me really sick but wow it does work.
Not sure if they still have this though because the neolibs have destroyed the state health system and replaced it with mandatory private insurance that doesn't include dental anymore.
I still get fluoride treatments from my dentist but now it's something he paints on, perhaps the same as what you've described.
Anyway, according to a dentist friend, whether you get cavities is also dependent on the natural groves in your teeth. Some people's genetics cause them to have more cavity prone teeth than others.
I was worried too about swallowing it but it was also the smell of it that made me sick. It was very strong. I really hated it.
And yeah I guess I'm not very prone to them, but it's very clear that the generations before me had much worse teeth than we do.
Also General Jack D Ripper has concerns about the impact to P.O.E. ;)
It's something that really helped, my dentist joked about being put out of business :P My parents' generation have really bad teeth that started going bad in their teens already.
It was indeed only for kids, the dentist said the enamel no longer absorbs it when the teeth are fully grown. But perhaps this has been disproven now. I'll ask my current dentist about it.