[pierrebeaucamp]

I hate to cite Wikipedia as a source [1], but it looks like the majority of countries do not add fluoride to tap water (only 24 countries in total do).

But Sweden seems to have an interesting history with it indeed.

[1] https://en.wikipedia.org/wiki/Water_fluoridation_by_country

[seanmcdirmid]

I bet that is roughly related to the countries that have potable tap water at all.