I mean you can buy it here in a normal store. So I’m not sure if you mean a dentist can’t use/provide it, or if you’re thinking about the nano forms of it.

Edit, just saw this:

the FDA regulates dental products like toothpaste as cosmetics rather than therapeutic agents for cavity prevention

Interestingly, many ingredients used in dental care, including fluoride, are employed off-label. This means they are used in ways not officially approved by the FDA but are still considered effective based on scientific evidence and clinical practice