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
I'm hesitant to swap DEs, XFCE has WM tweaks I really like (accessibility>hide title of windows when maximized) and on top of that I made my own ultra-minimal XFWM theme (frameless, 12px titlebar, works well for a rolled-up music player or watching a video in mpv looking like PiP).