Kinda. Studies say it works topically in toothpaste but at levels of 1000ppm or 1000 times greater than that of tap water. But you aren't supposed to swallow toothpaste because it's poisonous. Diluting it in water doesn't magically make it less poisonous.

In fact we only drink something like 1 or 2% of tap water the rest simply goes down the drain via toilet/shower etc. Fluoridation is simply a way of getting rid of toxic waste by diluting it down to 'safe' levels.