Fluoride in water goes to developing teeth, fluoride in toothpaste only targets erupted teeth, so the benefits are completely different.
But how many people drink unfiltered tap water anyway?
One of the municipalities was thinking about fluoridating the water, so I got curious and looked up the toxicity LD 50/30 per kg body weight for fluoride.
The level of efficacy is not very far from the level of toxicity and a small error in dosage at a water treatment plant could cause dangerous problems.
I suggested that it might not be a good idea for public works to be administering medication to people en masse.
If people are worried about getting enough fluoride, take supplements where the dosage can be closely controlled.