Sublingual drug administration is one of the most rapid uptake forms that exist. The list is basically: - Intravenous - Inhalation (for things easily aerosoli

Sublingual drug administration is one of the most rapid uptake forms that exist. The list is basically: - Intravenous - Inhalation (for things easily aerosolized) - Sublingual - Everything else (including intramuscular and subcutaneous) This is often the preferred route for oral medications that aren't too bitter for people, because it avoids stomach acids. So if the thought is that people don't want it in their bloodstream from ingestion, it's probably already there. That doesn't even get into the concentrations. Standard water fluoride rates is on the rate of 1 ppm, whereas toothpaste is typically well over 1000 ppm. The amount of fluoride you swallow as a by-process of brushing your teeth would far outweigh what you drink in a day.