How much toothpaste must be swallowed to cause a fluoride overdose?

Depends: It depends on toothpaste Fluoride concentration. To prevent it, children must be supervised until healthy toothbrushing habits have developed.

A lot: It's almost impossible to get a Fluoride overdose unless you are eating toothpaste on purpose. You can't get a Fluoride overdose from swallowing toothpaste during normal brushing with a pea sized amount of toothpaste. Children can sometimes eat toothpaste and get a mild Fluoride overdose. Keep toothpaste away from children just like any household chemical. If too much toothpaste ingested, go to er.