Long story short:
Is there a maximum number of teeth brushing per day without having fluoride poisoning?
It is certain that a high fluoride intake leads to health problems. This is related to ingestion only (that is swallowing toothpaste, drinking high-fluoride water, eating rich-fluoride food) of this element.
While, when we talk about fluoride in toothpastes, we have a completely different assumption and absorption mechanism.
Thus, I assume, there will be different AI (adequate intake) and UL (upper intake level) than for fluoride food assumption[a].
my assumption is sustained by the fact that most commercial toothpastes[b][c][d] have less than 1500 ppm of F− in them
Ultimately, does exist a daily upper safety level for fluorine absorbed from the toothpaste?