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Long story short:
Is there a maximum number of teeth brushing per day without having fluoride poisoning?

Full story:
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?

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    Where did you find the text quoted by you in your question where it says that toothpastes have exactly 1450ppm F in them? Is this the "dangerous assumption" you referred to? This part of your question is very unclear.
    – Chris Rogers
    Commented Sep 20, 2018 at 6:24
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    Neither of the two references you give for the fluoride concentration support your claim. The article's abstract mentions "standard toothpaste" as having 1450 (that doesn't mean all or most will have exactly 1450, only that that is a standard concentration for where the authors live) and the Wikipedia page you linked to claims that 1450ppm is the upper limit of the concentration in most toothpastes. Could you edit and clarify what you are asking?
    – terdon
    Commented Sep 20, 2018 at 17:02
  • dash.harvard.edu/bitstream/handle/1/8846762/msandier.html
    – Count Iblis
    Commented Sep 20, 2018 at 17:44
  • thanks for the feedbacks! I've tried to simplify the question
    – mattia.b89
    Commented Sep 20, 2018 at 19:36
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    There's no evidence that fluoride is absorbed in the mouth, so unless you're swallowing toothpaste instead of spitting it out, the ingestion levels are trivial compared to other sources.
    – Carey Gregory ♦
    Commented Sep 21, 2018 at 1:32

1 Answer 1

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TL;DR: Unless you brush your teeth multiple times an hour and swallow the toothpaste, you likely won't ingest a significant enough quantity of fluoride to cause any issues.

Per the label for Sodium Fluoride chewable tablets:

A treatment dose of Sodium Fluoride Chewable Tablets contains 0.25, 0.5 or 1.0 mg fluoride

A standard OTC toothpaste, in this case e.g. Crest Pro-Health, contains 0.454% fluoride. For you to get 1mg of fluoride from this toothpaste, you would have to swallow just over 220g. One tube is 130g.

If we assume that you use 5g of toothpaste with each brushing, you would have to brush your teeth, and swallow the toothpaste 44 times per day to get 1mg of fluoride, still within what is considered a normal dose for this substance.

Even redoing this calculation with a prescription only toothpaste, e.g. Prevident 1.1%, you would still need to brush and swallow 18 times per day to get 1mg of fluoride.

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