# Interference of Ca-EDTA with fluoride delivery in mouthwash

The goal of fluoride mouthwash is to deliver $$\ce{F-}$$ to the surface of the teeth to turn hydroxyapatite in the dental enamel into fluorapatite. Typically sodium fluoride or stannous fluoride are used.

ACT fluoride mouthwash also contains $$\ce{Ca}$$ in the form of $$\ce{Ca-EDTA}$$.

$$\ce{CaF2}$$ has a very low solubiliy product of $$3.9 × 10^{−11}$$, I would expect the $$\ce{F-}$$ to precipitate as $$\ce{CaF2}$$ and become unavailable. This is in agreement with the literature where $$\ce{EDTA}$$ has been used in the determination of $$\ce{F-}$$ through backtitration of $$\ce{Ca^2+}$$. This shows that the complex is less stable than the fluoride. http://www.sciencedirect.com/science/article/pii/S0003267000876369

Note:

It was suggested in the comments to use 10x the concentration of $$\ce{Ca-EDTA}$$. I don't see how this could work, all it would do is depress the concentration of available fluoride even more.

I suspect $$\ce{EDTA}$$ is used as an anti biofilm agent or preservative, and the $$\ce{Ca}$$ is used so it doesn't chelate dental $$\ce{Ca}$$. I assume this use is unrelated to the process of fluoride delivery.

• Good observation but don't surprised by the fact a lot of food items have EDTA. A mouth-wash is no major exception. You will have read the patent in order to get the idea why EDTA is beneficial in oral rinses patents.google.com/patent/WO1988000044A1/en – M. Farooq May 9 at 20:34
• Secondly you concern of NaF is not a . Ca-EDTA must be present in excess. – M. Farooq May 9 at 20:37
• EDTA suppresses biofilm formation and it also has antimicrobial properties. I assume this is why it as added, or maybe it is used as a preservative. Na-EDTA will scavenge Ca from the teeth, so presumably the Ca-EDTA will leave the Ca in the teeth. What I don't understand is why it does not react with the fluoride. – vodona May 9 at 21:55
• There is no $\ce{CaF}$. Presumably you mean $\ce{CaF2}$ – Buck Thorn May 11 at 7:53
• @NilayGhosh Thanks. You learn something new every day, sometimes two things. – Buck Thorn May 11 at 14:00