Sciencemadness Discussion Board

"Liquid Calcium" in toothpaste

Nixie - 4-7-2007 at 15:03

How does it work? The only thing it says is the calcium and potassium present restores enamel since far more calcium ions from the toothpaste than is in saliva.
But there's no calcium phosphate in the toothpaste. Ingredients show calcium sulfate (which is insoluble) and dipotassium phosphate. What reactions are here? Also there's fluoride in the toothpaste.

not_important - 4-7-2007 at 15:23

Quote:
Originally posted by Nixie...
But there's no calcium phosphate in the toothpaste. Ingredients show calcium sulfate (which is insoluble) and dipotassium phosphate. What reactions are here? ...

Solubility of calcium sulfate in pure water runs around 0,2 to 0,3 grams per 100 cc water. Various coumponds can increase that solubility, ammonium salts do as do some organic acids and even polyols.

Once those ionic salts are in solution, you have ions instead of compounds. You can no longer talk about calcium sulfate and potassium phosphate, you have Ca(2+) and K(1+) and SO4(2-) and likely a mix of HPO(2-) and H2PO4(1-) - the 3rd hydrogen comes off of phosphate under rather basic conditions that you don't want in your mouth, and even the 2nd isn't a very strong acid. So unless there's enough Ca and HPO4 to exceed the solubility constant of CaHPO4, it looks like 0,04 grams/100 cc would stay in solution and thus just be ions; Ca(H2PO4)2 is much more soluble, something on the order of a gram or so.

Nixie - 4-7-2007 at 15:27

So what would cause it to mineralize on the teeth? Is there perhaps some reaction with the fluoride?

12AX7 - 4-7-2007 at 17:46

I don't think there is any possibility of having excess calcium and phosphate ions deposit useful material on the teeth. Toothpase, a brush and a once-a-night (if that) application of paste isn't going to grow a smooth layer like stalactites growing in a cave over a few hundred years does. At best, you'd get something resembling plaque, which we all know dentists scrape off anyway -- since it harbors bacteria.

What's the solubility of hydroxylapatite, or considering it's toothpaste, fluorapatite?

Tim

Nixie - 4-7-2007 at 18:11

Fluoroapatite is formed because fluorine ions replace the hydroxide in the enamel's hydroxyapatite. Neither of these are soluble, so the reaction occurs with the hydroxyapatite as solid. But enamel is not completely impermeable; ions get between the crystals, so it's does go a little bit below the surface. Otherwise teeth whitening wouldn't work.
What I'm not sure is where the calcium comes in. However, I found the following in one paper abstract:
Quote:
Etched enamel surfaces were treated topically with combinations of acid phosphate fluoride and stannous fluoride solutions, and then exposed to constantly recirculated neutral calcium phosphate solutions. The calcium, phosphate, fluoride, and hydrogen ion reactions with the variously treated surfaces were compared. Results showed concurrent dissolution of calcium fluoride and diffusion of hydrogen fluoride from the surfaces, and indicated concurrent deposition of apatitic mineral into the surfaces.

A few places mention small caries actually being reversed as enamel slowly rebuilds sourcing calcium from the saliva--with plain fluoride toothpaste being used. There are special proteins in the enamel that are considered to have structural functions and affect crystal growth. But none reference the calcium sulfate and dipotassium phosphate mix that's in such toothpaste and whether it actually increases the availability of calcium and phosphate ions compared to what saliva provides.

[Edited on 4-7-2007 by Nixie]

SsgtHAZMAT - 24-7-2007 at 23:26

So what toothpaste should I use?

:)

not_important - 24-7-2007 at 23:40

Quote:
Originally posted by SsgtHAZMAT
So what toothpaste should I use?

:)


The ones without ethylene glycol or diethylene glycol in them.

SsgtHAZMAT - 24-7-2007 at 23:53

But what if I dont want my mouth to freeze??

not_important - 25-7-2007 at 00:26

Drink high alcohol content fluids?

Or hot drinks. Coffee to wake you up, chocolate to help you sleep, both together as mocha.

I suspect this is not a problem during the summer in Iraq...

16MillionEyes - 25-7-2007 at 08:00

Quote:

The ones without ethylene glycol or diethylene glycol in them.

What kind of toothpaste brand are you talking about? They don't list their ingredients except the active ones (such as fluoride).

Nixie - 25-7-2007 at 08:02

Quote:
Originally posted by __________
Quote:

The ones without ethylene glycol or diethylene glycol in them.

What kind of toothpaste brand are you talking about? They don't list their ingredients except the active ones (such as fluoride).

I'm in Canada and all toothpastes list all their ingredients.

16MillionEyes - 25-7-2007 at 08:39

Well, we all don't have the pleasure to live in Canada so we might be consuming some diethylene glycol without knowing it. :D

Xenoid - 25-7-2007 at 12:56

What I'd like to know is how do potassium and/or strontium nitrate work in toothpaste for sensitive teeth......... :D

Cation size... nitrate reaction.....?

Xenoid