Calcium carbonate is a common toothpaste ingredient with 5 key functions: whitening abrasive, white colorant, thickener, remineralization, and oral buffering. As for its safety, it's probably one of the safest ingredient in an oral care product.
Below is a concise summary with things to know about it when it's used in toothpaste. Clicking each link will take you to more in depth information or you can simply scroll.
Calcium Carbonate in toothpaste overview
Description: White colored calcium salt.
Benefits: Whitening abrasive, White colorant, Thickener, Remineralization, Oral buffering.
Synergists: Titanium dioxide.
Antagonists: Fluoride and Phosphates.
Side effects: Gastrointestinal disturbances, Cardiovascular diseases.
Safety: Non-toxic (safe to swallow).
Abrasiveness: 3 on Mohs hardness scale.
What is calcium carbonate?
Calcium carbonate (CaCO3) is a calcium salt often in the form of a white odorless powder but it can also be a colorless crystal. It is also insoluble in water.
Where it comes from:
Naturally found in rocks from the minerals calcite and aragonite.
Commonly found in limestone, eggshells, shellfish, and pearls.
As a matter of fact, according to the University of Florida, 95% of dry eggshell weight is from CaCO3. Yes, those very same eggs that we all love for breakfast.
Common uses:
Antacid - TUMS
Calcium supplement
Chalk
Cement, paint, cosmetics, rubber, plastics, ceramics, ink, adhesives, etc.
Most people don't realize it but the antacid TUMS which people often take for heartburn is made of calcium carbonate. It is literally listed as the active ingredient on the product label.
What calcium carbonate does in toothpaste
When incorporated as a toothpaste ingredient, calcium carbonate provides five key benefits:
Removes extrinsic stains.
Adds a white color to the toothpaste.
Thickens the paste.
Assists in teeth remineralization.
Rebalances oral pH via buffering.
Extrinsic stain removal
CaCO3 is mildly abrasive in that it naturally has a gritty texture. This abrasiveness is what bestows upon it the ability to mechanically abrade away tooth stains on the surfaces of the enamel and dentin.
It is due to its abrasive property that it is known as a whitening abrasive. That is also how the toothpaste is able to call itself as a whitening toothpaste.
Studies have shown that it is a more effective abrasive than silica.
The abrasiveness is also mild enough to not cause enamel damage.
Note: The abrasive type of teeth whitening is different from the chemical bleaching of the teeth which your dentist does.
Dyes toothpaste white
Serving as a white color dye isn't the most well known effect of CaCO3 but it does help in making the toothpaste white. Chalk and TUMS are made of it and that is why they look so white.
Therefore, adding it into the formulation along with titanium dioxide (another white colorant) helps to give the paste that characteristically white color that we're all used to seeing. Without it, the toothpaste would probably look translucent in color.
Thickens the paste
It is added to toothpaste to also help thicken it and bulk it up so that it has body. Without it, the paste may be too watery and will slump more easily.
Helps remineralization
Calcium carbonate helps in the remineralization of teeth by serving as an additional source of calcium (Ca). Ca is a vital tooth mineral which makes up the tooth structure and without it, the enamel cannot repair itself from tooth decay.
Studies have shown that the ideal ratio of calcium to phosphate for optimal remineralization is 1.6 but the oral environment is often at a 0.3 ratio. That means the limiting factor for remineralization is an insufficient supply of calcium.
However, with the addition of calcium carbonate to toothpaste, that bottleneck can be alleviated with the additional Ca+ ions.
Rebalances oral pH
Toothpastes with CaCO3 can rebalance the oral pH by neutralizing acids in the mouth and in the dental plaque. It is a natural buffering agent since it is composed of calcium and bicarbonate ions. The latter is what the saliva already contains and uses to deacidify the mouth.
Our mouth/saliva naturally uses three buffering systems to neutralize acids:
Bicarbonate system.
Phosphate system.
Protein buffer system.
Essentially what this toothpaste ingredient does is supercharge the bicarbonate system by supplying the mouth with excess bicarbonate ions.
Synergistic effects
When the toothpaste formulation includes calcium carbonate with titanium dioxide, a synergistic effect occurs. The toothpaste gains desensitization properties and also increased acid erosion resistance.
Additional benefits with TiO2:
Sensitivity reduction. Studies have demonstrated that when the two are combined, it led to an occlusion of exposed dentinal tubules. That means less tooth nerve stimulation thus less discomfort.
Acid erosion resistance. Studies found that it reduced acid attacks and it did not interfere with the oral buffering properties when combined together.
In summary, TiO2 with CaCO3 provided positive effects and additional toothpaste benefits.
Antagonists
Despite the wonderful effects of CaCO3, it can adversely affect fluoride and phosphates in the mouth. It will reduce their bioavailability for remineralization.
Fluoride
Sodium monofluorophosphate toothpastes when combined with calcium carbonate can help prevent cavities.
However, other forms of fluoride may have reduced anti-caries efficacy when formulated with calcium carbonate. This was mentioned in a study by the American Dental Association.
As it turns out, poorly soluble forms of CaCO3 will interact with fluoride to form CaF (calcium fluoride) thus reducing its bioavailability. That means the amount that can be adsorbed by your teeth will be reduced.
Studies: 50% fluoride ion reduction when calcium carbonate or calcium hydrogen phosphate dihydrate are combined.
The good news is that toothpastes with calcium in the form of casein phosphopeptide amorphous calcium phosphate (CPP-ACP) or tricalcium phosphate did not encounter this problem. They maintained a near 100% bioavailability of fluoride.
Phosphates
Calcium carbonate can negatively affect the phosphate in the oral cavity because of its phosphate binding affinity. That means it can reduce the amount of it available for tooth remineralization.
You may be surprised to know but CaCO3 is used to treat chronic kidney diseases such as hyperphosphataemia, where there is TOO MUCH calcium in the blood. What it does is bind to the phosphate so that it can be excreted instead of staying in the blood.
Yes, it is a well known phosphate-binder and that isn't good when you're trying to repair tooth decay.
Side effects
Calcium carbonate is a supplement and is also used as an antacid but it can have adverse effects when used improperly.
Potential side effects when overdosed or abused:
Coma
Confusion
Irregular heart rhythms
Muscle twitching
Bone pain
Abdominal pain
Pancreatitis
Acute renal failure
Kidney stones
Headache
Milk-alkali syndrome
Gall stones
Drug-Drug Interactions
Potential adverse effects when it is taken with these drugs:
Histamine-2 receptor antagonists
Glucocorticoids
Thiazide diuretics
Bisphosphonates
Fluoroquinolones
Tetracyclines
Thyroid hormones
Proton pump inhibitors (omeprazole)
Iron
Anti-arrhythmic drugs (verapamil)
Note: As a reminder, taking Vitamin D will help increase the absorption of CaCO3. After all vitamin D and calcium are beneficial for one another just like when you drink milk.
Is calcium carbonate safe in toothpaste?
Calcium carbonate is one of the safest toothpaste ingredients because you don't swallow toothpaste but even if you do, it is non-toxic.
You don't swallow toothpaste
We all know that we're not supposed to swallow toothpaste because you're supposed to spit it back out after you're done. As a matter of fact, you should give your mouth a good rinse too. Therefore the vast majority of CaCO3 doesn't even make it into your bloodstream nor the digestive system.
It's edible and non-toxic
In case you forgot, the antacid TUMS is made of CaCO3 so even if you swallow it, it is not harmful. As a matter of fact whenever we get heartburn, we intentionally take it, chew it and swallow it to help relieve discomfort from stomach acid.
If you're able to eat this ingredient without any adverse effects, surely it must be safe in a toothpaste that you spit back out. Hopefully you agree with us that calcium carbonate is probably the least harmful and least toxic ingredient in a toothpaste!
Abrasiveness
Calcium carbonate is considered a soft mineral with a 3 on Mohs scale of hardness and that makes it safe to use on enamel. The reason is because enamel has a 5 on Mohs hardness scale so it won't get scratched by it.
Mineral | Mohs Hardness Scale |
|---|---|
Calcium Carbonate | 3 |
Hydroxyapatite (Enamel) | 5 |
In summary, enamel is relatively much harder than CaCO3 so it is impossible to be harmed by it. Therefore, I wouldn't even worry about any potential enamel damage while brushing with this ingredient. I would consider it as an important part of preventative dentistry namely when used in toothpaste!
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