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Calcium Carbonate in Toothpaste: Benefits & Safety

Updated: Dec 21, 2023

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


 

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.


Calcium carbonate powder
Calcium carbonate powder

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.


4 white eggs - eggshells made of calcium carbonate
White eggs

Common uses:

  • Antacid - TUMS

  • Calcium supplement

  • Chalk

  • Cement, paint, cosmetics, rubber, plastics, ceramics, ink, adhesives, etc.


TUMS ultra strength 1000 antacid - 1000 mg calcium carbonate
Tums antacid

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.


TUMS ultra strength 1000 antacid - active ingredients label 1000 mg calcium carbonate
TUMS active ingredients 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.


Calcium carbonate in toothpaste 4 key functions
Key functions

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.


demineralization remineralization of teeth
Credit: Sangi Co

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.


Calcium carbonate buffering mechanism
Calcium carbonate buffering mechanism - Credit: Professor Patricia Shapley

Our mouth/saliva naturally uses three buffering systems to neutralize acids:

  • Bicarbonate system.

  • Phosphate system.

  • Protein buffer system.


calcium carbonate buffering among rock water air
CaCO3 buffering in natural environment - Credit: Professor Patricia Shapley

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.


Crushed calcium carbonate from TUMS
Crushed calcium carbonate from TUMS

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.


TUMS antacid - calcium carbonate tablet next to container
Taken for heartburn

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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About the author: Dr David Chen, DDS

Hello, I'm Dr Chen and I'm an actively practicing dentist in Long Island City, NY. I graduated from Columbia University College of Dental Medicine in 2016 but prior to going to dental school I was already working in the dental field. It's been more than a decade since I first got to know dentistry and let me tell you, time flies by quickly. Since then I've developed a fondness for writing, which is how this all got started!

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Medical Disclaimer:

This blog is purely meant for information purposes and should not be used as medical advice. Each situation in your mouth is unique and complex. It is not possible to give advice nor diagnose any oral conditions based on text nor virtual consultations. The best thing to do is to go in person to see your dentist for an examination and consultation so that you can receive the best care possible.

The purpose of all of this oral health information is to encourage you to see your dentist and to inform you of what you may expect during your visit. Due to the unfortunate nature of dentistry, there isn't really any true home remedies that will get rid of dental problems. Roughly 99.99% of them require in-person intervention by a healthcare professional.

Hint: That is the reason why you can't eliminate seeing dentists in your life!

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