Dear Lucy,

If you are anything like me, every day you squeeze a little toothpaste onto your toothbrush and brush your teeth. Toothpaste gets its cleaning power from a few different ingredients.

My friend Mark Leid was happy to tell us about how they work. Leid spent part of his career teaching future dentists. He is also dean of the Washington State University College of Pharmacy and Pharmaceutical Sciences.

Mark Leid headshot wearing grey suit and crimson tie
Mark Leid

First, he told me the outer covering of a tooth is called enamel. It’s the hardest tissue in the whole human body—even harder than bone—and it helps with things like chewing your food.

Inside your mouth and on your teeth, there are lots of tiny living things called microorganisms. They are so small you’d probably need a microscope to see them, but they like to eat the leftover food bits that get stuck in your teeth.

As they eat those leftover bits, they also make acid. That acid can break down your enamel, which can lead to cavities or tooth decay.

“We can’t make new enamel,” Leid said. “Once our enamel is gone, it’s gone.”

That’s part of the reason it is so important to brush our teeth. When you brush your teeth with toothpaste, it helps get rid of that acid.

Getting rid of acid

Leid said some ingredients that help get rid of the acid and leftover food in your teeth are called abrasives. These create scrubbing power and sometimes give the toothpaste a gritty texture. Abrasives are combinations of atoms, which are like building blocks, that come together to form something called a chemical compound.

One example is calcium carbonate, which is made up of carbon, oxygen and calcium atoms. Another is silica gel, which is made up of silicon and oxygen atoms. Some other compounds create scrubbing power, but these are two of the main ones.

Cartoon cat Dr. Universe looks up to the question about toothpaste

Meanwhile, other toothpaste ingredients help create foaming action, such as sodium lauryl sulfates and sodium N-lauryl sarcosinate. These are the same compounds that give soaps their foamy qualities.

Take a look at toothpaste

Take a look at the back of your toothpaste tube and see what ingredients you can find. Another ingredient you might notice is fluoride, which helps strengthen your enamel. You might also see other flavoring agents that give toothpaste its taste, like mint.

“Otherwise, it would taste pretty chalky and bitter,” Leid said.

When you brush your teeth, you are helping your mouth stay clean and healthy. In addition to brushing, flossing is also important. Floss helps remove any excess food between your teeth that might invite those acid-making bacteria.

It’s great to hear you are curious about toothpaste, Lucy. Who knows, maybe one day you will be a chemist, a dentist, a pharmacist or anything else you dream. Keep up the great brushing, keep asking great science questions and don’t forget to floss.

Dr. Universe

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