How modern toothpastes keep our teeth clean – and why we no longer use pee to brush

Difficulty: Challenger (Level 2)

Toothpaste makes your mouth smell fresh and feel clean. Brushing your teeth two times a day with toothpaste also helps prevent cavities, which are holes in your teeth.

Some toothpaste ingredients mix with saliva to make a foam, which turns into a slimy slop that you spit out.

Many toothpastes remove plaque, which are sticky globs that grow on your teeth and form cavities (see graphic).

Toothpaste may contain special ingredients that prevent holes from forming, such as xylitol (pronounced zy-luh-toll). When bacteria in plaque eat xylitol, they release less of the acid that makes cavities.

Fluoride (pronounced floor-ride) is another common ingredient in toothpaste.

Your teeth have tiny gaps on the surface that are so small you can only see them with a microscope. Fluoride fills these gaps to make your teeth strong, and it keeps nasty bacteria from dissolving your teeth.

What did people use before toothpaste was invented?

People who lived long ago thought getting holes in their teeth was part of growing up, so they tried to make their teeth look whiter by using tooth powders.

The first tooth powders were made of crushed animal bones, ox hooves, and the shells of eggs, snails and oysters. Some people even cleaned their teeth with toothpaste made from pee.

Luckily, we now have toothpastes that leave a better taste in our mouth, smell good and keep our teeth healthy.

Brush your teeth in the morning and before bed. When you brush your teeth, remember to spit out the toothpaste and avoid using too much. Don’t rinse it all away with water; keep a bit in your mouth to protect your teeth from nasty bacteria.

Dr Arosha Weerakoon is a senior lecturer and general dentist at the University of Queensland’s School of Dentistry. This article was first published by The Conversation.

Sample answers

• Stop and answer: Toothpaste removes plaque and fills holes in our teeth to keep bacteria from eating away at it.

• Consider this: People used to use crushed animal parts and even pee. The animal parts might have helped remove some plaque, but the pee probably added more bacteria.