What Really Causes Cavities?

  • By Anna Rothschild
  • Posted 01.28.16
  • NOVA

Hate going to the dentist? Keep the millions of microbes in your mouth happy. Find out how in this episode of Gross Science.

Running Time: 03:23


What Really Causes Cavities?

Posted: January 28, 2016

Did you know that you have whole communities of microbes living in your mouth right now? And if you don’t treat them right, they’ll make holes in your teeth.

I’m Anna Rothschild, and this is Gross Science.

No matter how much you brush, your mouth is filled with microbes. Thousands of bacteria live on every single one of your teeth—and that’s if you have excellent oral hygiene! You may even have some fungi and amoebas in there, too.

Which microbes are present changes all the time, based on, say, who you’re dating. We swap something like 80 million bacteria with every 10-second-long French kiss, and couples who live together tend to have similar microbes on their tongues. That said, there is what scientists call your “core microbiome.” That’s the 150-ish different species of microbes living in most people’s mouths.

Now, lots of these guys are totally harmless—and some are even helpful. For example, some microbes help keep you from getting thrush, which is a yeast infection of the mouth.

Increasingly, we’re learning that to have a healthy mouth we need healthy microbes, as well. In fact, cavities are a good example of what can happen when the balance of microbes in your mouth gets out of whack.

Many of the microbes living on your teeth form something called “plaque,” and in small quantities, these guys can be our friends. Plaque is what’s called a “biofilm”—essentially a community of different microbes that all stick to a surface, in this case, your teeth. The crazy thing is that these different microbes talk to each other, passing molecular signals back and forth, and swapping genetic material to keep on growing. Eventually, the community even develops what you could think of as a circulatory system to transfer water and nutrients.

And speaking of nutrients, the microbes in these biofilms need to eat, and one thing some of them really love is sugar. So, when you suck on a lollipop, you’re not the only one getting a tasty treat. After their meal, these candy and soda-hungry microbes release acid as a waste product. And that acid is what pulls out the minerals in your teeth, eventually causing cavities.

Now, if you stop eating sugary foods and clean off the plaque by brushing, your teeth have a chance to recover. But if, for example, you drink soda all the time, the bacteria just produce more and more acid, which not only causes cavities, but could actually kill off some of the other, good microbes hanging around. And as the balance of bacteria in your mouth changes, you could get even more tooth decay and other dental problems.

So what can you do about it? Don’t eat too many sugary foods, remember to brush and floss, and get regular cleanings from your dentist. Cause we need to keep our communities of microbes happy and healthy.




Host, Writer, Animator, Editor
Anna Rothschild
Camera, Sound
Katherine Hashimoto
Many thanks to Drs. Susan Perkins, Rob DeSalle, and Anne Tanner
Toy Box
Music Provided by APM
Original Footage
©WGBH Educational Foundation


Dental Plaque, SEM
Steve Gschmeissner/Science Photo Library
Dental Plaque Bacteria in Phase Microscope 600X Blue Filter
Lovers Kissing Romantic Romantic Beautiful Kissing Teens Couple in Hd
Elderly Couple
Dental Plaque From Human Sample 800Z Microscope
Flickr/Seth Lemmons
Candida albicans 2
Wikimedia Commons/GrahamColm
Decayed wisdom tooth
Wikimedia Commons/ProjectManhattan
Dental cavity1
Wikimedia Commons/Digantatalukdar
Digital cavity2
Wikimedia Commons/Digantatalukdar
Double big gulp
Wikimedia Commons/Russell Bernice from New York City, USA
Plaque Disclosing Tablets
Wikimedia Commons/Themolarbear
File: Sugar Cubes (7164573186)
Wikimedia Commons/david pacey from LEEDS, West yorkshire
File: The Dental cosmos (1912) (14769050452)
Wikimedia Commons/White, J.D. McQuillen, J.H. (John Hugh), 1826-1879. Ziegler, George Jacob, 1821-1895. White, James William, 1826-1891. Kirk, Edward C. (Edward Cameron), 1856-1933. Anthony, L. Pierce (Lovick Pierce), b. 1877.
File: Phagocytose Entamoeba gingivalis-PMN
Wikimedia Commons/Mark Bonner dmd, Institut International de Parodontie, www.parodontite.com
Oral thrush. Aphthae. Candida albicans.


Dun dun dun
Squeak Pack/squeak_10
Jelly/Jelly Mangling on Plate
Bubbles Popping
Produced by WGBH for PBS Digital Studios


Microbes and Lollipop
©WGBH Educational Foundation 2016


Want more info?

Welcome to the Microbiome, by Susan Perkins and Rob DeSalle:

Kissing and the microbiome:

More on thrush from the CDC:

The Role of Bacteria in the Caries Process:

Related Links