You probably have a vague idea that cavities come from eating sugar and not brushing, but what exactly is going on in there? This video introduces us to the bacteria in our mouth that cause cavities — and the friendly ones that round out the ecosystem.
The microbes in our mouths are, for the most part, a good thing. They keep other germs from taking hold, for example. But some of these microbes eat sugar, and they produce acid as a waste product. Brushing your teeth keeps the bacteria to a healthy minimum, and avoiding sugary foods gives them less of a chance to make the acid. Since the acid is what causes those holes in your teeth, it's good advice to follow.
What Really Causes Cavities [Gross Science]