What causes a cavity?

What causes a cavity?



Your mouth is a busy place. Bacteria - tiny colonies of living organisms are constantly on the move on your teeth, gums, lips and tongue.

Cavity AnimationHaving bacteria in your mouth is a normal thing. While some of the bacteria can be harmful, most are not and some are even helpful.

Certain types of bacteria, however, can attach themselves to hard surfaces like the enamel that covers your teeth. If they're not removed, they multiply and grow in number until a colony forms. More bacteria of different types attach to the colony already growing on the tooth enamel. Proteins that are present in your saliva (spit) also mix in and the bacteria colony becomes a whitish film on the tooth. This film is called plaque, and it's what causes cavities.


Severe Dental Decay

The hard, outside covering of your teeth is called enamel. Enamel is very hard, mainly because it contains durable mineral salts, like calcium. Mineral salts in your saliva help add to the hardness of your teeth. Mineral salts, however, are prone to attack by acids. Acid causes them to break down.

For an experiment about the power of acid, check out the Healthy Teeth Dental Experiments page!

The plaque that forms on your teeth and doesn't get washed away by saliva or brushed away by your toothbrush produces acid as it eats up sugar. This acid is produced inside the plaque and can't be easily washed away by your saliva. The acid dissolves the minerals that make your tooth enamel hard. The surface of the enamel becomes porous - tiny holes appear. After a while, the acid causes the tiny holes in the enamel to get bigger until one large hole appears. This is a cavity.

It's important to see your dentist before a cavity forms so that the plaque you can't reach with your toothbrush or floss can be removed.


Nerve fibres, the way that pain is sent through the body, aren't present in tooth enamel. While the acid is attacking the enamel, you can't feel a thing.

Once the acid has begun to create a cavity and attacks the dentin under the enamel, the nerve fibres begin to send out a message that something is wrong. But by then, you have tooth decay.

That's why it's important to have regular, preventive dental check-ups. Don't wait until it hurts