[header] How to know if you have a cavity [title] Know that cavities are holes in your teeth. [step] These can be visible, but they may not be. These holes in your teeth are caused by tooth decay. 
Untreated, they can cause a great deal as pain as well as damage to your teeth, bones, gums, and even make you very ill. If they become infected, you will need to seek medical attention to prevent abscesses and the spread of infection.