Cavities are caused by tooth decay — a process that occurs over time. It begins as the action of bacteria damages the hard surface (enamel) of your teeth, a process that can occur without any noticeable discomfort. Decay can then progress to the deeper layers of your teeth in the following steps:

  • Plaque forms. Your mouth, like many other parts of your body, naturally contains many types of bacteria. Some of these bacteria thrive on food and drinks that contain certain forms of sugar, also known as fermentable carbohydrates. When these sugars aren't cleaned off your teeth, the bacteria quickly begin feeding on them and producing acids. The bacteria, acids, food particles and saliva then form into dental plaque — a sticky film that coats your teeth. If you run your tongue along your teeth, you may be able to feel this plaque forming several hours after you've brushed. The plaque is slightly rough and is more noticeable on your back teeth, especially close to your gums.
  • Plaque attacks. The acids in plaque remove minerals in your tooth's hard, outer enamel. This erosion causes tiny openings or holes in the enamel — the first stage of cavities. Once areas of enamel are worn away, the bacteria and acid can reach the next layer of your teeth, called dentin. This layer is softer and less resistant to acid than is enamel.
  • Destruction continues. As tooth decay continues, the bacteria and acid continue their march through your teeth, moving next to the inner tooth material (pulp) that contains nerves and blood vessels. The pulp becomes swollen and irritated from the bacteria. The bone supporting your tooth also may be affected. When decay advances to this extent, you may have severe toothache, sensitivity, pain when biting or other symptoms. Your body also may respond to these bacterial invaders by sending white blood cells to fight the infection. This may result in a tooth abscess.
Apr. 28, 2011