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.