Tooth Decay - Causes

Tooth decay occurs when three factors are present: bacteria, sugar, and a weak tooth surface.

The sugar often comes from sweet foods such as sugar or honey. But it can also come from starchy foods such as bread and rice. When a starch breaks down in the mouth, it forms sugar. Bacteria that live on the surface of a tooth eat sugar. When they do so they change the sugar into an acid called lactic acid.

Healthy tooth enamel may be able to resist this acid. But tooth enamel often has tiny holes and weak spots. Lactic acid can soak into these holes and dissolve the minerals of which enamel is made. Over time, the hole may get larger and larger. If the hole penetrates into the next tooth layer, called the dentin, the tooth becomes sensitive to touch and temperature. Decay can even penetrate to the center of the tooth, the pulp. In that case, the inner tooth may become inflamed and begin to ache.