Dental caries is the scientific term for tooth decay or cavities. It is caused by specific types of bacteria. They produce acid that destroys the tooth's enamel and the layer under it, the dentin.
Many different types of bacteria normally live in the human mouth. They build up on the teeth in a sticky film called plaque. This plaque also contains saliva, bits of food and other natural substances. It forms most easily in certain places. These include:
Cracks, pits or grooves in the back teeth
Around dental fillings or bridgework
Near the gum line
The bacteria turn sugar and carbohydrates (starches) in the foods we eat into acids. The acids dissolve minerals in the hard enamel that covers the tooth's crown (the part you can see). The enamel erodes or develops pits. They are too small to see at first. But they get larger over time.