Most cavities are discovered in the early stages during routine checkups. The surface of the tooth may be soft and sticky when checked with a fine instrument. Pain may not be present until the advanced stages of tooth decay. Dental x-rays may show some cavities before they are visible to the eye.

Bacteria are normally present in the mouth. The bacteria convert all foods -- especially sugar and starch -- into acids. Bacteria, acid, food debris, and saliva combine in the mouth to form a sticky substance called plaque that adheres to the teeth. It is most prominent on the back molars, just above the gum line on all teeth, and at the edges of fillings. Plaque that is not removed from the teeth mineralizes into tartar. Plaque and tartar irritate the gums, resulting in gingivitis and if left untreated will ultimately result in periodontitis.

The dentist will restore teeth by removing the decay and replacing it with a material called composite resin, which closely matches the natural tooth appearance.