What is Tooth Decay or "Cavity"? Tooth decay or cavity is a disease that destroys the structure of teeth. If left untreated, it can lead to pain and infection and in severe cases, tooth loss. What causes tooth decay? Bacteria in the mouth feeding on sugar from diet/food produce acids that destroy tooth structure creating a "hole" in the tooth, otherwise known as cavity. What is the treatment for tooth decay? If detected at the earliest, tooth decay can be treated by simply filling the cavity with tooth color materials. If the decay is extensive causing pain or swelling, a root canal treatment is recommended. What are the filling materials that are used? The most commonly used dental filling materials are GlassIonomer Cement and composite (tooth color) materials.