The acids in plaque damage the enamel covering your teeth. It also creates holes in the tooth called cavities. Cavities usually do not hurt, unless they grow very large and affect nerves or cause a tooth fracture. An untreated cavity can lead to an infection in the tooth called a tooth abscess. Untreated tooth decay also destroys the inside of the tooth (pulp). This requires more extensive treatment, or possibly removal of the tooth.
Carbohydrates (sugars and starches) increase the risk of tooth decay. Sticky foods are more harmful than non-sticky foods because they remain on the teeth. Frequent snacking increases the time that acids are in contact with the surface of the tooth.