As with gum disease, dental decay is caused by the accumulation of plaque around and in between the teeth. Plaque is a combination of food and bacteria mixed together to make a thin film that covers your teeth. In this film, the bacteria are feeding on the food and producing toxins and acids.
Dental decay happens when the enamel and dentine of a tooth become demineralised or softened by an acidic attack from plaque, which causes a cavity, or hole in your tooth.
Decay may not cause discomfort, but even though it might not hurt, the tooth is still deteriorating. Your dentist is able to detect decay at an early stage to prevent excessive tooth damage.
When cavities are small, they are much easier and cheaper to treat. If left too long, a small cavity could grow enough to need a root canal treatment or even a tooth extraction if the damage is extensive enough.