Fillings are used to address tooth decay. If left untreated, you may experience severely compromised dental health. There are five key stages of tooth decay, including:Demineralization: In the early stages of tooth decay, tiny spots on the tooth may become visible, signaling a breakdown in the enamel. Enamel decay: As the damage progresses, the enamel continues to deteriorate. This stage is accompanied by visible tooth staining.Dentin decay: At this stage of tooth decay, sensitivity becomes an issue. You may also notice increased tooth discoloration. Pulp damage: The pulp of the tooth contains nerves and blood vessels, meaning any damage to this area results in significant pain. Gum redness and swelling are also common at this stage. Abscessed tooth: A tooth abscess is an infection that damages the tissues. However, this stage of tooth decay is particularly dangerous because the infection can spread to other parts of the body. In rare cases, infection can travel to the brain or the bloodstream. Pain from an abscessed tooth can radiate from the tooth to the jaw, face, and neck and swollen lymph nodes may also occur.