The pulp, or soft inner tissue is important during the tooth's development. Once a tooth is fully mature, the tooth can survive without the pulp because the tooth is nourished by tissues surrounding it. The pulp is normally surrounded and protected by a layer of dentin.
Above the gumline, the dentin is protected by a layer of enamel; below the gum-line the dentin is covered by cementum. When a crack or cavity destroys these protective layers, the pulp is exposed to irritants and bacteria in your mouth. This can result in inflammation then infection, and, eventually, an abscess. Periodontal (gum) disease or a severe blow to the tooth can also damage the pulp. Endodontic therapy removes the damaged pulp and usually the tooth returns to a healthy condition.
If an abscess was present before treatment the healing process may take up to 2 years.