Gum disease is caused by plaque, a sticky film of bacteria that constantly forms on the teeth. These bacteria create toxins that can damage the gums.
Periodontal diseases attack just below the gum line in the sulcus, where they cause the attachment of the tooth and supporting tissues to break down. As the tissues are damaged, the sulcus develops into a pocket; generally, the more severe the disease, the greater the depth of the pocket.
Periodontal diseases are classified according to the severity of the disease. The two major stages are gingivitis and periodontitis.