Periodontal (gum) diseases, including gingivitis and periodontitis, are serious infections that, left untreated, can lead to tooth loss. Periodontal disease is a chronic bacterial infection that affects the gums and bone supporting the teeth. The word periodontal literally means “around the tooth.” Periodontal disease can affect one tooth or many teeth. It begins when the bacteria in plaque (the sticky, colorless film that constantly forms on your teeth) causes the gums to become inflamed.
In the mildest form of the disease, gingivitis, the gums redden, swell, and bleed easily. There is usually little or no discomfort. Gingivitis is often caused by inadequate oral hygiene. Gingivitis is reversible with professional treatment and good oral home care.
Diagram from American Academy of Periodontology Information Pamphlet
Untreated gingivitis can advance to periodontitis. Toxins produced by the bacteria in plaque irritate the gums. The toxins stimulate a chronic inflammatory response in which the body in essence turns on itself, and the tissues and bone that support the teeth are broken down and destroyed. Gums separate from the teeth, forming pockets (spaces between the teeth and gums) that become infected. As the disease progresses, the pockets deepen and more gum tissue and bone are destroyed. Often, this destructive process has very mild symptoms. Eventually, teeth can become loose and may have to be removed. The main cause of periodontal disease is bacterial plaque, a sticky, colorless film that constantly forms on your teeth.
Diagrams from American Academy of Periodontology Information pamphlet and website
However, factors like the following also affect the health of your gums: