Healthy gums are firm and springy, and vary in color depending on the thickness of the outer layer. A change in normal color is one of the first signs of gum disease, which has three stages: gingivitis, periodontitis, and advanced periodontitis (pyorrhea). This progression is illustrated by the figures above.

Gingivitis-an inflammation of the gums-is the initial stage of gum disease and the easiest to treat. The direct cause of gingivitis is plaque the soft, sticky, almost colorless film that forms continuously on the teeth and gums. Plaque is not harmful if it is removed before it begins to accumulate. However, if teeth and gums are not cleaned thoroughly every twenty-four to thirty-six hours, the bacteria in plaque produce toxins and enzymes that inflame the gums. Due to this inflammation, the gums become slightly red and puffy and may bleed during brushing or flossing; the gums may also begin to recede (pull away) slightly from the tooth or teeth. During this early stage of gum disease, called gingivitis, damage can be reversed since the bone and connective tissue that hold the teeth in place are not yet affected.

Other factors that may contribute to gingivitis include habitual clenching and grinding of the teeth and mouth-breathing. A diet that is high in simple carbohydrates and sugar and deficient in vitamins also contributes to gingivitis, as well as the use of tobacco, drugs, and alcohol. Heredity, hormonal imbalances (during pregnancy and puberty), oral contraceptives,
and stress are other possible contributors.

If gingivitis is left untreated, the inflammation can spread to the roots of the teeth developing into periodontitis. During this second stage of gum disease, the plaque penetrates deeper into the gum tissues and eventually begins to affect the underlying bone. As the disease continues to advance, the gums further recede from the teeth giving them an elongated appearance. Gum pockets form, in which more plaque and food debris collects. These pockets prevent easy cleaning and elimination of plaque under the gums, causing halitosis (see Bad Breath in Part Two) and pain. Accumulation of bacteria causes infections that begin to destroy the bone. Abscesses may form, the teeth may shift or become loose, and the bite may change. Tartar or mineralized plaque deposits further irritate the gums. Any pressure on the gums during this stage may cause heavy bleeding or the discharge of pus.

The third stage of gum disease, advanced periodontitis or pyorrhea, is marked by major gum recession and severe bone loss. At this point, the teeth are often too loose to be saved and frequently have to be pulled.

Acute necrotizing ulcerative gingivitis (ANUG), also called Vincent's disease or trench mouth, is another type of gum disease. Symptoms of ANUG include ulcers along the gum line and between the teeth. It is often accompanied by fever, swollen glands, nausea, headaches, and general weakness. Although ANUG appears suddenly, its causative factors-poor oral hygiene, physical and mental stress, weakened immune system due to illness-usually have been present for some time.