Medical Health Encyclopedia

Some bacteria are related to gingivitis, but not plaque development. They include various streptococcal species.

The Autoimmune and Inflammatory Response

Evidence now suggests that periodontal disease is an autoimmune disorder, in which immune factors in the body attack the person's own cells and tissue -- in this case, those in the gum. It appears to work as follows:

• The bacteria that form plaque and tartar release toxins that stimulate the immune system to overproduce powerful infection-fighting factors called cytokines.
• Ordinarily, cytokines are important for healing. In excess, however, they can cause inflammation and severe damage. Cytokines of particular importance in periodontal disease are known as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta, which are very active in the mouth, and are important in causing destructive inflammation.
• In addition, white blood cells produced by the immune response to bacteria also release a family of enzymes called matrix metalloproteinases (MMPs), which break down connective tissue.

Studies suggest that this inflammatory response may have damaging effects not only in the gums but also in organs throughout the body, include the heart.

Viral Causes

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Certain herpes viruses (herpes simplex and varicella-zoster virus, the cause of chickenpox and shingles) are known causes of gingivitis. A 2000 study found that other herpes viruses (cytomegalovirus and Epstein-Barr) may play a role in the onset or progression of some types of periodontal disease, including aggressive and severe chronic periodontal disease. All herpes viruses go through an active phase followed by a latent phase and possibly reactivation.

Some experts hypothesize that these viruses may cause periodontal disease in different ways, including release of tissue-destructive cytokines, overgrowth of periodontal bacteria, suppressing immune factors, and initiation of other disease processes that lead to cell death.