Brushing Up on Gum Disease

by Food and Drug Administration (FDA)

Getting your teeth pulled because of a sore arm may sound farfetched. But it happened more than once, says Saul Schluger, D.D.S., professor emeritus at the University of Washington's school of dentistry in Seattle.

Schluger has been involved in the treatment and study of gum, or periodontal, disease for more than 50 years, and he recalls that the patients in these cases were professional baseball players who had the ill luck to have developed their dental (and arm) problems when the "focal infection" theory of periodontal disease was in vogue earlier this century. The theory held that periodontal disease always worsened, could only be stopped by pulling teeth, and that it could spread — not only from one area of the gums to another, but to other parts of the body. In the case of an affected ballplayer with a sore arm, explains Schluger, it was considered possible that migrating infection from the gums might be the cause of the sore arm. To prevent further problems it was sometimes thought best to simply pull the player's teeth.

For ordinary people, a more common scenario was the wholesale pulling of teeth at the first sign of gum disease. The reaction, says Schluger, was "almost Pavlovian. If you had gum disease, you had your teeth out. It was the cause of a lot of dentures."

Old Beliefs, New Data

Though the focal infection era is now behind us, its legacy remains. Many older people are toothless and wearing dentures for reasons now considered unnecessary. And many fears and beliefs formed during that period continue to hold sway. For instance, periodontal disease is commonly said to be responsible for 70 percent of the teeth lost after childhood. But, according to Brian Burt, Ph.D., a dental epidemiologist in the School of Public Health at the University of Michigan, this oft-repeated statement is based largely on a single study conducted in the early 1950s. A more recent study published in the January 1987 Journal of the American Dental Association found that dental decay was the most common disease-related reason for adult tooth extractions in the late 1970s and early 80s; only 9 percent were necessitated by periodontal disease. Clearly, much has changed. So what is the threat of periodontal disease today? And what can be done about it?

What Is Periodontal Disease?

In the broadest sense, periodontal disease can be considered any form of ill health affecting the periodontium — the tissues that surround and support the teeth. These include the gums (or gingiva), the bone of the tooth socket, and the periodontal ligament, a thin layer of connective tissue that holds the tooth in its socket and acts as a cushion between tooth and bone.

Inflammation or infection of the gums is called gingivitis; that of the bone, periodontitis. These conditions can arise for a variety of reasons. A severe deficiency of vitamin C can lead to scurvy and result in bleeding, spongy gums, and eventual tooth loss. And at least one periodontal disease — the uncommon but highly destructive juvenile periodontitis — is thought to have a strong genetic basis. But as the terms periodontal disease, gingivitis, and periodontitis are most commonly used, they refer to disease that is caused by the buildup of dental plaque.

Plaque is a combination of bacteria and sticky bacterial products that forms on the teeth within hours of cleaning. Its source is the natural bacteria in the mouth, of which more than 300 different species have been identified. In small amounts and when newly formed, plaque is invisible and relatively harmless. But when left to accumulate, it increases in volume (in large amounts, plaque can be seen as a soft whitish deposit), and the proportion of harmful species in the plaque grows.

Separating Gingivitis

The role played by plaque in the development of gingivitis was demonstrated in the early 1960s. Dental researchers had people stop brushing their teeth and let the plaque in their mouths build up. Within two to three weeks signs of inflammation appeared — redness, swelling, and an increased tendency to bleed — and when brushing resumed, the inflammation went away. Gingivitis is fairly common. Just about everybody, says Burt, has it in some degree. A recent nationwide survey by the National Institute of Dental Research, for example, found that 40 to 50 percent of the adults studied had at least one spot on their gums with inflammation that was prone to bleeding. At one time gingivitis and periodontitis were thought to be different phases of the same disease, meaning that the sort of inflammation detected in this study would lead inevitably to periodontitis if left untreated. Yet, dental researchers no longer believe this to be true. In the April 1988 Dental Clinics of North America, National Institute of Dental Research director Harald Loe, D.D.S., describes an ongoing study, then in its 15th year, of Sri Lankan tea workers who practice no oral hygiene. All have gingivitis — but not all have periodontitis.

This and other studies with similar results have led dental researchers to two conclusions. One, says dental epidemiologist Ronald J. Hunt, of the College of Dentistry at the University of Iowa, is that "gingivitis is not a particularly serious disease." The other is that "gingivitis and periodontitis are different disease entities."

From Periodontitis

Some people with gingivitis do, nonetheless, develop periodontitis. The plaque that causes gingivitis is located at or above the gum line and is referred to as supragingival plaque. With time, areas of supragingival plaque can become covered by swollen gum tissue or otherwise spread below the gum line (where it is called subgingival plaque), and in this airless environment the harmful bacteria within the plaque proliferate. These bacteria can injure tissues through the direct secretion of toxins. But they cause the greatest damage by stimulating a chronic inflammatory response in which the body in essence turns on itself, and the periodontal ligament and bone of the tooth socket are broken down and destroyed. This is similar to what happens in rheumatoid arthritis and, like rheumatoid arthritis, periodontitis is now considered primarily an inflammatory disease.

The bone destruction from periodontitis can be fairly even, resulting in receding gum lines. But more often it causes deep crevices between an individual tooth and its socket. These crevices are called periodontal pockets, and just as it once was thought that gingivitis inexorably progressed to periodontitis, so it was once believed that shallow periodontal pockets inevitably deepened, eventually becoming deep enough to jeopardize the socket's support of the adjacent tooth.

Recently, however, dental researchers have collected substantial evidence to support a theory called the burst hypothesis. This theory states that periodontal bone loss is not a steady process but results instead from periodic flare-ups of infection and inflammatory response inside the pocket. Writing in a 1988 issue of the Journal of Clinical Periodontology, researchers from the British Medical Research Council say this theory helps explain epidemiologic and clinical findings that many, if not most, periodontal pockets are not actively diseased. Rather, they are remnants of past infections that the body has overcome. Further, not all periodontal pockets inevitably deepen; some apparently partially heal and get shallower.

About the Author

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