14.3: Periodontal Disease

Periodontal disease is an infection of the tissues that surround a tooth (perio = around; dontal = tooth). In function, teeth are a part of the digestive system (tooth decay was discussed in Chap. 6). But in structure, teeth are more like bone—a skeleton does have teeth. Altogether, we normally form 52 teeth: 20 deciduous (“baby”) teeth and 32 permanent teeth.

Tooth enamel—the outer layer—is almost entirely mineral, and is the hardest part (about the hardness of stainless steel). The dentin underneath (see Figure 14.6), like bone, is about 70% mineral and 30% protein. The center of the tooth is full of the pulp that contains nerves and blood vessels that enter and exit through the root canals. As you’d expect, nutrients important in forming bone are similarly important in forming teeth.

Periodontal (around the tooth) tissues include the gums (gingiva), the periodontal ligament which surrounds the root, and the bone that supports the teeth. The supporting bone can be remodeled—the basis of orthodontics (repositioning teeth into better alignment). In young children, the upper front teeth can stick out from intense thumb-sucking (any distortion of the supporting bone and protruding teeth will usually correct itself if thumb- sucking stops before the upper permanent front teeth erupt—at about age 6).

Periodontal disease is the main cause of adult tooth loss. The disease begins with dental plaque that extends into the crevice between the tooth and gums (Figure 14.2). Bacteria in the plaque release substances that irritate the gums (gingiva), causing redness and swelling—gingivitis (inflammation of the gingiva). The plaque calcifies, forming a hard, rough substance called tartar (also called calculus) that also irritates the gums.

Other conditions can further aggravate the situation. Hormonal changes during the menstrual cycle or pregnancy, for example, can temporarily increase susceptibility to gingivitis. So can diabetes.

Figure 14.6: Tooth and Surrounding Structures

Gingivitis can largely be prevented by including the area of the tooth just below the gum-line when brushing and flossing. But despite diligent flossing and brushing with a “tartar-control” toothpaste, we still get some tartar. (Zinc chloride or pyrophosphate is the toothpaste ingredient that lessens tartar—but only above, not below, the gum line.) We’re advised to have our teeth cleaned of tartar twice a year by a dental hygienist.

Gingivitis is common, even during childhood. It’s so common that some people think swollen or bleeding gums are normal. Some people self‑prescribe big doses of vitamin C for bleeding gums. Just because it’s a symptom of scurvy (severe C deficiency), this doesn’t mean that bleeding gums indicates a deficiency; taking vitamin C in amounts higher than the RDA doesn’t help prevent gingivitis.

In most cases, swollen gums or gums that bleed during tooth-brushing indicate gingivitis caused by poor dental hygiene. Gingivitis is reversible, and itself wouldn’t be cause for much concern if it weren’t for the fact that it can progress to periodontitis, the more extensive inflammation of periodontal tissue.

When gingivitis progresses, the crevice between the tooth and gums widens and deepens, forming a pocket that provides a larger and more sequestered place for bacteria and debris to accumulate.* The periodontal ligament and supporting bone can then become infected, causing periodontitis. This can lead to loss of surrounding bone, which causes the tooth to loosen.

The extent of periodontitis is measured by the depth of the pocket between the tooth and gum. The tooth can be lost when there’s severe loss of the supporting bone and periodontal ligament.

Mild or moderate periodontitis is treated by cleaning the tartar off the teeth under the gums. This helps eliminate pockets by reducing inflammation and swelling of the gums. Severe periodontitis can require surgery to reach and clean to the bottom of the deep pockets around a tooth and to reshape the supporting bone.

Bacteria and tartar are the main contributors to periodontal disease, but other factors can hasten the loss of periodontal support once the disease process starts. Clenching and grinding one’s teeth increases stress on the surrounding tissue and bone.** Crowded teeth make the gum line harder to clean, and the teeth may have less supporting bone between them.

Periodontal disease may not be entirely preventable, but preventive measures can delay its onset and slow its progression. The loss of even a single tooth can result in the need for an expensive bridge or implant. Unreplaced missing teeth or the wearing of dentures not only can affect what you eat, but can markedly interfere with eating pleasure.

In the U.S. (2015-2018), 13% of those age 65 and older had lost all of their teeth. This percentage was much higher in this age group among those with less than a high school education (32%).

^{*Pockets of bacteria/debris are a common cause of bad breath. There are, of course, other causes, e.g., odoriferous substances in garlic are absorbed into blood, and some escape into the breath when blood circulates through the lungs. (The garlicky substances we associate with garlic aren’t in the intact clove. Enzymes that make them are released when the clove is crushed or cut.)
**Grinding your teeth also wears down enamel. Thin enamel or a cracked tooth is a common cause of a tooth being extra-sensitive to hot and cold. If you grind your teeth at night, your dentist can make a nightguard (a piece of plastic molded to fit between the upper and lower teeth) to wear at night.}