Tooth Decay

TOOTH DECAY

DEFINITION

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Tooth decay is the destruction of the enamel (outer surface) of a tooth. Tooth decay is also known as dental cavities or dental caries. Decay is caused by bacteria that collect on tooth enamel. The bacteria live in a sticky, white film called plaque (pronounced PLAK). Bacteria obtain their food from sugar and starch in a person's diet. When they eat those foods, the bacteria create an acid that attacks tooth enamel and causes decay.

DESCRIPTION

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Tooth decay is the second most common health problem after the common cold (see common cold entry). By some estimates, more than 90 percent of people in the United States have at least one cavity; about 75 percent of people get their first cavity by the age of five.

Anyone can get tooth decay. However, children and the elderly are the two groups at highest risk. Other high-risk groups include people who eat a lot of starch and sugary foods; people who live in areas without fluoridated water (water with fluoride added to it); and people who already have other tooth problems.

Tooth decay is also often a problem in young babies. If a baby is given a bottle containing a sweet liquid before going to bed, or if parents soak the baby's pacifier in sugar, honey, or another sweet substance, bacteria may grow on the baby's teeth and cause tooth decay.

Tooth Decay: Words to Know

Amalgam:

A mixture of mercury, silver, and other metals used to make fillings for cavities.

Caries:

The medical term for tooth decay.

Cavity:

A hole or weak spot in tooth enamel caused by decay.

Dentin:

The middle layer of a tooth.

Enamel:

The hard, outermost layer of a tooth.

Fluoride:

A chemical compound that is effective in preventing tooth decay.

Plaque:

A thin, sticky film composed of sugars, food, and bacteria that covers teeth.

Pulp:

The soft, innermost layer of a tooth.

Sealant:

A thin plastic substance that is painted on teeth to prevent cavities from developing.

CAUSES

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Tooth decay occurs when three factors are present: bacteria, sugar, and a weak tooth surface.

The sugar often comes from sweet foods such as sugar or honey. But it can also come from starchy foods such as bread and rice. When a starch breaks down in the mouth, it forms sugar. Bacteria that live on the surface of a tooth eat sugar. When they do so they change the sugar into an acid called lactic acid.

Healthy tooth enamel may be able to resist this acid. But tooth enamel often has tiny holes and weak spots. Lactic acid can soak into these holes and dissolve the minerals of which enamel is made. Over time, the hole may get larger and larger. If the hole penetrates into the next tooth layer, called the dentin, the tooth becomes sensitive to touch and temperature. Decay can even penetrate to the center of the tooth, the pulp. In that case, the inner tooth may become inflamed and begin to ache.

SYMPTOMS

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The signs of tooth decay are usually obvious. A tooth may be sensitive to the touch, to hot or cold temperatures, or to very sweet foods. Or it may simply start to ache. A tooth that starts hurting usually has something wrong with it.

DIAGNOSIS

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Tooth decay is often discovered during regular dental checkups. Many adults have a routine dental checkup every six months. During these checkups, a dentist looks at and probes the patient's teeth. If there is tooth decay, it is usually easy for the dentist to find.

Some cases of tooth decay are harder to detect. They may occur between or on the back of teeth. In such cases, they are diagnosed by taking an X ray of the patient's mouth. Decay shows up as a dark spot on the X-ray film.

Tooth decay in very young children is often not diagnosed. Parents may not think it necessary to take a young child to the dentist and decay may be well advanced before it is discovered. For this reason, many dentists recommend having children one to two years of age examined for tooth decay.

TREATMENT

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Tooth decay is usually treated with a filling. The dentist first removes all of the decayed material with a drill. The opening is then filled with some

long-lasting material. Two common materials are mercury amalgam (pronounced uh-MAL-gum) and composite resin. A mercury amalgam consists of a mixture of metals that is strong and resistant to wear. A composite resin is a sturdy, plastic-like material.

Additional treatment may be necessary if decay has reached the pulp of the tooth. In that case, the center part of the tooth may also have to be removed. This procedure is called a root canal. The decayed material is taken out and replaced with a metal pin. The tooth is then covered with an artificial coating called a crown.

PROGNOSIS

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The sooner tooth decay is treated, the less of a problem it is. Without treatment, decay attacks more and more of a tooth, which may make it necessary for a root canal. In extreme cases, a tooth may need to be removed.

PREVENTION

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It is easier and less expensive to prevent tooth decay than to treat it. The four major steps in preventing tooth decay are: proper oral (mouth) hygiene; fluoride treatments; use of sealants; and attention to diet.

THE FIRST DENTAL DRILLS

The first powered dental drill was invented by George Washington's dentist, John Greenwood (1760–1819). The drill was operated using the foot-treadle (pedal) from Greenwood's mother's spinning wheel. Greenwood's son continued to use the drill, but other dentists did not adopt the idea. Instead, they continued to use small picks to clean the decay from teeth.

The first dental drill operated by a motor was invented in 1864 by Englishman George F. Harrington. Harrington's drill was powered by a tightly-wound spring, like the spring in a clock. Only four years later, an American inventor, George F. Green, redesigned the drill. His model used the power of compressed air.

The dental drill is still an essential part of every dentist's equipment. However, today's drills are much more advanced than those of Harrington and Green. The finest drills operate at a speed of up to 400,000 revolutions per minute. By comparison, the earliest commercial drills were rather slow and ran at no more than about 600 to 800 revolutions per minute.

Oral Hygiene

The three steps in proper oral hygiene are brushing, flossing, and regular checkups. Dentists recommend brushing the teeth at least twice a day, after meals and snacks if possible. Regular brushing keeps plaque and bacteria from collecting on teeth.

Flossing removes food particles and plaque from between teeth and other areas not reached by a toothbrush. Regular visits to the dentist make it possible to catch tooth decay before it becomes too serious.

Fluoride Treatments

Fluorides are chemicals that help reduce tooth decay by combining with minerals in the teeth to form a hard, tough surface. Bones and teeth all contain fluorides naturally. Using extra fluoride increases the natural strength of tooth enamel. Some communities add fluorides to their water supplies. People in those communities get the fluoride they need from their drinking water. Many kinds of toothpaste and mouthwash also contain fluoride. In areas where fluoride is not added to the public water supply, it can be obtained from these sources. Fluoride treatments are also available from dentists. The fluorides can be brushed directly on tooth surfaces.

Fluorides are especially important for young children's dental health. The fluorides become part of new teeth as they develop and grow and become harder and more resistant to bacterial acids.

Sealants

A sealant is a thin, plastic material used to cover tooth surfaces. It protects enamel from attack by bacterial acids. Sealants are especially helpful on irregular surfaces of the teeth. They prevent food and plaque from getting trapped on these surfaces.

Sealants are usually clear or tooth-colored. They do not affect the appearance of a person's teeth and may last as long as ten years. Some dentists recommend the application of sealants as soon as a child's permanent teeth appear, in order to protect the teeth from ever becoming decayed.

Diet

Diet is an important factor in maintaining good oral health. People whose diet includes large amounts of sugar and starch are likely to have more tooth decay. Foods that stick to the teeth can also be a problem because they help bacteria stay on tooth surfaces longer.

FOR MORE INFORMATION

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Organizations

American Dental Association. 211 East Chicago Avenue, Chicago, IL 60611. (312) 440-2500. http://www.ada.org.

American Dental Hygienists' Association. 444 North Michigan Avenue, Chicago, IL 60611. (800) 847-6718.

National Institute of Dental Research. 31 Center Drive, MSC 2190, Building 31, Room 5B49, Bethesda, MD 20892-2190.