Tooth Decay

Definition

Tooth decay, which is also called dental cavities or dental caries, is the destruction of the outer surface (enamel) of a tooth. Decay results from the action of bacteria that live in plaque, which is a sticky, whitish film formed by a protein in saliva (mucin) and sugary substances in the mouth. The plaque bacteria sticking to tooth enamel use the sugar and starch from food particles in the mouth to produce acid.

Description

Tooth decay is a common health problem, second in prevalence only to the common cold. It has been estimated that 90% of people in the United States have at least one cavity, and that 75% of people had their first cavity by the age of five. Although anyone can have a problem with tooth decay, children and senior citizens are the two groups at highest risk. Other high-risk groups include people who eat a lot of starchy and sugary foods; people living in areas without a fluoridated water supply; and people who already have numerous dental restorations (fillings and crowns).

Baby bottle tooth decay

Baby bottle tooth decay is a dental problem that frequently develops in infants that are put to bed with a bottle containing a sweet liquid. Baby bottle tooth decay is also called nursing-bottle caries and bottle-mouth syndrome. Bottles containing such liquids as milk, formula, fruit juices, sweetened drink mixes, and sugar water continuously bathe an infant's mouth with sugar during naps or at night. The bacteria in the mouth use this sugar to produce acid that destroys the child's teeth. The upper front teeth are typically the ones most severely damaged; the lower front teeth receive some protection from the tongue. Pacifiers dipped in sugar, honey, corn syrup, or other sweetened liquid also contribute to bottle-mouth syndrome. The first signs of damage are chalky white spots or lines across the teeth. As decay progresses, the damage to the child's teeth becomes obvious.

Causes and symptoms

Tooth decay requires the simultaneous presence of three factors: plaque bacteria, sugar, and a vulnerable tooth surface. Although several microorganisms found in the mouth can cause tooth decay, the primary disease agent appears to be Streptococcus mutans. The sugars used by the bacteria are simple sugars such as glucose, sucrose, and lactose. They are converted primarily into lactic acid. When this acid builds up on an unprotected tooth surface, it dissolves the minerals in the enamel, creating holes and weak spots (cavities). As the decay spreads inward into the middle layer (the dentin), the tooth becomes more sensitive to temperature and touch. When the decay reaches the center of the tooth (the pulp), the resulting inflammation (pulpitis) produces a toothache.

Diagnosis

Tooth decay develops at varying rates. It may be found during a routine six-month dental checkup before the patient is even aware of a problem. In other cases, the patient may experience common early symptoms, such as sensitivity to hot and cold liquids or localized discomfort after eating very sweet foods. The dentist or dental hygienist may suspect tooth decay if a dark spot or a pit is seen during a visual examination. Front teeth may be inspected for decay by shining a light from behind the tooth. This method is called transillumination. Areas of decay, especially between the teeth, will appear as noticeable shadows when teeth are transilluminated. X rays may be taken to confirm the presence and extent of the decay. The dentist then makes the final clinical diagnosis by probing the enamel with a sharp instrument.

Tooth decay in pits and fissures may be differentiated from dark shadows in the crevices of the chewing surfaces by a dye that selectively stains parts of the tooth that have lost mineral content. A dentist can also use this dye to tell whether all tooth decay has been removed from a cavity before placing a filling.

Diagnosis in children

Damage caused by baby bottle tooth decay is often not diagnosed until the child has a severe problem, because parents seldom bring infants and toddlers in for dental check-ups. Dentists want to initially examine primary teeth between 12 and 24 months. Children still drinking from a bottle anytime after their first birthday are likely to have tooth decay.

Treatment

To treat most cases of tooth decay in adults, the dentist removes all decayed tooth structure, shapes the sides of the cavity, and fills the cavity with an appropriate material, such as silver amalgam or composite resin. The filling is put in to restore and protect the tooth. If decay has attacked the pulp, the dentist or a specialist called an endodontist may perform root canal treatment and cover the tooth with a crown.

In cases of baby bottle tooth decay, the dentist must assess the extent of the damage before deciding on the treatment method. If the problem is caught early, the teeth involved can be treated with fluoride, followed by changes in the infant's feeding habits and better oral hygiene. Primary teeth with obvious decay in the enamel that has not yet progressed to the pulp need to be protected with stainless steel crowns. Fillings are not usually an option in small children because of the small size of their teeth and the concern of recurrent decay. When the decay has advanced to the pulp, pulling the tooth is often the treatment of choice. Unfortunately, loss of primary teeth at this age may hinder the young child's ability to eat and speak. It may also have bad effects on the alignment and spacing of the permanent teeth when they come in.

Prognosis

With timely diagnosis and treatment, the progression of tooth decay can be stopped without extended pain. If the pulp of the tooth is infected, the infection may be treated with antibiotics prior to root canal treatment or extraction. The longer decay goes untreated, however, the more destructive it becomes and the longer and more intensive the necessary treatment will be. In addition, a patient with two or more areas of tooth decay is at increased risk of developing additional cavities in the future.

Prevention

It is easier and less expensive to prevent tooth decay than to treat it. The four major prevention strategies include: proper oral hygiene ; fluoride; sealants; and attention to diet.

Oral hygiene

GENERAL CARE OF THE MOUTH. The best way to prevent tooth decay is to brush the teeth at least twice a day, preferably after every meal and snack, and floss daily. Cavities develop most easily in spaces that are hard to clean. These areas include surface grooves, spaces between teeth, and the area below the gum line. Effective brushing cleans each outer tooth surface, inner tooth surface, and the horizontal chewing surfaces of the back teeth, as well as the tongue. Flossing once a day also helps prevent gum disease by removing food particles and plaque at and below the gum line, as well as between teeth. Patients should visit their dentist every six months for oral examination and professional cleaning.

MOUTH CARE IN OLDER ADULTS. Older adults who have lost teeth or had them removed still need to maintain a clean mouth. Bridges and dentures must be kept clean to prevent gum disease. Dentures should be relined and adjusted by a dentist whenever necessary to maintain proper fit. These adjustments help to keep the gums from becoming red, swollen, and tender.

MOUTH CARE IN CHILDREN. Parents can easily prevent baby bottle tooth decay by not allowing a child to fall asleep with a bottle containing sweetened liquids. Bottles should be filled only with plain, unsweetened water. The child should be introduced to drinking from a cup around six months of age and weaned from bottles by twelve months. If an infant seems to need oral comfort between feedings, a pacifier specially designed for the mouth may be used. Pacifiers, however, should never be dipped in honey, corn syrup, or other sweet liquids. After the eruption of the first tooth, parents should begin routinely wiping the infant's teeth and gums with a moist piece of gauze or a soft cloth, especially right before bedtime. Parents may begin brushing a child's teeth with a small, soft toothbrush at about two years of age, when most of the primary teeth have come in. They should apply only a very small amount (the size of a pea) of toothpaste containing fluoride. Too much fluoride may cause spotting (fluorosis) of the tooth enamel. As the child grows, he or she will learn to handle the toothbrush, but parents should control the application of toothpaste and do the followup brushing until the child is about seven years old.

Fluoride application

Fluoride is a natural substance that slows the destruction of enamel and helps to repair minor tooth decay damage by remineralizing tooth structure. Toothpaste, mouthwash, fluoridated public drinking water, and vitamin supplements are all possible sources of fluoride. Children living in areas without fluoridated water should receive 0.5 mg/day of fluoride (0.25 mg/day if using a toothpaste containing fluoride) from three to five years of age, and 1 mg/day from six to 12 years.

While fluoride is important for protecting children's developing teeth, it is also of benefit to older adults with receding gums. It helps to protect their newly exposed tooth surfaces from decay. Older adults can be treated by a dentist with a fluoride solution that is painted onto selected portions of the teeth or poured into a fitted tray and held against all the teeth.

Sealants

Because fluoride is most beneficial on the smooth surfaces of teeth, sealants were developed to protect the irregular surfaces of teeth. A sealant is a thin plastic coating that is painted over the grooves of chewing surfaces to prevent food and plaque from being trapped there. Sealant treatment is painless because no part of the tooth is removed, although the tooth surface is etched with acid so that the plastic will adhere to the rough surface. Sealants are usually clear or tooth-colored, making them less noticeable than silver fillings. They cost less than fillings and can last up to 10 years, although they should be checked for wear at every dental visit. Children should get sealants on their first permanent "6-year" molars, which come in between the ages of five and seven, and on the second permanent "12-year" molars, which come in between the ages of 11 and 14. Sealants should be applied to the teeth shortly after they erupt, before decay can set in. Although sealants have been used in the United States for about 25 years, one survey by the National Institute of Dental Research reported that fewer than 8% of American children have them.

Diet

The risk of tooth decay can be lowered by choosing foods wisely and eating less often. Foods high in sugar and starch, especially when eaten between meals, increase the risk of cavities. The bacteria in the mouth use sugar and starch to produce the acid that destroys the enamel. The damage increases with more frequent eating and longer periods of eating. For better dental health, people should eat a variety of foods, limit the number of snacks, avoid sticky and overly sweetened foods, and brush often after eating.

Drinking water is also beneficial for rinsing food particles from the mouth. Children can be taught to "swish and swallow" if they are unable to brush after lunch at school. Similarly, saliva stimulated during eating makes it more difficult for food and bacteria to stick to tooth surfaces. Saliva also appears to have a buffering effect on the acid produced by the plaque bacteria and to act as a remineralizing agent. Older patients should be made aware that some prescription medications may decrease salivary flow. Less saliva tends to increase the activity of plaque bacteria and encourage further tooth decay. Chewing sugarless gum increases salivation and thus helps to lower the risk of tooth decay.

KEY TERMS

Amalgam— A mixture (alloy) of silver and several other metals, used by dentists to make fillings for cavities.

Caries— The medical term for tooth decay.

Cavity— A hole or weak spot in the tooth surface caused by decay.

Dentin— The middle layer of a tooth, which makes up most of the tooth's mass.

Enamel— The hard, outermost surface of a tooth.

Fluoride— A chemical compound containing fluorine that is used to treat water or applied directly to teeth to prevent decay.

Mucin— A protein in saliva that combines with sugars in the mouth to form plaque.

Plaque— A thin, sticky, colorless film that forms on teeth. Plaque is composed of mucin, sugars from food, and bacteria that live in the plaque.

Pulp— The soft, innermost layer of a tooth containing blood vessels and nerves.

Sealant— A thin plastic substance that is painted over teeth as an anti-cavity measure to seal out food particles and acids produced by bacteria.

Transillumination— A technique of checking for tooth decay by shining a light behind the patient's teeth. Decayed areas show up as spots or shadows.

Resources

ORGANIZATIONS

American Dental Association. 211 E. Chicago Ave., Chicago, IL 60611. (312) 440-2500. 〈http://www.ada.org〉.

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

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

OTHER

Healthtouch Online Page. 〈http://www.healthtouch.com〉.

Tooth decay

Definition

Tooth decay, which is also called dental cavities or dental caries, is the destruction of the outer surface (enamel) of a tooth.

Description

Tooth decay results from the action of bacteria that live in plaque. Plaque is a sticky, whitish film formed by a protein in saliva (mucin) and sugary substances in the mouth. The plaque bacteria sticking to tooth enamel use the sugar and starch from food particles in the mouth to produce acid, which destroys the tooth's enamel.

Baby bottle tooth decay

Baby bottle tooth decay is a dental problem that develops in infants, especially infants that are put to bed with a bottle containing a sweet liquid. Baby bottle tooth decay is also called nursing-bottle caries and bottle-mouth syndrome. Bottles containing liquids such as milk, formula, fruit juices, sweetened drink mixes, and sugar water continuously bathe an infant's mouth with sugar. The bacteria in the mouth use this sugar to produce acid that destroys the child's teeth. The upper front teeth are typically the ones most severely damaged; the lower front teeth are protected to some degree by the tongue. Pacifiers dipped in sugar, honey, corn syrup, or other sweetened liquids also contribute to baby bottle tooth decay. The first signs of damage are chalky white spots or lines across the teeth. As decay progresses, the damage to the child's teeth becomes more obvious.

Demographics

Tooth decay is a common health problem, second in prevalence only to the common cold . It has been estimated that 90 percent of people in the United States have at least one cavity and that 75 percent of people had their first cavity by the age of five. Although anyone can have a problem with tooth decay, children are at particularly high risk. The good news is the number of children with cavities in the United States went down in the last few decades of the twentieth century. Some estimates are that as of the early 2000s cavities among adolescents have been reduced by nearly 40 percent. This rate decrease is explained in part by the fact that more areas have added fluoride to their drinking water and more children get regular, good dental care. However, children still drinking from a bottle anytime after their first birthday are more likely to have tooth decay.

Causes and symptoms

Tooth decay requires the simultaneous presence of three factors: plaque bacteria, sugar, and a vulnerable tooth surface. Although several microorganisms found in the mouth can cause tooth decay, the primary disease agent appears to be Streptococcus mutans. The simple sugars used by the bacteria are glucose, sucrose, and lactose. They are converted primarily into lactic acid. When this acid builds up on an unprotected tooth surface, it dissolves the minerals in the enamel, creating holes and weak spots (cavities). As the decay spreads inward into the middle layer (the dentin), the tooth becomes more sensitive to temperature and touch. When the decay reaches the center of the tooth (the pulp), the resulting inflammation (pulpitis) produces a toothache .

When to call the doctor

If a child complains of tooth or jaw pain and his or her cheek is swollen, and if he or she has a fever over 100°F (37.8°C), a dentist should be called right away. A dentist should be called during normal business hours if the child has tooth or jaw pain for more than a day, if white spots are noticed on an infant's teeth, or if there appear to be any other problems with the teeth or gums.

Diagnosis

Tooth decay develops at varying rates. It may be found during a routine six-month dental checkup before the individual is even aware of a problem. In other cases, the individual may experience common early symptoms, such as sensitivity to hot and cold liquids or localized discomfort after eating very sweet foods. The dentist or dental hygienist may suspect tooth decay if a dark spot or a pit is seen during a visual examination. Front teeth may be inspected for decay by shining a light from behind the tooth. This method is called transillumination. Areas of decay, especially between the teeth, will appear as noticeable shadows when the teeth are transilluminated. X rays may be taken to confirm the presence and extent of the decay. The dentist then makes the final clinical diagnosis by probing the enamel with a sharp instrument.

Tooth decay in pits and fissures may be differentiated from dark shadows in the crevices of the chewing surfaces by a dye that selectively stains parts of the tooth that have lost mineral content. A dentist can also use this dye to tell whether all tooth decay has been removed from a cavity before placing a filling.

Damage caused by baby bottle tooth decay is often not diagnosed until the child has a severe problem, because many parents do not schedule regular dental exams for their small children. It is recommended that a child's first trip to the dentist be before one year of age and that trips to the dentist occur regularly every six months after that.

Treatment

To treat most cases of tooth decay in older children, the dentist removes all decayed tooth structure, shapes the sides of the cavity, and fills the cavity with an appropriate material, such as silver amalgam or composite resin. The filling is put in to restore and protect the tooth. If decay has attacked the pulp, the dentist or a specialist called an endodontist may perform root canal treatment and then cover the tooth with a crown.

In cases of baby bottle tooth decay, the dentist must assess the extent of the damage before deciding on the treatment method. If the problem is caught early, the teeth involved can be treated with fluoride, followed by changes in the infant's feeding habits and better oral hygiene . Primary teeth with obvious decay in the enamel that has not yet progressed to the pulp need to be protected with stainless steel crowns. Fillings are not usually an option in small children because of the small size of their teeth and the concern of recurrent decay. When the decay has advanced to the pulp, pulling the tooth is often the treatment of choice. Unfortunately, loss of primary teeth at this age may hinder the young child's ability to eat and speak. It may also have negative effects on the alignment and spacing of the permanent teeth when they come in.

Prognosis

With timely diagnosis and treatment, the progression of tooth decay can be stopped relatively painlessly. If the pulp of the tooth is infected, the infection may be treated with antibiotics prior to root canal treatment or extraction. The longer the decay goes untreated, however, the more destructive it becomes and the longer and more intensive the necessary treatment will be. In addition, an individual with two or more areas of tooth decay is at increased risk of developing additional cavities.

Prevention

It is easier and less expensive to prevent tooth decay than to treat it. The four major prevention strategies are proper oral hygiene, fluoride, sealants, and attention to diet.

Oral hygiene

The best way to prevent tooth decay is to brush the teeth at least twice a day, preferably after every meal and snack, and floss daily. Cavities develop most easily in spaces that are hard to clean. These areas include surface grooves, spaces between teeth, and the area below the gum line. Effective brushing cleans each outer tooth surface, inner tooth surface, and the horizontal chewing surfaces of the back teeth, as well as the tongue. Flossing once a day helps prevent gum disease by removing food particles and plaque at and below the gum line, as well as between teeth. Patients should visit their dentists every six months for oral examination and professional cleaning.

Parents can easily prevent baby bottle tooth decay by not allowing a child to fall asleep with a bottle containing sweetened liquids. If a bottle is necessary when the child is falling asleep it should be filled only with plain, unsweetened water. The child should be introduced to drinking from a cup around six months of age and usually weaned from bottles by 12 months. If an infant seems to need oral comfort between feedings, a pacifier specially designed for the mouth may be used. Pacifiers, however, should never be dipped in honey, corn syrup, or other sweet liquids.

After the eruption of the first tooth, parents should begin routinely wiping the infant's teeth and gums with a moist piece of gauze or a soft cloth, especially right before bedtime. Parents may begin brushing a child's teeth with a small, soft toothbrush at about two years of age, when most of the primary teeth have come in. They should apply only a very small amount (the size of a pea) of toothpaste containing fluoride. Too much fluoride may cause spotting (fluorosis) of the tooth enamel. As the child grows, he or she will learn to handle the toothbrush, but parents should control the application of toothpaste and do the follow-up brushing until the child is about seven years old.

Fluoride application

Fluoride is a natural substance that slows the destruction of enamel and helps to repair minor tooth decay damage by remineralizing tooth structure. Toothpaste, mouthwash, fluoridated public drinking water, and vitamin supplements are all possible sources of fluoride. Children living in areas without fluoridated water should receive 0.25 mg/day of fluoride before age three, 0.5 mg/day of fluoride from three to six years of age, and 1 mg/day after age six. Sometimes children can also have their teeth treated with fluoride at the dentist's office.

Sealants

Because fluoride is most beneficial on the smooth surfaces of teeth, sealants were developed to protect the irregular surfaces of teeth. A sealant is a thin plastic coating that is painted over the grooves of chewing surfaces to prevent food and plaque from being trapped there. Sealant treatment is painless, because no part of the tooth is removed, although the tooth surface is etched with acid so that the plastic will adhere to the rough surface. Sealants are usually clear or tooth-colored, making them less noticeable than silver fillings. They cost less than fillings and can last up to 10 years, although they should be checked for wear at every dental visit. Children should get sealants on their first permanent "six-year" molars, which come in between the ages of five and seven, and on the second permanent "12-year" molars, which come in between the ages of 11 and 14. Sealants should be applied to the teeth shortly after they erupt, before decay can set in. Although sealants have been used in the United States for about 25 years, one survey by the National Institute of Dental Research reported that fewer than 8 percent of American children have them.

Diet

The risk of tooth decay can be lowered by choosing foods wisely and eating less often. Foods high in sugar and starch, especially when eaten between meals, increase the risk of cavities. The bacteria in the mouth use sugar and starch to produce the acid that destroys the enamel. The damage increases with more frequent eating and longer periods of eating. For better dental health, children should eat a variety of foods, limit the number of snacks, avoid sticky and overly sweetened foods, and brush often after eating. Drinking water is also beneficial for rinsing food particles from the mouth. Children can be taught to rinse their mouth out with water after eating if they are unable to brush after lunch at school.

Parental concerns

If tooth decay is not treated, it can result in other, more serious, problems involving the gums, cheeks, or jaw. Baby bottle tooth decay that is not treated quickly can result in the affected teeth being removed. Although the child will eventually develop adult teeth to replace the baby teeth, missing baby teeth can result in overcrowding when the adult teeth come in. Missing baby teeth can also result in the adult teeth coming in crooked, the child having to chew on one side of his or her mouth, and speech delays. As of 2004, most cavities could be fixed without much discomfort by a medical professional and without any serious longterm consequences if the cavities are found and treated early.

KEY TERMS

Amalgam —A mixture (alloy) of silver and several other metals used by dentists to make fillings for cavities.

Caries —The medical term for tooth decay.

Cavity —A hole or weak spot in the tooth surface caused by decay.

Dentin —The middle layer of a tooth, which makes up most of the tooth's mass.

Enamel —The hard, outermost surface of a tooth.

Fluoride —A chemical compound containing fluorine that is used to treat water or applied directly to teeth to prevent decay.

Mucin —A protein in saliva that combines with sugars in the mouth to form plaque.

Plaque —A sticky, colorless film of bacteria, sugars, and mucin that forms on teeth and causes tooth decay.

Pulp —The soft, innermost layer of a tooth that contains its blood vessels and nerves.

Sealant —A thin plastic substance that is painted over teeth as an anti-cavity measure to seal out food particles and acids produced by bacteria.

Transillumination —A technique of checking for tooth decay by shining a light behind the patient's teeth. Decayed areas show up as spots or shadows.

Resources

BOOKS

Mittelman, Jerome, Beverly Mittelman, and Jean Barilla. Healthy Teeth for Kids: A Preventive Program: Prebirth through the Teens. Collingdale, PA: DIANE Publishing, 2004.

PERIODICALS

"Achievements in Public Health, 1990–1999: Fluoridation of Drinking Water to Prevent Dental Caries." Journal of the American Medical Association 283, no. 10 (March 8, 2000): 1283–86.

ORGANIZATIONS

American Dental Association. 211 E. Chicago Ave., Chicago, IL 60611. Web site: <www.ada.org>.

American Dental Hygienists' Association. 444 North Michigan Ave., Chicago, IL 60611. Web site: <www.adha.org>.

National Institute of Dental Research. 31 Center Drive, MSC 2190, Building 31, Room 5B49, Bethesda, MD 20892–2190. Web site: <www.nidcr.nih.gov/>.

Tish Davidson, A.M.

TOOTH DECAY

DEFINITION

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

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

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

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

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

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

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

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

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.