Dental Caries

Definition

Dental caries, also known as tooth decay, 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. Tooth decay can result in tooth loss.

Description

Thanks to the benefits of fluoride and fluoridated water, dental caries, also called dental cavities, are not as prevalent as in the years before and including the 1980s. While the majority of senior citizens a generation ago lost all their teeth, the vast majority of the elderly today have some or all of their natural teeth.

Although anyone can have a problem with tooth decay, children and senior citizens are the two high-risk groups. While both groups experience a diminishing caries rate, senior citizens are getting more cavities than children. Since older adults are keeping their teeth longer, they have become more prone to root caries, or root decay. 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 who 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 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 receiving some protection from the tongue. Pacifiers dipped in sugar, honey, corn syrup, or other sweetened liquids 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.

The elderly are more prone to dental caries because more than 95% of senior citizens have lost some of the gum tissue that protects the tooth roots, exposing the roots to plaque and decay. It also is common to see decay around filling margins. Over time, fillings tend to weaken, fracture, and leak around the edges, which fosters the accumulation of bacteria. Another reason that the elderly get more cavities is that many take medications that reduce saliva, which naturally protects the teeth from caries.

Chewing tobacco is another culprit that increases the risk of tooth decay. A study showed that men who use chewing tobacco are four times more likely to have one or more decayed or filled root surfaces, compared to those who had never chewed tobacco.

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 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 take their infants and toddlers 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 a bad effect on the alignment and spacing of the permanent teeth when they arrive.

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.

Scientists are working on several advances in the reversal and prevention of tooth decay. The advances under development include: Smart fillings to prevent further tooth decay, toothpaste to strengthen and restore tooth minerals, and mouthwashes and chewing gums that reverse early decay. Scientists are studying the use of calcium phosphate cements (CPC), used to repair cranial defects, for fractures and bone loss from gum disease. CPC might provide a successful drug delivery system in Smart fillings to prevent tooth decay from recurring around existing fillings and surrounding teeth. Other calcium phosphate-based technologies used in chewing gum and mouth rinses are being tested to remineralize hard tooth tissues or slow demineralization produced by caries. Scientists are researching controlled-release fluoride systems, placed between the teeth or in tooth pits and fissures, that deliver high fluoride concentrations to localized areas. Research is also being done on the use of filling materials to repair exposures of the tooth pulp, which could eliminate the need for root canal therapy.

Health care team roles

Dental assistants can provide patients and their families with education in caries prevention. This often includes instructions for home care and fluoride information. Dental assistants often participate in the treatment of dental caries, performing such tasks as taking x rays, assisting with materials during treatment, and setting up and maintaining treatment rooms. In some dental practices, dental hygienists assist with patient charting and taking x rays. Dental hygienists interpret findings and are often the first to see the decay during routine cleanings.

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 to 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 an 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 a 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 liquid. Bottles should be filled with plain, unsweetened water. A child should be starting to drink from a cup at around six months of age, and weaned from bottles at 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 an infant's teeth and gums with a moist piece of gauze or soft cloth, especially 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. It is important to note that bottled water and water from home purifiers often does not contain fluoride, so people who drink from these sources may have to supplement their fluoride use. 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 the 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 none 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

Choosing foods wisely and eating less often can lower the risk of tooth decay. 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 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 by 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 people 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

BOOKS

"Dental Caries and Its Complications—Tooth Decay." In The Merck Manual of Diagnosis and Therapy, 17th ed. Edited by Mark H. Beers, Robert Berkow, and Mark Burs. Rahway, NJ: Merck Research Laboratories, 1999.

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.

Anna Nelson, Certified Dental Assistant, and president of the American Dental Assistants' Association. 203 N. LaSalle St., Suite 1320, Chicago, IL 60601-1225. (312) 541-1550 or for Anna Nelson direct (415) 239-3479. 〈www.dentalassistant.org〉.

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

OTHER

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

Dental caries

Definition

Dental caries, also known as tooth decay, 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. Tooth decay can result in tooth loss.

Description

Thanks to the benefits of fluoride and fluoridated water, dental caries, also called dental cavities, are not as prevalent as in the years before and including the 1980s. While the majority of senior citizens a generation ago lost all their teeth, the vast majority of the elderly today have some or all of their natural teeth.

Although anyone can have a problem with tooth decay, children and senior citizens are the two high-risk groups. While both groups experience a diminishing caries rate, senior citizens are getting more cavities than children. Since older adults are keeping their teeth longer, they have become more prone to root caries, or root decay. 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 who 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 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 receiving some protection from the tongue. Pacifiers dipped in sugar, honey, corn syrup, or other sweetened liquids 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.

The elderly are more prone to dental caries because more than 95% of senior citizens have lost some of the gum tissue that protects the tooth roots, exposing the roots to plaque and decay. It also is common to see decay around filling margins. Over time, fillings tend to weaken, fracture, and leak around the edges, which fosters the accumulation of bacteria. Another reason that the elderly get more cavities is that many take medications that reduce saliva, which naturally protects the teeth from caries.

Chewing tobacco is another culprit that increases the risk of tooth decay. A study showed that men who use chewing tobacco are four times more likely to have one or more decayed or filled root surfaces, compared to those who had never chewed tobacco.

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 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 take their infants and toddlers 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 a bad effect on the alignment and spacing of the permanent teeth when they arrive.

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.

Scientists are working on several advances in the reversal and prevention of tooth decay. The advances under development include: Smart fillings to prevent further tooth decay, toothpaste to strengthen and restore tooth minerals, and mouthwashes and chewing gums that reverse early decay. Scientists are studying the use of calcium phosphate cements (CPC), used to repair cranial defects, for fractures and bone loss from gum disease. CPC might provide a successful drug delivery system in Smart fillings to prevent tooth decay from recurring around existing fillings and surrounding teeth. Other calcium phosphate-based technologies used in chewing gum and mouth rinses are being tested to remineralize hard tooth tissues or slow demineralization produced by caries. Scientists are researching controlled-release fluoride systems, placed between the teeth or in tooth pits and fissures, that deliver high fluoride concentrations to localized areas. Research is also being done on the use of filling materials to repair exposures of the tooth pulp, which could eliminate the need for root canal therapy .

Health care team roles

Dental assistants can provide patients and their families with education in caries prevention. This often includes instructions for home care and fluoride information. Dental assistants often participate in the treatment of dental caries, performing such tasks as taking x rays, assisting with materials during treatment, and setting up and maintaining treatment rooms. In some dental practices, dental hygienists assist with patient charting and taking x rays. Dental hygienists interpret findings and are often the first to see the decay during routine cleanings.

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 to 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 an 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 a 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 liquid. Bottles should be filled with plain, unsweetened water. A child should be starting to drink from a cup at around six months of age, and weaned from bottles at 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 an infant's teeth and gums with a moist piece of gauze or soft cloth, especially 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. It is important to note that bottled water and water from home purifiers often does not contain fluoride, so people who drink from these sources may have to supplement their fluoride use. 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 6-12 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 the 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 none 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 5 and 7, 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

Choosing foods wisely and eating less often can lower the risk of tooth decay. 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 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 by 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 people 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

BOOKS

"Dental Caries and Its Complications—Tooth Decay." In The Merck Manual of Diagnosis and Therapy, edited by Mark H. Beers, Robert Berkow, and Mark Burs. 17th ed. Rahway, NJ: Merck Research Laboratories, 1999.

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.

Anna Nelson, Certified Dental Assistant, and president of the American Dental Assistants' Association. 203 N. LaSalle St., Suite 1320, Chicago, IL 60601-1225. (312) 541-1550 or for Anna Nelson direct (415) 239-3479. <www.dentalassistant.org>.

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

OTHER

Healthtouch Online. <http://www.healthtouch.com>.

Lisette Hilton

dental caries Tooth decay, which involves the destruction of the enamel layer of the tooth by acids produced by the action of bacteria on sugar. Bacteria can bind to teeth on dextran, a sticky substance derived from sucrose. The bacterial cells and other waste attached to dextran gives rise to plaque. If dental caries is not treated it can spread to the dentine and pulp of the tooth, which leads to infection and death of the tooth.

dental caries n. see caries.

dental caries See caries.