Tooth Decay

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Tooth Decay

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Picture of a tooth (cross section)

This topic provides information on tooth decay and cavities. If you are looking for information on:

What is tooth decay?

Tooth decay is damage that occurs when germs (bacteria) in your mouth make acids that eat away at a tooth. It can lead to a hole in the tooth, called a cavity. If not treated, tooth decay can cause pain, infection, and tooth loss.

A tooth has three layers.

  • The hard outer layer is called enamel.
  • The middle layer is called dentin.
  • The center of the tooth is called the pulp. It contains nerves and blood vessels.

The more layers that are affected by decay, the worse the damage.

What causes tooth decay?

Bacteria and food can cause tooth decay. A clear, sticky substance called plaque is always forming on your teeth and gums. Plaque contains bacteria that feed on the sugars in the food you eat.

As the bacteria feed, they make acids. The acids attack the teeth for 20 minutes or more after you eat. Over time, these acids destroy tooth enamel, causing tooth decay.

Things that make you more likely to have tooth decay include:

  • Not brushing and flossing your teeth regularly and not seeing a dentist for checkups and cleanings.
  • Eating foods that are high in sugar and other carbohydrates, which feed the bacteria in your mouth.
  • Not getting enough fluoride. Fluoride helps prevent tooth decay by making teeth more resistant to acids produced by plaque. Fluoride is added to most public water supplies.
  • Not having enough saliva. Saliva washes away food and harmful sugars, so it helps protect your teeth from decay. A dry mouth may be caused by a condition such as xerostomia or Sjögren's syndrome, by taking certain medicines, or by breathing through your mouth. Older adults are more likely to have a dry mouth.
  • Having diabetes.
  • Smoking, using spit (smokeless) tobacco, or breathing secondhand smoke.

Children, whose teeth are still growing, are more likely than adults to have tooth decay. This is because the minerals in new teeth are not very strong and are easier for acids to eat away.

Even babies can be at risk for tooth decay. Babies who are put to bed with a bottle can get "bottle mouth"—tooth decay caused by the sugar in milk, formula, or juice. Babies aren't born with decay-causing bacteria in their mouths. But they can get bacteria from adults who share spoons, forks, or other utensils with them.

What are the symptoms?

Tooth decay usually doesn't cause symptoms until you have a cavity or an infected tooth. When this happens, you may have:

  • A toothache, which is the most common symptom.
  • Swelling in your gums near a sore tooth. This can be a sign of severe tooth decay or an abscessed tooth.
  • Bad breath or a bad taste in your mouth.
  • White, gray, brown, or black spots on your teeth.

If you have a toothache, see a dentist. Sometimes the pain will go away for a while, but the tooth decay will keep growing. If you don't get treatment, your cavities could get worse and your tooth could die.

How is tooth decay diagnosed?

To diagnose tooth decay, your dentist will:

  • Ask questions about your past dental and medical problems and care.
  • Check your teeth, using a pointed tool and a small mirror.
  • Take X-rays of your teeth and mouth to find tooth decay that can't be seen with the eyes alone.

How is it treated?

The best treatment for tooth decay depends on how severe it is. If tooth decay is caught early, before a cavity forms, you may be able to stop it by brushing with fluoride toothpaste or getting fluoride treatments. That's one good reason to see your dentist on a regular basis.

If the decay has eaten through the enamel, you may need one or more of these treatments:

  • A filling if a cavity has formed. After the decay is removed, the dentist uses a material to fill the hole and restore the tooth to its original shape.
  • A crown if the decay is severe and your tooth is badly damaged. A crown, or cap, is a man-made replacement for part of a tooth.
  • A root canal if the pulp of your tooth is infected. A root canal removes the diseased pulp of a tooth.
  • Removal (extraction) if the root of the tooth is severely damaged. The dentist may replace the tooth with a bridge or an implant.

If you have pain and swelling, you can take steps at home to relieve it.

  • Use an ice pack on the outside of your cheek. Don't use heat.
  • Take an over-the-counter pain reliever such as acetaminophen or ibuprofen. Be safe with medicines. Read and follow all instructions on the label.

How can you prevent tooth decay?

You can prevent most tooth decay with these tips:

  • Take good care of your teeth. Brush your teeth twice a day, in the morning and before bedtime. Use fluoride toothpaste. Floss once a day.
  • See your dentist for checkups once or twice a year so problems can be found before they're serious.
  • Don't snack before bedtime. Food left on the teeth overnight is more likely to cause cavities.
  • Avoid foods that have a lot of sugar, especially sugar-coated cereals, desserts, and sticky foods like taffy and raisins. The longer sugar is in contact with your teeth, the more damage it will do.

If you have children, get them regular dental checkups, and take steps early to prevent tooth decay.

  • To help prevent baby bottle tooth decay, don't put your baby to bed with a bottle of milk, formula, or juice.
  • To help prevent the spread of decay-causing bacteria, don't feed your baby from utensils you have used.
  • Teach your children to brush their teeth in the morning and at night.
  • Keep your children away from tobacco smoke.
  • Ask your dentist about:
    • Fluoride supplements if your water doesn't have enough fluoride.
    • Sealants to help protect your child's teeth from decay.

Other Places To Get Help


American Dental Association
211 East Chicago Avenue
Chicago, IL  60611-2678
Phone: (312) 440-2500
Web Address:

The American Dental Association (ADA), the professional membership organization of practicing dentists, provides information about oral health care for children and adults. The ADA can also help you find a dentist in your area.

Centers for Disease Control and Prevention (CDC): Division of Oral Health
4770 Buford Highway, NE, MS F-10
Atlanta, GA  30341-3717
Phone: (707) 488-6054
Web Address:

This Web site offered by the CDC provides knowledge, tools, and networks to promote good oral health and to prevent and control tooth decay, gum disease, and oral cancers.

Know Your Teeth
211 East Chicago Avenue
Suite 900
Chicago, IL  60611-6660
Phone: 1-888-243-3368 ext. 5300
Fax: (312) 440-0559
Web Address:

This Web site by the Academy of General Dentistry provides information on dental care and oral hygiene.

National Institute of Dental and Craniofacial Research (NIDCR)
National Institutes of Health
Bethesda, MD 20892-2190
Phone: (301) 496-4261
Fax: (301) 480-4098
Web Address:

The National Institute of Dental and Craniofacial Research (NIDCR) is a governmental agency that provides information about oral, dental, and craniofacial health. By conducting and supporting research, the NIDCR aims to promote health, prevent diseases and conditions, and develop new diagnostics and therapeutics.


Other Works Consulted

  • Campbell PR (2009). Carious lesions. In NO Harris et al., eds., Primary Preventative Dentistry, 7th ed., pp. 29–42. Upper Saddle River, NJ: Pearson.
  • Hodges KO (2009). Periodontal diseases. In NO Harris et al., eds., Primary Preventive Dentistry, 7th ed., pp. 46–66. Upper Saddle River, NJ: Pearson.
  • Klein U (2011). Dental caries section of Oral medicine and dentistry. In WW Hay et al., eds., Current Diagnosis and Treatment: Pediatrics, 20th ed., pp. 443–445. New York: McGraw-Hill.
  • National Institutes of Health (2011). NIH fact sheet: Tooth decay. Available online:


ByHealthwise Staff
Primary Medical ReviewerAdam Husney, MD - Family Medicine
Specialist Medical ReviewerArden Christen, DDS, MSD, MA, FACD - Dentistry
Last RevisedJanuary 4, 2013

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