Merck Manual

Please confirm that you are not located inside the Russian Federation

Quick Facts



The Manual's Editorial Staff

Last full review/revision Apr 2020| Content last modified Apr 2020
Click here for the Professional Version
Get the full details
NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Topic Resources

The hard outer surface on your teeth is called the enamel. The pulp is deep inside the tooth and contains blood vessels and nerves. Bacteria can damage different parts of the tooth.

What are cavities?

Cavities are decayed parts of your tooth.

  • Bacteria build up on your tooth enamel and make acids that cause holes in the tooth—the holes are called cavities

  • Tooth pain happens as cavities get bigger and go through the enamel to the inside of your tooth

  • Dentists find cavities by looking at your teeth and taking x-rays

  • Treatment includes drilling out decay and filling the hole

  • Regularly brushing your teeth, getting dental check-ups, and avoiding sugary foods can help prevent cavities



What causes cavities?

Bacteria build up on your teeth and make acid that causes decay.

Bacteria, saliva (spit), and bits of food form a thin layer called plaque that clings to your teeth. Plaque hardens over time and turns into tartar. Tartar is usually yellow. You sometimes see it at the base of teeth. Bacteria living in plaque and tartar are hard to get rid of.

You’re more likely to get cavities if you:

  • Have a lot of plaque and tartar in your mouth

  • Eat and drink sugary or acidic foods, such as cola sodas or juice

  • Have too little fluoride (a mineral that makes your enamel harder) in your teeth

  • Don’t have much saliva (spit) in your mouth (a condition called dry mouth)

  • Have gums that have shrunk down the bottom of your teeth (receding gums)

Decay-causing bacteria live on the food in your mouth. The bacteria like sugar. That's why food with a lot of sugar tends to cause cavities. It's not just a problem for adults. Putting babies to bed with a bottle of formula, milk, or juice (anything but plain water) keeps the bacteria on their teeth in contact with food for a long time. This increases the likelihood of tooth decay.

What are the symptoms of cavities?

A shallow cavity in your enamel doesn't hurt. Cavities that are a little deeper may cause pain when you eat hot, cold, or sweet foods or drinks.

A cavity that gets deep enough to reach the pulp causes pulpitis. Pulpitis causes toothache even when you’re not eating or drinking. If the pulp gets infected, you may develop a pocket of pus called a dental abscess.

How can dentists tell if I have cavities?

Dentists diagnose cavities by:

  • Looking at your teeth and probing them with dental tools

  • Taking x-rays of your teeth

How do dentists treat cavities?

If your cavity is very small and only on the enamel, the tooth can fix itself if you have enough fluoride.

Dentists treat cavities that are deeper than the enamel by drilling out the decayed part of the tooth and putting in a filling. The filling can be made of:

  • Silver amalgam (a combination of silver, mercury, copper, tin, and sometimes other metals), often used in back teeth where it will be out of sight

  • Composite resins, which match the color of your teeth

  • Glass ionomer, which is tooth-colored and releases fluoride, good for people with a lot of tooth decay

  • Gold

Root canal treatment or tooth removal

When tooth decay goes deep enough to reach the pulp and it becomes severely inflamed, dentists will give you pain medicine and either:

  • Do a root canal to remove the pulp from your tooth and then fill and seal the tooth canal

  • Take out the tooth if it can't be saved

If you have an infection, they'll also give you antibiotics.

How can I prevent cavities?

You can prevent cavities by:

  • Brushing your teeth with toothpaste that contains fluoride (in the morning and evening and after eating sugary foods)

  • Flossing your teeth daily

  • Getting regular dental care

  • Eating healthy foods and cutting back on food and drinks that have a lot of sugar or acid

It's important to get enough fluoride. Fluoride is a mineral that protects your teeth from cavities. Fluoride is added to the public water supply in some areas. If it's not in your water, the dentist may prescribe fluoride supplements for children up to age 8, or apply fluoride treatments to your teeth.

If you still get a lot of cavities, dentists may:

  • Put sealants on your teeth (sealants are a hard plastic coating that prevent cavities in teeth with deep crevices)

  • Have you use an antibacterial mouth rinse that helps kill cavity-causing bacteria

NOTE: This is the Consumer Version. DOCTORS: Click here for the Professional Version
Click here for the Professional Version
Others also read

Also of Interest