All About Dental Fillings

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Dental exam

One reason people go to the dentist is because they've felt a rough spot or a hole on a tooth. This could be a cavity—the dental term for the tooth problem caused by tooth decay. A dental filling is the way to treat a cavity. Dentists use a small drill to remove the tooth decay and then fill in the gap with a filling.

Tooth decay happens when bacteria in your mouth produce acids that eat away at the enamel covering of your teeth. Bacteria can form a sticky coating on your teeth, called plaque. This harms the enamel. But the acids can also work their way through cracked or loose fillings. This can cause decay between or beneath fillings you already have. If this happens, your dentist may need to replace an old filling.

How long do fillings last?

The life of a filling depends on many things, including the size and the location of the filling. The type of filling material your dentist uses also makes a difference. If you need a cavity filled, talk to your dentist about the pros and cons of these different types of fillings:

  • Amalgam fillings. These are the silver-colored fillings most people are familiar with. Dentists have used them for more than 100 years. The amalgam is a combination of metals, including silver, copper, tin and mercury. Some people think mercury fillings are dangerous and should be removed. However, there's no good evidence to support this. Amalgam fillings are the strongest type of filling. They're also the best fillings for large cavities and for fillings in teeth that do lots of hard chewing, like molars.

  • Composite fillings. These fillings are similar to the color of natural teeth. This is one reason people sometimes prefer them. They're made from plastic resins and glass-like particles, and aren't as strong or long-lasting as amalgam. These fillings also take longer to put in and are more costly. However, they are best choice for small or mid-size cavities.

  • Glass ionomers. These fillings are also tooth-colored. They're made from a mixture of glass powders and fluoride. The fluoride may add some protection against future tooth decay. However, these fillings aren't as strong as other fillings. They're usually best for baby teeth or for fillings on parts of teeth that are not used for chewing.

A filling should last for many years, but all fillings wear out over time. There's no exact answer for how long your filling will last, but studies show average lifespans. The longest-lasting fillings are amalgam. They can last up to 20 years, and more than half last 12 or more years. You may need to replace composite and glass ionomer fillings after about 4 to 5 years.

How should you care for your fillings?

The best way to care for your fillings—and for your teeth and mouth overall—is to see your dentist regularly. Your dentist will check all of your fillings for cracks and decay. He or she may take X-rays to see if decay is forming under a filling. This is important because decay that's not treated can cause infection in the root of a tooth. You then would need a dental procedure called a root canal, which is much more complex than a filling.

Tell your dentist if you grind your teeth. This can cause a filling to crack. Ask your sleeping partner or roommate if you grind your teeth at night.

 Also, practice good oral hygiene:

  • Brush your teeth twice every day.

  • Floss at least once a day.

  • Avoid food and drinks with added sugar. Sugar feeds the bacteria in your mouth and can lead to more plaque.
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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2021 Feb 27
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.

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  2. Chadwick B, Dummer P, Dunstan F, et al. How long do fillings last? Evid Based Dent. 2002;3:96-99.

  3. Decay. American Dental Association.

  4. Dental Filling Options. American Dental Association.  

  5. Different Filling Materials. Oral Health Foundation.

  6. Forss H, Widström E. From amalgam to composite: selection of restorative materials and restoration longevity in Finland. Acta Odontol Scand. 2001 Apr;59(2):57-62.

  7. When a Filling Needs Replacement. American Dental Association.