Cavities (Tooth Decay): Causes, Symptoms & Treatment

cavities, teeth, health, fillings
Teeth showing cavities, on the left, and after treatment with a composite filling.
Credit: Lighthunter | Shutterstock

Cavities, also referred to tooth decay or caries, are holes in the teeth. Cavities are the second-most common health disorder in the United States, according to the National Institutes of Health  (the first is the common cold) and a very common disorder worldwide.

Cavities usually occur in the teeth of children and young adults, but they can happen at any age. Cavities are a common cause of tooth loss in young people.


Cavities are the result of two primary factors: bacteria in the mouth and a high-sugar and starch diet. Because of how these two elements work together, cavities are characterized as a dietobacterial disease.

Bacteria + sugar leads to plaque and tartar

The mouth’s normal bacteria combine with food pieces and saliva to form plaque. Plaque is a sticky, invisible substance that accumulates quickly. Sugar- or starch-rich foods make plaque stickier. If plaque stays on the teeth for more than a few days, it gets harder and becomes a hard substance called tartar.

Cavities form when bacteria in plaque and tartar convert sugar into acid. The acid dissolves tooth enamel. After the enamel is worn away, the acid reaches the next layer of the teeth. This layer, called dentin, is softer and susceptible to acid. The bacteria and acid continue to work their way through the tooth, creating a bigger and bigger hole.

Cavities are most commonly found where plaque is highly prevalent, such as on the molars, between teeth, near the gum line, and at the edges of fillings.


There are often no symptoms of cavities. If there are symptoms, they usually do not appear until the tooth decay has reached the dentin level. If tooth decay reaches the next level, the pulp, you may experience a severe toothache, tooth sensitivity, and pain when biting.

Symptoms of cavities at any stage include:

  • Tooth pain, especially after having sweet, hot, or cold foods and drinks
  • Visible pits or holes in the teeth. Cavities on the front teeth are the easiest to see and will look like a brown or black spot. Cavities in other parts of the mouth are often not visible without an X-ray.


Just as there are two factors that cause cavities, there are two main factors to preventing them: oral hygiene and diet change.

Good oral hygiene includes brushing your teeth at least twice a day, flossing at least once, having a professional teeth cleaning every six months, and having X-rays and an dental exam annually to detect cavity development.

Reducing the amount of sugar — especially sugary drinks and juices — can help prevent cavities. You may consider brushing your teeth or rinsing your mouth after eating sticky foods. Minimizing snacking, avoiding constant sipping of sugary drinks, and not sucking on candy or mints can all help, too, because they produce a constant supply of acid in the mouth.

Dental sealants may help prevent cavities and are most frequently applied to the teeth of children after their molars come in. Sealants are thin, plastic-like coatings on the surface of the molars that prevents the accumulation of plaque.

Fluoride is another cavity-prevention strategy. It can be consumed in drinking water or as a supplement. Topical fluoride is frequently applied as part of routine dentist visits. Your dentist may also prescribe a fluoride toothpaste or mouthwash.


Treatments for cavities/tooth day include fillings, crowns, and root canals.


Dentists do fillings by removing the decayed tooth material with a drill and replacing it with silver alloy, gold, porcelain or composite resin. Many dentists consider silver alloy and gold to be stronger than porcelain or resin, but because these materials are quite visible, dentists usually only use them on back teeth. Front-tooth cavities usually are filled with porcelain or composite resin, which more closely matches the tooth’s natural appearance.

Crowns or caps

These are used if tooth decay is more extensive, the tooth is weakened, and there is little remaining tooth structure. The decayed or weakened area is removed and a crown is fitted over the remainder of the tooth. Crowns are usually made of gold, porcelain, or porcelain attached to metal.

Root canal

Root canals are done if decay or injury has killed the nerve in the tooth. The decayed area and the center of the tooth, including the pulp, are removed. The root is filled with a sealing material, the tooth is filled, and a crown is usually applied.

Tooth abscesses

A tooth abscess is a complication of tooth decay. Bacteria get into the pulp of the tooth through the cavity and cause infection. Pus then collects in the center of the tooth, causing an abscess. Abscesses can also be caused by trauma to the tooth, such as chipping or breaking.

Tooth abscesses can be a serious problem, leading to complications such as tooth loss, blood infection, and infection in soft tissue, jaw bone and other areas. Untreated tooth abscesses can cause life-threatening complications.

Symptoms of tooth abscesses include:

  • Severe toothache (the most common symptom)
  • Bitter taste in the mouth
  • Painful chewing
  • Sensitivity of the teeth to hot or cold
  • Swelling of the gum over the infected tooth (it may look like a pimple)
  • Bad breath
  • General discomfort
  • Fever
  • Swollen neck glands
  • Swollen area of the upper or lower jaw (this is a very serious symptom)

If your toothache stops, it is still important to see a dentist. Sometimes toothaches stop if the pulp dies, but the infection may still spread.


Your dentist may prescribe antibiotics to kill the infection, warm salt-water rinses to soothe the area and over-the-counter pain relievers.

Root canals can sometimes save the tooth, but if the infection is severe the tooth may need to be removed. Surgery may be required to drain the abscess.

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