Tooth decay

Alternative names
Caries; Dental cavities; Cavities - tooth

Cavities are holes that damage the structure of teeth.

Causes, incidence, and risk factors

Tooth decay is one of the most common of all disorders, second only to the common cold. It usually occurs in children and young adults but can affect any person. It is the most important cause of tooth loss in younger people.

Bacteria are normally present in the mouth. The bacteria convert all foods - especially sugar and starch - into acids. Bacteria, acid, food debris, and saliva combine in the mouth to form a sticky substance called plaque that adheres to the teeth. It is most prominent on the back molars, just above the gum line on all teeth, and at the edges of fillings. Plaque that is not removed from the teeth mineralizes into tartar. Plaque and tartar irritate the gums, resulting in gingivitis and ultimately periodontitis.

Plaque begins to accumulate on teeth within 20 minutes after eating (the time when most bacterial activity occurs). If this plaque is not removed thoroughly and routinely, Tooth decay will not only begin, but flourish.

The acids in plaque dissolve the enamel surface of the tooth and create holes in the tooth (cavities). Cavities are usually painless until they grow very large inside the tooth and destroy the nerve and blood vessels in the tooth. If left untreated, a Tooth abscess can develop. Untreated Tooth decay also destroys the internal structures of the tooth (pulp) and ultimately causes the loss of the tooth.

Sugars and Starches increase the risk of Tooth decay. Sticky foods are more harmful than nonsticky foods because they remain on the surface of the teeth. Frequent snacking increases the time that acids are in contact with the surface of the tooth.


  • Toothache - particularly after sweet, hot, or cold foods and drinks  
  • Visible pits or holes in the teeth

Signs and tests
Most cavities are discovered in the early stages during routine checkups. The surface of the tooth may be soft when probed with a sharp instrument. Pain may not be present until the advanced stages of Tooth decay. Dental x-rays may show some cavities before they are visible to the eye.


Destroyed tooth structure does not regenerate. However, the progression of cavities can be stopped by treatment. The goal is to preserve the tooth and prevent complications.

In filling teeth, the decayed material is removed (by drilling) and replaced with a restorative material such as silver alloy, gold, porcelain, or composite resin. Porcelain and composite resin more closely match the natural tooth appearance, and may be preferred for front teeth. Many dentists consider silver amalgam (alloy) and gold as stronger and are often used on back teeth, although there is a trend to use high strength composite resin in the back teeth as well.

Crowns are used if decay is extensive and there is limited tooth structure which may cause weakened teeth. Large fillings and weak teeth increase the risk of the tooth breaking. The decayed or weakened area is removed and repaired and a covering jacket or “cap” (crown) is fitted over the remainder of the tooth. Crowns are often made of gold, porcelain or porcelain fused to metal.

A root canal is recommended if the nerve in a tooth dies from decay or from a traumatic blow. The center of the tooth, including the nerve and blood vessel tissue (pulp), is removed along with decayed portions of the tooth. The roots are filled with a sealing material. The tooth is filled and a crown may be placed over the tooth if needed.

Expectations (prognosis)
Treatment often preserves the tooth. Early treatment is less painful and less expensive than treatment of extensive decay. Anesthetics - local, nitrous oxide (laughing gas), or other prescription medications - may be required in some cases to relieve pain during or following drilling or other treatment of decayed teeth. For those who fear dental treatment, nitrous oxide in combination with anesthesia may be preferred.


  • Tooth abscess  
  • fractured tooth  
  • discomfort or pain  
  • tooth sensitivity  
  • inability to bite down on tooth

Calling your health care provider

  • Call your dentist if you have a toothache.  
  • Call your dentist for a routine cleaning and examination if you have not had one in the last 6 months to 1 year.


Oral hygiene is necessary to prevent cavities. This consists of brushing at least twice a day and flossing at least daily, and regular professional cleaning (every 6 months). X-rays may be taken yearly to detect possible cavity development in high risk areas of the mouth.

Chewy, sticky foods (such as dried fruit or candy) are best if eaten as part of a meal rather than as a snack. If possible, brush the teeth or rinse the mouth with water after eating these foods. Minimize snacking, which creates a constant supply of acid in the mouth. Avoid constant sipping of sugary drinks or frequent sucking on candy and mints.

Dental sealants can prevent cavities. Sealants are thin plastic-like coating applied to the chewing surfaces of the molars. This coating prevents the accumulation of plaque in the deep grooves on these vulnerable surfaces. Sealants are usually applied on the teeth of children, shortly after the molars erupt. Older people may also benefit from the use of tooth sealants.

Fluoride is often recommended to protect against dental caries. It has been demonstrated that people who ingest fluoride in their drinking water or by fluoride supplements have fewer dental caries. Fluoride ingested when the teeth are developing is incorporated into the structure of the enamel and protects it against the action of acids.

Topical fluoride is also recommended to protect the surface of the teeth. This may include a fluoride toothpaste or mouthwash. Many dentists include application of topical (applied to a localized area of the skin) fluoride solutions as part of routine visits.

Johns Hopkins patient information

Last revised: December 4, 2012
by Harutyun Medina, M.D.

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All ArmMed Media material is provided for information only and is neither advice nor a substitute for proper medical care. Consult a qualified healthcare professional who understands your particular history for individual concerns.