Cavities (Tooth Decay): Causes, Symptoms & Treatment
Teeth showing cavities, on the left, and after treatment with a composite filling.
Credit: Lighthunter | Shutterstock

Cavities, also referred to as 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. According to Dr. Margaret Culotta-Norton, a dentist in Washington, D.C., and former president of the D.C. Dental Society, cavities are the most chronic childhood disease in the United States. 

Some groups have a higher risk for cavities, Culotta-Norton told Live Science, including:

  • Lower-income families (children and adults).
  • Senior citizens of all socio-economic status.
  • People living in areas where the drinking water in not fluoridated.
  • People with diseases and/or medication use that causes a decrease in salivary flow.
  • People undergoing radiation therapy.
  • People with diabetes.
  • Tobacco users — both smoking and chewing.
  • Alcohol and drug users.
  • People who consume large amounts of carbonated and sugar drinks.

Cavities are the result of two primary factors: bacteria in the mouth and a high-sugar and starch diet. It is natural to have bacteria in the mouth but it becomes problematic in the case of poor oral hygiene. 

According to the National Institutes of Health, the mouth's normal bacteria combine with food pieces and saliva to form plaque. Plaque is a sticky, invisible substance that accumulates quickly. Foods rich in sugar or starch make plaque stickier. If plaque stays on the teeth for more than a few days, it gets harder and becomes a  substance called tartar.

Cavities form when bacteria in plaque and tartar convert sugar into acid. According to Culotta-Norton, Streptococcus mutans and Streptococcus sobrinus are bacteria especially likely to combine with fermentable carbohydrates like sucrose, fructose and glucose and produce acid. “The acid demineralizes the hard structure of the tooth, which over time creates a soft spot, or hole in the tooth called a cavity,” Culotta-Norton said.

The destruction doesn't stop there, reports the Mayo Clinic. 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, into the pulp, creating a bigger and bigger hole.

According to the NIH, 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, which is why Culotta-Norton stressed the importance of visiting a dentist and having “radiographs taken periodically so that cavities can be diagnosed and treated early before they get large enough to cause symptoms.” She reported that the most common early symptoms of cavities are a "chalky white or discolored spot on a tooth" and "sensitivity to cold." 

"As the cavity progresses, the decay gets near the nerve (pulp) and can cause pain, which gets progressively worse especially with exposure to heat, cold, sweet foods or drinks," she continued. “If the decay gets large enough, part of the tooth may fracture off, leaving a large visible hole, and the tooth may be sensitive to biting pressure. Bad breath and or a bad taste in the mouth are also symptoms."

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.

According to the NIH, good oral hygiene includes brushing your teeth at least twice a day and flossing at least once, having a professional teeth-cleaning every six months, and having X-rays and a 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. The NIH also suggests incorporating sugary, chewy foods such as dried fruit and candy into a meal rather than eating them as a snack. 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.

The Mayo Clinic suggests looking into dental sealants. 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 prevent the accumulation of plaque.

Fluoride is another cavity-prevention strategy encouraged by the Mayo Clinic. 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 recommend a fluoride toothpaste or mouthwash.

Treatments for cavities include fillings, crowns and root canals. "If the lesion is very small and just beginning, it can be treated with fluoride paste and varnish to help stop the progression of the demineralization," Culotta-Norton said. If the cavity is formed, however, there is only one option: to remove the decay and put a filling in its place. 

According to Culotta-Norton, “If the decay is removed completely and a good filling is placed, the cavity will be gone for a long time, sometimes forever." Though the cavity itself may not return, most people do need to have their fillings replaced several times over a lifetime. "Acids in the oral cavity, wear and poor oral hygiene can cause the fillings to break down, causing micro leakage and subsequent recurrent decay to form," she said.

Dentists do fillings by removing the decayed tooth material with a drill and replacing it with silver alloy, gold, porcelain or composite resin. "Today, most fillings are composites or tooth-colored.  Sometime a silver filling (amalgam) has to be used," Culotta-Norton said. According to the NIH, 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.

According to Culotta-Norton, "If the cavity is very large it may be restored with a crown." These are used if tooth decay is more extensive, the tooth is weakened and there is little remaining tooth structure. The dentist removes the decayed or weakened part of the tooth and fits a crown over the remainder of the tooth. Crowns are usually made of gold, porcelain, or porcelain attached to metal, according to the NIH.

The NIH reports that 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.

Culotta-Norton said that a new treatment for cavities may be on the horizon. A process called electrically accelerated and enhanced remineralization (EAER) is being developed in London. She explained that this process "accelerates the natural movement of calcium and phosphorous minerals into the cavity to repair it.  This process would eliminate drills and injections. It emits tiny electrical currents into the tooth to push the minerals into the repair site. It encourages the tooth to repair itself." According to The Guardian, this new process could be available by 2017. 

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, according to the NIH. 

The NIH warns that 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.

According to the NIH, 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.

According to the Mayo Clinic, 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.

This article is for informational purposes only, and is not meant to offer medical advice.