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Tooth Decay / Cavities / Dental Caries

What is Tooth Decay?

Tooth decay is caused by streptococcus mutans bacteria.

Figure 1: A scanning electron micrograph of a colony of Streptococcus mutans bacteria, such as those found in the fuzzy plaque on teeth. These are the bacteria responsible for the vast majority of tooth decay. (Image from http://www.zahnarzt-stuttgart.com, used with permission).

Tooth decay (dental caries) is a bacterial illness believed to be caused by a single strain of bacteria known as Streptococcus mutans, although Lactobacillus may also be involved. These bacteria use sugars from the food and drinks we eat, to produce acids and enzymes that attack tooth enamel.

Tooth decay (also known as dental caries, or cavities.)

A sugary diet and poor oral hygiene results in tooth decay (caries).

Directly consumed acids, such as phosphoric acid found in many soft drinks, can also attack tooth enamel, resulting in the decay of the tooth. Food and drink containing citric acid (for example, lemons) should be consumed in moderation.

Tooth decay can devastate teeth, even with all that is known about its causes, and all of the excellent preventive measures available to stop the disease. Proper nutrition and excellent oral hygiene are the keys to avoidance of tooth decay.

How does the dentist diagnose Tooth Decay?

Note: ToothIQ.com contains general information. Only a dentist can properly diagnose your specific condition.

Traditionally, dentists have detected tooth decay in one of three ways: visual and tactile examination; and dental X-ray images.

Visual/Tactile Exam

Sectioned tooth shows fissure smaller than single toothbrush bristle, making it difficult to clean.

Pits and fissures in teeth may be too deep and narrow to allow access for even one toothbrush bristle, as illustrated by this cross section of a tooth.

Some tooth decay is visually obvious; other tooth decay may develop in the deep pits and fissures of teeth. Some studies suggest as many as 80% of tooth decay begins in pits and fissures.

A dental explorer on a tooth.

Dental explorers have been used for many years to detect early tooth decay.

Dentists typically use an instrument called a dental explorer, a sharp, wiry instrument for probing the depths of the pits and fissures. If the base of the pit or fissure is softened by tooth decay, the instrument will stick in the tooth.

X-ray Images

A dental periapical dental X-ray image showing tooth decay.

Tooth decay has occurred where an impacted wisdom tooth (third molar) has been leaning against a second molar tooth (See arrow). Without the dental X-ray image, the decay would have gone undetected.

Tooth decay is visible as dark areas of the tooth on X-rays. Dentists use dental X-rays to look for tooth decay where a visual/tactile examination is not possible, most notably between the teeth.

Tooth Decay Detection By Laser

Laser caries detection enables tooth decay to be diagnosed without using X-rays.

An artist’s rendering of the tip of a laser fluorescence tooth decay detection meter emits a focused beam of 655nm wavelength light into the pits and fissures, causing fluorescence of decayed tooth structure. The amount of fluorescence is directly related to the extent of the tooth decay. Healthy tooth enamel does not fluoresce.

An extremely sensitive diagnostic tool for determining whether the pits and fissures in teeth have begun to decay at their base is the laser fluorescence caries detection device, the tip of which is shown in the image below.

Healthy teeth do not fluoresce, and decayed teeth fluoresce in proportion to the amount of bacteria present in the tooth. This device measures the fluorescence pattern of teeth, and produces a reading on a meter which is recorded by the dentist.

Diagnosis of pit and fissure cavities is most effective when a combination of visual/tactile examination, appropriate use of laser fluorescence caries detection devices, and X-ray images are used.

How is Tooth Decay treated?

Depending on the severity of the decay, restoring teeth with tooth decay may involve fillings, inlays, onlays, crowns or tooth extraction. Tooth decay that reaches the inner pulp of the tooth may require root canal treatment to eliminate the bacteria. Sometimes early decay can be slowed down or stopped by applying topical fluoride to the affected area. Photographs and radiographs (dental X-rays) are useful for monitoring tooth decay.

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Author: Thomas J. Greany, D.D.S. / Editor: Ken Lambrecht

This page was last updated on March 2, 2018.

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