How is tooth decay diagnosed?

Tooth decay is best diagnosed by your dentist. Recession of the gums away from the teeth, combined with an increased incidence of gum disease, can expose tooth roots to plaque, causing tooth decay. Decay around the edges, or margins, of fillings is also common to older adults.

Your dentist will use several methods to diagnose tooth decay. First, a visual inspection of the tooth is done. Your dentist is looking for a hole in the tooth or a stained area which could indicate a cavity. Second, a tactile examination of the teeth is done. Your dentist is checking for an area of the tooth that is sticky as it is being checking with a dental explorer. Third, dental x-rays are taken to check for cavities especially between the teeth. Using the results from all three diagnostic tests, your dentist will decide if your tooth has a cavity and if it needs fixing with a filling.

Aaron B. Schwartz, DDS
Pediatric Dentistry
Clinically: A visual examination by your dentist and he/she tactilly examining your teeth with dental instrments
Radiographically: taking dental radiographs (x-rays) will diagnose tooth decay.
Dan Jenkins
Decay of the teeth is diagnosed by determining how soft the tooth structure is compared to other tooth structure in the mouth. While it is true that not everyone's teeth are the same hardness it is pretty standard that if a sharp instrument can stick into a part of a tooth it is sufficiently soft enough that it should be cleaned out and protected from further softening.

Thus, for most of the cavities a sharp instrument called an "explorer" is poked at the tooth surface to explore how hard or soft it is and x-rays are used to determine how much softer one area of a tooth is than others.

There are other products out that do the same thing with a laser beam or a bright light to assist the dentist in determining what is a cavity and what is the beginning of a cavity and what is NOT a cavity. It still will come down to the judgment of your dentist.

Tooth decay is diagnosed with radiographs (X-ray's), a visual inspection, and with an instrument to test the hardness of the tooth. Not all cavities show up on an X-ray. A visual inspection can show discoloration of the tooth structure and a sharp instrument called an explorer is used to see if it penetrates the tooth. The explorer will not penetrate the tooth unless it is soft enough. 

Tooth decay is diagnosed with several methods that include:

  • visual exam
  • use of metal probe instrument
  • radiographs
  • laser diagnostic tools
  • transillumination

Although the various diagnostic methods help in decay detection, it is often important to make a radiograph (x-ray) to further evaluate the extent of the decay and possible involvement of other areas of the tooth.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.