Infrared Imaging Detects Dental Caries in Posterior Teeth

Dentistry Today


Optical coherence tomography (OCT), an imaging method based on infrared radiation, can be used to detect dental caries on the surfaces of posterior teeth, according to Okayama University. As infrared light is non-ionizing, the method is safer than radiography, which involves X-rays, researchers at the university said.

Dental caries affects more than 90% of the world’s adult population, the researchers noted, adding that it often is detected too late, requiring invasive treatment. Visual examination and radiography are the main tools for diagnosing caries, though they aren’t completely efficient for detecting caries in posterior teeth, the researchers said. Also, radiography is considered problematic for pregnant women and infants.

OCT, which is non-invasive and does not involve X-rays, can be used to create 3-D representations of teeth. After testing its accuracy for diagnosing caries in posterior teeth, the researchers said that OCT could become a viable alternative for radiography.

In OCT, a sample is irradiated with infrared light. Different types of tissue scatter and absorb the infrared radiation differently. Scattering/absorption images that are two-dimensional obtained for many different irradiation angles then can be combined into a 3-D visualization of the sample. Dental caries has a specific response to the radiation, so it can be detected on the 3-D image in principle, the researchers said.

To check whether OCT is accurate enough for detecting caries in posterior teeth, the researchers compared radiography and OCT results for 51 proximal surfaces of 36 molars that were mounted in silicone blocks in a way corresponding to their normal anatomical position. The degree of caries present on the surface was marked histologically with a score from 0 to 5, corresponding to “sound tooth surface” and “distinct cavity with visible dentin,” respectively.

To make a quantitative comparison between radiography and OCT, parameters such as sensitivity and specificity for the detection of caries were evaluated by 13 dentists. A statistical analysis then led to the conclusion that OCT appears to be a suitable method for diagnosing proximal enamel damage and for following up on whether noninvasive treatment, typically based on stopping and reversing the demineralization of the enamel layer, is successful.

The researchers concluded that OCT can be a safer option for diagnosing proximal caries in posterior teeth that can be applied to patients without X-ray exposure.

The study, “3D Imaging of Proximal Caries in Posterior Teeth Using Optical Coherence Tomography,” was published by Scientific Reports.

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