Optical coherence tomography (OCT) is interferometric technique using near infrared laser as a light source to construct tomographic images of internal biological structure. When teeth are imaged using OCT, entire enamel layer can be visualized in OCT under suitable clinical condition. Furthermore, dentin can also be visualized and dentin-enamel junction (DEJ) is displayed at the boundary between enamel and dentin. OCT is capable of imaging dental caries and other dental diseases with high imaging resolution.

A major advantage of OCT is that it can capture cross-sectional images of the internal tooth structure without using X-rays, making it safe for repeated examinations even in pregnant women and children. Furthermore, it offers high image resolution and provides high sensitivity and specificity in the diagnosis of dental caries. It demonstrates outstanding diagnostic accuracy, especially for early enamel caries through moderate dentin caries.

When a crack develops in the tooth crown, the OCT laser is scattered at the crack surface, creating a white-line image. For enamel cracks, it is necessary to differentiate them from anatomical structures such as enamel lamellae and enamel tufts. Since OCT images provide depth information, it is possible to distinguish the potential cracks that have reached the dentin, which present severe clinical symptoms. This enables precise treatment for the patient.

Furthermore, cavity adaptation and interfacial gap formation of composite restorations can also be imaged in OCT. Currently, OCT is recognized as a new technology as non-destructive assessment of adhesive restorations and has been widely utilized for evaluation of various dental materials.