Validity of Swept-source Optical Coherence Tomography (SS-OCT) for the Diagnosis of Dentin Caries

<p> Purpose: Dental caries remains one of the most prevalent diseases in the world. An operative approach with surgical treatment is usually applied to dentin caries with bacterial infection that has progressed into dentin. Accurate diagnosis of caries progression is essential to provide a foundation for selecting the caries treatment. Optical coherence tomography (OCT) is a new diagnostic modality using light, and can create cross-sectional images of biological structures without X-ray exposure. Swept-source OCT (SS-OCT) is a new version of OCT of which the imaging depth is improved over the conventional version of OCT, and is expected to be used in dental clinics. In this study, SS-OCT imaging was performed to dentin caries on the occlusal and proximal surfaces to assess the diagnostic accuracy of SS-OCT.</p><p> Methods: Extracted human teeth with and without dentin caries on occlusal or proximal surfaces were mounted in silicone blocks. SS-OCT scanning (Yoshida Dental OCT, Yoshida Dental) was performed from the occlusal surface of extracted teeth to construct a 3D data set. 2D cross-sectional images were extracted from the 3D data to visualize the caries. After SS-OCT imaging, digital intraoral radiographs (Dentnavi Hands XD35, Yoshida Dental) were captured from the buccal surface of the mounted teeth. The presence and extent of caries were evaluated by 10 dentists and scored using a four-rank depth scale. Sensitivity, specificity and kappa coefficient of SS-OCT and intraoral radiography for the diagnosis of dentin caries on the occlusal and proximal surfaces were calculated and compared at the significance level of α=0.05.</p><p> Results: SS-OCT showed significantly higher sensitivity for the diagnosis of dental caries for both the occlusal and proximal surfaces than intraoral radiography (p<0.05). However, the sensitivity of SS-OCT at the occlusal surfaces was significantly lower than that at the proximal surfaces (p<0.05). Although SS-OCT showed excellent values of the kappa coefficient for both the occlusal and proximal surfaces (p>0.05), intraoral radiography showed significantly lower values at the proximal surfaces (p<0.05).</p><p> Conclusion: SS-OCT is considered to be useful for the diagnosis of dentin caries on occlusal and proximal surfaces. The results of SS-OCT imaging were influenced by the caries location and projection geometry, suggesting the importance of understanding image characteristics in SS-OCT.</p>