The early detection and diagnosis of caries in pits and fissures remain major problems in clinical dentistry. Optical coherence tomography(OCT) is an emerging, non-invasive, high-resolution, optical diagnostic technique. This approach can provide information on morphology and depth of early caries without the interference of enamel hypocalcification and stain. As the porosity of demineralized dental tissue increases, micro-interfaces within the micropores augment reflection and multiple scattering. Based on low-coherence interferometry, OCT can detect the reflected or backscattered signals to the incident beam at various vertical extents. OCT can also generate 2D/3D images of early enamel caries and dentine caries on the occlusal surface, and quantify lesion severity by calculating the integrated reflectivity. OCT is a promising prospect for the diagnosis of occlusal caries, anti-caries efficacy estimation, and assistance in the selective removal of demineralized tooth tissue by laser. This review focuses mainly on different types of OCT, namely, the conventional, polarization-sensitive, swept-source, and cross-polarization OCT. This review also highlights the abovementioned OCT applications in imaging and quantitative analysis, diagnostic efficiency, and therapeutic monitoring of occlusal caries.
