# Dental Applications of Optical Coherence Tomography (OCT) in Cardiology
###### Abstract
Marks define the region of interest (ROI); (**b**) In the cross-sectional image of the ROI, generated using spectral domain OCT, bright shadowed spots reveal the lesion area is limited to the first half of the enamel (E); (**c**) After sectioning, demineralization can be imaged using dark-field light microscopy (DFLM) corresponding to the lesion details in the OCT image. D: dentin, EDJ: enamel-dentin junction. Figure 2: Screenshot, in vivo image of a human incisor. Partial conformance of visual assessment with OCT. A carious lesion (L) of ICDAS II Code 2 can be detected visually at the air-dried enamel surface (red arrow). In the SD-OCT B-scan, this lesion appears as a bright shadowed area without cavitation. Compared to visual assessment, the OCT signal reveals an extended lesion body with dentin (D) involvement and a mineral-rich and porous surface layer (*). In addition, defects, or cracks in the enamel (E) are seen to cause shadowing (white arrows). G: gingiva, EDJ: enamel-dentin junction. whether a separation between sound and diseased is possible over the entire spectrum of carious lesions [14]. Furthermore, there is a substantial need for the assessment of dental restorations, which is technically demanding. Challenges include quality evaluation in terms of material homogeneity (bubble formation within material or at increments), or the detection of material overhangs at restoration margins. Currently there are no suitable methods available to enable dentists to self-check the quality of intermediate steps during restoration placement. Moreover, it is important to have the possibility to assess the bond at restoration margins and along the tooth-restoration interface, as well as to detect carious lesions adjacent to restorations (secondary caries) and compare different restoration materials in clinical trials or in in vitro studies. Today, the in vivo evaluation of marginal integrity can only be performed visually [15; 16] and by a sensitive technique with a time-consuming quantitative margin analysis using scanning electron microscopy (SEM) [17]. However, the detection of early lesions adjacent to restorations is still a challenge [1]. Against the background of these demands, optical coherence tomography seems to be a promising technique. The method, which is based on low coherence interferometry, was first presented by [PERSON] et al. [18]. In medicine, OCT is currently primarily used in ophthalmology for evaluating the pathological changes in retinal layers and the optic nerve [19; 20; 21; 22]. Further applications are found in dermatology [23; 24] and cardiology [25]. The first images of human dental tissues were presented by [PERSON] et al. [26; 27] and [PERSON] et al. [28]. Since then, the number of studies using OCT have increased markedly [29; 30]. Seven features which make it particularly suitable for clinical application are non-invasive action avoiding radiation-induced tissue damage; easy to understand cross-sectional and 3D-images of soft and hard tissues; as well as defects at a very early stage with high spatial resolution. Structural changes can be obtained qualitatively as well as quantitatively. In particular, high speed data acquisition allows real-time imaging in vitro, ex vivo and in vivo [9; 30]. Although OCT has been widely used in dental research, it nevertheless stands at the beginning of its application career. Numerous functional OCT systems [31; 32], methodological extensions (e.g., polarization sensitive OCT [10]), as well as evaluation methods have been described [31; 32; 33], and also show the potential of this technology in characterizing specific material characteristics [33], or to improve the optical performance of the method, such as detection sensitivity or depth penetration [31; 34]. This review presents applications of optical coherence tomography in the field of cariology, which includes subsections on caries prevention, detection, and assessment of carious lesions, as well as caries therapy.