Across all medical disciplines, therapeutic interventions are based on previously acquired diagnostic information. In cariology, which includes the detection and assessment of the disease “caries” and its lesions, as well as non-invasive to invasive treatment and caries prevention, visual inspection and radiology are routinely used as diagnostic tools. However, the specificity and sensitivity of these standard methods are still unsatisfactory and the detection of defects is often afflicted with a time delay. Numerous novel methods have been developed to improve the unsatisfactory diagnostic possibilities in this specialized medical field. These newer techniques have not yet found widespread acceptance in clinical practice, which might be explained by the generated numerical or color-coded output data that are not self-explanatory. With optical coherence tomography (OCT), an innovative image-based technique has become available that has considerable potential in supporting the routine assessment of teeth in the future. The received cross-sectional images are easy to interpret and can be processed. In recent years, numerous applications of OCT have been evaluated in cariology beginning with the diagnosis of different defects up to restoration assessment and their monitoring, or the visualization of individual treatment steps. Based on selected examples, this overview outlines the possibilities and limitations of this technique in cariology and restorative dentistry, which pertain to the most clinical relevant fields of dentistry.

In clinical dental practice, it is often difficult or even impossible to detect and assess interfacial adhesive defects at adhesive restorations by means of visual inspection or other established diagnostic methods. However, nondestructive optical coherence tomography (OCT) may provide a better picture in this diagnostic scenario. The aim of this study was to evaluate the suitability of swept source OCT (SS-OCT) for the nondestructive assessment of interfacial deficiencies at composite restorations and the evaluation of cohesive defects within composite material. Ten class V composite restorations that were not adhesively luted were taken as validation objects and examined for frequency of interfacial gaps, air entrapments, and defects between composite layers using SS-OCT with a 1325-nm center wavelength. Light microscopy was used to inspect for inherent structures. SS-OCT detected $79.5%±1.8%$ of the total gap lengths at the enamel interface and $70.9%±0.4%$ at the dentin interface. Additionally, defective structures in composite restorations were displayed. It was shown that OCT imaging has the potential to nondestructively assess the interfacial adaptation of composite restorations and to detect internal defects in the layered composite material.