In order to fully exploit the diagnostic potential of optical coherence tomography (OCT) in contemporary restorative dentistry, an intraorally applicable OCT probe has been constructed. The probe was connected to a commercially available OCT system. The handling of the probe and the quality of the OCT images were optimized and evaluated on human extracted teeth fixed in a patient-equivalent simulation. In addition, the probe was applied intraorally to volunteers. With the intraoral OCT probe hard tooth substances, carious lesions in enamel and dentin and composite restorations could be imaged. In vivo, the probe allowed OCT imaging of all tooth surfaces except the vestibular surfaces of third molars and proximal surface areas of molars within a "blind spot" at a distance of 2.5 mm from the tooth surface. Superficial tissue structures of the marginal gingiva could also be imaged. The intraoral OCT probe is a promising tool for non-invasive imaging and monitoring of healthy and diseased hard tooth substances and tooth-colored restorations. It can be a valuable addition to established methods for caries diagnosis and restoration evaluation.