Near-infrared (NIR) dental imaging using scanning fiber endoscope (SFE) is being developed with advantages of miniature size (1.6mm), flexible shaft, video frame rate (7Hz), and expandable field of view (60 degrees). Using 1310, 1460, and 1550 nm laser diodes, the multispectral NIR SFE provides high contrast of lesion with transparency of stained and non-calcified plaque. However, capabilities of scanned NIR imaging remain unknown. Artificial interproximal lesions are created in extracted human posterior teeth by preparing a cavitation on the mesial or distal surface and then the cavitated artificial lesions were filled with hydroxyapatite powder and sealed with cyanoacrylate resin. Lesions are prepared at different occlusal-gingival depths from marginal ridges, lesion drilling depths and lesion size. Endoscopic reflectance images were acquired and compared to micro-CT scans and 1310 nm OCT images of the lesions to evaluate performance of the nirSFE. Results show that NIR SFE can image deep lesions under sound enamel with thickness of ≤4mm. All three wavelengths can detect deep lesions through the occlusal enamel which are not visible by naked-eye. 1460 nm has the highest contrast between lesion and sound enamel while 1310nm more clearly shows the contrast between enamel and dentin. Our nirSFE system can detect artificial interproximal lesions less than 4 mm below the occlusal surface, distinguish different drilling depth both in enamel and in dentin layer. Furthermore, the nirSFE realtime imaging and video functionality renders better lesion contrast and helps distinguish specular reflection and lesion signal. In conclusion, the NIR SFE has the potential to measure volume of these lesions due to the many viewing angles achievable by the miniature and flexible probe tip.
We present a scanning fiber endoscope (SFE) designed for near-infrared (nir) imaging. The SFE piezo actuator drives a single mode fiber in spiral patterns; meanwhile return fibers collect the reflective light; then signals from detector are mapped onto an image according to the fiber scan trajectory. Many SFE prototypes have been developed based on red/green/blue reflectance, enhanced spectral, fluorescence, optical coherence, and multimodal imaging. These forward-view SFE prototypes have the advantage of miniature size (1-3mm), flexible shaft, video-speed frame rate (10-30Hz), wide field of view (60-100 degree) and good resolution quality. A new SFE prototype is being developed that operates entirely in near-infrared wavelength range, which is expected to have great potential in imaging dental lesions and monitoring therapy. The first nirSFE probe has a diameter of around 3mm, frame rate of 17Hz, 53 degree FOV and spatial resolution of 40um. Although the specific optical fibers made for nir makes the probe stiffer than previous prototypes, the flexible 2m shaft allows for easy orientation. Using this prototype we can achieve reflectance mode imaging and also switch between different wavelengths (1310nm, 1460nm, 1550nm) and light sources (SLD or laser). In the development of this prototype, we encounter several issues: 1) the speckle noise caused by interference of laser beams, 2) uneven illumination and reduced visual field caused by collection fiber distribution and numerical aperture, and 3) specular reflection patterns which can obscure important enamel target detail. We explore solutions to these issues by using multiple detector channels, light sources, and filtering.
Near-infrared (NIR) wavelength range of 1300-1500nm has the potential to outperform or augment other dental imaging modalities such as fluorescence imaging, owing to its lower scattering coefficient in enamel and trans- parency on stains and non-cariogenic plaque. However, cameras in this wavelength range are bulky and expensive, which lead to difficulties for in-vivo use and commercialization. Thus, we have proposed a new imaging device combining the scanning fiber endoscopy (SFE) and NIR imaging technology. The NIR SFE system has the advantage of miniature size (1.6 mm), flexible shaft, video frame rate (7Hz) and expandable wide field-of-view (60 degrees). Eleven extracted human teeth with or without occlusal caries were scanned by micro-computed X-ray tomography (micro-CT) to obtain 3D micro-CT images, which serve as the standard for comparison. NIR images in reflection mode were then taken on all the occlusal surfaces, using 1310nm super luminescent diode and 1460nm laser diode respectively. Qualitative comparison was performed between near-infrared im- ages and micro-CT images. Enamel demineralization in NIR appeared as areas of increased reflectivity, and distinguished from non-carious staining at the base of occlusal fissures or developmental defects on cusps. This preliminary work presented proof for practicability of combining NIR imaging technology with SFE for reliable and noninvasive dental imaging with miniaturization and low cost.
Optical imaging modalities and therapy monitoring protocols are required for the emergence of non-surgical interventions for treating infections in teeth to remineralize the enamel. Current standard of visual inspection, tactile probing and radiograph for caries detection is not highly sensitive, quantitative, and safe. Furthermore, the latter two are not viable options for interproximal caries. We present preliminary results of multimodal laser-based imaging and uorescence spectroscopy in a blinded clinical study comparing two topical therapies of early interproximal caries in children. With a spacer placed interproximally both at baseline and followup examinations, the 405-nm excited red porphyrin uorescence imaging with green auto uorescence is measured and compared to a 12-month follow-up. 405-nm laser-induced uorescence spectroscopy is also measured from the center of selected multimodal video imaging frames. These results of three subjects are analyzed both qualitatively by comparing spectra and quantitatively based on uorescence region segmentation, and then are compared to the standard of care(visual examination and radiograph interpretation). Furthermore, this study points out challenges associated with optically monitoring non-surgical dental interventions over long periods of time in clinical practice and also indicates future direction for improvement on the protocol.