Sensors-14261-2016.R1 Fabrication of Two Different Probe Architectures for Ultra-Compact Image Sensors for Root Canal Observations 1 Abstract—With the development of dental instruments such as dental microscopes and cone beam computed tomography (CBCT), the precision of current dental diagnosis and treatment has greatly improved. However, the observation of deep periodontal pockets, fractures near the root apex, and collaterals of root canals is difficult using these instruments. To solve these problems, we developed two types of micro-image sensors that can be used for the observation of root canals. The first image sensor is an external-irradiation probe that uses an external light source. This probe has high-resolution and a wide field of view. The other sensor is an internal-irradiation probe, which can be used to observe an image and transmit the illumination light with a single probe. The external-irradiation probe has an image fiber with a diameter of 600 μm and a gradient index (GRIN) lens. The internal-irradiation probe has an image fiber with a diameter of 300 μm, a GRIN lens, and 40 optical fibers with a diameter of 40 μm each as a light source. Using these probes, we captured the image of a resolution chart; line spaces with widths of 10 to 100 μm were observed using both types of probes. The evaluations of the visibility of the captured image showed higher measurement values than those of commercially available endoscopes. We will apply this ultra-compact image sensor to various fields besides dentistry, such as medical and industrial applications. Index Terms— endoscope, GRIN lens, image fiber, root canal I. INTRODUCTION EETH are the hardest tissue in the human body and have numerous fine structures as shown in Fig. 1. Fig. 1 (a) shows the cross-sectional view of the human tooth, which includes hard tissue called enamel that is harder than bone or dentin. Soft tissue called dental pulp that includes a combination of nerves and blood vessels is also contained inside the teeth. As a marked structure of a tooth, canals including thin pulp, called root canals, exist in each tooth root. Dental caries (Figs. 1 (a, b)), a common disease observed in a tooth, sometimes damages dental pulp, and dentists eventually remove whole dental pulp, to relieve patients from serious pain. In the field of dentistry, a dentist is forced to treat root canal and deep periodontal pocket blindly without visual corroboration. While performing a surgical procedure such as the treatment of deep periodontal pockets, the affected area can be viewed; however, the surgical treatment places a large burden on the patient, and cannot be applied to all patients. On the other hand, when dental caries reach the dental pulp, and the bacterial infection reaches the periodontal tissue at the apex, endodontic treatment is necessary [1]. Specifically, in endodontic treatment, dental pulp and materials causing the bacterial infection are removed from the root canal. First, the dentist cuts away the dental caries with a machine called an air turbine. After all the caries are removed, the unnecessary parts of tooth crown are also removed to view the entrance of the root canal more clearly. Then, all the dental pulps of the root canal are removed and the root canals are washed with a cleaning solution. The entrance of the root canal is very small and has a complicated shape; in most cases, dentists operate using an instrument and perform the treatment blindly [2-4]. Fabrication of Two Different Probe Architectures for Ultra-Compact Image Sensors for Root Canal Observations Masataka Fujimoto 1 , Shinji Yoshii 1 , Satoshi Ikezawa 2 , Toshitsugu Ueda 2 , and Chiaki Kitamura 1 1. Div. of Endodontics and Restorative Dentistry Kyushu Dental University, Japan 2. Graduate School of Information, Production and Systems Waseda University, Japan T Fig. 1. (a) Cross-sectional view of the human tooth and (b) photograph of the dental caries Fig. 2. Developed dental instruments (a) dental microscope, (b) CBCT This is the author's version of an article that has been published in this journal. Changes were made to this version by the publisher prior to publication. The final version of record is available at http://dx.doi.org/10.1109/JSEN.2016.2562118 Copyright (c) 2016 IEEE. Personal use is permitted. For any other purposes, permission must be obtained from the IEEE by emailing pubs-permissions@ieee.org.