Development of novel image sensor for root canal observation

Abstract

The development of dental instruments such as dental microscope and cone-beam computed tomography has greatly improved the precision of current dental treatments. However, observation of fractures near the apex collateral of the root canal remains difficult when using these instruments. In this study, we developed two types of probes: an ‘external-irradiation system’ and an ‘internal-irradiation system’. The external-irradiation probe is composed of an image fibre with a diameter of 500 μm and a gradient-index lens (GRIN lens) with the same diameter as the image fibre. The internal-irradiation probe is composed of an image fibre, GRIN lens, and five optical fibres for illumination, with diameters of 300, 250, and 65 μm, respectively. In an observation experiment of the resolution chart using these probes, both probes could observe lines and spaces of 10–100 μm using an external light source. To evaluate resolution, visibility was measured for each image, and higher visibility was observed as the lines and spaces were increased. We attempted to illuminate the observation area with optical fibres inside the probe; however, it was difficult because of the low intensity of the light. Furthermore, we observed the actual root canal of an extracted tooth. In future, we would like to redesign the GRIN lens and a suitable offset of the optical fibres.