Development of dental endoscope for root-canal observation

With the development of dental instruments such as dental microscopes and techniques like cone-beam computed tomography (CBCT), the precision of dental treatment has greatly improved. However, the observation of fractures near the apex collateral of root canals using these instruments remains difficult. In this study, we developed two types of probes that employ external and internal irradiation, respectively. The external-irradiation probe comprises an image fiber and a gradient-index (GRIN) lens, each with a diameter of 500 μm. The internal-irradiation probe comprises an image fiber 300 μm in diameter; a GRIN lens 250 μm in diameter; and five optical fibers for illumination, each 65 μm in diameter. Both probes observed lines and spaces 10 to 100 μm in width on a sample when using a light source from the outside. The visibility of the obtained images increased with the width of the lines and spaces. The illumination of the observation area with the optical fibers inside of the probe was difficult because of a lack of light. In this study, we obtained high-resolution pictures of a root canal. In the future, we will re-design the lens to determine a suitable offset for the optical fiber.