Abstract: A mouth held plate for use in tomography is divided into two portions, a gum-shaped inner plate and an arc-shaped symmetric outer plate that are integrally connected to each other. A plurality of cavities for holding a molding substance are disposed on the inner plate, and the inner plate is connected to the outer plate at the middle point thereof. The outer plate is provided with a horizontally calibrated x-axis and a vertically calibrated y-axis are accompanied with a grid-marked area respectively. A square hole is disposed adjacent the x-axis on the outer plate for mounting a camera which can take tomograms by consecutive exposures under X-rays. The inner plate is held by the mouth of a patient and bitten by the teeth of the patient at the same time so as to keep the dental data of the patient recorded on the molding substance when it becomes solidified.