**3. Essential CBCT concepts related to endodontics**

The most important concepts in the use of CBCT in endodontics are the field of vision and the spatial resolution of the machine.

The visual field to be studied or Field of View (FOV) is directly related to the area to be scanned which will be digitally represented on the computer. The FOV measurement for face studies in dentistry with conical beam tomography is 14 cm. what determines the quality of the tomographic image (the size of the pixel and the voxel) is the division between FOV and the matrix. Roughly speaking, CBCT systems can be classified into two categories: limited (dental or regional) or complete (ortho or facial). The limited range FOV is 40–100 nm, while the field of view of the full range is 100–200 nm. A typical FOV consists of millions of voxels [8].

In endodontics, the FOV can be small or "focused" (5 cm by 5 cm or less) because the root canal treatment generally involves one tooth in an arch. This reduction in FOV reduces the amount of effective radiation dose [9]. Other advantages of a small FOV field of view are decreased time to process and read the image, better ability to avoid metallic structures that can cause interference, greater spatial resolution and improved diagnostic potential [10]. Most small FOV machines produce an effective radiation dose in the same order of magnitude as a panoramic radiograph or a periapical series [11].

The degree of spatial resolution is determined by the voxel size, it is desirable that the resolution of a CBCT machine used for endodontics should not exceed 200 μm, the average width of the periodontal space. Otherwise no pathological changes will be identified.
