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In 2D images, the resolution depends on the number of pixels. A pixel is the smallest unit of a digital image that can be displayed and represented on a digital display device, also known as a picture element (pix = picture, el = element). A pixel is represented by a dot or square on a computer display screen. Pixels are the basic building blocks of a digital image or display and are created using geometric coordinates. Depending on the graphics card and display monitor, the quantity, color combination, and size of pixels vary and are measured in terms of the display resolution. A full high‐definition (full HD) image is 1920 pixels in width and 1080 pixels in height, totaling 2.07 megapixels. Ultra HD (also known as 4 K) resolution has 3840 × 2160 pixels, totaling 8.3 megapixels.

The 3D version of a pixel is called a voxel. In general, the smaller the voxel size is, the better quality a 3D reconstructed model will have.

The quality of radiographic images depends on contrast resolution and spatial resolution. Contrast resolution is proportional to the size of the contrast scale available to produce the image. As a result, the higher the contrast resolution of an image, the easier it will be to distinguish between multiple densities. In digital imaging, contrast resolution depends on the bit‐depth of the imaging method, following a logarithmic scale. Therefore, a panoramic radiograph produced with an 8‐bit system can show 2⁸ = 256 different gray‐scale levels distributed from black to white. A CBCT device with a 12‐bit system will offer 2¹² = 4096 gray‐scale values. Spatial resolution is the ability of an imaging method to identify the actual limits and differentiate two adjacent structures [2–4].

Resolutions in 3D CAD files basically depends on the size and densities of the meshes. The quality of the respective manufactured device, however, is also dependent on factors related to CAM (e.g., resolution of 3D printers or milling devices). For 3D printers, there will be factors related to the resolution such as the number of layers and layer thicknesses. For milling machines, the resolution will be dependent on the number of axes and size of burs (see Chapter 3).