**4.1. Data preparation**

CAD generation of the missing facial part can take various forms. Data capture of unaffected areas of the face can be undertaken and images 'mirrored' in order to virtually replace those affected or missing. This may be suitable for missing ears or orbital areas where there are usually bilateral structures. However, this may not be appropriate or possible for single or isolated structures including nasal structures or where surgery has already been undertaken to remove the affected part. Alternatively, open‐source CAD databases are now increasingly available—www.turbosquid.com—and these can offer CAD users direct links to download‐ able content. These may include non‐specific facial shapes covering a wide range of anatomical form, from those considered 'generic' to those with interesting or characteristic features. Although easily accessible, there are some issues with these sources. Although geometrically accurate, the peripheral area can be quite variable and not suited to cover the affected areas in specific patients. Additionally, the surface detail can be highly faceted and unsuitable for direct modelling. However, these files can provided good starting points for CAD design and allow adaptation to enable conformation to the affected area. Various software can be used to alter theses captured or acquired data files including 3‐Matic (Materialise, Leuven, Belgium). These can then be used to alter the surface detail and to refine the geometry in order to provide individual and bespoke characteristics for the missing facial part (**Figure 3**).

**Figure 3.** Image detailing manipulation of the CAD prosthesis to refine the shape and fit of the final part (Approx. part Dim: 40 × 24 × 25 mm).
