## 3 Discussion
After the patient data acquisition, it is possible to design the virtual prosthesis with the aid of the acquisition of the digital data from the patient's daughter or sister/brother, similar to that in the presented case report, using specific design software, such as Geomagic studio (Geomagic Inc., Cary, NC, USA),  
Figure 11: (**a**) STL after rehabilitation using the designed ephitesis (scan_POST); (**b**) STL of the combination of the patient and the daughter’s face scans (scan_REF); (**c**) the obtained distance mapping between scan POST and scan_REF. 3-Matic (Materialise, Leuven, Belgium), Freeform Model Plus (SensAble Technologies, Boston, MA, USA), or to make use of a digital library. Implementing a digital design and using digital libraries may provide faster, repeatable, and shareable CAD models of the prosthesis. The connecting substructure of the prosthesis can also be designed with CAD technologies [20; 22]. Once the virtual design of the prosthesis is completed, the process involves manufacturing the final prosthesis with silicone. Therefore, this workflow is essential to minimize visits, for example by fabricating templates of the prosthesis volume and the substructure for a single clinical check on the patient's face. In the case presented here, it was possible to manufacture a realistic prosthesis template for a clinical try-in on the patient's face (Figure 9), using a cutting-edge 3D printing technology, previously described by our research group to build facial portions of a multi-material patient-specific simulator [25]. The great potential of such 3D printing technology is the capability of printing both rigid and rubber-like materials in a single part, so that it is possible to manufacture both the rigid substructure and the soft nasal prosthesis during the same printing process. Several studies documented using digital design and CNC milling technologies to fabricate retentive component systems for facial prosthesis devices [26; 27; 28]. [PERSON] et al. [29] described a workflow for creating a four-dimensional (4D) facial expression model to fabricate nasal prostheses over several time points, from neutral to smiling expressions. They emphasized the importance of the prosthesis fit during patient's facial movements. The silicone processing and the intrinsic and extrinsic coloring are still made with traditional procedures; the use of colorimetry and spectrophotometry systems may provide easily acquired and repeatable skin-color matching [30]. Furthermore, previous digital protocols [15; 31; 32; 33] improved other aspects of this kind of removable facial prosthesis, especially those related to stability and function. In this study, the design of the substructure provided a four-hole retention in the rear part of the glabellar surface of the eyeglasses that ensured a stable connection by distributing the functional loads all over the connecting area. A fundamental feature of this new connection is the usage of custom-made micro screw-females inserted and relined with PMMA resin (Split-Line) in the framework of eyeglasses (Figure 6B). This new system guaranteed a more balanced load distribution without overloading a single screw. Moreover, the laser melting 3D printing technology allowed for the manufacturing of a metal substructure with a minimal thickness (1 mm). This feature is conducive to reducing the prosthesis's weight and minimize the space necessary to overcover the underlying irregular scar skin tissue when it cannot be surgically remodeled with further plastic surgery, as in this case. At the same time, the minimal thickness of the metal substructure allowed for hiding of the metal color inside a 2 mm thickness of the final relined silicone, thus generating an over-contouring of at least 3 mm for the residual skin surface. The reduction of the silicone thickness was also essential to guarantee enough elasticity of the prosthesis that, at the peripheral margins of the defect, can quickly adapt to the muscular movements of the skin.