## 2 Case Presentation
### Computer-Aided Design  
The digital workflow (Figure 2) began with an extraoral impression: a 3 dMD scanner (3 dMD Inc., Atlanta, GA, USA) was used to make the facial impression and included the ears to allow for the correct virtual positioning of the digitalized eyeglasses. The eyeglasses were scanned separately with a lab scanner (E2, 3 Shape, Erlangen, Germany) and then virtually positioned on the patient's face. Due to the loss of the original native anatomy of the nose and the upper lip, a digital extraoral impression was made to the front of the patient's daughter to restore a more harmonious face profile than that achievable using the Ear and Nose Digital Library. Other methods described in the literature to obtain a digital model of the missing part of the patient's face include the CAD design of the nose from scratch or the use of a digital copy of the patient's nose preserved before surgical resection; a suitable method is to create an own database (ear and nose library) by digitally scanning patients or patient's face casts [15; 16]. The STL (Standard Tessellation Language) files resulting from the mother's and daughter's face scans were imported into 3-Matic (Materialise, Leuven, Belgium), a certified CAD software for medical use. The daughter's face scan was positioned on the mother's face scan to cover the entire defect, adjusting the size and the position using some anatomical landmarks, such as the eyes and the ears. Once the position was satisfactory, a local smoothing on the surface of the defect area and the Boolean union of the two facial scans were performed (Figure 3). The Boolean union result was used to design the final prosthesis. According to the defect area, the margins of the prosthesis were selected by including the nose and approximately 2 cm of the surrounding skin and the upper lip (Figure 4). Once the surface of the nasal prosthesis was designed, with Move Surface tool, the selected surface was extruded to obtain a thickness of 4 mm. For the external margins of the prosthesis (about 1 cm from the outer edge), a thickness between 1 and 2 mm was obtained using the Chamfer Edge tool, which creates a beveel  
Figure 1: The residual defect after the surgical complication (flap necrosis). Figure 3: STL files of the facial scan of the patient (**A**), of the patient’s daughter (**B**), and the result of the Boolean union of the two scans (**C**). Figure 2: Graphic representation of the digital workflow used for the realization of the nasal–facial prosthesis. Then, the resulting margins were moved by applying a negative 1 mm offset to obtain under-contoured margins to have a compressive effect on the patient's skin (Figure 4). A solid geometry similar to the daughter's nostrils was created, and the nostrils on the prosthesis were obtained with the Boolean Subtraction tool. The final step consisted of the alignment of the digitalized eyeglasses on the patient's face scan to later design the connecting substructure: the digital model of the eyeglasses was positioned, taking care that the rims of the lenses were parallel to the pupils' axis; the temple arms were digitally placed over the ears and the bridge of the optical frame was put in contact with the upper part of the nasal prosthesis (Figure 5). The connecting substructure was designed, considering the minimal volume constraints to guarantee the mechanical support, and the aesthetic requirements of thickness: the substructure was designed to remain entirely within the silicone facial prosthesis, except for the upper part, where it was connected to the eyeglasses behind the optical frame. This connecting part of the substructure was an innovative design: a wide metal platform entirely reproduced the rear surface of the interocular frame of the eyeglasses, and four holes were provided to allow for screwing of the fixing screws to the corresponding female parts that were resin-splinted (Splint Line, Lang Dental Mfg., Wheeling, IL, USA) in the resin framework of the eyeglasses (Figure 6A-C).