## 4 Discussion
In 2015, [PERSON] reported a cost between $2000 and $6000 for commercial products such as MIMICS (Materialize N.V., Louven, Belgium) which includes virtual planning assistance and cutting guides [33]. In 2017, Bosc reported that the complete service for the CAD/CAM system has a cost between 3000 and 5000 euro for each patient and the delivery times are longer than three weeks [34]. With such a long delivery time, the risk of cancer progression and metastasis increases. The idea of rapid in-house prototyping can help to reduce costs and save time in performing surgery. In our study, rapid in-house prototyping and 3D-printing protocols were developed to virtually plan a mandibular reconstruction after cancer resection [25]. After the initial purchase of the 3D printer, at a cost of about 3000 euro, the cost related to the design of each case is about three euro, the sum necessary for the purchase of the material for the printing. Computer-assisted surgery also provides a greater precision in mandibular reconstruction with a clear gain for the patient in terms of functionality and quality of life [35]. However, a high level of reconstruction is difficult to achieve due to the various inaccuracies that can occur in the different phases, such as in the image acquisition, segmentation, 3D printing, surgery, and evaluation of the post-operative results [36; 37]. In maxillofacial traumatology, the use of VSP has made it possible to optimize outcomes in this area with a high esthetic impact. In cases of orbital-floor fractures, a perfect reconstruction is still a challenge for the surgeon due to the possible complications that may arise, such as diplopia and enophthalmos. In the literature, several authors describe the possibility of using customized titanium meshes for orbital reconstruction [38; 39]. Unfortunately, also in this case, the high cost and long prototyping times make this method inapplicable. The protocol we apply involves in-house prototyping in order to model the mesh based on the patient's anatomy. The time spent during the design allows a clear reduction in the operating time. The accuracy of the printing depends on the accuracy of the CT, which must have slices thinner than 1-2 mm. During the health crisis related to the COVID-19 pandemic, it has been essential to protect healthcare workers by providing them with adequate personal protective equipment. Considering the main transmission pathways of SARS-CoV-2, face masks have proved to be a fundamental tool to prevent contamination [40; 41]. Nowadays, there is clear evidence in the literature of the high accuracy of 3D facial scanning and it is accepted that facial digitizing procedures produce clinically acceptable outcomes for virtual treatment planning [42]. In our region, the COVID-19 emergency started on 9 th March 2020 and we began to design and print the Mask3d on 16 th March 2020. The perfect fitting of the mask to the skin surface allows for the breathing function to be performed exclusively through the filter unit, providing a good personal protection for the worker [43]. Using Bellus 3D, a free mobile application, the present workflow protocol is accessible to anyone. As reported by [PERSON] et al., the introduction of new generation smartphones with two cameras and dedicated applications, like Bellus3D, makes this system practical and available worldwide [44]. Our protocol is based on a low-cost, \"home-made\" rapid prototyping facial mask. The estimated cost of the prototyping process is less than 5 euro per case. Currently, due to the COVID-19 emergency, there are no certifications available. However, the use of \"home-made\" masks has been approved by the Italian government.