Introduction
Transparent facial pressure masks with silicone sheeting are used as a non-invasive treatment option for hypertrophic scarring following oncological facial reconstruction. These masks are fabricated using conventional plaster moulds, which is labour-intensive and requires an experienced orthotist or prosthetist. 3D scanning and 3D printing are promising technologies that could replace the current traditional fabrication process. The aim of this thesis is to evaluate whether 3D technology is suitable to replace the traditional fabrication method of transparent facial pressure masks; and is able to produce a mask that provides adequate pressure therapy.

Methods
First, a systematic review was performed to identify suitable 3D scanning and 3D printing techniques for fabrication of the facial mask and to find pressure assessment tools.
Subsequently, 3D scanners, 3D printers, software and pressure assessment tools were analyzed for technical feasibility and availability.
Based on this analysis, a pilot study was performed in which the most optimal workflow to fabricate facial pressure masks using 3D technology was designed. The most optimal workflow was identified in terms of (1) workload (man-hours, degree of automation and need for human expertise); (2) patient comfort; (3) total time; and (4) costs;
Two masks were fabricated for a healthy volunteer using two different moulds: a 3D printed mould and a conventional plaster mould. These masks were compared in terms of comfort and blanching of the skin as indirect measures for pressure distribution.

Results
A hand-held structured light 3D scanner (Artec Eva, Artec 3D), easy-to-use CAD software (Meshmixer, Autodesk, Inc.) and Fused Deposition Modeling (Ultimaker 2+, Ultimaker) appear to be the most suitable tools for the fabrication of a facial mask. As pressure distribution cannot be assessed directly yet, due to the lack of reliable sensors, the most suitable tools to assess pressure distribution indirectly are patient comfort and blanching of the skin.
The most optimal workflow to fabricate a facial mask using 3D printing techniques consists of 3D scanning and 3D printing of a positive mould followed by vacuum forming of Silon-STS® over the positive mould. This is a partly automated process that still needs human expertise. Based on an estimation of time and costs, the fabrication process is quicker and cheaper than the conventional method. Although the manipulation process during aftercare takes longer and is more expensive, the number of man-hours remains the same and patient comfort increases.
The facial mask fabricated using 3D scanning and printing techniques for the moulding process causes undesirable blanching of the skin at the nasal bridge and the healthy volunteer expressed discomfort due to this pressure point. The facial mask fabricated using a conventional plaster mould causes discomfort at the cheeks. Therefore, both masks will need design adjustments to provide adequate pressure therapy.

Conclusion
Based on our preliminary results 3D technology seems suitable to partly replace the traditional fabrication method of transparent facial pressure masks. To further optimize and validate the proposed workflow, future research should focus on digital mould modification and more objective pressure measurement tools. Future goals in a clinical setting will be to evaluate (1) cost-effectiveness; (2) long-term clinical effects in patients and (3) patient reported outcome measures.