**9. Discussion and conclusion**

In this chapter, it can be demonstrated that using modern technology and applying some of the traditional methods of the maxillofacial anaplastologist, it is technically feasible to rapidly and directly manufacture realistic soft tissue prostheses using 3D printing. Using available 3D imaging techniques, which are more accurate and convenient than taking impressions, and less harmful to the patient than CT or laser imaging, it can be shown that it is possible to generate a precise life like 3D model of a traumatised or defective area. Furthermore, by incorporating attachments, a prosthesis of exceptional fit and retention can be produced.

To achieve a lifelike and naturally looking prosthesis, any method of 3D printing would also have to incorporate accurate colour management processes, which converts patient's skin tone into a machine‐readable format for 3D printing, and provide an accurate intrinsically coloured prosthesis that matches the patient's own skin colour. Furthermore, if suitable infiltration materials are utilised then extrinsic colouring can be added to the prosthesis, either through a coloured infiltrant or painted on by the prosthetist. In addition to the colour management, it is possible to generate a two‐part texture design workflow that allows production to accurately match the patient's original features. Using automatic height‐field mapping and manual carving to enhance the features, it is possible to generate a prosthesis that resembles the patient's original morphology and skin texture. Given the materials that can be used to print such models consideration must be given to the accuracy that can be achieved, not only in terms of surface texture, but also optimisation of the infiltration protocols. These will inevitably improve the production process and the overall finished look.

To enhance the peripheral fit of the prosthesis, consideration must also be given to the site of fitting and protocols developed that will allow the production of a prosthesis with a durable seal and thin feathered edges or well‐defined edges where appropriate. The latter points may be determined by the condition of the existing site, surgery the patient has undergone or the preference of the prosthetist. Given the accuracy of the process and the flexibility to produce either type of periphery, the protocols developed would be suitable for both adhesive or attachment retained prostheses.

There are several significant advantages to the process described in this chapter. By printing the prosthesis directly using biocompatible materials, several steps can be eliminated from the traditional process, including impression taking, mould making, setting the prosthesis in silicon and intermediate fitting steps. Current methods require two to four patient visits over several weeks and significant man hours to produce the final prosthesis. Replacements must use existing moulds or the process must be restarted, and given that old moulds may not be accurate due to changes in disease state or other patient factors, it may not be appropriate to use these for replicating the prostheses. Furthermore, the method described is contactless apart from the final fitting of the prosthesis. As a result, the patient experiences minimal discomfort and inconvenience and data capture is quicker than traditional methods. Furthermore, it enables the prosthetist to store this data electronically for future use and record keeping. Using this digital process, the imaging and colour reference appointment takes approximately 10– 15 min. Additionally, the production time is significantly reduced to approximately 48–72 h between imaging and fitting of the finished prosthesis, and as detailed, this process has the potential to produce multiple parts (60–80) in the same timescale and thus reduce the relative production times for each prosthesis significantly. The process is only limited by the CAD input (i.e. image processing and model design/manipulation) although the process is also largely automated. CAD programs can either be used separately, or integrated into one bespoke software that seamlessly passes the model between programs. The only human intervention occurs at the CAD input, design and post‐processing infiltrant stages.

**Figure 11.** Clinical photograph shows the fitting of a 3D printed nasal prosthesis retained by magnet attachments.

In this chapter, it can be demonstrated that using modern technology and applying some of the traditional methods of the maxillofacial anaplastologist, it is technically feasible to rapidly and directly manufacture realistic soft tissue prostheses using 3D printing. Using available 3D imaging techniques, which are more accurate and convenient than taking impressions, and less harmful to the patient than CT or laser imaging, it can be shown that it is possible to generate a precise life like 3D model of a traumatised or defective area. Furthermore, by incorporating attachments, a prosthesis of exceptional fit and retention can be produced.

To achieve a lifelike and naturally looking prosthesis, any method of 3D printing would also have to incorporate accurate colour management processes, which converts patient's skin tone into a machine‐readable format for 3D printing, and provide an accurate intrinsically coloured prosthesis that matches the patient's own skin colour. Furthermore, if suitable infiltration materials are utilised then extrinsic colouring can be added to the prosthesis, either through a coloured infiltrant or painted on by the prosthetist. In addition to the colour management, it is possible to generate a two‐part texture design workflow that allows production to accurately match the patient's original features. Using automatic height‐field mapping and manual carving to enhance the features, it is possible to generate a prosthesis that resembles the patient's original morphology and skin texture. Given the materials that can be used to print such models consideration must be given to the accuracy that can be achieved, not only in

**9. Discussion and conclusion**

104 New Trends in 3D Printing

One other benefit of developing and using this technology is the significant cost benefits. The average cost to the health care system to produce a soft tissue prostheses in the UK using traditional methods is approximately £2000–£6000, and the cost remains largely the same for each replacements prosthesis. The per‐unit cost of 3D printed parts with attachments is significantly reduced due to the reduction in labour costs as well as the numbers that can be produced at any one time. Given that the average prosthesis has a lifetime of 1–2 years, and there is an ever more aging population, the long‐term time and cost savings would be significant using this new technology.

However, there are some limitations to this methodology. The process would be dependent on practitioners acquiring new skills, namely software and CAD usage, and this again will be highly specialised. However, in recent years, this technology has been available for conven‐ tional hard tissue and dental prostheses, for example, custom‐made dental crowns, bridges, implant abutments and various other hard tissue prostheses. Given that the software associ‐ ated with these developments has been widely accepted and is considered user friendly and intuitive, the introduction of such technology for soft tissue prostheses should not be difficult. Another consideration may be the limited availability of virtual CAD models that may be required if existing patient data did not exist. However, these are becoming more available and given that once patients have had parts made existing electronic data can also be used for repeat prostheses for the same patient or adapted for new patients. Another limitation may be the initial start‐up costs, which are not insignificant. At present, equipment costs are high, however, with the advancement of new printing techniques and the emergence of numerous manufacturers in the market place, costs are dropping significantly. Furthermore, collabora‐ tive or 'hub and spoke' arrangements may mean that the data capture and manipulation of missing parts could be undertaken at a local/regional level, whilst the manufacturing process could be centralised to a few specialist production centres. Given that the data will be stored electronically, electronic communications are largely effortless, and similar protocols are seen with other manufacturing industries, this should be easily achievable.

In conclusion, the utilisation of modern manufacturing technologies including 3D printing can provide a quality product quickly and at a significantly reduced cost, labour and patient inconvenience. As detailed, this is a viable method for manufacturing prosthesis using commercially available equipment and software and could easily be implemented clinically.
