R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

Case studies 263
the patient’s defect. Firstly, the external and fi tting surfaces are shaped so
that the contours of the prosthesis are established. This is often done with
the patient present for test fi ttings. The detail is gradually refi ned using
sculpting tools to defi ne features, creases, folds and smaller skin details that
recreate missing anatomy (perhaps using old photographs as a guide) and
that match the topography of the surrounding anatomy.
In order to create a more realistic appearance for the prosthesis skin
texture may be added. This can be achieved in a variety of techniques, such
as stippling with a stiff brush or taking an impression from orange peel or
gauze. Conversely, a fl ame torch may be used to locally melt or soften the
wax in order to selectively smooth areas or decrease the prominence of
textures and bumps. When the wax sculpting is complete, a plaster mould
is made from it. The mould surface picks up the texture and detail of the
wax carving. Once the plaster mould is set, the wax is melted out and
the mould is packed with silicone elastomer that has been matched to the
patient’s skin colour. Other details may be added at this stage such as
the use of red rayon fi bres that replicate superfi cial capillaries and veins.
The silicone is heated under pressure to produce the fi nal solid but fl exible
prosthesis. Depending on the complexity and size of the prosthesis, this
process may take two to three days.
Improved surgical and medical techniques have led to improved survival
rates from accidents and cancer treatments, which has in turn led to an
increased workload for MPTs. This has driven growing interest in the
application of advanced computer-aided design and manufacturing technologies.
Technologies such as computer-aided design (CAD) and rapid
prototyping (RP) have shown benefi ts in reducing time and labour in
product design and development, and initial research suggests that similar
benefi ts may be realised in the production of facial prosthetics. However,
whilst some RP technologies have been successfully exploited in maxillofacial
surgery for many years, their application in facial prosthetics remains
relatively unexplored (3). Recent technological advances have increased
opportunities for MPTs to benefi t from these technologies, and this can be
seen in the recent research (4–12). Despite this interest and some promising
results, most of this research has focused on the creation of the overall
shape of the prosthesis and has not considered the importance of the
smaller details that make a prosthesis visually convincing. Given the importance
of details such as texture and wrinkles in achieving a natural and
realistic result, it was important to explore the problem through the study
described here.
This research aimed to identify and assess suitable technologies that may
be used to create and produce fi ne textures and wrinkles that may be conveniently
incorporated into prosthesis design and production techniques.