R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

188 Medical modelling
6.55 The fi nal design.
The unaffected side of the patient’s skull was copied and laterally inverted
to provide a base part from which a well-matched implant could be designed
(Fig. 6.58). As in all cases attempted in this manner thus far, the laterally
inverted copy does not precisely fi t the defect; however, the FreeForm ®
software enables the form to be modifi ed and adapted to produce a prosthetic
design that shows good aesthetic appearance and a precise fi t at the
margins. The software also enabled the implant design to be produced in
a very smooth manner, which will prove suitable for a double processed
and polished acrylic implant. As in the previous case, the implant design
was manufactured using stereolithography and test fi tted to an existing
model of the patient defect, as shown in Fig. 6.59.
6.10.5 Future development and benefi ts
This experiment has proved only that it is feasible to use CAD techniques
to design and fabricate implants such as cranioplasty plates. However, the
benefi ts are already apparent. The advantage is that no material is used or
wasted in the design and development of the implant. Only when the design
is fi nalised is the implant fabricated. The computer-controlled fabrication
methods can be made to compensate automatically for manufacturing
characteristics such as shrinkage in the mould. The use of digital media