R_Bibb_Medical_Modelling_The_Application_of_Adv.pdf

Case studies 131
6.14 The effect of fi le size versus quality (low quality left, high quality
right).
6.15 Positioning the contralateral ear.
The surgeon and prosthetists then used 3D software to mirror the copy of
the ear and position it relative to the head in an anatomically and aesthetically
appropriate location (Fig. 6.15).
Cylinders were created to represent the implants. These cylinders were
positioned on the ear in the position preferred by the prosthetists observing
a lateral view (Fig. 6.16). The soft tissue entities were then removed to see
where the implants intersect with the bone as can be seen in the fi gure. The
bone quality at the implant sites was then assessed to check that they would
be suitable for implants. Sectioning the virtual model enabled the quality
and thickness of the bone to be accurately measured (Fig. 6.17). When the
team were satisfi ed with the implant sites, a block was created that overlapped
the implants and the surface of the skull (Fig. 6.18). Then, by using
a Boolean operation, the skull and implant cylinders were subtracted from
the block to create a template design (Fig. 6.18).
This template, shown in Fig. 6.19, was produced directly in a medically
appropriate material by stereolithography (7, 8). See Section 5.2 for a full
description of stereolithography. The fact that at the time this was the only
RP material that had been tested to a standard recognised by the FDA for