INTRODUCTION

 

Since the first documented case of
auricular prosthesis by Ambroise Pare (1510-1590), a famous French surgeon1,
the fabrication process has come a long way successfully rehabilitating
patients with missing external auricle1. The anatomic morphology of the
prosthesis, matching the morphology of the contralateral ear, is currently
obtained by different methods: (i) producing a cast of the patient’s
contralateral ear by direct
impression, and sculpting a mirror pattern corresponding to the missing ear;
(ii) producing a cast using the ear of a family member or an individual with
compatible ear morphology, and using it for producing the ear prosthesis; (iii)
producing a cast of the

patient’s contralateral normal ear, and
creating its photo image on a transparent

sheet (viewing the image from the
reverse side gives the morphology of the ear prosthesis

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to be sculpted)2; or (iv) making a wax cast of the
contralateral normal ear of the patient, sectioning the cast into 1-mm slices,
and reversing the sections to create a mirrored pattern3. The final outcome in
terms of quality is highly subjective depending on the skills of
anaplastologist, prosthodontist or laboratory technicians involved. The
conventional methods of fabrication of auricular prosthesis requires
experience, takes considerable time and is error-prone4. Consistent good
quality prosthesis may be achieved using advanced technologies including
optical scanning, computeraided design (CAD) and 3D printing which are more
objective in nature.

 

CASE REPORT

 

22 years old male reported to the
Department of Dental Surgery and Oral Health Sciences with the chief complaint
of missing left external auricle. Patient gave a history of a road traffic
accident one and half years ago in which he reportedly lost his external ear.

 

On examination the left external
auricle was found missing with the tragus intact. Superficial skin around the
missing auricle shows diffuse scarring involving temple region, pre auricular
region upto the mandibular angle region. Hairline was also noted to be shifted
upwards due to the scar. The external auditory meatus was present and the
patient had normal hearing abilities.

An adhesive retained silicone
auricular prosthesis was planned to be undertaken to rehabilitate the patient.
An optical impression of the face was made using Artec 3D scanner and
subsequent 3D reconstruction done using proprietary software. Using the optical
scan data the right normal auricle was copied and a mirror image was produced
in a CAD software. The resultant Image was superimposed in place of the missing
left auricle  and blended to match the
local anatomy. Newly developed left auricle was extracted in .stl format to be
3D printed using an Fused Deposition Modelling machine and subsequently a
prototype model of the intended left auricle was obtained in ABS resin.

The model was duplicated in PVS
impression material and wax was poured into it to obtain a wax pattern of the
missing auricle. The wax pattern was tried on the patient for its location,
orientation and projection and invested to fabricate a three piece mould. HTV
silicone was packed after proper base shade matching and intrinsic staining.
After curing the prosthesis as retrieved and characterised by extrinsic
pigments to exactly match the shade of the patients opposing ear. Finally the
prosthesis was retained with the help of 
a medical grade adhesive and necessary post insertion instructions were
prescribed to the patient.

 

DISCUSSION

 

3D printing or rapid protonyping
techniques have been employed effectively for fabrication

of facial prosthesis over the past
decade5. It is a process in which the final desired part is manufactured by
incremental addition
of multiple layers of material on top of each other6. The key idea of this
innovative method is that the three dimensional CAD (3D-CAD) model is sliced
into many thin layers and the manufacturing equipment uses this geometric data
to build each layer sequentially until the part is completed. This technology
can yield arbitrarily complex shapes with cavities and undercuts; frequently
the case in human anatomy structures7.

 

Impression making with any impression
material will introduce some kind of distortion of the normal auricular anatomy
no matter how mucostatic the impression material may be. This is not the case
with an optical scanner which makes no physical contact with the tissues while
exactly recording its anatomy. CAD software exactly replicates the anatomy of
patients normal ear by creating an mirror image pattern of the same using the
scan data3.

The involvement of technology has made
the process of fabrication more scientific, individualistic and time saving.
More over the 3D printed mould and the CAD data can be used subsequently to
fabricate a new prosthesis in the event of loss or physical damage of the
fabricated prosthesis hence inducing cost effectiveness too in the long run.

 

CONCLUSION

With the advancement in CAD and 3D
printing technologies, it is possible to benefit from this in different dental
practices, particularly in the field of maxillofacial prosthetics which
encompasses highly variable and complex anatomical sturctures. However the
limitations of the RP technology include the high cost of the tools,
complicated machinery engaged and dependency on an expertise to run the machinery
during production.

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