Authors : Prof.(Dr.) Krishna Prasad D ., Prof.(Dr.) Manoj Shetty
Man's need for artificial replacements to supply missing or lost body parts has probably existed as long as man himself. Auricular defects can be a consequence of trauma, malignant diseases ,congenital deformities¹ . Facial defects can cause not only functional problems but also some serious psychological problems that could cause the individual to avoid social contact. Modern plastic surgery techniques  can help to restore some lost tissues but in cases of radical surgery they cannot replace the lost tissue in a way which creates an acceptable illusion of normal appearance . The age and general medical condition  of the patient may also contraindicate major reconstructive surgery. Thus, a prosthetic rehabilitation should be followed for such patients to help fill this void.

Common problems with auricular prosthesis are retention and colour matching.

OBJECTIVES OF  MAXILLOFACIAL REHABILITATION:²

Primary objectives  being maintainence of form ,function and preservation of hard and soft tissues leading to secondary objectives of restoring individual to society and therapeutic or healing effect.

General cosmetic Principles of auricular prosthesis are

Skin grafting , smooth edges, pigmentation , Retention of tragus to camouflage anterior border.

Impression Procedure

1. The patient is prepared; should be positioned on their side to allow full access to the area. Defect area is to be isolated with drapes ,cotton  placed in the ear canal.
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2. Marks should be made with an indelible pencil in the defect area, so as to allow correct alignment of the prosthesis with the natural ear.The areas to be marked are :

1. 1. The junction of the helix with the side of the head.
   2. The junction of the lobe with the side of the head. (figures 1&2)

3. Adjacent hair is  applied with petroleum jelly ³.
4. Irreversible hydrocolloid is mixed with 50% more water than recommended by the manufacturer to improve the flow. Disposable syringes are useful for depositing  impression material to inaccessible areas.⁴

Figure 1 : marks made for allignment of the prosthesis with the natural ear

Figure 2 : marks made for allignment of the prosthesis with the natural ear

PROPER PLACEMENT OF THE AURICLE IS ACHIEVED BY

1. Axis
2. Level
3. Distance from orbit

Figure 3 : Axis & level of the prosthesis

AXIS

It is difficult to define exactly the positioning of the axis, but it can be described as the “Line of Balance” through the long dimension of the ear.
An angulation of 20 degree from vertical position seems to be satisfactory . (figure 3)

LEVEL

1. Assessed with the head in the anatomic vertical position.
2. The highest part of the helix is on a line roughly with that of the eyebrow,
3. The lowest part of the lobule is on a line at the base of columella or slightly below that . (figure 3)

DISTANCE FROM THE ORBIT

The ideal distance of the prosthesis from the lateral orbital rim is about one ear length, or 6.5 to 7.5 cm. (figure 4). The superior aspect of the tragus is most commonly located 10 mm posterior to the temporomandibular joint⁵.  Draw vertical lines perpendicular to the temple bar lines in the same anteroposterior position on the arms of the eyeglasses, preferably 1 cm anterior to the tragus.

Figure 4: Ideal distance of the prosthesis from the lateral orbital rim is about one ear length

Conformers

Various conformers can be used to define and make the impression. Customized trays can also be made using impression compound which conforms to the ear/rudimentary ear but should not impinge on it. Minimal distortion of the impression and cast accuracy are important criteria for achieving a successful prosthesis . Position the patient’s head with the auricular area as horizontal as possible.

Wax Patterns

Wax Patterns can be made by Sculpting technique or Donor technique . Better results are obtained with Sculpting technique  if the ear is carved from  a mirror image of the patients natural ear, where patient’s normal side cast and ear is used as reference for sculpting . First wax adaptation is started with forming base , then scaphoid  area is carved followed  by  wax adaptation in helical area. Donor technique on the other hand is an easier method where in a person with ear contours that closely mimic those of the patient is selected. An impression is obtained of the appropriate ear of the donor  and a  wax cast is retrieved. The wax ear is adapted and recontoured as necessary. Nusinov  in 1980⁸ suggested making reverse image of ear by using parallel lines transferred to casts , A vertical camera capable of reproducing three dimensional objects and tracing paper.. James . C. lemon in 1996⁹ used rapid prototyping technique for the same . Leonardo Ciocca in 2004¹° gave a  technique to create a cast by laser scanning of a stone cast of the existing ear which develops an integrated 3D digital image of the unaffected ear.

The entire surface is stippled to match the skin textures of the patient. The stipple is made a little more prominent, since some details is lost during processing. The prosthesis must match the color and form of normal ear and also the texture of the opposite ear and adjacent skin.

Try-in¹¹

Waxed prosthesis is placed on the patient’s ear during the try – in appointment where patient is evaluated for the fit of the prosthesis on the tissue, correct horizontal alignment with the natural ear, Projection of the ear in relation to the side of the head, integrity of the margins during simple jaw movements.

Investing

The wax prosthesis is sealed to the model and the leading edge is thinned as much as possible so as to allow the silicone edges to feather into the natural skin. A three part mould is necessary to achieve easy placement of silicone⁸ and processing done after intrinsic colour matching . Swatch technique is followed with making different swatches for different areas.  Color match is done under natural day light under proper illumination. Three piece mold is then packed with different swatches . Intrinsic coloration is color applied within the mold during the casting procedure. This allows one to simulate the laminar structure of skin. Depth of color and translucency can be more accurately achieved through intrinsic techniques. A realistic three dimensional quality is accomplished by incorporating subsurface details such as blood vessels, freckles, and moles that enhance the overall esthetic result.

After 24 hours prosthesis is retrieved from the mould and tried in the patient. To get a proper color match extrinsic staining is done. Laminar glazes are layers of color painted individually into the mold before packing the base color. The application of laminar glazes is an attempt to mimic the histologic structure of human skin.

Retention

Retention is obtained from various means such as Adhesives¹² , Implants ,Spring steel bands , Double sided adhesive tape , Magnets¹³. Adhesives have shortcomings like lack of firm functional retention under flexion/extension during speech, facial expressions, Partial lack of contact due to perspiration , potential for tissue irritation. On the other hand implants have advantages over adhesives in the form of retention and stability, elimination of skin reactions, ease and enhanced accuracy of prosthesis placement, improved skin hygiene and patient comfort, decreased daily maintenance , increased longevity of prosthesis, enhanced esthetics at the lines of junction between the prosthesis and skin¹⁴.

Case Report 1

Female Patient aged 17 yrs with loss partial loss of right ear due to burn injury who reported to the department of  prosthodontics was successfully rehabilitated with RTV silicone (Cosmesil,Principality medical Ltd, U.K) (figure 5)

Figure 5: Auricular prosthesis for burn injury case	Figure 6 & 7: Special tray impresion and  final silicone prosthesis

Case Report 2

A female patient aged 16 years who reported for replacement of old implant retained prosthesis was rehabilitated efficiently by replacing the old rider clips , acrylic substructure and silicone prosthesis. In this case definitive impression was made using custom made acrylic trays and elastomeric impression material at open mouth position to maintain marginal integrity during function. (figure 6 & 7)

Discussion

Auricle is mainly made of fibro cartilage lined by skin except few parts like lobule, which consists of skin covering the connective tissue . An alternative to surgical reconstruction is the creation of a silicone auricular prosthesis. These prostheses provide a cost-effective and cosmetically acceptable means of camouflage for patients who decline or postpone surgical reconstruction. Most of the times auricular prosthesis is mechanically retained due to economical  reasons. However the use of osseointegrated implants in conjunction with magnets , retentive clips and bars have led to less compromise in retention and contours and maintenance of the prosthesis. The ideally constructed prosthesis must duplicate the missing facial features so precisely that the casual observer notices nothing that would draw attention to the prosthetic reconstruction. Though it is a challenge, if certain minimal guidelines are followed it would be of great help to the practitioners to provide a natural simulation of the opposing ear.

Summary and conclusion

Patient acceptance factors such as flexibility, translucency, esthetics, compatibility, durability  and prosthetic considerations like availability of materials, ease of processing, ease of duplication lead to success of treatment making the  prosthesis look  life like and  giving the patient social confidence.

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