to work on. Sheets of softened wax were then added to the plaster to create a more contoured and realistic breast shape. This was then duplicated in wax, and positioned inside the patient’s bra.
Once set, the wax was removed with boiling water. The mould was left to cool and a separator, Isolant (Dentsply, Addlestone, Surrey UK), was applied to both halves with a brush.
The underside of the pattern (the part in contact with the skin) was modified by softening and removing wax to achieve a more natural, slightly concave fit to rest against the chest wall and also to help reflect changes that will occur with bodily movements. The pattern was then sculpted to simulate the contours of the natural breast. The pattern was removed and the wax made smooth. An impression of the patient’s existing nipple areola was taken using a silicone-based material (Exafast injection type, GC Ltd, Newport, Buckinghamshire, UK) and filled with wax to produce a nipple areola. It was then softened to gain a slight curvature for easy positioning onto the wax pattern within the bra.
Fifty grams of maxillofacial silicone M511, shore hardness 25-30, were mixed with 10% M513 softening agent and 10% M514 anti-slump agent (Technovent Ltd, Principality House, Western Valley Road, Rogerstone, Newport, UK) and applied in a very thin layer to both halves of the mould, taking care to eliminate any air bubbles. The application was extended slightly beyond the edges and also thickened to ensure a seal of the two halves. A thicker layer was applied to the areola.
An Alginate (Heraus, Kulzer, GmbH, Gruner Weg 11, 63450, Germany) two-part mould of the wax pattern, backed with impression composition (Kemdent, ADP Ltd, Purton, Swindon, UK) was then made. This was separated and placed in water to prevent shrinkage of the alginate for later use (Figure 1).
Figure 1. Alginate two-part mould.
The wax pattern was invested in a two-part mould, using Crystacal R (British Gypsum) and sprayed with Aurofilm (Bego, Bremen, Germany), to relieve surface tension.
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The pattern was turned over with the nipple areola facing downwards and, using a hot wax knife, the fitting surface was cut away approximately half an inch from the edge. At this point, the wax pattern was carefully held and filled with water which was measured to determine the approximate amount of silicone foam needed for the prosthesis. It held 250ml of water which equates to 250g of silicone foam.7
“The hollow prosthesis weighed 247g, a difference of 428g... reducing the weight by almost two thirds”
The existing prosthesis provided only a very basic outline of a nipple areola with no visible protrusion. Once the wax nipple was in position it highlighted the importance of regaining some symmetrical projection. At the end of the appointment, a skin shade match was recorded. Before investing the pattern, a plaster model was cast to the fitting surface of the wax pattern to provide a base, and to record the fit surface for the foam-filled prosthesis later on. This model was then put aside.
The wax within the mould was left to cool naturally, removed, and the alginate disposed of, leaving the hollow wax pattern. The hole in the top was sealed and the pattern replaced onto the plaster model to check for any distortion (Figure 3b).
Figure 2a. Application of silicone in a two-part mould.
Figure 2b. The addition of gauze for stability.
Two hundred and fifty grams of silicone M4408 (Abacus, 7 Oxford place, Bradford, U.K), with a shore hardness of 8 was mixed with A-302 thixotropic agent (Factor 2, Lakeside, USA), for ease of application. It was then added to the mould directly on top of the M511 in a uniform layer approximately 5-10mm thick, and to the nipple area, filling it completely (Figure 2a). Strips of gauze were placed within the silicone layers on the fitting surface half of the mould to provide stability against the chest wall (Figure 2b). The mould was placed in a clamp and bench-cured for 48 hours, after which time the mould was opened and the prosthesis trimmed and finished. Foam-filled prosthesis The composition-backed alginate mould (Figure 1) was retrieved from the water and the two halves held together with thick elastic bands. Using a scalpel, a large hole was cut in the top between the two alginate halves. Molten wax was poured into the mould and immediately poured back out (Figure 3a). The mould was immersed into very cold water and this process was repeated two more times, each time the layer of wax thickening to produce a shell of approximately 3mm thick. The wax shell will determine the thickness of the silicone layer, which will cover the foam for the finished prosthesis.
THE JOURNAL OF MAXILLOFACIAL PROSTHETICS & TECHNOLOGY
The pattern was then dried off, returned to the model and the nipple areola removed by carefully cutting around the periphery with a scalpel. A funnel was then formed by curving a sheet of wax into the shape of a cylinder to the same diameter as the nipple areola. This was then sealed into the hole to allow any excess foam to escape without the risk of contacting the outside of the wax pattern. A two-part platinum self-skinning foam M3240 (Abacus, 7 Oxford Place, Bradford, U.K) with the expansion rate of five times the overall volume was stirred and poured through the wax sheet funnel. As the foam expanded up through the funnel (Figure 4a), it also filled the inside of the wax pattern against the model creating the fitting surface (Figure 4b). The pattern was held down onto the plaster base for approximately three minutes until expansion was complete. All of the wax surrounding the foam, including the funnel, was taken away and the excess foam removed with a scalpel. A separator was applied to the original Crystacal mould and 250g of M511 maxillofacial silicone was mixed with 10%M513 softening agent; 10% M14 anti-slump was colour matched as before and applied to the concave half of the mould (containing the nipple areola) in an even layer. M4408 silicone was again used in the nipple area. The foam was positioned onto the other half of the mould and coated with silicone extending the material down onto the plaster base. The flask was pressed together and left in a clamp to bench cure overnight. Once cured, the prosthesis was removed
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from the mould, the flash trimmed away and cleaned with an alcoholic wipe. A one-part silicone dispersion sealant ME10 – 6607 (NuSil USA) was then applied using a brush to the exposed foam on the underside of the prosthesis and left to dry for approximately one hour.
Results and discussion Both finished prostheses (Figures 5a and 5b) were weighed. The hollow prosthesis weighed 247g, a difference of 428g when compared to the manufactured prosthesis, reducing the weight by almost two thirds. The foam-filled prosthesis weighed 398g, a difference of 277g. Although more than the hollow prosthesis, it was still significantly less than the stock prosthesis, reducing the weight by over one third. Both the hollow and the foam-filled custom made prostheses were fitted. The hollow prosthesis naturally responds to pressure and once positioned inside the bra became self-supporting. The softness of the prosthesis helped it to mould against the skin on the chest wall, distributing the weight evenly and deflecting it away from
Figure 3a. Pouring the hollow wax pattern.
Figure 3b. Wax template taken from the mould and replaced back on to the plaster model.
Figure 4a. Expansion of the silicone foam within the wax pattern becoming visible as it travels up through the funnel.
Figure 4b. The exposed foam on the underside of the pattern.
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