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A two-section metal mold for an ear prosthesis
A two-section
metal mold
for an ear prosthesis*
Carlos R. Ballast Canario, D.D.S.** University of Puerto Rico, School of Dentistry,
San Juan, P. R.
lhe patient with a malformed or mutilated ear, due to cancer, congenital defect, or trauma, needs to be rehabilitated because of the emotional situation he encounters in society. A prosthodontist with maxillofacial training may be faced with this responsibility. There are different modalities for the proper management of these patients which have been used with results ranging from acceptable to excellent. These are reconstructive surgery, maxillofacial prosthetics, or a combination of b0th.l Reconstructive surgery has the disadvantage of the need for secondary surgical procedures with the obvious postoperative discomfort, and it may hide a recurrence. the construction of ear prostheses poses several In maxillofacial prosthetics, problems because of the anatomic structure and varied sizes and forms of the ear. Factors such as thick ears, pronounced lobules, and prominent conchae may add to the difficulties. An ear prosthesis may be sculptured in wax or plasteline. Another method that may be used is making impressions of sound ears with alginate and pouring melted wax in them.2 Once the sculptured ear is obtained, it is tried on the patient, and if acceptable, molds are made. These molds may be made by using dental stone, metal, or plastic aluminum. The material to make the actual prosthesis may be acrylic resin, vinyl resin, or silicone.3 It is the purpose of this article to describe a method for the construction of a metal mold to produce an ear prosthesis of a flexible material. This technique results in a two-section mold that is easier to construct and to use than others. METHODS Fabrication of the metal mold. The mold is used to confine material in a specific form until it cures or polymerizes. Molds may be made in one piece, but they have to be destroyed to recover the prosthesis. Other molds are made up of two sections. When making an ear prosthesis, one section may be the defect surface and the other surface to be restored. In this method, difficulties are encountered in *Supported in part by grant No. 13P-5569/Z from Social and Rehabilitation **Resident, Maxillofacial Prosthetics.
Services. 343
344
Canario
J. Prosthet. Dent. March, 1974
Fig. 1. A two-section metal mold: A, the two sections; B, removing the prosthesis; C, the recovered prosthesis. removing the prosthesis from the undercut.s. The prosthesis often breaks or is deformed (Fig. 1). More frequently, a mold of three sections is used (Fig. 2). One section is the defect area, another the undercut area, and the third section the external part of the ear, but certain problems are inherent in this method: constructing three separate sections that must match each other; painting separating material on each section separately and then bringing them together; and the occurrence of flash in more than one location. The alternative method. The following are the steps to be followed in producing a two-section mold for an ear prosthesis: 1. Make convenient indices to the model of the defect, and fasten the sculptured ear to it (Fig. 3). 2. Adapt and fix a piece of waxed cardboard around the highest contour of the helix or in that area where the flash, that eventually will be produced, is less conspicuous (Fig. 4). 3. Prepare a partial boxing for the undercut area of the ear, and around it, and pour alginate having a waterpowder ratio of 3 : 1 (Fig. 5) . 4. Remove the cardboard boxing and the partial boxing after the alginate is set. Leave the alginate section in place, and make indices on the top part of it.
s%r:r:; u
Fig. Fig. Fig. Fig. Fig.
Mold
for an ear prosthesis
345
2. A three-section metal mold. 3. A sculptured ear fastened to the cast of the defect. 4. Cardboard is fixed around the highest contour of the helix of the ear. 5. Alginate
poured into the undercut
6. The undercut
alginate
area. Note the partial
boxing.
section is in place with the indices already
made.
BOX around the base and the alginate section to a height of 3 cm. over the highest part of the ear pattern (Fig. 6). 5. Pour alginate, having a waterpowder ratio of 3: 1, into the exposed surfaces to within 1.5 cm. of the top of the boxing. Immerse paper clips bent to an “L” shape into the alginate before it sets (Fig. 7). Pour quick-setting plaster on top of the alginate to the height of the boxing (Fig. 8) : This is done in order to give firmness to the alginate impression. 6. Separate this last impression, box it, and pour grey (refractory) investment material around it (Fig. 9).
346
Canario
J. Prosthet. Dent. March. 1974
Fig. 7. Paper clips partly immersed in the alginate before it hardens. Note the gummed paper boxing. Fig. 8. Plaster is poured on top of the alginate.
Fig. , 9. (A) The impression of the external surface of the pattern for the ear after being boxeId. (B) The cast is in grey refractory investment obtained from the impression. 7. Remove the sculptured ear from the cast of the defect. Great care is needed to avoid pulling the alginate impression out of the undercut part (see step NO. 3) (Fig. 10). Box th ese surfaces, and make an impression of them (Fig. 11) . Alginate and rapid-setting plaster are used (following step No. 5). box it, and make an impression of it 8. Separate the impression obtained, following step No. 5; this is often called “the impression of the impression” (Fig. 12). Pour grey refractory investment in this last impression after boxing it (Fig. 13). 9. Make a wax-up (three thicknesses) of the grey investment material casts with the respective sprues and air vents (Fig. 14). 10. Place the wax-up in custom-made galvanized zinc rings (an approximate size of 10 cm. high and 6 cm. in diameter), and invest it with grey refractory investment material (Fig. 15). Remove the wax with hot water after the investment has set. Place the rings in an oven for 15 hours at a temperature of 225O F. to dry. 11. Melt linotype metal to a temperature of 270’ F., and pour it through the
Volume 31 Number 3
Mold
Fig. 10. A cast of the defect with the undercut after removing the sculptured ear pattern. Fig. 11. The impression section. Fig. 12. The impression
of the unit formed
section
of the impression
by the cast of the defect and the alginate
347
in place undercut
of the impression.
Fig. 13. The cast in grey refractory Fig. 14. Wax-up
alginate
for an ear prosthesis
investment
of the casts in grey investment
Fig. 15. The invested wax-up
in a casting ring.
obtained
from the impression
and sprues.
of the impression.
348
J. Prosthet. Dent. March, 1974
Canarto
Fig. 16. The two-section metal mold: A, the two sections; B, removing the cured prosthesis; C, comparison of the prostheses obtained from different molds. sprues into the refractory mold. These are heated for five minutes to avoid bubbles. Allow the rings to cool. Recover and clean the molds, and reduce the sprues and air vents to convenient lengths. Now the mold is ready to receive the flexible material for making the prosthesis (Fig. 16). SUMMARY Several of the techniques employed in making metal molds for the fabrication of ear prostheses are mentioned. An alternative method for preparing metal molds for making an ear prosthesis of flexible material is presented. This method results in a two-section mold that is easy to construct and use. I wish to express my gratitude to Arturo Santiago, D.M.D., Associate Professor, University of Puerto Rico, School of Dentistry, for his guidance during the preparation of this article. References 1. King, G. E.: Maxillofacial Prosthetic Rehabilitation, J. Oral Surgery. 29: 805-811, 1971. 2. Santiago, A.: Prosthetic Ears: A Case Report, J. Prosthet. Dent. 17: 418-421, 1967. 3. Rahn, A., and Boucher, L. J.: Maxillofacial Prosthetics-Principles and Concepts, ed. 1, Philadelphia, 1970, W. B. Saunders Company. UNIVERSIDAD NACIONAL PEDRO ENR~QUEZ ESCUELA DENTAL SANTO DOMINGO, REPGBLICA D~MINICANA
UREGA
metal mold
for an ear prosthesis*
Carlos R. Ballast Canario, D.D.S.** University of Puerto Rico, School of Dentistry,
San Juan, P. R.
lhe patient with a malformed or mutilated ear, due to cancer, congenital defect, or trauma, needs to be rehabilitated because of the emotional situation he encounters in society. A prosthodontist with maxillofacial training may be faced with this responsibility. There are different modalities for the proper management of these patients which have been used with results ranging from acceptable to excellent. These are reconstructive surgery, maxillofacial prosthetics, or a combination of b0th.l Reconstructive surgery has the disadvantage of the need for secondary surgical procedures with the obvious postoperative discomfort, and it may hide a recurrence. the construction of ear prostheses poses several In maxillofacial prosthetics, problems because of the anatomic structure and varied sizes and forms of the ear. Factors such as thick ears, pronounced lobules, and prominent conchae may add to the difficulties. An ear prosthesis may be sculptured in wax or plasteline. Another method that may be used is making impressions of sound ears with alginate and pouring melted wax in them.2 Once the sculptured ear is obtained, it is tried on the patient, and if acceptable, molds are made. These molds may be made by using dental stone, metal, or plastic aluminum. The material to make the actual prosthesis may be acrylic resin, vinyl resin, or silicone.3 It is the purpose of this article to describe a method for the construction of a metal mold to produce an ear prosthesis of a flexible material. This technique results in a two-section mold that is easier to construct and to use than others. METHODS Fabrication of the metal mold. The mold is used to confine material in a specific form until it cures or polymerizes. Molds may be made in one piece, but they have to be destroyed to recover the prosthesis. Other molds are made up of two sections. When making an ear prosthesis, one section may be the defect surface and the other surface to be restored. In this method, difficulties are encountered in *Supported in part by grant No. 13P-5569/Z from Social and Rehabilitation **Resident, Maxillofacial Prosthetics.
Services. 343
344
Canario
J. Prosthet. Dent. March, 1974
Fig. 1. A two-section metal mold: A, the two sections; B, removing the prosthesis; C, the recovered prosthesis. removing the prosthesis from the undercut.s. The prosthesis often breaks or is deformed (Fig. 1). More frequently, a mold of three sections is used (Fig. 2). One section is the defect area, another the undercut area, and the third section the external part of the ear, but certain problems are inherent in this method: constructing three separate sections that must match each other; painting separating material on each section separately and then bringing them together; and the occurrence of flash in more than one location. The alternative method. The following are the steps to be followed in producing a two-section mold for an ear prosthesis: 1. Make convenient indices to the model of the defect, and fasten the sculptured ear to it (Fig. 3). 2. Adapt and fix a piece of waxed cardboard around the highest contour of the helix or in that area where the flash, that eventually will be produced, is less conspicuous (Fig. 4). 3. Prepare a partial boxing for the undercut area of the ear, and around it, and pour alginate having a waterpowder ratio of 3 : 1 (Fig. 5) . 4. Remove the cardboard boxing and the partial boxing after the alginate is set. Leave the alginate section in place, and make indices on the top part of it.
s%r:r:; u
Fig. Fig. Fig. Fig. Fig.
Mold
for an ear prosthesis
345
2. A three-section metal mold. 3. A sculptured ear fastened to the cast of the defect. 4. Cardboard is fixed around the highest contour of the helix of the ear. 5. Alginate
poured into the undercut
6. The undercut
alginate
area. Note the partial
boxing.
section is in place with the indices already
made.
BOX around the base and the alginate section to a height of 3 cm. over the highest part of the ear pattern (Fig. 6). 5. Pour alginate, having a waterpowder ratio of 3: 1, into the exposed surfaces to within 1.5 cm. of the top of the boxing. Immerse paper clips bent to an “L” shape into the alginate before it sets (Fig. 7). Pour quick-setting plaster on top of the alginate to the height of the boxing (Fig. 8) : This is done in order to give firmness to the alginate impression. 6. Separate this last impression, box it, and pour grey (refractory) investment material around it (Fig. 9).
346
Canario
J. Prosthet. Dent. March. 1974
Fig. 7. Paper clips partly immersed in the alginate before it hardens. Note the gummed paper boxing. Fig. 8. Plaster is poured on top of the alginate.
Fig. , 9. (A) The impression of the external surface of the pattern for the ear after being boxeId. (B) The cast is in grey refractory investment obtained from the impression. 7. Remove the sculptured ear from the cast of the defect. Great care is needed to avoid pulling the alginate impression out of the undercut part (see step NO. 3) (Fig. 10). Box th ese surfaces, and make an impression of them (Fig. 11) . Alginate and rapid-setting plaster are used (following step No. 5). box it, and make an impression of it 8. Separate the impression obtained, following step No. 5; this is often called “the impression of the impression” (Fig. 12). Pour grey refractory investment in this last impression after boxing it (Fig. 13). 9. Make a wax-up (three thicknesses) of the grey investment material casts with the respective sprues and air vents (Fig. 14). 10. Place the wax-up in custom-made galvanized zinc rings (an approximate size of 10 cm. high and 6 cm. in diameter), and invest it with grey refractory investment material (Fig. 15). Remove the wax with hot water after the investment has set. Place the rings in an oven for 15 hours at a temperature of 225O F. to dry. 11. Melt linotype metal to a temperature of 270’ F., and pour it through the
Volume 31 Number 3
Mold
Fig. 10. A cast of the defect with the undercut after removing the sculptured ear pattern. Fig. 11. The impression section. Fig. 12. The impression
of the unit formed
section
of the impression
by the cast of the defect and the alginate
347
in place undercut
of the impression.
Fig. 13. The cast in grey refractory Fig. 14. Wax-up
alginate
for an ear prosthesis
investment
of the casts in grey investment
Fig. 15. The invested wax-up
in a casting ring.
obtained
from the impression
and sprues.
of the impression.
348
J. Prosthet. Dent. March, 1974
Canarto
Fig. 16. The two-section metal mold: A, the two sections; B, removing the cured prosthesis; C, comparison of the prostheses obtained from different molds. sprues into the refractory mold. These are heated for five minutes to avoid bubbles. Allow the rings to cool. Recover and clean the molds, and reduce the sprues and air vents to convenient lengths. Now the mold is ready to receive the flexible material for making the prosthesis (Fig. 16). SUMMARY Several of the techniques employed in making metal molds for the fabrication of ear prostheses are mentioned. An alternative method for preparing metal molds for making an ear prosthesis of flexible material is presented. This method results in a two-section mold that is easy to construct and use. I wish to express my gratitude to Arturo Santiago, D.M.D., Associate Professor, University of Puerto Rico, School of Dentistry, for his guidance during the preparation of this article. References 1. King, G. E.: Maxillofacial Prosthetic Rehabilitation, J. Oral Surgery. 29: 805-811, 1971. 2. Santiago, A.: Prosthetic Ears: A Case Report, J. Prosthet. Dent. 17: 418-421, 1967. 3. Rahn, A., and Boucher, L. J.: Maxillofacial Prosthetics-Principles and Concepts, ed. 1, Philadelphia, 1970, W. B. Saunders Company. UNIVERSIDAD NACIONAL PEDRO ENR~QUEZ ESCUELA DENTAL SANTO DOMINGO, REPGBLICA D~MINICANA
UREGA