Direct wax method for fabrication metal molds
of three-piece
K. Oral, D.D.S., M.S.D., Ph.D.,* and I. Zini** Eye and Ear Hospital of Pittsburgh and University of Pittsburgh, Pittsburgh, Pa.
M
eta1 molds can be used with all currently available facial materials except hard acrylic in the construction of facial prostheses. The construction of metal molds for the fabrication of an artificial ear is complicated by the presence of severe undercuts between the external ear and the region of the temporal bone. A step-by-step procedure has been described previously.’ However, such techniques entail repeated steps and consume a great deal of time. In a previous article* the direct wax method for fabrication of two-piece molds was described, a technique which proved to be valuable in the fabrication of an artificial nose or other simple anatomic sites. This article describes a three-piece mold technique for the construction of artificial ears.
IMPRESSION PROCEDURES Presurgical impressions are made of the affected ear. If the ear is not distorted by the lesion the preoperative cast is used as a guide in sculpting the replacement ear. However, if the lesion has destroyed the anatomic configuration the cast is used only as a record. After surgery the final impression is made from the defect side.
Fig.
1.
The clay carving is finished on the master 1zast.
TECHNICAL PROCEDURE Qrientation marks are placed on the face. The proper impression material is chosen and an impression is made with orientation markings transferred into the impression. The impression is poured into artificial stone, and the cast is cleaned and trimmed.
This study was supported in part by National Cancer Institute Contract NIH-NCI-55184-05. *Ass&t Professor of Prosthodontics, School of Dental Medicine. **Artist, Regional Center for Maxillofacial Prosthetic Rehabilitation, Eye and Ear Hospital of Pittsburgh.
558
NOVEMBER
1978
VOLUME
40
NUMBER
5
Fig. 2. The wax pattern an the posterior region wit :h the clay guide.
0X2-3913/78/110558
+ 05900.50f06
1978 The C. V. Mwby
Co.
DIRECT
WAX METHOD
FOR METAL
MOLDS
Fig. 3. The wax pattern of the external surface of the sculpt. Fig. 4. The tissue surface of the clay carving is imbedded in the mold.
Fig. 5. Wax is applied to form the tissue surface of the mold, and the three-piece wax molds are completed. Fig. 6. The wax molds are separated. Tinfoil is applied to the defect, and clay keys are added to the border around the pattern. The clay pattern is sculpted to restore the missing anatomic structures (Fig. 1). Lubricant is applied to the clay pattern and the stone cast surrounding it. Extra-hard wax is melted; using a large, soft-bristled brush, the wax is applied to the internal surface of the clay pattern with sufficient bulk to provide clean, squared finishing lines around the margins of the
THE JOURNAL
Of PROSTHETIC
DENTISTRY
pattern. A groove is made on the superior part of the wax pattern. One or two vent sprues and one casting sprue are added; the casting sprue should be placed at the lowest point of the pattern. The use of the sprues allows the metal to fill up gradually from the deepest portion of the mold to the superior surface. A clay guide is made around the wax pattern short of the height of the wax (Fig. 2). A separator is applied to the external surface of the wax pattern.
559
ORAL AND ZINI
Fig. 7. The wax molds are separated. Fig. 8. The wax patterns are painted with investment material.
Fig. 9. Investing rings. Fig. 10. Completed metal mold. Care should be exercised when waxing up this part. To avoid melting the first section the wax should not
The
be overheated (Fig. 3). One or two vent sprues and one casting sprue are added. Once the exposed part of the clay pattern is encased in the wax mold patterns, the wax patterns with the clay prosthesis are removed (Fig. 4). Petroleum jelly is applied as a separator over the wax pattern and the exposed area of the clay pattern to facilitate separation of the wax sections after cooling.
are carefully separated and the clay pattern is removed (Figs. 6 and 7). The wax pattern is cleaned and invested by painting the pattern with a layer of investment %-inch thick. Once the initial set has taken place, the investing procedure is completed by submerging the patterns gradually in casting rings after filling them with investment (Fig. 8). After the investment has set, the
560
waxing
technique
previously
mentioned
is
repeated (Fig. 5). The wax mold patterns
NOVEMBER
1478
VOLUME
40
NUMBER
s
DIRECT
WAX METHOD
FOR METAL
MOLDS
Fig. II. Completed metal mold. Fig. 12. The finished prosthesis is on the mold
Fig. 13. The defect side. Fig. 14. Ear prosthesis after placement. wax is eliminated by immersing the flasks in boiling water. The molds are flushed by pouring hot water through the sprue holes. The casting rings are placed in an oven* at 250°F overnight for drying. After the investment has dried completely the rings are removed from the oven. Linotype metal is melted and poured through the sprue holes. The rings are bench-cooled (Fig. 9) before the mold pieces from the investment are removed (Figs. 10 and 11). Metal molds are used to fabricate ear prostheses in any available flexible facial material. The fitting of ‘Isotemp
Oven,
Model
177, Fisher
THE JOURNAL OF PROSTHETIC
Scientific,
DENTLSTRY
Pittsburgh,
Pa.
the three sections utilizing the described technique is excellent and reduces the possibility of creating a flash at the rim of the helix (Figs. 12 to 14). DISCUSSION
AND SUMMARY
A method has been described for the construction of a three-piece metal mold for facial prosthesis. The need for the hydrocolloid impression and a positive impression of the hydrocolloid negative impression is eliminated. The disadvantages of other methods are that they are more time consuming, investing takes longer, and the impression may be distorted, causing inaccuracies in the final metal mold. Three-piece metal
561
ORAL AND ZINt
maids save time and make better fitting molds. The resultant prosthesis has more accurate margins and will fit patient’s facial structures precisely.
2.
Zini, I., Krill, R., and Aramany, M. A.: Direct wax method for fabrication of metallic facial molds. J PROSTHET DENT 33:85, 1975,
Reprint wquests to: DR. KORAY ORAL
REFERENCES 1. Chalian, V.: Maxillofacial Prosthesis. Houston, 1960, The University of Texas, Dental Branch, M. D. Anderson Hospital and Tumor Institute.
EYE AND EAR HOSPITAL 230 LOTHROP ST. PITIXBURGH, PA. 15213
OF PITTSXJRGH
ARTICLES TO APPEAR IN FUTURE ISSUES
Edmund0 B. Nery, D.M.D.,
Kenneth L. Lynch, Ph.D., and George E. Rooney, D.D.S.
Construction of a bwcal fkuqp obturator Koray Orai, D.D.S., M.S.D., Ph.D.
A comlaanation obturator Gregory R. Parr, D.D.S.
S. J. Piliero, Ph.D., S. Carson, Ph.D., M. LiCalai, D.D.S., L. Pentel, D.D.S., J. A. Piliero, A. B., E. G. Kaufman, D.D.S., A. Schulman, D.D.S., MS., and D. A. Willigan, D.V.M., Ph.D.
562
NOVEMBER
1978
VOLUME
40
NUMBER
S
of three-piece
K. Oral, D.D.S., M.S.D., Ph.D.,* and I. Zini** Eye and Ear Hospital of Pittsburgh and University of Pittsburgh, Pittsburgh, Pa.
M
eta1 molds can be used with all currently available facial materials except hard acrylic in the construction of facial prostheses. The construction of metal molds for the fabrication of an artificial ear is complicated by the presence of severe undercuts between the external ear and the region of the temporal bone. A step-by-step procedure has been described previously.’ However, such techniques entail repeated steps and consume a great deal of time. In a previous article* the direct wax method for fabrication of two-piece molds was described, a technique which proved to be valuable in the fabrication of an artificial nose or other simple anatomic sites. This article describes a three-piece mold technique for the construction of artificial ears.
IMPRESSION PROCEDURES Presurgical impressions are made of the affected ear. If the ear is not distorted by the lesion the preoperative cast is used as a guide in sculpting the replacement ear. However, if the lesion has destroyed the anatomic configuration the cast is used only as a record. After surgery the final impression is made from the defect side.
Fig.
1.
The clay carving is finished on the master 1zast.
TECHNICAL PROCEDURE Qrientation marks are placed on the face. The proper impression material is chosen and an impression is made with orientation markings transferred into the impression. The impression is poured into artificial stone, and the cast is cleaned and trimmed.
This study was supported in part by National Cancer Institute Contract NIH-NCI-55184-05. *Ass&t Professor of Prosthodontics, School of Dental Medicine. **Artist, Regional Center for Maxillofacial Prosthetic Rehabilitation, Eye and Ear Hospital of Pittsburgh.
558
NOVEMBER
1978
VOLUME
40
NUMBER
5
Fig. 2. The wax pattern an the posterior region wit :h the clay guide.
0X2-3913/78/110558
+ 05900.50f06
1978 The C. V. Mwby
Co.
DIRECT
WAX METHOD
FOR METAL
MOLDS
Fig. 3. The wax pattern of the external surface of the sculpt. Fig. 4. The tissue surface of the clay carving is imbedded in the mold.
Fig. 5. Wax is applied to form the tissue surface of the mold, and the three-piece wax molds are completed. Fig. 6. The wax molds are separated. Tinfoil is applied to the defect, and clay keys are added to the border around the pattern. The clay pattern is sculpted to restore the missing anatomic structures (Fig. 1). Lubricant is applied to the clay pattern and the stone cast surrounding it. Extra-hard wax is melted; using a large, soft-bristled brush, the wax is applied to the internal surface of the clay pattern with sufficient bulk to provide clean, squared finishing lines around the margins of the
THE JOURNAL
Of PROSTHETIC
DENTISTRY
pattern. A groove is made on the superior part of the wax pattern. One or two vent sprues and one casting sprue are added; the casting sprue should be placed at the lowest point of the pattern. The use of the sprues allows the metal to fill up gradually from the deepest portion of the mold to the superior surface. A clay guide is made around the wax pattern short of the height of the wax (Fig. 2). A separator is applied to the external surface of the wax pattern.
559
ORAL AND ZINI
Fig. 7. The wax molds are separated. Fig. 8. The wax patterns are painted with investment material.
Fig. 9. Investing rings. Fig. 10. Completed metal mold. Care should be exercised when waxing up this part. To avoid melting the first section the wax should not
The
be overheated (Fig. 3). One or two vent sprues and one casting sprue are added. Once the exposed part of the clay pattern is encased in the wax mold patterns, the wax patterns with the clay prosthesis are removed (Fig. 4). Petroleum jelly is applied as a separator over the wax pattern and the exposed area of the clay pattern to facilitate separation of the wax sections after cooling.
are carefully separated and the clay pattern is removed (Figs. 6 and 7). The wax pattern is cleaned and invested by painting the pattern with a layer of investment %-inch thick. Once the initial set has taken place, the investing procedure is completed by submerging the patterns gradually in casting rings after filling them with investment (Fig. 8). After the investment has set, the
560
waxing
technique
previously
mentioned
is
repeated (Fig. 5). The wax mold patterns
NOVEMBER
1478
VOLUME
40
NUMBER
s
DIRECT
WAX METHOD
FOR METAL
MOLDS
Fig. II. Completed metal mold. Fig. 12. The finished prosthesis is on the mold
Fig. 13. The defect side. Fig. 14. Ear prosthesis after placement. wax is eliminated by immersing the flasks in boiling water. The molds are flushed by pouring hot water through the sprue holes. The casting rings are placed in an oven* at 250°F overnight for drying. After the investment has dried completely the rings are removed from the oven. Linotype metal is melted and poured through the sprue holes. The rings are bench-cooled (Fig. 9) before the mold pieces from the investment are removed (Figs. 10 and 11). Metal molds are used to fabricate ear prostheses in any available flexible facial material. The fitting of ‘Isotemp
Oven,
Model
177, Fisher
THE JOURNAL OF PROSTHETIC
Scientific,
DENTLSTRY
Pittsburgh,
Pa.
the three sections utilizing the described technique is excellent and reduces the possibility of creating a flash at the rim of the helix (Figs. 12 to 14). DISCUSSION
AND SUMMARY
A method has been described for the construction of a three-piece metal mold for facial prosthesis. The need for the hydrocolloid impression and a positive impression of the hydrocolloid negative impression is eliminated. The disadvantages of other methods are that they are more time consuming, investing takes longer, and the impression may be distorted, causing inaccuracies in the final metal mold. Three-piece metal
561
ORAL AND ZINt
maids save time and make better fitting molds. The resultant prosthesis has more accurate margins and will fit patient’s facial structures precisely.
2.
Zini, I., Krill, R., and Aramany, M. A.: Direct wax method for fabrication of metallic facial molds. J PROSTHET DENT 33:85, 1975,
Reprint wquests to: DR. KORAY ORAL
REFERENCES 1. Chalian, V.: Maxillofacial Prosthesis. Houston, 1960, The University of Texas, Dental Branch, M. D. Anderson Hospital and Tumor Institute.
EYE AND EAR HOSPITAL 230 LOTHROP ST. PITIXBURGH, PA. 15213
OF PITTSXJRGH
ARTICLES TO APPEAR IN FUTURE ISSUES
Edmund0 B. Nery, D.M.D.,
Kenneth L. Lynch, Ph.D., and George E. Rooney, D.D.S.
Construction of a bwcal fkuqp obturator Koray Orai, D.D.S., M.S.D., Ph.D.
A comlaanation obturator Gregory R. Parr, D.D.S.
S. J. Piliero, Ph.D., S. Carson, Ph.D., M. LiCalai, D.D.S., L. Pentel, D.D.S., J. A. Piliero, A. B., E. G. Kaufman, D.D.S., A. Schulman, D.D.S., MS., and D. A. Willigan, D.V.M., Ph.D.
562
NOVEMBER
1978
VOLUME
40
NUMBER
S
