coping for an esthetic
veneer
crown
G. Roger Troendle, DDS, MS,a and Karen B. Troendle, DDSb The University of Texas Health Science Center at San Antonio, San Antonio, Tex. Esthetic veneer crowns should be waxed is cut back. This procedure ensures that proper contours. A technique is described thickness of 0.3 to 0.5 mm, that is stable, PROSTHET DENT 1992;68:649-52.)
to full contour before the veneer surface patterns and metal copings will have the for making a coping that has an ideal and that is unlikely to fracture. (J
he importance of waxing an esthetic veneer crown to full contour was emphasized by Shillinburg et a1.l and by Rosentiel et a1.2Veneering surfaces are subsequently cut back to a thickness of 0.3 to 0.5 mm. The closer the veneering surface of the pattern is to 0.3 mm, the less time is spent on finishing the metal when the framework is cast. Some of the difficulties encountered in cutting back a wax pattern include (1) creating a correct and uniform thickness for the veneering surface; (2) avoiding cracking of the fragile wax pattern; and (3) creating a smooth internal adaptation to the preparation, especially in the veneering area. The advantages of using the matrix material for the coping are: (1)
the pattern is not as likely to crack when it is cut back; (2) a uniform thickness is ensured; (3) less metal finishing is required; and (4) the internal surface of the coping is smooth and closely adapted. This article describes a procedure for forming a coping maker that creates stable copings of an ideal thickness to
YXnical Associate Professor, Department of Restorative Dentistry. bAssociate Professor, Department of Restorative Dentistry. 10/l/38842
2. Hole cut in lid of jar leaving 2 mm rim around inner circumference of jar lid.
Fig.
1. Materials needed to form the coping maker. a, Plastic eggshell that holds Silly Putty material; b, the Fig.
putty; c, sheet of thermoplastic
temporary
THE JOURNAL
OF PROSTHETIC
splint material; Fig.
d, small jar with plastic lid.
DENTISTRY
3. Silly Putty material
is formed to concave shape.
549
TROENDLE
Fig. 4. Matrix inside lid.
material
AND
TROENDLE
cut to rest on rim of jar and to fit
Fig. 6. Lubricated die with margins marked, ready to insert into heated matrix material.
Fig. 5. Completed matrix maker ready for use.
help eliminate with cutback.
many of the problems commonly associated
PROCEDURE Materials (Fig. 1)
Fig. 7. Heating matrix material with a Hanau torch.
1, Small 3 oz jar with a plastic lid 2. An “egg” of Silly Putty (Binney and Smith, Inc., Easton, Pa.) 3. One 5 x 5 inch sheet of 0.020-inch temporary splint material
Forming
the matrix
maker
1. Use a bur made for cutting acrylic resin and cut a 2.5 cm circular hole in the center of the plastic jar lid, leaving a rim of approximately 2 mm around the inside circumference of the lid (Fig. 2). 2. Place the Silly Putty in the jar and create a slight concavity in the putty in the center of the jar (Fig. 3).
550
3. Cut a 2.7 mm diameter rary splint material. Its rim of the 3 oz jar (Fig. 4. Place a small amount thumb and index finger circular piece of splint 5. Screw the lid on the jar terial in place (Fig. 5).
Making
circle from the piece of tempocircumference must rest on the 4) and it must fit inside the lid. of die lubricant between the and lubricate both sides of the material. to hold the piece of matrix ma-
the matrix
1. Pour, trim, and space the dies. Place a small amount of die lubricant between the thumb and index finger and
SEPTEMBER
1992
VOLUME
68
NUMBER
3
PLASTIC
COPING
FOR
VENEER
CROWN
Fig. 8. Die pushed into heated matrix enough to slightly cover margins of die.
material
deep
Fig. 10. Folded excess matrix material ing matrix from die.
Fig. 9. Slitting the excess matrix material to make it easier to remove from die.
facilitates
ren
below margin
lubricate the die. Mark the margin on the die with a red pencil (Fig. 6). 2. While the dies are still out of the master cast, heat the matrix material through the hole in the lid of the jar with a Hanau torch (Teledyne Hanau, Buffalo, N.Y.) until it becomes clear and slumps onto the putty (Fig. 3. Slowly plunge a die into the hot matrix material. The putty and matrix material should cover the margin of the die (Fig. 8). 4. Allow the matrix material to cool for a few minutes, then unscrew the lid and remove the matrix on the die from the putty. 5. Cut approximately eight slits into the excess matrix material below the margin of the die with a pair of small scissors (Fig. 9). 6. Bold the die by the base, turn the slits up to the
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 11. Well-fitting, stable matrix trimmed 0.2 mm of die margins.
within 1.5 to
occlusal surface, and pull the matrix off the 10). 7. With the scissors, remove the excess material 1.5 to 0.2 mm of the margin. Examine the fit bility of the matrix on the die (Fig. 11). If it fit well, remake the matrix.
die 1(Fig. to wi ithin and stadoesi not
551
TROENDLE
12. Thickness gauge used to measure facial thickness of matrix.
Fig.
AND
TROENDLE
14. Facial surface of full contour premolar wax-up cut back to expose plastic coping.
Fig.
DISCUSSION
Pig. 13. Coping covered with wax carved to full contour.
Copings that are too thin can be remade or they can be used if wax is allowed to remain in the matrix after the full contour pattern has been cut back. The latter remedy is not advised because it defeats the purpose for which the material is used. There are a number of precautions to ensure that the matrix material does not thin out too much. First, be certain when heating the matrix material to heat it from the periphery and not to overheat the matrix material where the die will be placed. Second, slowly push the die into the matrix material so that the matrix material has time to cool. Finally, the die can be placed in a freezer for 5 minutes before it is placed in the heated matrix material. AI1 three of these methods may be altered to control the thickness of the coping. REFERENCES
8. Measure the facial surface of the coping with a thickness gauge (Miltex gauge, Lake Success, N.Y.) (Fig. 12). If it is not between 0.3 and 0.5 mm thick, see Discussion section for ways to correct it. 9. Wipe the die lubricant off the coping with an alcohol wipe so that the wax will stick to the coping. Apply wax over the coping and carve it to full contour (Fig. 13). 10. Cut back the facial veneer to .the elastic coping to ensure an adequate and uniform thickness of the casting without overbulking (Fig. 14).
552
1. Shillinburg HT, Hobo S, Whisett LD. Fundamentals of fixed prosthodontics. 2nd. ed. Chicago: Quintessence Publishing Co, Inc, 1981:Chapter 19. 2. Rosentiel SF, Land MF, Fugimoto J. Contemporary fixed prosthodontics. St. Louis: CV Mosby, 1988:Chapter 16.
Reprintrequeststo: DR. G. ROGER TROENDLE UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER DENTAL SCHOOL 7703 FLOVD CURL DRIVE SAN ANTONIO, TX 78284
SEPTEMBER
1992
VOLUME
66
NUMBER
3
veneer
crown
G. Roger Troendle, DDS, MS,a and Karen B. Troendle, DDSb The University of Texas Health Science Center at San Antonio, San Antonio, Tex. Esthetic veneer crowns should be waxed is cut back. This procedure ensures that proper contours. A technique is described thickness of 0.3 to 0.5 mm, that is stable, PROSTHET DENT 1992;68:649-52.)
to full contour before the veneer surface patterns and metal copings will have the for making a coping that has an ideal and that is unlikely to fracture. (J
he importance of waxing an esthetic veneer crown to full contour was emphasized by Shillinburg et a1.l and by Rosentiel et a1.2Veneering surfaces are subsequently cut back to a thickness of 0.3 to 0.5 mm. The closer the veneering surface of the pattern is to 0.3 mm, the less time is spent on finishing the metal when the framework is cast. Some of the difficulties encountered in cutting back a wax pattern include (1) creating a correct and uniform thickness for the veneering surface; (2) avoiding cracking of the fragile wax pattern; and (3) creating a smooth internal adaptation to the preparation, especially in the veneering area. The advantages of using the matrix material for the coping are: (1)
the pattern is not as likely to crack when it is cut back; (2) a uniform thickness is ensured; (3) less metal finishing is required; and (4) the internal surface of the coping is smooth and closely adapted. This article describes a procedure for forming a coping maker that creates stable copings of an ideal thickness to
YXnical Associate Professor, Department of Restorative Dentistry. bAssociate Professor, Department of Restorative Dentistry. 10/l/38842
2. Hole cut in lid of jar leaving 2 mm rim around inner circumference of jar lid.
Fig.
1. Materials needed to form the coping maker. a, Plastic eggshell that holds Silly Putty material; b, the Fig.
putty; c, sheet of thermoplastic
temporary
THE JOURNAL
OF PROSTHETIC
splint material; Fig.
d, small jar with plastic lid.
DENTISTRY
3. Silly Putty material
is formed to concave shape.
549
TROENDLE
Fig. 4. Matrix inside lid.
material
AND
TROENDLE
cut to rest on rim of jar and to fit
Fig. 6. Lubricated die with margins marked, ready to insert into heated matrix material.
Fig. 5. Completed matrix maker ready for use.
help eliminate with cutback.
many of the problems commonly associated
PROCEDURE Materials (Fig. 1)
Fig. 7. Heating matrix material with a Hanau torch.
1, Small 3 oz jar with a plastic lid 2. An “egg” of Silly Putty (Binney and Smith, Inc., Easton, Pa.) 3. One 5 x 5 inch sheet of 0.020-inch temporary splint material
Forming
the matrix
maker
1. Use a bur made for cutting acrylic resin and cut a 2.5 cm circular hole in the center of the plastic jar lid, leaving a rim of approximately 2 mm around the inside circumference of the lid (Fig. 2). 2. Place the Silly Putty in the jar and create a slight concavity in the putty in the center of the jar (Fig. 3).
550
3. Cut a 2.7 mm diameter rary splint material. Its rim of the 3 oz jar (Fig. 4. Place a small amount thumb and index finger circular piece of splint 5. Screw the lid on the jar terial in place (Fig. 5).
Making
circle from the piece of tempocircumference must rest on the 4) and it must fit inside the lid. of die lubricant between the and lubricate both sides of the material. to hold the piece of matrix ma-
the matrix
1. Pour, trim, and space the dies. Place a small amount of die lubricant between the thumb and index finger and
SEPTEMBER
1992
VOLUME
68
NUMBER
3
PLASTIC
COPING
FOR
VENEER
CROWN
Fig. 8. Die pushed into heated matrix enough to slightly cover margins of die.
material
deep
Fig. 10. Folded excess matrix material ing matrix from die.
Fig. 9. Slitting the excess matrix material to make it easier to remove from die.
facilitates
ren
below margin
lubricate the die. Mark the margin on the die with a red pencil (Fig. 6). 2. While the dies are still out of the master cast, heat the matrix material through the hole in the lid of the jar with a Hanau torch (Teledyne Hanau, Buffalo, N.Y.) until it becomes clear and slumps onto the putty (Fig. 3. Slowly plunge a die into the hot matrix material. The putty and matrix material should cover the margin of the die (Fig. 8). 4. Allow the matrix material to cool for a few minutes, then unscrew the lid and remove the matrix on the die from the putty. 5. Cut approximately eight slits into the excess matrix material below the margin of the die with a pair of small scissors (Fig. 9). 6. Bold the die by the base, turn the slits up to the
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
Fig. 11. Well-fitting, stable matrix trimmed 0.2 mm of die margins.
within 1.5 to
occlusal surface, and pull the matrix off the 10). 7. With the scissors, remove the excess material 1.5 to 0.2 mm of the margin. Examine the fit bility of the matrix on the die (Fig. 11). If it fit well, remake the matrix.
die 1(Fig. to wi ithin and stadoesi not
551
TROENDLE
12. Thickness gauge used to measure facial thickness of matrix.
Fig.
AND
TROENDLE
14. Facial surface of full contour premolar wax-up cut back to expose plastic coping.
Fig.
DISCUSSION
Pig. 13. Coping covered with wax carved to full contour.
Copings that are too thin can be remade or they can be used if wax is allowed to remain in the matrix after the full contour pattern has been cut back. The latter remedy is not advised because it defeats the purpose for which the material is used. There are a number of precautions to ensure that the matrix material does not thin out too much. First, be certain when heating the matrix material to heat it from the periphery and not to overheat the matrix material where the die will be placed. Second, slowly push the die into the matrix material so that the matrix material has time to cool. Finally, the die can be placed in a freezer for 5 minutes before it is placed in the heated matrix material. AI1 three of these methods may be altered to control the thickness of the coping. REFERENCES
8. Measure the facial surface of the coping with a thickness gauge (Miltex gauge, Lake Success, N.Y.) (Fig. 12). If it is not between 0.3 and 0.5 mm thick, see Discussion section for ways to correct it. 9. Wipe the die lubricant off the coping with an alcohol wipe so that the wax will stick to the coping. Apply wax over the coping and carve it to full contour (Fig. 13). 10. Cut back the facial veneer to .the elastic coping to ensure an adequate and uniform thickness of the casting without overbulking (Fig. 14).
552
1. Shillinburg HT, Hobo S, Whisett LD. Fundamentals of fixed prosthodontics. 2nd. ed. Chicago: Quintessence Publishing Co, Inc, 1981:Chapter 19. 2. Rosentiel SF, Land MF, Fugimoto J. Contemporary fixed prosthodontics. St. Louis: CV Mosby, 1988:Chapter 16.
Reprintrequeststo: DR. G. ROGER TROENDLE UNIVERSITY OF TEXAS HEALTH SCIENCE CENTER DENTAL SCHOOL 7703 FLOVD CURL DRIVE SAN ANTONIO, TX 78284
SEPTEMBER
1992
VOLUME
66
NUMBER
3
