- Email: [email protected]
The effect of impression-die systems on crown margins
The effect of impression-die crown margins Edward J. Plekavich,
D.D.S., M.S.,*
systems on
and John M. Joncas, D.D.S.**
Georgetown University, School of Dentistry, Washington, D.C.
T
An 1953 Waerhaug’ reported that the gingival tissue adjacent to the margin of an artificial crown contained a chronic inflammatory infiltrate. He also believed that this inflammation resulted from the accumulation of bacterial plaque at the microscopic opening of the margins of the restorations.’ In 1970 Silness) demonstrated that the periodontal tissues surrounding teeth restored with artificial crowns were not as healthy as untreated contralateral teeth. These factors cast doubt on the purported accuracy of impression and die materials. In 1974 Cooney4 noted that silver-plated dies from a polysulfide impression were not appreciably different from stone diesformed in the sameimpressionmaterial. Both types of dies were clinically acceptablereproductions of teeth; however, stone dies from a silicone impressionmaterial more closely reproduced the original. In 1975 Stackhouse’reported lessthan 1% dimensional change of stonedies from polyether and silicone impressionmaterials. Krug and Markley6 showed that silver-plated dies can effectively improve the margins of cast restorations by permitting indirect burnishing. This technique presents an advantage for refining complete crown margins on a die becauseof the inaccessibility of the margin of the tooth.
PURPOSE Due to the availability of a variety of accurate impressionmaterials and clinical techniques, selection of the most appropriate procedure is difficult. This investigation compares the marginal openings of crowns produced from three combinations of impressions and die materials. Presented Wash. *Associate **Associate
772
before
the Academy
Professor, Department Professor, Department
of Denture
Prosthetics,
of Fixed Prosthodontics. of Operative Dentistry.
Seattle,
-Gold
VERTICAL DEFECT
Fig. 1. Schematic of crosssection of tooth and artificial crown.
MATERIAL
AND
METHODS
Twenty-six freshly extracted human molars were prepared in vitro with a water-cooled tapered diamond bur (856-025, Brassler U.S.A. Inc., Lombard, Ill.) in an ultrahigh-speed handpiece. Complete crowns were prepared with a gingival chamfer and care was taken not to excessivelytaper the preparation. The teeth were stored in a sealedcontainer with */i inch of water. Twenty-one prepared teeth were randomly divided
JUNE
1983
VOLUME
49
NUMBER
6
1MPRESSlON-DIE
SYSTEMS
Table 1. Margin _
AND
openings -_-..-
_.--
CROWN
(in microns)
Group I: silicone rubber improved stone A
Group polyether improved
119 77 140 70 49
B
H
140 56 119 h3 161 189 126 86 163 119 13.5 148 I35 135 RI 141 81 94 135 95 108
D
E
F
G
II: rubber stone
Group III: polysulfide rubber silver electroplate 66 55
0
121 110
I
161
c
MARGINS
99 110 120 99 77 LG
P
121 110
M
N
108
27 270
81
110 55
AA
T
U
22 44 33 110 55 44 I32 66 33 22 44 33 154 176 66 77 0 55 0 88 0 27
18
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
4.5 14 9 4.5 4.5 4.5 18 45 4.5
HB
CC
DD
18
4.5 4.5 0 9 0 18 0
EE
108
RI _-.
into three groups. A different combination of impression-die material was used for each group. The groups were: 1. Silicone rubber (Xanthopren, Unitek Corp., Monrovia, Calif.); die stone (Vel-Mix, Kerr Mfg. Co., Romulus, Mich.) 2. Polyether rubber (Impregum, Premier Dental Products Co., Philadelphia, Pa.); die stone (Vel-Mix, Kerr Mfg. Co.) 3. Polysuifide rubber (Omniff ex, Coe Laboratories, Chicago, Ill.); silver electroplate Autopolymerizing acrylic resin (Formatray, Kerr Mfg. Co.) trays were made with 2 mm relief and were bench cured for 24 hours. The impression materials were thoroughly mixed and injected around the prepared teeth, which had been in a water bath at 37” C. The trays were filled and seated with light hand pressure and held until the material was completely set. After removal from the prepared teeth, the silicone and polyether impressions were immediately poured in
6 0
66 110
ll<
99 132 143 143 176 143 88 77 88 77 77 54
Group IV: no die
..-.-__-__
mechanically mixed die stone, 12 ml water to 50 gm powder. The polysulfide impression was treated with Silversol (Hanau Engineering Co., Buffalo, N. Y.) and placed in an electroforming unit (Junior Electroformer, Hanau Engineering Co.) containing electrolyte (Kerr silverplating electrolyte, Kerr Mfg. Co.). When sufficient thickness of silver had been deposited, autopolymerizing resin was poured into the silver to provide bulk. After recovery and inspection of the dies, rounded crown contours were formed in wax (Blue Inlay Wax, regular, Kerr Mfg. Co.). The occlusal portion of the wax patterns was coated with plastic beads to aid retention in the embedding medium. The patterns were attached to sprue formers and invested in a normal mix’ of investment (Lustrecast, Kerr Mfg. Co.) (17 ml water to 50 gm powder). The invested patterns were immersed in a 100” F water bath for 30 minutes. The invested patterns were volatilized in tempera-
773
PLEKAVICH
12Or
J
T
E a SiliconeImproved Polyether. Improved Polysulflde Sliver-Plated
Stone Stone Rubber Die
No Die
Fig. 2. Mean margin opening in microns.
tures up to 900” F for 1 hour and cast in type III dental gold (B-2, J. M. Ney Co., Bloomlield, Conn.). The five remaining teeth were waxed directly to form similar contours. These wax patterns were treated in the same manner and castings made. All the castings were examined for defects, and when free of debris the castings were placed on the dies or teeth. Finishing consisted of sanding with a fine cuttle disk on the stone dies rotating from the gold to the die and followed by tripoli on a felt wheel also rotating from gold to die. The margins of the castings were hand burnished on the silver dies, sanded with the fine cuttle disk, and hand burnished again. Only light polishing was necessary to achieve a mirror finish. After finishing, the crowns were tried on the prepared teeth and examined for adaptation to the margin. Vents were cut in the crown, and they were cemented with zinc phosphate cement (Fleck’s, Mizzy Inc., Clifton Forge, Va.) (1.3 gm powder to 0.05 ml liquid) using firm finger pressure. The crowns and teeth were placed in a Model UTSM Chatillon (John Chatillon and Sons, New York, N. Y.) at 80 psi8 until the cement was set. Two crowns were cemented at a time. The teeth were then embedded in a hard resin 774
AND
JONCAS
(Polystyrene, Chemco, San Leandro, Calif.). Sections for microscopic examination were made by cutting the blocks with a diamond saw (A. D. McBurney Co., Glendale, Calif.) and wet sanded with 400 grit silicone carbide paper (3 M Co., St. Paul, Minn.) to remove any drawn gold. The cut specimens were examined under a light microscope at a magnification of X100. Margin defects were measured by means of a linear ocular micrometer (Micrometer 1406A, American Optical, Buffalo, N. Y.) from the finish line of the prepared tooth to the edge of the casting (Fig. 1). After the block was sectioned and subsequently sanded, the measurements of four areas on each tooth for a total of 104 measurements were tabulated. RESULTS The margin openings for crowns produced on dies ranged from a mean of 64.7 pm for the silver dies to 114.3 pm for the stone dies and silicone impression (Table I and Fig. 2). The marginal distortion was also widely variable not only between teeth but on the same tooth. Crowns fabricated directly on the teeth in contrast demonstrated minimal margin openings with only minor variation. Evidently, some burnishing of the margins accompanied the finishing process, which was performed directly on the teeth. The crowns burnished on the silver dies produced a characteristic cross section of the margin (figs. 3 and 4). The metal appeared to have been lengthened, reducing the margin opening. Figs. 5 and 6 illustrate cross sections through the margin of crowns produced on stone dies that did not demonstrate this lengthened metal. DISCUSSION The magnitude of the margin openings produced in this study are discouraging but not inconsistent with previous studies. Cooney’ found that a master casting would not completely seat onto stone and silver-plated dies. He noted margin openings of 16 pm to 113 pm for silicone and 84 pm to 110 pm for polysulfide impression materials. Stackhousej also reported that castings seated on a prepared master tooth die without cement left margin openings from 0.003 inch to 0.005 inch or 76.2 Ctrn to 127 pm. Cooper et a1.9 cemented vented crowns to a stainless steel test die, and the marginal openings for zinc phosphate cement ranged from 33 pm to 180 pm (SD 43.5 pm). The wide variation in opening on the same tooth could be due to the hydraulic pressure and resultant filtration of the cement as described by Jorgensen.‘O There is a distinct advantage to burnishing the JUNE
1983
VOLUME
49
NUMBER
6
IMPRESSION-DIE
SYSTEMS
AND
CROWN
MARGINS
Figs. 3 and 4. Cross section
of tooth and artificial
Figs. 5 and 6. Cross section T? iE JOURNAL
OF PROSTHETIC
DENTISTRY
crown
of tooth and artificial
finished
crown
on silver-plated
finished
die.
on stone dies.
PLEKAVICH
margins of the crown on a metal die because the burnished margins in this study were 44% smaller than the unburnished crown margins.
3. Silness, J.: Periodontal
SUMMARY
5. Stackhouse,
4.
6. 7. 8. 9.
10.
REFERENCES
2.
JONCAS
conditions in patients treated with dental bridges. J Periodont Res 5~60, 1970. Cooney, J. P.: A comparison of silver-plated and stone dies from rubber-base impressions. J PROSTHET DENT 32262, 1974.
This study compared the adaptation of the margins of gold crowns produced from three impression-die combinations. Gold crowns were fabricated and cemented to prepared human teeth. After sectioning, the degree of margin opening was measured and the groups were compared. Crowns produced on silver dies from polysulfide impressions had a smaller margin opening than crowns made on dies of improved stone.
1.
AND
Waerhaug, J.: Tissue reactions around artificial crowns. J Periodontol 24~172, 1953. Waerhaug, J.: Histologic considerations which govern where the margins of restorations should be located in relation to the gingiva. Dent Clin North Am 6~161, 1960.
J. A.: A comparison of elastic impression materials. J PROSTHET DENT 34~305, 1975. Krug, R. S., and Markley, M. R.: Cast restorations with gold-foil-like margins. J PROSTHET DENT 22:54, 1969. Asgar, K., Mahler, D. B., and Peyton, F. A.: Hygroscopic technique for inlay casting using controlled water additions. J PROSTHET DENT 5:711, 1955. Peyton, F. A., and Craig, R. G., editors: Restorative Dental Materials, ed 4. St. Louis, 1971, The C. V. Mosby Co., pp 122-123. Cooper, T. M., Christensen, G. J., Laswell, H. R., and Baxter, R.: Effects of venting on cast gold full crowns. J PROSTHET DENT 26:621, 1971. Jorgensen, K. D.: Factors affecting the film thickness of zinc phosphate cements. Acta Odontol Stand l&479, 1960.
Reprint requests lo: DR. EDWARD J. PLEKAVICH GEORGETOWN UNIVERSITY SCHOOL OF DENTISTRY WASHINGTON, DC 20007
Bound volumes available to subscribers of the JOURNAL OF PROSTHE~C DENTISTRY areavailableto subscribers (only) for the 1983 issues from the at a cost of $39.00 ($49.00 international)for Vol. 49 (January-June) and Vol. 50 (July-December). Shipping charges are included. Each bound volume contains a subject and author index, and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Mr. Deans Lynch at The C. V. Mosby Co., 11830 We&line Industrial Drive, St. Louis, MO 63141, USA. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular ~JOURNAL subscription. Bound publisher
776
volumes
JUNE
1983
VOLUME
49
NUMBER
6
D.D.S., M.S.,*
systems on
and John M. Joncas, D.D.S.**
Georgetown University, School of Dentistry, Washington, D.C.
T
An 1953 Waerhaug’ reported that the gingival tissue adjacent to the margin of an artificial crown contained a chronic inflammatory infiltrate. He also believed that this inflammation resulted from the accumulation of bacterial plaque at the microscopic opening of the margins of the restorations.’ In 1970 Silness) demonstrated that the periodontal tissues surrounding teeth restored with artificial crowns were not as healthy as untreated contralateral teeth. These factors cast doubt on the purported accuracy of impression and die materials. In 1974 Cooney4 noted that silver-plated dies from a polysulfide impression were not appreciably different from stone diesformed in the sameimpressionmaterial. Both types of dies were clinically acceptablereproductions of teeth; however, stone dies from a silicone impressionmaterial more closely reproduced the original. In 1975 Stackhouse’reported lessthan 1% dimensional change of stonedies from polyether and silicone impressionmaterials. Krug and Markley6 showed that silver-plated dies can effectively improve the margins of cast restorations by permitting indirect burnishing. This technique presents an advantage for refining complete crown margins on a die becauseof the inaccessibility of the margin of the tooth.
PURPOSE Due to the availability of a variety of accurate impressionmaterials and clinical techniques, selection of the most appropriate procedure is difficult. This investigation compares the marginal openings of crowns produced from three combinations of impressions and die materials. Presented Wash. *Associate **Associate
772
before
the Academy
Professor, Department Professor, Department
of Denture
Prosthetics,
of Fixed Prosthodontics. of Operative Dentistry.
Seattle,
-Gold
VERTICAL DEFECT
Fig. 1. Schematic of crosssection of tooth and artificial crown.
MATERIAL
AND
METHODS
Twenty-six freshly extracted human molars were prepared in vitro with a water-cooled tapered diamond bur (856-025, Brassler U.S.A. Inc., Lombard, Ill.) in an ultrahigh-speed handpiece. Complete crowns were prepared with a gingival chamfer and care was taken not to excessivelytaper the preparation. The teeth were stored in a sealedcontainer with */i inch of water. Twenty-one prepared teeth were randomly divided
JUNE
1983
VOLUME
49
NUMBER
6
1MPRESSlON-DIE
SYSTEMS
Table 1. Margin _
AND
openings -_-..-
_.--
CROWN
(in microns)
Group I: silicone rubber improved stone A
Group polyether improved
119 77 140 70 49
B
H
140 56 119 h3 161 189 126 86 163 119 13.5 148 I35 135 RI 141 81 94 135 95 108
D
E
F
G
II: rubber stone
Group III: polysulfide rubber silver electroplate 66 55
0
121 110
I
161
c
MARGINS
99 110 120 99 77 LG
P
121 110
M
N
108
27 270
81
110 55
AA
T
U
22 44 33 110 55 44 I32 66 33 22 44 33 154 176 66 77 0 55 0 88 0 27
18
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
4.5 14 9 4.5 4.5 4.5 18 45 4.5
HB
CC
DD
18
4.5 4.5 0 9 0 18 0
EE
108
RI _-.
into three groups. A different combination of impression-die material was used for each group. The groups were: 1. Silicone rubber (Xanthopren, Unitek Corp., Monrovia, Calif.); die stone (Vel-Mix, Kerr Mfg. Co., Romulus, Mich.) 2. Polyether rubber (Impregum, Premier Dental Products Co., Philadelphia, Pa.); die stone (Vel-Mix, Kerr Mfg. Co.) 3. Polysuifide rubber (Omniff ex, Coe Laboratories, Chicago, Ill.); silver electroplate Autopolymerizing acrylic resin (Formatray, Kerr Mfg. Co.) trays were made with 2 mm relief and were bench cured for 24 hours. The impression materials were thoroughly mixed and injected around the prepared teeth, which had been in a water bath at 37” C. The trays were filled and seated with light hand pressure and held until the material was completely set. After removal from the prepared teeth, the silicone and polyether impressions were immediately poured in
6 0
66 110
ll<
99 132 143 143 176 143 88 77 88 77 77 54
Group IV: no die
..-.-__-__
mechanically mixed die stone, 12 ml water to 50 gm powder. The polysulfide impression was treated with Silversol (Hanau Engineering Co., Buffalo, N. Y.) and placed in an electroforming unit (Junior Electroformer, Hanau Engineering Co.) containing electrolyte (Kerr silverplating electrolyte, Kerr Mfg. Co.). When sufficient thickness of silver had been deposited, autopolymerizing resin was poured into the silver to provide bulk. After recovery and inspection of the dies, rounded crown contours were formed in wax (Blue Inlay Wax, regular, Kerr Mfg. Co.). The occlusal portion of the wax patterns was coated with plastic beads to aid retention in the embedding medium. The patterns were attached to sprue formers and invested in a normal mix’ of investment (Lustrecast, Kerr Mfg. Co.) (17 ml water to 50 gm powder). The invested patterns were immersed in a 100” F water bath for 30 minutes. The invested patterns were volatilized in tempera-
773
PLEKAVICH
12Or
J
T
E a SiliconeImproved Polyether. Improved Polysulflde Sliver-Plated
Stone Stone Rubber Die
No Die
Fig. 2. Mean margin opening in microns.
tures up to 900” F for 1 hour and cast in type III dental gold (B-2, J. M. Ney Co., Bloomlield, Conn.). The five remaining teeth were waxed directly to form similar contours. These wax patterns were treated in the same manner and castings made. All the castings were examined for defects, and when free of debris the castings were placed on the dies or teeth. Finishing consisted of sanding with a fine cuttle disk on the stone dies rotating from the gold to the die and followed by tripoli on a felt wheel also rotating from gold to die. The margins of the castings were hand burnished on the silver dies, sanded with the fine cuttle disk, and hand burnished again. Only light polishing was necessary to achieve a mirror finish. After finishing, the crowns were tried on the prepared teeth and examined for adaptation to the margin. Vents were cut in the crown, and they were cemented with zinc phosphate cement (Fleck’s, Mizzy Inc., Clifton Forge, Va.) (1.3 gm powder to 0.05 ml liquid) using firm finger pressure. The crowns and teeth were placed in a Model UTSM Chatillon (John Chatillon and Sons, New York, N. Y.) at 80 psi8 until the cement was set. Two crowns were cemented at a time. The teeth were then embedded in a hard resin 774
AND
JONCAS
(Polystyrene, Chemco, San Leandro, Calif.). Sections for microscopic examination were made by cutting the blocks with a diamond saw (A. D. McBurney Co., Glendale, Calif.) and wet sanded with 400 grit silicone carbide paper (3 M Co., St. Paul, Minn.) to remove any drawn gold. The cut specimens were examined under a light microscope at a magnification of X100. Margin defects were measured by means of a linear ocular micrometer (Micrometer 1406A, American Optical, Buffalo, N. Y.) from the finish line of the prepared tooth to the edge of the casting (Fig. 1). After the block was sectioned and subsequently sanded, the measurements of four areas on each tooth for a total of 104 measurements were tabulated. RESULTS The margin openings for crowns produced on dies ranged from a mean of 64.7 pm for the silver dies to 114.3 pm for the stone dies and silicone impression (Table I and Fig. 2). The marginal distortion was also widely variable not only between teeth but on the same tooth. Crowns fabricated directly on the teeth in contrast demonstrated minimal margin openings with only minor variation. Evidently, some burnishing of the margins accompanied the finishing process, which was performed directly on the teeth. The crowns burnished on the silver dies produced a characteristic cross section of the margin (figs. 3 and 4). The metal appeared to have been lengthened, reducing the margin opening. Figs. 5 and 6 illustrate cross sections through the margin of crowns produced on stone dies that did not demonstrate this lengthened metal. DISCUSSION The magnitude of the margin openings produced in this study are discouraging but not inconsistent with previous studies. Cooney’ found that a master casting would not completely seat onto stone and silver-plated dies. He noted margin openings of 16 pm to 113 pm for silicone and 84 pm to 110 pm for polysulfide impression materials. Stackhousej also reported that castings seated on a prepared master tooth die without cement left margin openings from 0.003 inch to 0.005 inch or 76.2 Ctrn to 127 pm. Cooper et a1.9 cemented vented crowns to a stainless steel test die, and the marginal openings for zinc phosphate cement ranged from 33 pm to 180 pm (SD 43.5 pm). The wide variation in opening on the same tooth could be due to the hydraulic pressure and resultant filtration of the cement as described by Jorgensen.‘O There is a distinct advantage to burnishing the JUNE
1983
VOLUME
49
NUMBER
6
IMPRESSION-DIE
SYSTEMS
AND
CROWN
MARGINS
Figs. 3 and 4. Cross section
of tooth and artificial
Figs. 5 and 6. Cross section T? iE JOURNAL
OF PROSTHETIC
DENTISTRY
crown
of tooth and artificial
finished
crown
on silver-plated
finished
die.
on stone dies.
PLEKAVICH
margins of the crown on a metal die because the burnished margins in this study were 44% smaller than the unburnished crown margins.
3. Silness, J.: Periodontal
SUMMARY
5. Stackhouse,
4.
6. 7. 8. 9.
10.
REFERENCES
2.
JONCAS
conditions in patients treated with dental bridges. J Periodont Res 5~60, 1970. Cooney, J. P.: A comparison of silver-plated and stone dies from rubber-base impressions. J PROSTHET DENT 32262, 1974.
This study compared the adaptation of the margins of gold crowns produced from three impression-die combinations. Gold crowns were fabricated and cemented to prepared human teeth. After sectioning, the degree of margin opening was measured and the groups were compared. Crowns produced on silver dies from polysulfide impressions had a smaller margin opening than crowns made on dies of improved stone.
1.
AND
Waerhaug, J.: Tissue reactions around artificial crowns. J Periodontol 24~172, 1953. Waerhaug, J.: Histologic considerations which govern where the margins of restorations should be located in relation to the gingiva. Dent Clin North Am 6~161, 1960.
J. A.: A comparison of elastic impression materials. J PROSTHET DENT 34~305, 1975. Krug, R. S., and Markley, M. R.: Cast restorations with gold-foil-like margins. J PROSTHET DENT 22:54, 1969. Asgar, K., Mahler, D. B., and Peyton, F. A.: Hygroscopic technique for inlay casting using controlled water additions. J PROSTHET DENT 5:711, 1955. Peyton, F. A., and Craig, R. G., editors: Restorative Dental Materials, ed 4. St. Louis, 1971, The C. V. Mosby Co., pp 122-123. Cooper, T. M., Christensen, G. J., Laswell, H. R., and Baxter, R.: Effects of venting on cast gold full crowns. J PROSTHET DENT 26:621, 1971. Jorgensen, K. D.: Factors affecting the film thickness of zinc phosphate cements. Acta Odontol Stand l&479, 1960.
Reprint requests lo: DR. EDWARD J. PLEKAVICH GEORGETOWN UNIVERSITY SCHOOL OF DENTISTRY WASHINGTON, DC 20007
Bound volumes available to subscribers of the JOURNAL OF PROSTHE~C DENTISTRY areavailableto subscribers (only) for the 1983 issues from the at a cost of $39.00 ($49.00 international)for Vol. 49 (January-June) and Vol. 50 (July-December). Shipping charges are included. Each bound volume contains a subject and author index, and all advertising is removed. Copies are shipped within 30 days after publication of the last issue in the volume. The binding is durable buckram with the journal name, volume number, and year stamped in gold on the spine. Payment must accompany all orders. Contact Mr. Deans Lynch at The C. V. Mosby Co., 11830 We&line Industrial Drive, St. Louis, MO 63141, USA. Subscriptions must be in force to qualify. Bound volumes are not available in place of a regular ~JOURNAL subscription. Bound publisher
776
volumes
JUNE
1983
VOLUME
49
NUMBER
6