CLINICAL
DISCRIMINATION
OF PORCELAIN
Indeed, the esthetic result may be superior to the original glazed surface. The decrease in visual discrimination between the two test surfaces evidenced after additional glazing procedures may be attributed to structural changes experienced by the porcelain.
2. Klausner LH, Cartwright CB, Charheneau G’P. Polished versus autoglazed porcelain surfaces. J PROSTHET DENT 1982;47:157-62. 3. Newitter DA, Schlissel ER, WoltTMS. An evaluation of adjustment and uostadiustment finishing techniques on the surface of porcelain-honded-to-metal crowns. J P~OSTHJ& DENT 1982;483388-95. 4. Bessing C, Wiktorsson A. Comparison of two different methods of polishing porcelain. Stand J Dent Res 1983;91:482-7. Reprint
REFERENCES 1. Sulik WD, Plekavich EJ. Surface THET DENT 1981:46:217-21.
A controlled Barry
Marshak,
Tel
University,
Aviv
finishing
of dental
porcelain.
putty-wash
J PROS-
requests
to:
DR. JANE D. BREWER SCHO~~L OF DENTAL. MEDICINE SUNY AT BUFFALO BUFFALO, NY 14214
impression
technique
B.D.S.,* David Assif, D.M.D.,** and Raphael Faculty of Medicine, Tel Aviv, Israel
Pilo, D.M.D.*
Sackler
A precise impression is imperative for the construction of an accurately fitting indirect cast restoration. The putty-wash technique is commonly used in making impressions with silicone elastomers. Errors in manipulation may lead to inaccurate impressions. A technique is presented ensuring exact reseating of the putty impression tray and creation of a uniform wash space, which are essential for accurate results. (J PROSTAET DENT 1990;64:635-6.)
T
he putty-wash technique is commonly used in making impressions with silicone elastomers. This consists of polymerizing a low-viscosity elastomer (light-body or wash) against a high-viscosity elastomer (putty).’ The putty, used in a perforated metal stock tray, simulates a custom-made tray. Notwithstanding the properties of polysiloxane materials, the following errors in manipulation may lead to an inaccurate impression.
4. Some manufacturers provide a polyethelene spacer to be placed over the putty for making the putty impression. This procedure has the major drawbacks of (1) no landmarks, guiding planes, or posterior stops left in the putty impression, making accurate replacement of the tray during the wash stage difficult, and (2) an inaccurate or arbitrarily repositioned tray that cannot achieve a uniform wash space.
Errors
TECHNIQUE
leading
to inaccurate
impression
1. An excess bulk of wash material can result in dimensional changes proportional to the thickness of the material during setting. A consistent layer of 2 mm has been recommended as the optimal thickness for the wash material.2-5 2. Undercuts or projections into the putty affect the accuracy of the impression.6 3. Inaccurately seating the putty tray containing the wash material may lead to an excess bulk of wash material around the abutment teeth, resulting in wash material being forced away from the abutment tooth because of overseating and a nonuniform layer of wash left around the abutment.
*In&ructor, Department of Prosthodontics. **Coordinator, Department of Prosthodontics; Senior Clinical Lecturer, Department of Prosthodontics. 10/l/22126
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
The following technique is suggested to overcome the problems of errors in manipulation: 1. The putty impression is made with resin provisional restorations in place on the prepared teeth and allowed to set. The provisionals act as occlusal stops for seating of the impression tray. If the restoration is a fixed partial denture, individual resin restorations made on a stone cast are used so that a uniform impression is made of the edentulous space. 2. When the impression is removed, the provisional restorations are detached from the set putty. A wash space, equivalent to the dimensions of the provisional restoration, will be created in the putty surrounding the prepared tooth. When design of the finish line is such that an adequate bulk of wash material cannot be achieved because of the thin margins of the provisional restoration, a strip of putty corresponding to the finish line should be cut away. 3. To enable accurate reseating of the putty impression and venting away excesswash material, all undercuts, pro-
635
MARSEIAR,
ASSIF,
AND
PILO
jections into embrasures or tooth material should be cut away from the putty before loading of the wash material. 4. The exact amount of wash needed to fill the wash space cannot be clinically calculated. An excess of wash is usually present. To ensure venting out this excess, escape channels should be cut into the putty from the gingival margin to the outer border of the tray. A No. 8 round bur or No. 15 scalpel blade can be used for this purpose. The previous removal of the embrasure projections will also assist in venting away excess wash material. 5. Large embrasure spaces in the dental arch should be blocked out before impression making. Utility wax (Columbus Dental, St. Louis, MO.) can be used for this purpose. This blockout facilitates removal of the tray once the wash material has set, avoiding distortion on withdrawal, possible separation of the putty wash complex from the stock tray, and damage to teeth with diminished periodontal support.
removal of undercuts and projections permits the wash to set with minimal dimensional changes. The completed impression can be removed from the mouth with minimal distortion. Finally, the preparation of the putty impression tray requires little time and effort.
SUMMARY
Reprint requeststo:
A technique was presented to achieve an accurate-seating putty impression tray by use of unprepared teeth and provisional restorations in the arch as landmarks, stops, and guiding planes. Venting out excess wash material by
REFERENCES 1. Sandrik JL, Vacco JL. Tensile and bond strength of putty-wash elastomeric impression materials. J PROSTHET DENT 1983;58:358-61. 2. Eames WB, Sieweke JC, Wallace SW, Rogers CB. Elastomeric impression materials. Effect of bulk on accuracy. J PROSTHET DENT 1979; 41:304-7. 3. Johnston
JF, Phillips RW, Dykema RW. Modern practice in crown and bridgeprosthodontics. 4th ad. Philadelphia: WB SaundersCo, 1986;11029. 4. Phillips RW. Skinner’s science of dental materials. 7th ed. Chicago: WB Saunders Co, 1973. 5. Shillingburg HI, Hobo S, Whitaett LD. Fundamentals of fixed prosthodontics. Chicago: Quintessence Publishing Co, 1978;169-90. 6. De Arauyo PA, Jorgenson KD. Effect of bulk and undercuts on the accuracy of impression materials. J PROSTHET DENT 1985;54:791-4.
DR. DAVID AWF SCHOOL OF DENTAL MEDICINE TEL Aw UNIVERSITY RAMAT-AVIV 69978 TFLAvN ISRAEL
Gingival margins for crowns: A review Part II: Discrepancies and configtirations A. J. Hunter, B.D.S., M.D.%., Dunedin, New Zealand
D.R.D.R.C.S.,
and A. R. Hunter,
and discussion. B.D.S., M.D.S.
While there is variation regarding the maximum acceptable marginal discrepancy, there is little argument that poorly 5tting margins are a frequent finding. Large discrepancies are clinically signi5cant, since they facilitate plaque retention. Margins incorporating slip joint geometry have usually been favored as a method of minimizing seating and sealing discrepancies. However, many of these discussions largely ignored the effects of the cementing medium and the clinical applicability of slip joint geometry is based on questionable assumptions with regard to casting accuracy and seating. Greater understanding of the role of restorative margins and gingival health indicates the need for shallow margin placement within the crevice, which requires a reassessment of the use of long bevels. Horizontal margins can be made accurately and, when combined with procedures to maximize crown seating, may firovide the best method of minimizing seating discrepancies and maximizing gingival health. (J PROSTHET DENT 1990;64:636-42.)
M
aking a casting involves a series of controlled compensations for the dimensional changes occurring throughout the process.lp2 Because there is always a discrepancy between the tooth and the cast restoration,3-8 itsfit”... has become an intense preoccupation.“2 Gulkerg
10/l/22123
636
stated that even good castings often exhibit discrepancies of 200 pm, but others have reported much smaller discrepancies.splo* l1 Dedmon12 discovered that prior to cementation only 9% of castings had sealing discrepancies greater than $9 Nrn. Discrepancies are commonly increased following cementation,2v lo, I19I39l4 usually because of poor crown seating.14-ls McLean and von Fraunhoferlg reported that inaccuracies of fit of 0.1 mm were normal.
DECEMBER
lB90
VOLUME
64
NUMBER
6
DISCRIMINATION
OF PORCELAIN
Indeed, the esthetic result may be superior to the original glazed surface. The decrease in visual discrimination between the two test surfaces evidenced after additional glazing procedures may be attributed to structural changes experienced by the porcelain.
2. Klausner LH, Cartwright CB, Charheneau G’P. Polished versus autoglazed porcelain surfaces. J PROSTHET DENT 1982;47:157-62. 3. Newitter DA, Schlissel ER, WoltTMS. An evaluation of adjustment and uostadiustment finishing techniques on the surface of porcelain-honded-to-metal crowns. J P~OSTHJ& DENT 1982;483388-95. 4. Bessing C, Wiktorsson A. Comparison of two different methods of polishing porcelain. Stand J Dent Res 1983;91:482-7. Reprint
REFERENCES 1. Sulik WD, Plekavich EJ. Surface THET DENT 1981:46:217-21.
A controlled Barry
Marshak,
Tel
University,
Aviv
finishing
of dental
porcelain.
putty-wash
J PROS-
requests
to:
DR. JANE D. BREWER SCHO~~L OF DENTAL. MEDICINE SUNY AT BUFFALO BUFFALO, NY 14214
impression
technique
B.D.S.,* David Assif, D.M.D.,** and Raphael Faculty of Medicine, Tel Aviv, Israel
Pilo, D.M.D.*
Sackler
A precise impression is imperative for the construction of an accurately fitting indirect cast restoration. The putty-wash technique is commonly used in making impressions with silicone elastomers. Errors in manipulation may lead to inaccurate impressions. A technique is presented ensuring exact reseating of the putty impression tray and creation of a uniform wash space, which are essential for accurate results. (J PROSTAET DENT 1990;64:635-6.)
T
he putty-wash technique is commonly used in making impressions with silicone elastomers. This consists of polymerizing a low-viscosity elastomer (light-body or wash) against a high-viscosity elastomer (putty).’ The putty, used in a perforated metal stock tray, simulates a custom-made tray. Notwithstanding the properties of polysiloxane materials, the following errors in manipulation may lead to an inaccurate impression.
4. Some manufacturers provide a polyethelene spacer to be placed over the putty for making the putty impression. This procedure has the major drawbacks of (1) no landmarks, guiding planes, or posterior stops left in the putty impression, making accurate replacement of the tray during the wash stage difficult, and (2) an inaccurate or arbitrarily repositioned tray that cannot achieve a uniform wash space.
Errors
TECHNIQUE
leading
to inaccurate
impression
1. An excess bulk of wash material can result in dimensional changes proportional to the thickness of the material during setting. A consistent layer of 2 mm has been recommended as the optimal thickness for the wash material.2-5 2. Undercuts or projections into the putty affect the accuracy of the impression.6 3. Inaccurately seating the putty tray containing the wash material may lead to an excess bulk of wash material around the abutment teeth, resulting in wash material being forced away from the abutment tooth because of overseating and a nonuniform layer of wash left around the abutment.
*In&ructor, Department of Prosthodontics. **Coordinator, Department of Prosthodontics; Senior Clinical Lecturer, Department of Prosthodontics. 10/l/22126
THE
JOURNAL
OF PROSTHETIC
DENTISTRY
The following technique is suggested to overcome the problems of errors in manipulation: 1. The putty impression is made with resin provisional restorations in place on the prepared teeth and allowed to set. The provisionals act as occlusal stops for seating of the impression tray. If the restoration is a fixed partial denture, individual resin restorations made on a stone cast are used so that a uniform impression is made of the edentulous space. 2. When the impression is removed, the provisional restorations are detached from the set putty. A wash space, equivalent to the dimensions of the provisional restoration, will be created in the putty surrounding the prepared tooth. When design of the finish line is such that an adequate bulk of wash material cannot be achieved because of the thin margins of the provisional restoration, a strip of putty corresponding to the finish line should be cut away. 3. To enable accurate reseating of the putty impression and venting away excesswash material, all undercuts, pro-
635
MARSEIAR,
ASSIF,
AND
PILO
jections into embrasures or tooth material should be cut away from the putty before loading of the wash material. 4. The exact amount of wash needed to fill the wash space cannot be clinically calculated. An excess of wash is usually present. To ensure venting out this excess, escape channels should be cut into the putty from the gingival margin to the outer border of the tray. A No. 8 round bur or No. 15 scalpel blade can be used for this purpose. The previous removal of the embrasure projections will also assist in venting away excess wash material. 5. Large embrasure spaces in the dental arch should be blocked out before impression making. Utility wax (Columbus Dental, St. Louis, MO.) can be used for this purpose. This blockout facilitates removal of the tray once the wash material has set, avoiding distortion on withdrawal, possible separation of the putty wash complex from the stock tray, and damage to teeth with diminished periodontal support.
removal of undercuts and projections permits the wash to set with minimal dimensional changes. The completed impression can be removed from the mouth with minimal distortion. Finally, the preparation of the putty impression tray requires little time and effort.
SUMMARY
Reprint requeststo:
A technique was presented to achieve an accurate-seating putty impression tray by use of unprepared teeth and provisional restorations in the arch as landmarks, stops, and guiding planes. Venting out excess wash material by
REFERENCES 1. Sandrik JL, Vacco JL. Tensile and bond strength of putty-wash elastomeric impression materials. J PROSTHET DENT 1983;58:358-61. 2. Eames WB, Sieweke JC, Wallace SW, Rogers CB. Elastomeric impression materials. Effect of bulk on accuracy. J PROSTHET DENT 1979; 41:304-7. 3. Johnston
JF, Phillips RW, Dykema RW. Modern practice in crown and bridgeprosthodontics. 4th ad. Philadelphia: WB SaundersCo, 1986;11029. 4. Phillips RW. Skinner’s science of dental materials. 7th ed. Chicago: WB Saunders Co, 1973. 5. Shillingburg HI, Hobo S, Whitaett LD. Fundamentals of fixed prosthodontics. Chicago: Quintessence Publishing Co, 1978;169-90. 6. De Arauyo PA, Jorgenson KD. Effect of bulk and undercuts on the accuracy of impression materials. J PROSTHET DENT 1985;54:791-4.
DR. DAVID AWF SCHOOL OF DENTAL MEDICINE TEL Aw UNIVERSITY RAMAT-AVIV 69978 TFLAvN ISRAEL
Gingival margins for crowns: A review Part II: Discrepancies and configtirations A. J. Hunter, B.D.S., M.D.%., Dunedin, New Zealand
D.R.D.R.C.S.,
and A. R. Hunter,
and discussion. B.D.S., M.D.S.
While there is variation regarding the maximum acceptable marginal discrepancy, there is little argument that poorly 5tting margins are a frequent finding. Large discrepancies are clinically signi5cant, since they facilitate plaque retention. Margins incorporating slip joint geometry have usually been favored as a method of minimizing seating and sealing discrepancies. However, many of these discussions largely ignored the effects of the cementing medium and the clinical applicability of slip joint geometry is based on questionable assumptions with regard to casting accuracy and seating. Greater understanding of the role of restorative margins and gingival health indicates the need for shallow margin placement within the crevice, which requires a reassessment of the use of long bevels. Horizontal margins can be made accurately and, when combined with procedures to maximize crown seating, may firovide the best method of minimizing seating discrepancies and maximizing gingival health. (J PROSTHET DENT 1990;64:636-42.)
M
aking a casting involves a series of controlled compensations for the dimensional changes occurring throughout the process.lp2 Because there is always a discrepancy between the tooth and the cast restoration,3-8 itsfit”... has become an intense preoccupation.“2 Gulkerg
10/l/22123
636
stated that even good castings often exhibit discrepancies of 200 pm, but others have reported much smaller discrepancies.splo* l1 Dedmon12 discovered that prior to cementation only 9% of castings had sealing discrepancies greater than $9 Nrn. Discrepancies are commonly increased following cementation,2v lo, I19I39l4 usually because of poor crown seating.14-ls McLean and von Fraunhoferlg reported that inaccuracies of fit of 0.1 mm were normal.
DECEMBER
lB90
VOLUME
64
NUMBER
6
