All-Porcelain Labial Margin for Ceramometal Crowns Lewis Harrison, D.M.D.* Terry HufSman, C.D.T. Marvin Goldfogel, D.D.S.
'
The elimination of the labiogingival metal collar of a porcelain-fused-to-metal (PFM) restoration is an attempt to achieve an improved esthetic result. In their expectation of a more cosmetic tooth restoration, patients may influence dentists to use the all-porcelain labial margin to avoid metal showing in the final restoration. Success of this type of restoration depends upon proper tooth preparation. The allporcelain margin requires a 1.2-mmwide labiogingivalshoulder of approximately 70 or 90 degrees wrapping into the interproximal area. Much of the effectiveness of the restoration depends upon the design of the metal substructure. The following change is made in the design of this substructure for this modified PFM crown: the labiogingival portion of the metal is Rnished back to the gingival-pulpal line angle with the metal against the axial wall being from 0.3mm to 0.5 mm thick. This allows for 0.2 to 0.3 mm of opaque and 0.7 to 1.0mm of shoulder porcelain. The direct liftoff technique is a useful method of achieving clinically acceptable all-porcelain margins. Such restorations may give excellent results.
P
erceived deficiencies at the labiogingival collar area of porcelain-fused-to-metal (PFM)crowns can usually be related to one of the following factors: Exposure of the metal margin: opaque show through in the cervical third: or overcontour of the cervical area of the crown (Figs. 1-3). Traditionally, a PFM restoration incorporates a narrow metal collar in the cosmetically critical area of the labiogingival area. The elimination of the labiogjngivalmetal collar is an attempt to achieve an improved esthetic result, thus addressing cosmetic disappointment that sometimes occurs. l There have been several techniques2-10proposed in an attempt to achieve this goal. These include various proposed finish lines, metal contlgurations, use of platinum or gold foil, refractory dies, direct lift-off, and various separating solutions. One of the most important considerations is preparation design. The preparation must meet the requirements of adequate reduction of tooth structure at the gingival area to provide sufficient space for the metal or ceramic material, provide retention and resistance, and have a smooth margin design with which the ceramist
can work. The shoulder with a bevel preparation has the advantage of excellent marginal integrity for PFM restorations. l2 The platinum foil technique, the oldest of the techniques, uses the foil to support the porcelain as it isbuilt up on the die and dried to maturity. Slumping of the porcelain and rolling of the porcelain edge is often the result of this technique. An additional disadvantage to this procedure is that the margin cannot be properly evaluated until the crown is completed and the foil removed.
*Assistant Professor: t Technician:$ Professor and Chairman: University of Colorado Health Sciences Center. School of Dentistry, Department of Restorative Dentistry. Denver, Colorado Address reprint requests to: Lnvis Harrison. D.M.D.. University of Colorado School of Dentistry, Department of Restorative Dentistry. 4200 East Nlnth Ave.. C284. Denver, CO 80262-0284 6 1992 Decker Perlodicds Inc.
PyeUre 1. PFM restoration with metal showing. 154
All-Porcelain Margin for Ceramometal Crowns
Figure 2. PFMrestorationwithopaque discoloration at gingival third.
Figure 4. A 10-year result for an all-porcelain labial margin
When porcelain manufacturers developed margin porcelains that fuse at temperatures 30 to 80°F lower than the parent porcelain, the foil-less direct liflprocess became popular.l0These newer margin porcelains resist pyroplastic flow and allow for direct lift-off from the die with minimal deformation. Though complete elimination of sintering shrinkage is theoretically impossible, a carefully controlled procedure can minimize shrinkage and yield clinicallyacceptable results (Fig.4). This article shows the steps used to make this a successful treatment procedure.
tissue are factors that influence the dentist in assessing the need for an all-porcelain labial margin. In addition, the patient's oral hygiene must be considered, since the tooth-crown junction of the all-porcelain labial margin is seldom as smooth as the metal-collar margin, and plaque accumulation may be a factor.I3
INDICATIONS Patients, in their expectation for a cosmetic tooth restoration, are influencing dentists to use the allporcelain labial margin to avoid metal showing in the finalrestoration. Lip-line, the thickness and color of the gingival margin, and the location of the free gingival
restoration for the lateral incisor.
Advantages and Disadvantages The advantages of this technique include improved esthetics for PFM crowns. With this, the preparation can be kept supragingival or just slightly apical to the free gingival margin in most cases. This small sulcular marginal depth is a periodontal advantage14and permits a more gentle impression technique. A major disadvantage and objection of this technique is that the loss of the metal margin may give a less optimal margin closure. Also, it is possible that fracture of the facial porcelain caused by lack of metal support may be increased.The direct life-off technique presents another potential disadvantage because of possible displacement during the porcelain shoulder build-up and pyroplastic deformation during firing. These disadvantages can be overcome with careful technique.
PreparationDesign
Figure 3. An overcontoured PFM restoration.
Success of this type of restoration depends upon proper tooth preparation. The all-porcelain labial margin requires a 1.2-mm wide labiogingival shoulder of approximately 70 or 90 degrees wrapping into the interproximal area. A chamfer margin or shoulder with abevelisusedforallothermarginareas.Thelabiogjngival margin will usually be placed near or slightlybelow the free gingivalmargin for most teeth. The shoulder should be even and smooth when viewed with magnifying loops.
Figure 6. Shows completed metal copings ready for porcelain
Pigure 5. Shows a silver-plateddie with die spacer applied.
application.
Impressions and Dies
Vita Zahnfabrik, Sackingen, Germany) to the shoulder area of the die. 5. Mix shoulder porcelain (Vita Shoulder Porcelain? Vita Zahnfabrik) with normal liquid medium. 6 . Seat the framework on the die making sure the framework seats completelyand begin the actual shoulder build-up by picking up a fluid mix of shoulder porcelain with a porcelain carver or brush. This mix of fluid porcelain is flowed onto the opaque base and directed first to the shoulder area with the point of the instrument or brush. The porcelain is carried up onto the opaqued metal a short distance above the shoulder so that the body porcelain will slightly overlap the marginal porcelain for color blend (Fig.8). 7. Overbuild the shoulder porcelain slightly to allow for shrinkage when condensed. Condense the porcelain. Remove the framework from the die and fire at the manufacturer’s recommended temperature under vacuum.
An impression must accurately record all prepared surfaces. The conventional method of impression making usually involves gingival retraction using chord packing into the sulcus. But, if the tissues are thin and friable, it is sometimes less traumatic to the gingival tissues to use the tube impression technique.15 Although conventional stone dies are adequate, it is the experience of some clinicians and technicians that silver plating the die will give a strong and accurate reproduction of the shoulder area with which the technician can work. A die spacer is recommended for the die before wax up of the metal substructure (Fig. 5).16
Metal Coping Design Much of the effectivenessof the restoration depends upon the design of the metal substructure. The following change ismade in the design of this substructure for this modifledPFM crown: the labiogingivalportion of the metal is flnished back to the gingivo-pulpal line angle with the metal against the axial wall being from 0.3 to 0.5 mrn thick (Fig. 6 ) .This allows for 0.2 to 0.3 mm of opaque and 0.7 to 1.Omm of shoulder porcelain.
TECHNIQUE FOR PORCELAIN APPLICATION 1. Complete the metal substructure, sandblast,
and place in the ultrasonic cleaner (distilled water) for 6 minutes. 2. Degas the framework, sandblast a second time, and place in the ultrasonic cleaner (distilled water) for 6 minutes. 3. Apply opaque porcelain and fire at the manufacturer’s recommended temperature (Fig. 7). 4. Apply a release agent (ModisolInsulating Penm
Figure 7. Opaque porcelain applied to the coping.
156
All-Porcelain Margin for Ceramometal Crowns
Figure 10. A completed restoration for the canine.
14. Check the fit of the porcelain margin. If neces-
sary, reapply release agent on the die and use a thin watery mix of shoulder porcelain to perfect the marginal fit (Fig. 9).Fire the porcelain again. 15. When completely satisfied with the porcelain, polish the exposed metal. Clean the internal surfaces of the metal with a 5 0 - ~aluminous oxide abrasive unit. Disinfect the crown before seating.
Figure 8. Shows application of the shoulder porcelain and the overbuilding of the shoulder porcelain.
8. Allow the porcelain to cool slowly and reseat carefully on the die. 9. Due to the small amount of shoulder porcelain shrinkage, a second application of porcelain at the margin area is usually necessary. Fire the porcelain again. 10. Refit the crown onto the die as before. 11. Follow the full contour buildup of the body and incisal porcelain following recommended firing temperatures. 12. Shape porcelain and make additions if necessary. 13. Finish porcelain margin using high magnifkation. Clean in ultrasonic cleaner (distilledwater) for 6 minutes.
Seating of Restoration At the seating appointment, the fit of the restoration is checked with special attention given to the margin adaptation, contour, and occlusion. The quality of the restoration must provide a n environment promoting long-term maintenance of periodontal health. The profile of the restoration as it emerges from the gingival margin is particularly important toward this goal. Custom staining is often required to give the best esthetic result” (Fig. 10).
CONCLUSION The all-porcelain labial margin is one of the options available to improve the cosmetic value of PFM restorations. Several techniques have been recommended for fabrication of these restorations. The preparation is crucial and requires a 70 to 90 degree shoulder that is at least 1.2mm in width. The shoulder must be smooth and even with no bevel. The direct MI-off technique is a useful method of achieving clinically acceptable allporcelain labial margins. Such restorations give excellent results.
REFERENCES 1. Chiche G , Radiguet J, Pinault A, Genini P. Improved esthetics for the ceramo-metal crown. Int J Periodont Res Dent 1986: 1:77-87.
Figure 9. Shows the h a l application of a thin wash of the shoulder porcelain.
157
JOUmAL OF E!XHE?1C DENTISTRY VOLUME 4.NUMBER 5 Septernber/October 1992
2. Goodacre CH, et al. The collarless metal-ceramic restoration with a facial butted margin. J Prosthet Dent 1977; 1. 37(5):517-52 3. Sozio RP,Riley EJ. A precision ceramic-metal restoration with afacial butted margin. J Prosthet Dent 1977:37:517. 4. Toogood GD, Archibald JF. Technique for establishing porcelain margins. J Prosthet Dent 1978;40:464. 5. FTlnce J. DonovanT. The esthetic metal-ceramic margin: a comparison of techniques. J Prosthet Dent 1983;50(6): 185-192. 6. Vryonis P.A simplified approach to the complete porcelain margin. J Prosthet Dent 1979;42:592. 7. LaHoste CH. The porcelain butt margin. Quintessence Dent Tech 1981;2:149. 8. Robinson MI. Porcelain margins without platinum foil. Quintessence Dent Tech 1982:6:251. 9. Zalldnd M. A labial porcelain butt-joint in ceramo-metal restorations. Quintessence Int 1984:15:117-120. 10. Ferguson R. Porcelain margin restorations: an update on techniques. Trends Techniq 1991;8:29-36.
158
11. Donovan T. Daftary F. Esthetic results with full restorations. J Am Dent Assoc 1987;(Special Issue);75E-81E. 12. Schillingburg HT, Hobo S,Fisher DW. Preparation design and margin distortion in porcelain fused-to-metal restorations. J Prosthet Dent 1973:29:276-284. 13. Keenan MP. Shillingburg HT, Duncanson MG, Wade CK. Effects of cast gold surface Mshing on plaque retention. J Prosthet Dent 1980;43(2):16&173. 14. Loe H.Reactions of marginal periodontal tissue to restorative procedures. Int Periodont Res Dent 1968;4:759-778. 15. Goldfogel M. Bomberg TJ. Bomberg SE. Tube impressions: an alternative technique for taking difficult crown and bridge impressions with minimal gingival trauma. Quintessence Int 1989;20(8):555-560. 16. Eames W. ONeal S,MonteiroJ, Miller C. Roan J, Choen K. Techniques to improve the seating of castings. J Am Dent Assoc 1978;96:432437. 17. Goldfogel M,Bomberg T. Custom characterization of the porcelain-fused-to-metal restoration. Quintessence Dent Tech 1987;11(3):181-185.
'
The elimination of the labiogingival metal collar of a porcelain-fused-to-metal (PFM) restoration is an attempt to achieve an improved esthetic result. In their expectation of a more cosmetic tooth restoration, patients may influence dentists to use the all-porcelain labial margin to avoid metal showing in the final restoration. Success of this type of restoration depends upon proper tooth preparation. The allporcelain margin requires a 1.2-mmwide labiogingivalshoulder of approximately 70 or 90 degrees wrapping into the interproximal area. Much of the effectiveness of the restoration depends upon the design of the metal substructure. The following change is made in the design of this substructure for this modified PFM crown: the labiogingival portion of the metal is Rnished back to the gingival-pulpal line angle with the metal against the axial wall being from 0.3mm to 0.5 mm thick. This allows for 0.2 to 0.3 mm of opaque and 0.7 to 1.0mm of shoulder porcelain. The direct liftoff technique is a useful method of achieving clinically acceptable all-porcelain margins. Such restorations may give excellent results.
P
erceived deficiencies at the labiogingival collar area of porcelain-fused-to-metal (PFM)crowns can usually be related to one of the following factors: Exposure of the metal margin: opaque show through in the cervical third: or overcontour of the cervical area of the crown (Figs. 1-3). Traditionally, a PFM restoration incorporates a narrow metal collar in the cosmetically critical area of the labiogingival area. The elimination of the labiogjngivalmetal collar is an attempt to achieve an improved esthetic result, thus addressing cosmetic disappointment that sometimes occurs. l There have been several techniques2-10proposed in an attempt to achieve this goal. These include various proposed finish lines, metal contlgurations, use of platinum or gold foil, refractory dies, direct lift-off, and various separating solutions. One of the most important considerations is preparation design. The preparation must meet the requirements of adequate reduction of tooth structure at the gingival area to provide sufficient space for the metal or ceramic material, provide retention and resistance, and have a smooth margin design with which the ceramist
can work. The shoulder with a bevel preparation has the advantage of excellent marginal integrity for PFM restorations. l2 The platinum foil technique, the oldest of the techniques, uses the foil to support the porcelain as it isbuilt up on the die and dried to maturity. Slumping of the porcelain and rolling of the porcelain edge is often the result of this technique. An additional disadvantage to this procedure is that the margin cannot be properly evaluated until the crown is completed and the foil removed.
*Assistant Professor: t Technician:$ Professor and Chairman: University of Colorado Health Sciences Center. School of Dentistry, Department of Restorative Dentistry. Denver, Colorado Address reprint requests to: Lnvis Harrison. D.M.D.. University of Colorado School of Dentistry, Department of Restorative Dentistry. 4200 East Nlnth Ave.. C284. Denver, CO 80262-0284 6 1992 Decker Perlodicds Inc.
PyeUre 1. PFM restoration with metal showing. 154
All-Porcelain Margin for Ceramometal Crowns
Figure 2. PFMrestorationwithopaque discoloration at gingival third.
Figure 4. A 10-year result for an all-porcelain labial margin
When porcelain manufacturers developed margin porcelains that fuse at temperatures 30 to 80°F lower than the parent porcelain, the foil-less direct liflprocess became popular.l0These newer margin porcelains resist pyroplastic flow and allow for direct lift-off from the die with minimal deformation. Though complete elimination of sintering shrinkage is theoretically impossible, a carefully controlled procedure can minimize shrinkage and yield clinicallyacceptable results (Fig.4). This article shows the steps used to make this a successful treatment procedure.
tissue are factors that influence the dentist in assessing the need for an all-porcelain labial margin. In addition, the patient's oral hygiene must be considered, since the tooth-crown junction of the all-porcelain labial margin is seldom as smooth as the metal-collar margin, and plaque accumulation may be a factor.I3
INDICATIONS Patients, in their expectation for a cosmetic tooth restoration, are influencing dentists to use the allporcelain labial margin to avoid metal showing in the finalrestoration. Lip-line, the thickness and color of the gingival margin, and the location of the free gingival
restoration for the lateral incisor.
Advantages and Disadvantages The advantages of this technique include improved esthetics for PFM crowns. With this, the preparation can be kept supragingival or just slightly apical to the free gingival margin in most cases. This small sulcular marginal depth is a periodontal advantage14and permits a more gentle impression technique. A major disadvantage and objection of this technique is that the loss of the metal margin may give a less optimal margin closure. Also, it is possible that fracture of the facial porcelain caused by lack of metal support may be increased.The direct life-off technique presents another potential disadvantage because of possible displacement during the porcelain shoulder build-up and pyroplastic deformation during firing. These disadvantages can be overcome with careful technique.
PreparationDesign
Figure 3. An overcontoured PFM restoration.
Success of this type of restoration depends upon proper tooth preparation. The all-porcelain labial margin requires a 1.2-mm wide labiogingival shoulder of approximately 70 or 90 degrees wrapping into the interproximal area. A chamfer margin or shoulder with abevelisusedforallothermarginareas.Thelabiogjngival margin will usually be placed near or slightlybelow the free gingivalmargin for most teeth. The shoulder should be even and smooth when viewed with magnifying loops.
Figure 6. Shows completed metal copings ready for porcelain
Pigure 5. Shows a silver-plateddie with die spacer applied.
application.
Impressions and Dies
Vita Zahnfabrik, Sackingen, Germany) to the shoulder area of the die. 5. Mix shoulder porcelain (Vita Shoulder Porcelain? Vita Zahnfabrik) with normal liquid medium. 6 . Seat the framework on the die making sure the framework seats completelyand begin the actual shoulder build-up by picking up a fluid mix of shoulder porcelain with a porcelain carver or brush. This mix of fluid porcelain is flowed onto the opaque base and directed first to the shoulder area with the point of the instrument or brush. The porcelain is carried up onto the opaqued metal a short distance above the shoulder so that the body porcelain will slightly overlap the marginal porcelain for color blend (Fig.8). 7. Overbuild the shoulder porcelain slightly to allow for shrinkage when condensed. Condense the porcelain. Remove the framework from the die and fire at the manufacturer’s recommended temperature under vacuum.
An impression must accurately record all prepared surfaces. The conventional method of impression making usually involves gingival retraction using chord packing into the sulcus. But, if the tissues are thin and friable, it is sometimes less traumatic to the gingival tissues to use the tube impression technique.15 Although conventional stone dies are adequate, it is the experience of some clinicians and technicians that silver plating the die will give a strong and accurate reproduction of the shoulder area with which the technician can work. A die spacer is recommended for the die before wax up of the metal substructure (Fig. 5).16
Metal Coping Design Much of the effectivenessof the restoration depends upon the design of the metal substructure. The following change ismade in the design of this substructure for this modifledPFM crown: the labiogingivalportion of the metal is flnished back to the gingivo-pulpal line angle with the metal against the axial wall being from 0.3 to 0.5 mrn thick (Fig. 6 ) .This allows for 0.2 to 0.3 mm of opaque and 0.7 to 1.Omm of shoulder porcelain.
TECHNIQUE FOR PORCELAIN APPLICATION 1. Complete the metal substructure, sandblast,
and place in the ultrasonic cleaner (distilled water) for 6 minutes. 2. Degas the framework, sandblast a second time, and place in the ultrasonic cleaner (distilled water) for 6 minutes. 3. Apply opaque porcelain and fire at the manufacturer’s recommended temperature (Fig. 7). 4. Apply a release agent (ModisolInsulating Penm
Figure 7. Opaque porcelain applied to the coping.
156
All-Porcelain Margin for Ceramometal Crowns
Figure 10. A completed restoration for the canine.
14. Check the fit of the porcelain margin. If neces-
sary, reapply release agent on the die and use a thin watery mix of shoulder porcelain to perfect the marginal fit (Fig. 9).Fire the porcelain again. 15. When completely satisfied with the porcelain, polish the exposed metal. Clean the internal surfaces of the metal with a 5 0 - ~aluminous oxide abrasive unit. Disinfect the crown before seating.
Figure 8. Shows application of the shoulder porcelain and the overbuilding of the shoulder porcelain.
8. Allow the porcelain to cool slowly and reseat carefully on the die. 9. Due to the small amount of shoulder porcelain shrinkage, a second application of porcelain at the margin area is usually necessary. Fire the porcelain again. 10. Refit the crown onto the die as before. 11. Follow the full contour buildup of the body and incisal porcelain following recommended firing temperatures. 12. Shape porcelain and make additions if necessary. 13. Finish porcelain margin using high magnifkation. Clean in ultrasonic cleaner (distilledwater) for 6 minutes.
Seating of Restoration At the seating appointment, the fit of the restoration is checked with special attention given to the margin adaptation, contour, and occlusion. The quality of the restoration must provide a n environment promoting long-term maintenance of periodontal health. The profile of the restoration as it emerges from the gingival margin is particularly important toward this goal. Custom staining is often required to give the best esthetic result” (Fig. 10).
CONCLUSION The all-porcelain labial margin is one of the options available to improve the cosmetic value of PFM restorations. Several techniques have been recommended for fabrication of these restorations. The preparation is crucial and requires a 70 to 90 degree shoulder that is at least 1.2mm in width. The shoulder must be smooth and even with no bevel. The direct MI-off technique is a useful method of achieving clinically acceptable allporcelain labial margins. Such restorations give excellent results.
REFERENCES 1. Chiche G , Radiguet J, Pinault A, Genini P. Improved esthetics for the ceramo-metal crown. Int J Periodont Res Dent 1986: 1:77-87.
Figure 9. Shows the h a l application of a thin wash of the shoulder porcelain.
157
JOUmAL OF E!XHE?1C DENTISTRY VOLUME 4.NUMBER 5 Septernber/October 1992
2. Goodacre CH, et al. The collarless metal-ceramic restoration with a facial butted margin. J Prosthet Dent 1977; 1. 37(5):517-52 3. Sozio RP,Riley EJ. A precision ceramic-metal restoration with afacial butted margin. J Prosthet Dent 1977:37:517. 4. Toogood GD, Archibald JF. Technique for establishing porcelain margins. J Prosthet Dent 1978;40:464. 5. FTlnce J. DonovanT. The esthetic metal-ceramic margin: a comparison of techniques. J Prosthet Dent 1983;50(6): 185-192. 6. Vryonis P.A simplified approach to the complete porcelain margin. J Prosthet Dent 1979;42:592. 7. LaHoste CH. The porcelain butt margin. Quintessence Dent Tech 1981;2:149. 8. Robinson MI. Porcelain margins without platinum foil. Quintessence Dent Tech 1982:6:251. 9. Zalldnd M. A labial porcelain butt-joint in ceramo-metal restorations. Quintessence Int 1984:15:117-120. 10. Ferguson R. Porcelain margin restorations: an update on techniques. Trends Techniq 1991;8:29-36.
158
11. Donovan T. Daftary F. Esthetic results with full restorations. J Am Dent Assoc 1987;(Special Issue);75E-81E. 12. Schillingburg HT, Hobo S,Fisher DW. Preparation design and margin distortion in porcelain fused-to-metal restorations. J Prosthet Dent 1973:29:276-284. 13. Keenan MP. Shillingburg HT, Duncanson MG, Wade CK. Effects of cast gold surface Mshing on plaque retention. J Prosthet Dent 1980;43(2):16&173. 14. Loe H.Reactions of marginal periodontal tissue to restorative procedures. Int Periodont Res Dent 1968;4:759-778. 15. Goldfogel M. Bomberg TJ. Bomberg SE. Tube impressions: an alternative technique for taking difficult crown and bridge impressions with minimal gingival trauma. Quintessence Int 1989;20(8):555-560. 16. Eames W. ONeal S,MonteiroJ, Miller C. Roan J, Choen K. Techniques to improve the seating of castings. J Am Dent Assoc 1978;96:432437. 17. Goldfogel M,Bomberg T. Custom characterization of the porcelain-fused-to-metal restoration. Quintessence Dent Tech 1987;11(3):181-185.
