4/13/2014 A Technique for Repair of a Fractured Porcelain-Fused-to-Metal Bridge

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A Technique for Repair of a Fractured Porcelain-Fused-to-Metal

Bridge

Written by Gregori M. Kurtzman, DDS, and Allen L. Schneider, DDS

Saturday, 31 December 2005 19:00

Fracture of the overlaying porcelain on a porcelain-fused-to-metal (PFM) prosthesis can be a challenging problem. Ideally, replacing

the PFM prosthesis is the best treatment, but this may not be financially within the patient’s means.1 This becomes more costly with

long-span prostheses. Repair of the damaged prosthesis may be the next best treatment and allows further function of the

prosthesis until a more permanent solution can be rendered.

Figure 1. The patientpresented with a fracture ofthe cervical porcelain on amultiunit PFM removableprosthesis.(All photos provided by Dr.Allen L. Schneider.)

Figure 2. Removableportion of the PFMprosthesis has beenremoved intraorally, showingthe fixed metal copings onthe abutment teeth used toretain the removable portion.

Loss of a portion of the porcelain from the prosthesis creates an aesthetic issue that may be corrected at chairside using adhesive

materials.2 Surface damage to the PFM may be broken into 2 categories, depending on which type of material is exposed. The first

category is porcelain chipping. This is identified by a piece of missing porcelain with no exposure of the underlying metal

substructure. The second category is porcelain debonding, where the porcelain fracture has exposed an area of metal substructure

(Figures 1 and 2). The category of damage determines how the surface to be repaired is treated to increase retention of the

overlaying material.3

PORCELAIN CHIPPING

This type of repair requires bonding to the remaining porcelain and is more difficult to achieve if the area comes into occlusal contact.

Small chips at the cervical area are easier to repair and less likely to debond due to lower loading forces being placed on this area

during mastication. When the chip involves the incisal edge, preparation extending onto the lingual surface will provide more bulk for

the repair in the area where mastication forces work to debond it. These can prove challenging, as incisal chips may have occurred

due to the occlusal scheme and excursive contacts.

Repairs when the damage is confined within porcelain are initiated by roughening with a coarse diamond to create some

mechanical retention.4 A silane agent has been recommended to activate the porcelain surface and increase bondability between

the porcelain and adhesive.

PORCELAIN DEBONDING

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4/13/2014 A Technique for Repair of a Fractured Porcelain-Fused-to-Metal Bridge

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Figure 3. Exposed metal

has been roughened with adiamond in a high-speedhandpiece to increasemechanical retention.

Figure 4. Further

mechanical retention isachieved by sandblasting theexposed metal andsurrounding porcelainmargins.

These types of repairs require bonding to 2 different surfaces—metal and porcelain. As with porcelain chipping, repair is initiated by

roughening both the metal and porcelain surfaces. A coarse diamond is moved over both the porcelain and metal to receive the

repair (Figure 3). A carbide bur may be used to create small, retentive dimples in the metal. If necessary, penetration of the metal to

the underlying tooth structure may be done to increase retention. Application of aluminum oxide in an air-abrasion micro-etcher will

create micro retention to augment the macro retention placed by the diamonds and carbides (Figure 4).

Figure 5. Metal Primer II is

applied to the exposed metalto increase bond strength ofthe resin used to repair themissing porcelain.

Exposed metal is treated with Metal Primer II (GC America), applying 2 coats and allowing each coat to dry for a few seconds (Figure

5). Metal Primer II contains a special monomer (MEPS thiophosphoric methacrylate), which promotes bonding by penetrating the

metal alloy and co-polymerizing with the overlying resin to produce both a mechanical and chemical resin-to-metal bond. The

improved tensile bond strength from alkane thiol molecule absorption significantly enhances the normal mechanical bond of the

overlying resin. This primer can be used with either nonprecious or precious alloys, eliminating the need to tin plate exposed metal

prior to bonding.

Figure 6. Ceramic Primer isapplied to the porcelainmargins surrounding theexposed metal to increaseresin bond strength.

Next, Ceramic Primer (GC America) is mixed (a drop from bottles A and B mixed together prior to application) and applied to the

porcelain margins to receive bonding (Figure 6). This is allowed to dry for several seconds prior to the next step in the repair process.

The Ceramic Primer activates the porcelain surface, silanating the porcelain and depositing methyl-methacrylate, which will

increase bond strength to the ceramic surface. Contact of Ceramic Primer with metal will not hamper the bond to the pretreated

metal surface.

Figure 7. A thin layer of

flowable composite resin is

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4/13/2014 A Technique for Repair of a Fractured Porcelain-Fused-to-Metal Bridge

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applied over the exposedmetal and porcelain margins,then cured.

A flowable composite resin (Unifil Flow, GC America) is flowed in a thin layer over the treated metal/ceramic surfaces and cured with

a hand-held curing light (Figure 7). Use of a flowable resin allows locking into the mechanical retention previously created and will

permit some masking of the metal’s gray color. Use of a white opaque shade rather than a tooth color may be more beneficial to

masking. Because the layer of flowable is very thin, the brightness of the white opaque flowable will not be difficult to neutralize with

the overlying composite.

Figure 8. A microhybridcomposite resin isincrementally placed to coverthe exposed metal andporcelain margins.

Figure 9. Compositeinstruments are used toachieve a normalcontour.

Next, a microhybrid composite (Gradia Direct, GC America) in a shade to match the adjacent porcelain is applied and sculpted to full

contour of the desired final result (Figures 8 and 9). Because the layer of microhybrid will be less than 2 mm in thickness, it can be

placed in bulk; incremental layering is not necessary. Thorough curing with a hand-held curing light is performed.

Figure 10. Following finalshaping with rotaryinstruments, flowable resin isapplied to the repairedsurface.

Figure 11. Completedrepair of the fracturedremovable prosthesis.

Figure 12. Repairedprosthesis intraorally.

Finishing is accomplished using diamonds and finishing carbides in a high-speed handpiece. A final coat of flowable composite is

applied over the repair to provide a smooth, aesthetic surface (Figures 10 to 12). Occlusion should be checked, specifically contact

with the incisal edge during both centric and lateral excursions. All occlusal contacts should be removed from the repair material and

kept on sound crown surface.

DISCUSSION

Damage to PFM prostheses may be multicausal.5 Porcelain chipping may be the result of contact with a harder substance loaded at

an angle to the porcelain surface (shearing forces), causing micro cracks to spread, and leading to visible loss of porcelain.

Porcelain debonding also may result from shearing loads. Another possible cause of chipping and debonding in fixed bridges is

torque placed on the prosthesis under function. Since porcelain is a stiff material, these torquing forces twist the cast framework

microscopically, leading to failure either within the porcelain (through micro cracks) or at the porcelain-to-metal interface (due to their

dissimilar properties). A repair made from composite resin, which has more flexural strength than porcelain, may tolerate these

4/13/2014 A Technique for Repair of a Fractured Porcelain-Fused-to-Metal Bridge

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micro torsional strains and remain in function.

Occlusion plays a part in how successful the repair will be and how long it will last. Centric contacts should be kept off the repair

material or its junction with the porcelain or metal when possible. Care should be taken to adjust lateral excursion contacts so that

shear load can be minimized on the resin repair and a decrease in “pop-off” can be achieved.

CONCLUSION

When failure occurs in the overlying porcelain of a PFM prosthesis, replacement of the prosthesis may not be financially possible.

Repair of the prosthesis will permit improved aesthetics and functional use until a more permanent solution may be possible.Note:

The clinical case described in this article was performed by Dr. Schneider.

References

1. Rosen H. Chairside repair of ceramo-metallic restorations. J Can Dent Assoc. 1990;56:1029-1033.

2. Galiatsatos AA. An indirect repair technique for fractured metal-ceramic restorations: a clinical report. J Prosthet Dent.

2005;93:321-333.

3. Yanikoglu N. The repair methods for fractured metal-porcelain restorations: a review of the literature. Eur J Prosthodont Restor

Dent. 2004;12:161-165.

4. Burke FJ, Grey NJ. Repair of fractured porcelain units: alternative approaches. Br Dent J. 1994;176:251-256.

5. Ahmad I. Salvaging fractured porcelain crowns with a direct composite repair technique. Pract Proced Aesthet Dent. 2002;14:233-

238.

Dr. Kurtzman is in private practice in Silver Spring, Md, and is an assistant clinical professor at the University of Maryland-Baltimore

School of Dentistry, Department of Endodontics, Prosthetics, and Operative Dentistry. He has lectured both nationally and

internationally on the topics of restorative dentistry, endodontics, dental implant surgery, and prosthetics, and has had numerous

journal articles published in peer-reviewed publications. He can be contacted at dr_kurtzman@maryland-implants.com.

Dr. Schneider is in private practice in Springfield, Va, and is an adjunct instructor of the Restorative Department, Tufts University

School of Dental Medicine. He lectures nationally and internationally and has had numerous articles published in peer-reviewed

publications. He is a consultant to the VA in Martinsburg, WVa, as well as various major manufacturers in the field of restorative and

implant dentistry. He can be reached at aldds@aol.com.

Disclosure: Dr. Schneider is a paid lecturer for GC America.

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