Tanoue et al.

Int Chin J Dent 2006; 6: 17-20.

Repair of an anterior fixed partial denture with a resin-bondedovercasting and a dual functional metal priming agent: A clinicalreportNaomi Tanoue, DDS, PhD,a Toshiaki Ogata, DT, PhD,b Hiroyasu Koizumi, DDS, PhD,c,dand Hideo Matsumura, DDS, PhDc,dab

Department of Specialized Dentistry, and Dental Laboratory Center, Nagasaki University Hospital ofcdMedicine and Dentistry, Nagasaki, Department of Crown and Bridge Prosthodontics, and Division ofAdvanced Dental Treatment, Dental Research Center, Nihon University School of Dentistry, Tokyo,Japan
This clinical report describes the repair of a fixed partial denture (FPD) with fracture of porcelain using anovercasting. Porcelain veneer of a maxillary six-unit FPD made of cobalt-chromium was fractured. Veneered
areas were cut with a diamond rotary instrument, and an overcasting restoration was made with gold alloy andfeldspathic porcelain. The two-unit overcasting restoration was seated with a combination of the Alloy Primer
conditioning agent and Super-Bond adhesive resin. The repaired FPD, overcasting, and abutments have beenfunctioning satisfactorily for more than two years and two months. (Int Chin J Dent 2006; 6: 17-20.)
Key Words: adhesive, fixed partial denture, overcasting, primer, repair.

Introduction
Fracture of tooth-colored veneers in a fixed partial denture (FPD) is troublesome, especially in the anteriordentition. A technique to repair broken metal-ceramic restorations was described by Johnston et al.1 Various
methods of making an overcasting were thereafter reported.2-14 Due to insufficient retentive structure similar tothree-quarter crown restorations or saddle-shaped onlays, a strong bond between the overcasting and theundercasting is required. Several metal priming agents capable of improving the bonding of resin to castingalloys have been introduced.15-18 This article reports the repair and bonding techniques of a six-unit FPD with aporcelain-fused-to-metal (PFM) overcasting and a dual functional metal adhesive system.

Clinical Report
Examination and treatment planning
A 63-year-old female patient presented with the chief complaint of esthetic dissatisfaction and masticatory
disturbance resulting from fracture of the porcelain veneer of the right maxillary incisors. The central incisor
was an intermediate retainer and the lateral incisor was a pontic of a six-unit metal-ceramic FPD (Fig. 1). The
fracture was suspected to be caused by insufficient bonding between the metal substructure and sinteredporcelain. There was remarkable discoloration of the metal surface and staining of the porcelain. Also, the two
incisors on the left had already been repaired with a two-unit overcasting restoration. Overall, bonding between
the porcelain and metal framework appeared to be unsatisfactory. Complete replacement of the prosthesis wasrecommended to avoid consecutive fracture of canine retainers. The patient, however, preferred conservative
repair instead of replacement of the FPD. A second-time repair with an overcasting was therefore suggested andthe patient consented to treatment with the overcasting technique.
Clinical and laboratory procedure
The fractured porcelain veneer was removed with a high-speed diamond rotary cutting instrument. Area ofpreparation included the facial, incisal, and lingual surfaces of the casting (Fig. 2). A retentive hole wasprepared at the edge of the central incisor abutment (Fig. 3).

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Int Chin J Dent 2006; 6: 17-20.

Fig. 1. Fractured porcelain veneer.

Fig. 2. Removal of porcelain.

Fig. 3. Retentive hole in the incisor.

Fig. 4. Working cast.

Fig. 5. Waxing of overcasting.

Fig. 6. Gold alloy framework.

Fig. 7. Completed overcasting.

Fig. 8. Air-abrasion with alumina.

Fig. 9. Application of Alloy Primer.

Fig. 10. Air-abraded undercasting.

Fig. 11. Application of Alloy Primer.

Fig. 12. Removing flew-outluting agent.

Figs. 13 and 14. Facial and incisal views of the seated overcasting.

Fig. 15. The repaired FPD after
one year and four months.

After blocking out the embrasures and sub-pontic spaces with a cavity sealer, an impression of the entire
maxilla was taken with a silicone elastomeric material (Exafine, Putty and Injection, GC Corp., Tokyo, Japan).
A transitional acrylic resin restoration was seated with tooth-colored self-curing resin.
The impression was primarily poured with die stone and then with lab stone, and a working cast withremovable dies stabilized with dowel pins was prepared. Embrasures and sub-pontic spaces were modified with18

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Int Chin J Dent 2006; 6: 17-20.

a die stone material (Fig. 4). A wax pattern was fabricated and the framework was cast with a gold alloy formetal-ceramic restorations (Degudent U, Degussa AG, Frankfurt, Germany) (Figs. 5 and 6).

Feldspathic

porcelain (VMK 68, Vita Zahnfabrik GmbH, Bad Säckingen, Germany) was applied to the casting (Fig. 7).
Seating the restoration
At the second appointment, the overcasting was tried-in, and the inner surface to be bonded was air-abradedwith 70 µm alumina (Hi-Aluminas, Shofu Inc., Kyoto, Japan) by means of an airborne particle abrader (Jet-BlastII, J. Morita Corp., Suita, Japan) (Fig. 8). A single liquid metal priming agent (Alloy Primer, Kuraray MedicalInc., Tokyo, Japan) was applied to the overcasting (Fig. 9).

The Alloy Primer material contained both6-(4-vinylbenzyl-n-propyl) amino-1,3,5-triazine-2,4-dithiol, or dithione tautomer (VTD) and 10-methacryloyloxydecyl dihydrogen phosphate (MDP) in acetone. The abutment and pontic of the undercasting made of acobalt-chromium (Co-Cr) alloy (Biocast, Rx Generic Corp., Wallingford, CT, USA) were isolated with a rubberdam. The adjacent teeth were protected against particle abrasion with a polymer-solvent coating agent (ProtectVarnish, Kuraray Medical Inc.). The intraoral metal surface was also air-abraded with alumina with a hand-held
air-abrader (Airbrush, Paasche Airbrush Co., Chicago, IL, USA) (Fig. 10). The Alloy Primer material wasapplied to the undercasting (Fig. 11). The overcasting was then seated with a tri-n-butylborane initiated adhesiveresin (Super-Bond C&B, Sun Medical Co., Ltd., Moriyama, Japan) using a brush-dip technique (Figs. 12-14).
Clinical course
The patient was satisfied with the restoration and entered into a maintenance program. Fig. 15 shows thefacial view of the overcasting restoration after one year and four months. During an observation period of twoyears and two months, the repaired FPD functioned satisfactorily.

Discussion
An overcasting restoration is usually applied to repair a multi-unit FPD.

This technique, however, iscontraindicated in cases of failure of bond between porcelain and metal substructure. Considerable staining of
the fractured veneer and metal framework shown in Fig. 1 suggests that bonding between the Co-Cr alloy
framework and sintered porcelain material appeared to be insufficient for this FPD. This six-unit FPD, however,
was repaired twice with overcasting restorations.

One of the reasons is that the canine metal-ceramic

restorations had been successively and successfully functioning as abutments for both the FPD and removablepartial denture. In addition, the primarily seated overcasting on the left two incisors had been functioning for
more than three years without detachment or fracture. The patient, therefore, preferred a second repair withovercasting rather than dislodging and re-fabrication of the FPD.
Repair of intermediate porcelain fracture is usually accomplished with a saddle-form overcasting. This typeof casting is less retentive and more difficult to stabilize than a full cast restoration or three-quarter restoration.
Additional preparation of a retentive hole in the current case helped to improve retention of theovercasting.1-3,5,6,9
A dual functional metal priming agent (Alloy Primer) that contains both the VTD thione monomer and theMDP hydrophobic phosphate monomer was used for seating the overcasting.

According to the literature

concerning adhesive bonding of dental casting alloys, VTD was effective for bonding noble metal alloys,17,18
whereas the MDP was effective for bonding base metal alloys.16 Considering the fact that adherend materials in
the current case are Co-Cr alloy and gold alloy, it is reasonable to consider that MDP in the Alloy Primer agent

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is effective for bonding the Co-Cr undercasting, and VTD is substantially effective for bonding the gold alloy
overcasting.
Acknowledgment
This clinical report associated with survival analysis of resin-bonded castings and bonding of dental casting alloys was
supported in part by a Grant-in-Aid for Scientific Research C 17592030 (2005-2007) from the Japan Society for thePromotion of Science (JSPS), by Uemura Fund (2005), Nihon University School of Dentistry, and by the Nihon University
Multidisciplinary Research Grant for 2004 (#04-017).

References
1. Johnston JF, Dykema RW, Cunningham DM. The use and construction of gold crowns with a fused porcelain veneer -Aprogress report. J Prosthet Dent 1956; 6: 811-21.
2. Miller TH, Thayer KE. Intraoral repair of fixed partial dentures. J Prosthet Dent 1971; 25: 382-8.
3. Bakland LK. Replacing porcelain veneers in the mouth. Quintessence Int 1972; 3: 45-9.
4. Welsh SL, Schwab JT. Repair technique for porcelain-fused-to-metal restorations. J Prosthet Dent 1977; 38: 61-5.
5. Dent RJ. Repair of porcelain-fused-to-metal restorations. J Prosthet Dent 1979; 41: 661-4.
6. Mucko K. Repair of a damaged ceramo-metallic anterior fixed partial denture. Quintessence Int 1983; 14: 513-8.
7. Gelbman J, Biber CL. Salvaging the broken porcelain fused to metal partial prosthesis. Clin Prev Dent 1986; 8: 22-3.
8. Finger IM. Salvaging the restoration. Dent Clin North Am 1987; 31: 487-503.
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Dent 1989; 62: 390-2.
10. Bertolotti RL, Paganetti C. Adhesion monomers utilized for fixed partial denture (porcelain/metal) repair. Quintessence Int1990; 21: 579-82.
11. Wood M, Litkowski LJ, Thompson VP, Church T. Repair of porcelain/metal restoration with resin bonded overcasting. JEsthet Dent 1992; 4: 110-3.
12. Matsumura H, Atsuta M. Repair of an eight-unit fixed partial denture with a resin-bonded overcasting: A clinical report. JProsthet Dent 1996; 75: 594-6.
13. Robbins JW. Intraoral repair of the fractured porcelain restoration. Oper Dent 1998; 23: 203-7.
14. Mancuso A. Salvaging a porcelain/metal bridge with a bonded porcelain-fused-to-metal overcasting. Gen Dent 2003; 51:456-7.
15. Tanaka T, Fujiyama E, Shimizu H, Takaki A, Atsuta M. Surface treatment of nonprecious alloys for adhesion-fixed partialdentures. J Prosthet Dent 1986; 55: 456-62.
16. Matsumura H, Tanaka T, Taira Y, Atsuta M. Bonding of a cobalt-chromium alloy with acidic primers and tri-n-butylboraneinitiated luting agents. J Prosthet Dent 1996; 76: 194-9.
17. Atsuta M, Matsumura H, Tanaka T. Bonding fixed prosthodontic composite resin and precious metal alloys with the use of avinyl-thiol primer and an adhesive opaque resin. J Prosthet Dent 1992; 67: 296-300.
18. Matsumura H, Kamada K, Tanoue N, Atsuta M. Effect of thione primers on bonding of noble metal alloys with an adhesive
resin. J Dent 2000; 28: 287-93.

Correspondence to:
Dr. Naomi Tanoue
Esthetic Dentistry, Department of Specialized Dentistry
Nagasaki University Hospital of Medicine and Dentistry
1-7-1, Sakamoto, Nagasaki 852-8588, Japan
Fax: +81-95-849-7689 E-mail: t-naomi@net.nagasaki-u.ac.jp
Received December 22, 2005. Revised January 13, 2006. Accepted January 20, 2006.
Copyright ©2006 by the International Chinese Journal of Dentistry.

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