Koizumi et al.

Asian Pac J Dent 2012; 12: 7-10.

Application of a metal bonding system in fabrication of acollarless composite veneered fixed partial denture: A case report
Hiroyasu Koizumi, DDS, PhD,a,b Mariko Nishimaki, DDS,a Kiyoshi Nagano, PhD,c andHideo Matsumura, DDS, PhDa,bab

Department of Fixed Prosthodontics, Division of Advanced Dental Treatment, Dental Research
cCenter, Nihon University School of Dentistry, Tokyo, and Nagasaki University Hospital, Nagasaki,Japan
This case report describes application of a metal bonding system in fabrication of a composite resin veneered
fixed partial denture (FPD) with reduced retentive structure. A four-unit framework was fabricated with a silverpalladium-copper-gold alloy (Castwell M.C.12). The surface to be veneered was air-abraded with alumina,
followed by priming with a metal adhesive agent (V-Primer). The framework was then veneered with alight-polymerized composite material (Cesead). The completed FPD was seated with a glass ionomer luting
agent (HY-Bond Glass Ionomer). After an observation period of five years and two months, the FPD wasfunctioning satisfactorily. The technique described here is applicable in fabrication of composite veneered
restorations for vital abutment teeth. (Asian Pac J Dent 2012; 12: 7-10.)
Key Words: adhesive, primer, silver-palladium-copper-gold alloy, thione

Introduction
Silver-palladium-copper-gold alloy (Ag-Pd-Cu-Au alloy) is used in prosthodontic practice due to its excellent
handling properties as well as age-hardenability.

The alloy is applied to single restorations, fixed partial

dentures (FPDs), and removable denture frameworks. One of the problems associated with restorations made ofAg-Pd-Cu-Au alloy, however, has been insufficient bonding ability with indirect composite materials. Several
metal adhesive agents are currently available to alleviate the problem.

Although laboratory evaluations

demonstrated improved bond strength to noble metal alloys with the use of the metal adhesive systems,1-5 limited
information is available about bonding techniques between the framework and veneering composite.6 This
article presents an adhesive veneering procedure for the Ag-Pd-Cu-Au alloy framework of a maxillary anterior
FPD with a light-polymerized composite material.

Clinical ReportA 54-year-old male patient was seen with esthetic and functional disturbances as a result of a missing
maxillary right lateral incisor.

Several treatment options were proposed: 1) single-tooth implant; 2) FPD

veneered with composite resin; 3) porcelain-fused-to-metal FPD; or 4) a removable partial denture. The patientchose the second of the proposed prostheses. The laboratory and clinical procedures were then explained indetail and consent was obtained from the patient.
Prior to fabrication of the FPD, endodontic treatment and dowel core seating were completed for the central
incisors (Figs. 1-4). The dowel cores were made of a Ag-Pd-Cu-Au alloy (Castwell M.C. 12; GC Corp., Tokyo,Japan) and seated with a glass ionomer luting cement (Fuji Ionomer I; GC Corp.). Under local anesthesia for theright canine, a vital tooth, reduction was performed for the three abutment teeth by means of diamond rotary
cutting instruments with water coolant (Fig. 4). An impression of the entire maxilla was made with silicone
elastomeric materials (Exafine Putty and Injection; GC Corp.) using a stock tray (Fig. 5).

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Asian Pac J Dent 2012; 12: 7-10.

Fig. 1. Preparation for dowel coresFig. 2. Impression for dowel coresFig. 3. Provisional FPD

Fig. 4. Reduced abutments

Fig. 5. Impression for the FPD

Fig. 6. Labial view of the wax patternFig. 7. Lingual view of the wax patternFig. 8. Labial view of cut-back surface Fig. 9. Lingual view of cut-back area

Fig. 10. Retentive beads adhesiveFig. 11. Application of the adhesiveFig. 12. Application of retentive beads

Fig. 13. Polymerization with a UV-unit

Fig. 14. Cast metal framework

Fig. 15. Reduction of framework

Die stone material (Fuji Rock; GC Corp.) was poured into the impression, and a working cast was prepared.
The stone cast was mounted in an articulator with an opposing cast. The pattern of the retainer and pontic wasfabricated using an inlay wax material (Inlay Wax; GC Corp.: Figs. 6 and 7). After cutting-back the labialsurface (Figs. 8 and 9), a thin layer of an adhesive for retentive beads (Particle Bond; Toho Dental Products,Saitama, Japan) was applied to the wax surface (Figs. 10-11). Retentive beads 200 µm in average diameter

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Asian Pac J Dent 2012; 12: 7-10.

(Retention Beads II; GC Corp.) were next sprinkled on the adhesive layer (Fig. 12). The Particle Bond adhesive
was light-polymerized with a UV-light polymerization unit for 20 s (Twinkle Q; Toho Dental Products: Fig. 13).
The wax pattern was invested in a cristobalite mold material (Cristobalite Micro; GC Corp.) and Ag-Pd-Cu-Au
alloy (Castwell M.C. 12; GC Corp.) was cast in the mold with a centrifugal casting apparatus. A four-unit FPDframework consisting of three retainers and a pontic was fabricated (Fig. 14). The labial metal collar andretentive structures were reduced in part with a rotary cutting instruments (Fig. 15). The surface to be veneered
was air-abraded with 50- to 70-µm grain sized alumina (Hi-Aluminas; Shofu Inc., Kyoto, Japan: Fig. 16) using
an airborne particle abrader (Micro Blaster MB102; Comco Inc., Burbank, CA, USA), and treated with a single
liquid primer designed for noble metal alloys (V-Primer; Sun Medical Co., Ltd., Moriyama, Japan). The buccal
surface of the framework was veneered with an indirect composite material (Cesead; Kuraray Co., Ltd., Osaka,Japan) according to the specification of the manufacturer (Figs. 17 and 18). A successional material of theCesead composite is currently available as Epricord (Kuraray Medical Inc., Tokyo, Japan).

Fig. 16. Air-abrasion with alumina

Fig. 19. Seated FPD

Fig. 17. Completed FPD

Fig. 18. Collarless structure

Fig. 20. Occlusal view

On the next appointment, the completed FPD was tried-in, and seated with a glass ionomer luting cement(HY-Bond Glass Ionomer; Shofu Inc.: Figs. 19 and 20). The patient entered a maintenance program and wasexamined twice per year. After an observation period of five years and two months, the FPD was functioning
satisfactorily.

Discussion
As shown in the laboratory procedure of the present case, indirect composite material is bonded to theframework both mechanically and chemically. Koizumi et al.7 compared the undercuts generated with the use of
two retentive beads adhesives. It was found that the ratio of diameter of bonded area and retentive bead at anidentical cross section was 0.65 for the Particle Bond adhesive and 0.49 for the GC Adhesive. The authors
judged the undercut generated with the use of two adhesives was acceptable in fabrication of composite veneeredrestorations. The clinical course of the current case supports their experimental conclusion.

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Asian Pac J Dent 2012; 12: 7-10.

Retentive structure in the present case was reduced considerably (Fig. 15). Reduction of retentive structure iseffective for color reproducibility of tooth-colored materials especially for vital abutment teeth. During theobservation period, retention of the composite material was not negatively affected by reduction of the retentive
beads. This favorable clinical course may be derived from combined application of mechanical and chemicalbonding systems. According to clinical studies, restorations veneered with the Cesead composite exhibited
excellent performances8,9 especially for the chemically bonded cases.8 The result of the current case agrees withthe previous report,8 in which usefulness of a tin-plating chemical bonding system was reported for bonding
between the Cesead composite and the Castwell Ag-Pd-Cu-Au alloy.
The remaining problem to be solved is bonding between the composite material and dentin at the labial
cervical area.

The authors consider that a resin based luting agent should be used for seating collarless

restorations together with appropriate priming agents.
Acknowledgments
This work is supported in part by Grant-in-Aid for Scientific Research (C23592871, 2011) from the Japan Society for the Promotion ofScience (JSPS) and Sato Fund (2011) from Nihon University School of Dentistry.

References
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2. 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.
3. Mukai M, Fukui H, Hasegawa J. Relationship between sandblasting and composite resin-alloy bond strength by a silica
coating. J Prosthet Dent 1995; 74: 151-5.
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8. Matsumura H, Nakamura M, Tanoue N, Atsuta M. Clinical evaluation of an urethane tetramethacrylate-based composite
material as a prosthetic veneering agent. J Oral Rehabil 27: 846-52, 2000.
9. Shimizu H, Takahashi Y. A resin-bonded overcasting with highly filled composite resin to salvage a broken metal-ceramic
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Correspondence to:Dr. Hiroyasu Koizumi
Department of Fixed Prosthodontics, Nihon University School of Dentistry
1-8-13 Kanda-Surugadai, Chiyoda-ku, Tokyo 101-8310, Japan
Fax: +81-3-3219-8351 E-mail: koizumi@dent.nihon-u.ac.jp
Copyright ©2011 by the Asian Pacific Journal of Dentistry.

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Accepted December 27, 2011.
Online ISSN 2185-3487, Print ISSN 2185-3479