Shimizu et al.

Int Chin J Dent 2006; 6: 61-64.

The use of a resin-bonded overcasting restoration adjacent to anexisting metal ceramic fixed partial denture in maxillary anterior
teeth: A clinical report
Hiroshi Shimizu, DDS, PhD, and Yutaka Takahashi, DDS, PhD
Division of Removable Prosthodontics, Department of Oral Rehabilitation, Fukuoka Dental College,Fukuoka, Japan
A resin-bonded silver-palladium-copper-gold alloy overcasting restoration was incorporated with an existingmaxillary anterior adjacent metal ceramic gold alloy fixed partial denture using a metal conditioner (AlloyPrimer) and an adhesive resin (Super-Bond C&B Ivory). The resin-bonded overcasting restoration had beenfunctioning satisfactorily for more than 5.5 years for the 49-year-old female patient. However, one of theretainers, which was bonded to the palatal surface of the metal ceramic restoration of the adjacent fixed partial
denture, lost retention after six years. The resin-bonded overcasting restoration and the adjacent denture werecompletely removed and then replaced by a new large fixed partial denture with conventional metal ceramic
restorations. This case report including a six-year clinical follow-up indicated that mobile abutments and amaxillary anterior location may be negative factors for resin-bonded prostheses.
(Int Chin J Dent 2006; 6: 61-64.)
Key Words: adhesive resin, metal ceramic fixed partial denture, conditioner, overcasting, silver-palladium alloy.

Introduction
When the tooth next to an existing prosthesis is lost, the prosthesis must be removed and a new larger one that
includes the missing tooth must be fabricated. Although this conventional modality is reliable, it requires a long
treatment period, and the cost is high. Therefore, patients do not always wish to choose such a treatment option.
The overcasting technique1-5 is one of the treatment modalities offering a solution in these particular situations.
The use of resin-bonded prostheses has recently become a well-accepted clinical technique. Dental bonding
techniques have long been restricted to the tooth hard tissue (enamel and dentin) but the development of metal
conditioners and clinical techniques expanded their applications. A time-saving procedure, enabling a fixed
splint to be made without removing the adjacent full cast crowns with the particular abutment preparation of themetal surfaces, was reported.6 The present clinical report describes the fabrication and 6-year clinical follow-up
of a resin-bonded overcasting restoration incorporated with an existing adjacent metal ceramic fixed partial
denture using a metal conditioner and an adhesive resin.

Clinical Report
A 49-year-old woman was seen with the chief complaint of poor esthetics resulting from a missing rightmaxillary lateral incisor (Fig. 1). The right maxillary canine was vital and almost intact except for a labial
composite restoration. The right maxillary central incisor was endodontically treated and served as one of theabutment teeth of the existing adjacent metal ceramic fixed partial denture (FPD). Examination revealed a slightmobility of the two abutments of the FPD, whereas the bone support around the canine was clinically sufficient
to receive the applied occlusal force. The patient did not want a single-tooth implant with a single-tooth
removable partial denture, and preferred the fixed prosthetic treatment. In addition, she strongly hoped that itwould not be necessary to remove the existing FPD, mainly due to the discomfort of removal as well as for
economic reasons. Therefore, the addition of a resin-bonded overcasting restoration to replace the missing toothwith minimal tooth reduction of the right maxillary canine and particular abutment preparation to the palatal

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metal surface of the right maxillary central incisor were proposed, and she chose this treatment option.

1

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5

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Fig. 1.
Fig. 2.
Fig. 3.
Fig. 4.
Fig. 5.
Fig. 6.
Fig. 7.

Missing right maxillary lateral incisor.
Preparations of the central incisor and canine.
Master cast.
Intaglio of the resin-bonded overcasting restoration.
Resin-bonded overcasting restoration blends well.
Occlusal view of the resin-bonded overcasting restoration.
Debonding of the retainer of the central incisor after six years.

Partial reduction was limited to the palatal and proximal surfaces. Vertical grooves at the proximal surfaces
and a pinhole in one of the palatal rest seats were sunk for mechanical retention (Fig. 2). An impression wasmade with a combined agar/alginate hydrocolloid impression material, and a working cast was prepared (Fig. 3).
A wax pattern was fabricated, sprued, and invested into a cristobalite mold material. A silver-palladiumcopper-gold alloy (Castwell M.C. 12, G-C Corp., Tokyo, Japan) was cast in the mold by means of a centrifugal
casting machine. The overcasting restoration was fabricated using an indirect composite material (Solidex,Shofu Inc., Kyoto, Japan) (Fig. 4). It was tried-in, adjusted and polished, and the surface to be bonded wasair-abraded with 50 µm grain-sized aluminum oxide (Aluminous Powder WA 360, Pana Heraeus Dental Inc.,Osaka, Japan) using a grit blaster (Micro Blaster MB102, Comco Inc., Burbank, CA, USA). Just before
insertion, a thione-phosphate metal conditioner (Alloy Primer, Kuraray Medical Inc., Tokyo, Japan) was applied
to the inner surfaces of the retainers with a sponge pellet. The canine was cleaned and etched with 37%
phosphoric acid, whereas the prepared metal surface of the metal ceramic restoration of the central incisor wasair-abraded with 50 µm aluminum oxide using a portable air-abrader (Microetchblow, Morimura Dental Co.,Tokyo, Japan), and the same metal conditioner was applied. The overcasting restoration was then seated with anadhesive luting agent (Super-Bond C&B Ivory, Sun Medical Co., Ltd., Moriyama, Japan) (Figs. 5 and 6). Thenthe patient began a regular program of check-ups every 6 months.
The resin-bonded overcasting restoration functioned satisfactorily for more than 5.5 years, including theretainer on the canine, and the patient was satisfied with the service period of the overcasting restoration.
However, six years after seating, loss of retention of the retainer of the central incisor was detected (Fig. 7)

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Int Chin J Dent 2006; 6: 61-64.

although the patient did not realize it or feel anything wrong at all. The patient chose the treatment option ofhaving the resin-bonded overcasting restoration and the adjacent FPD completely removed, and a new large FPD
with conventional full-coverage metal ceramic restorations substituted.

Discussion
The use of a resin-bonded overcasting restoration incorporated with an existing adjacent metal ceramic FPD
was presented in this case report. The overcasting technique was originally a technique designed to avoid
removal of restorations, such as fractured metal ceramic fixed partial dentures1,2,4 or adjacent FPDs.3 The
technique remarkably developed through the use of an adhesive resin cement with metal conditioners.2,5,6 An
overcasting restoration may provide faster treatment, fewer appointments, less discomfort, simpler laboratory
procedures, and lower cost compared to replacement of the restoration.
In the present situation, the existing adjacent FPD had been made of metal ceramic gold alloy(Degudent-Universal, Mitsubishi Metal Corp., Tokyo, Japan), according to the patient’s clinical records in ourhospital; the overcasting restoration was made of a silver-palladium-copper-gold alloy. The combined use of athione-phosphate metal conditioner and an adhesive luting agent is effective at bonding silver-palladiumcopper-gold alloy7,8 as well as metal ceramic gold alloy.7 Therefore, the bond durability of the adhesive luting
agent joined to both the inner surface of the overcasting restoration and the prepared surface of the metal ceramic
FPD should be enhanced. Six years after seating, however, debonding of the retainer of the central incisor wasobserved, whereas the retainer of the canine was fine. This failure can be attributed mainly to a slight mobilityof the abutments of the existing denture and the maxillary anterior location. It is well known that the mobility of
the abutment teeth is one of the decisive prognostic factors for the success of resin-bonded FPDs, as are thecasting alloy, the pretreatment of the bonding surfaces, and the luting agent.9 Longitudinal follow-up studies ofresin-bonded FPDs and the survival rates have been reported,9-13 and the conclusions with regard to location
factors are sometimes conflicting. The present situation indicates that there is a possibility that the maxillaryanterior location is one of the negative factors for resin-bonded prostheses because this location involves
anterior-guided occlusion. The reduction of the palatal surface of the central incisor was restricted to the nonocclusal surface area in order to completely integrate the overcasting restoration without altering the original
anterior guidance. Thus, only the occlusal surface areas of the original palatal surface of the existing partial
denture had guided the protrusive movement of the mandible for more than 5.5 years. The repetitive functional
force from the antagonistic mandibular teeth is likely to peel the retainers gradually from the abutments. In
addition, the lower emission pressure of a portable air-abrader compared to a laboratory grit blaster also may
affect the bond durability between the two alloys,14 but further work is required to clarify this hypothesis.
The vinyl-thiol metal conditioner (V-Primer, Sun Medical Co., Ltd.)15 and thiouracil metal conditioner(Metaltite, Tokuyama Dental Corp., Tokyo, Japan)7 as well as the thione-phosphate metal conditioner (AlloyPrimer, for both of noble and base metal alloys), used in the present situation, can also be used with asilver-palladium-copper-gold alloy and metal ceramic gold alloy.
Acknowledgment
Editorial assistance by Mrs. Jeanne Santa Cruz is appreciated.

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Am J Dent 2004; 17: 161-4.
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Correspondence to:Dr. Hiroshi Shimizu
Division of Removable Prosthodontics, Department of Oral Rehabilitation, Fukuoka Dental College
2-15-1, Tamura, Sawaraku, Fukuoka 814-0193, Japan
FAX: +81-92-801-0513 E-mail: simizuh1@college.fdcnet.ac.jp
Received April 9, 2006. Accepted May 8, 2006.
Copyright ©2006 by the International Chinese Journal of Dentistry.

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