TWO-PARTRESIN-BONDEDFPD

research is indicated to investigate the bond strength between the “two-part pontics.” The two-part resin-bonded, acid-etched FPD was especially useful if the undercuts of abutments were excessive and the patient could not endure tooth preparation. In addition, the upper and lower parts of the TFPD might have greater retentive strength than the retention created by the bond strength of resin to enamel, the critical retention force of a conventional resin-bonded FPD. The chief disadvantage of the new design was the complex formulation of the wax-up and precise casting technique.

SUMMARY Anew framework was designed for the resin-bonded, acid-etched FPD so that the natural undercuts of the abutments were used for retention of the FPD. This new design (TFPD) divided the conventional Maryland FPD into an upper and lower “pontic” part, each with a separate path of insertion. The two insertion directions were different so the pontic parts could not be displaced during function. Thirty-five patients have had missing teeth replaced with a TFPD since 1988 in the prosthodontic department. The results of the clinical testing have been extremely encouraging because, in the 35 pairs of TFPDs-the oldest in service 23 months and the most recent 4 months-there has been no debonding at the enamel surfaces or at the interfaces between the two-part pontics.

Resin-bonded David Israel

Madjar, Defense

Forces

cast coverage

REFERENCES 1. Simonsen R, Thompson V, Barrack G. Etched cast restorations: ciinical and laboratory techniques. Chicago: Quintessence Publishing Co, 1983:169. 2. Kishimoto M, Shillingburg HT, Duncanson MG. Influence of preparation features on retention and resistance. Part II. Three-quarter crowns. J PROSTHET DENT 1983;49:168-92. 3. Pegorro LF, Barrack G. A comparison of bond strength of adhesive-cast restoration using diierent designs, bonding agents, and luting resins. J PROSTHFX DENT 1987;57:133-8. 4. Burgess JO, McCartney JG. Anterior

retainer design for resin-bonded acid-etched 6xed partial dentures. J PROSTHET DENT 1987;61:433-6. 5. W&shire WA. Resin bonded fixed partial dentures utibziig additional pin retention. Quintessence Int 1986;17:343-7. 6. Meiers JC, Meetz HK. Design modifications for etched-metal, resinbonded retainers. Gen Dent 1985;33:41-4. I. Barrack G. Recent advances in etched cast restorations. J PROSTHET DENT 1984;52:619-26. 8. Williams VD, Thayer

KE, Denehy GE, Bayer DB. Cast metal, resinbonded prostheses: a lo-year restrospective study. J PROSTHET DENT 1989;61:436-41. 9. Simonsen R, Thompson V, Barrack G. Etched cast restorations: cliicai and laboratory techniques. Chicago: Quintessence Publishing Co, 198341-56. 10. Buonocore MG. A simple method of increasing the adhesion of acrylic filling material to enamel surfaces. J Dent Res 1955;34:849-53. Reprint requests to: DR. JI-HUA CHEN PROSTHODONTIC DEPARTMENT STOMATOLOGICAL HOSPITAL FOURTH MILITARY MEDICAL UNWERS~~Y XIAN 710032 CHINA

for fractured

posterior

teeth

DMD,a and Irit Divon-Kupershmidt, DMDb Center for Oral and Dental Medicine, Tel Hashomer, Israel

Enamel-dentin fracture without pulpal involvement of intact posterior teeth demands restoration of form and function while preserving as much sound tooth material as possible. A partial-coverage restoration cast in nonprecious metal and air-abraded and bonded to the tooth by an adhesive resin is suggested. The strong bond of the adhesive resin to the enamel and dentin of the tooth and to the airabraded metal allows for simple fabrication of a cast partial coverage that requires only minimal tooth preparation. (J PROSTHET DENT 1992,68:15-18.)

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\

The views expressed herein are private ones of the authors and do not necessarily reflect those of the Medical Corps, Israel Defense Forces. *Major, Israel Defense Forces, Department of Prosthodontics and Maxillofacial Prosthetics. bCaptain, Israel Defense Forces, Department of Prosthodontics and Maxillofacial Prosthetics. 1Q/1/35787 THE

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raumatic forceful closure of teeth after a blow to the chin often leads to crown or crown and root fracture of one or more intact teeth. The indirect trauma mechanism applies a sudden, rapid load to the teeth, causing cuspal fracture and exposure of dentin with or without pulpal involvement1-3 (Figs. 1 and 2). Salis et a.l.,4 in an in vitro study, found that when dynamic forces are applied to in15

MADJAR

Fig.

1. Enamel

dentin

fracture

of the palatal

Fig. 2. Enamel

dentin fracture involving molar. Because fracture site is surrounded Fig. 3. Casting is fabricated on individual

Fig. 4. Finished

restoration

extends interproximally

tact teeth, most fracture paths run obliquely from the occlusal fissure to the cervical region. In such fractures restoration of the deficient tooth material with composite resin may not be sufficient, whereas full coverage sacrifices too much sound tooth material. Therefore a conservative cast partial-coverage restoration is suggested for enameldentin fractured teeth without pulpal involvement, combining the well-established clinical performance of resinbonded fixed partial dentures5 with the improved bond strength of adhesive resin to dentin and nonprecious metals.6, 7

TECHNIQUE Tooth preparation Minimal occlusal modification should be performed to ailow for occlusal clearance. A positive seat of the casting should be created by “shoeing” the fractured cusp site. If the fracture line includes the central fossa, the preparation

16

cusp of maxillary

supporting (facial) by enamel, minimal die.

AND

DIVON-KUPERSHMIDT

first premolar. cusp of mandibular first extension is needed.

and to inner aspect of intact

cusp.

should be extended to the inner aspect of the intact cusp and restricted to enamel only. The preparation should be extended interproximally to include the contact areas so as to enhance the resistance forms and reach the enamel borders. Gingival margin placement in enamel or dentin requires a shallow chamfer to ensure accurate fit and marginal seal.

Impressions Gingival retraction may be necessary if the finishing line approximates the gingiva or is subgingival. Impressions are made with elastomeric heavy tray material followed by wash of light body material.

Provisional

coverage

Provisional coverage is fabricated with composite resin coverage of the exposed dentin; for easy removal, etching and bonding are not performed.

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Fig. Fig.

LABORATORY

TEETH

5. Occlusal view of restored cusp. Restoration 6. Facial view of restored cusp.

PROCEDURES

1. Prepare the individual dies from the master cast by sawing through the neighboring teeth, taking care not to damage the preparation’s proximal extensions. 2. Ditch the finishing line and remove excess stone, leaving a clearly defined and accessible preparation site. 3. Carve the wax pattern to proper contour so the cusp is in functional contact with the opposing tooth. 4. Invest the wax pattern and then cast with nonprecious metal (Rexillium III, Generic Industries, Wallingford, Conn.) (Fig. 3). 5. After the try-in and refinement of occlusion, air abrade the casting with 50 pm aluminum oxide.

Cementation The tooth is isolated with a rubber dam and cleaned with water and pumice. Liner should be placed only on very thin dentinal walls. The preparation site is etched, rinsed with water, and dried. Panavia Ex adhesive resin (Kuraray Co., Ltd., Osaka, Japan) is mixed according to the manufacturer’s instructions and applied to the casting. The casting is seated and held in place for 3 minutes. Excess material is removed, and the margins are covered with Oxyguard (Kuraray Co., Ltd.). After the material has completely set, the Oxyguard is washed, the occlusion is checked, and the restoration finished.

IscussIoN Restoration of form and function to posterior teeth presenting enamel-dentin fractures involving cusps is difficult. The application of composite resin restores form but cannot restore cusps to full occlusal function.g Furthermore, the large area and the bulk of the composite resin restoration enhance the possibility of marginal microleakage caused by polymerization shrinkage.lO, l1 Choosing full

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is in occlusal function.

or three-quarter crowns as an alternative treatment will solve the problems. However, sound tooth material is unnecessarily reduced and can be avoided by using the proposed procedure. The proposed adhesive resin-bonded restoration cast in nonprecious metal needs minimal preparation. Proximal extension is restricted to the enamel to resist horizontal displacement, and a positive seat is created occlusally to shape the resistance form of the restoration. Crown contour is restored to enable the supporting or guiding cusps to function in full occlusal contact (Figs. 4 through 6). The bond of Panavia Ex material to air-abraded, nonprecious metals is strong and resistant to thermal cycling and immersion in water.12> l3 It was found to be strong enough for clinical purposes, 14, l5 three times greater than the bond of Panavia Ex to enamel.16 Air abrasion of surfaces to be bonded is easy to accomplish and not as technique-sensitive as other procedures. The bond strength of Panavia to etched enamel was found to be as strong as the conventional composite resins.6 The bond of adhesive resins to dentin can be increased by etching the dentin. The enlarged dentinal tubuli apertures formed by etching are sealed by resin tags of the adhesive resin.i7, I8 Inokoshi et all9 found that after etching the prepared walls, including enamel and dentin, and restoring with an adhesive resin, there was less pulp irritation and less bacteria, probably because of the reduced microleakage. Fabrication of the restoration is a simple and economical procedure that requires only two clinical sessions. The disadvantage of this method is mainly an esthetic one. It should be used primarily to restore posterior teeth where esthetic considerations are not of prime importance.

SUMMARY A cast partial-coverage, adhesive resin-bonded restoration for teeth with enamel-dentin fractures is presented as

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MADJAR

an alternative to composite resin restoration, full coverage crowns, or three-quarter crowns. The minimal tooth preparation required for positive seat and proximal extensions with the adhesive properties of the Panavia Ex material in bonding to air-abraided metal, enamel, and dentin ensures a stable and functioning restoration that can protect the pulp against microleakage.

11.

12.

13.

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DIVON-RUPERSHMIDT

10. Eick D, Welch

REFERENCES 1. Oikarinen K. Pathogenesis and mechanism of traumatic injuries to teeth. Endodont Dent Traumatol1987;3:220-3. 2. Andreasen JO. Challenges in clinical dental traumatology. Endodont Dent Traumatol1985;1:45-55. 3. Sabs SG, Hood JAA, Kirk EEJ, Stokes ANS. Impact fracture energy of human premolar teeth. J PROSTHET DENT 1978;58:43-8. 4. Sahs SG, Hood JAA, Stokes ANS, Kirk EEJ. Patterns of indirect fracture in intact and restored human premolar teeth. Endodont Dent Traumatol1987;3:10-4. 5. Wiliiis VD, Tbayer KE, Denehy GE, Bayer DB. Cast metal, resin bonded prostheses: A lo-year retrospective -study. J PROSTHET DENT 1989;16:436-41. 6. Rueggeberg FA, Caughman WF, Gao F, Kovarik RE. Bond strength of Panavia Es to dental amalgam. Int J Prosthodont 1989;2:371-5. 7. Omura I, Yamauchi J, Harada I, Wada T. Adhesive and mechanical properties of anew dental adhesive [Abstract]. J Dent Res 1984,63(special issue):233. 8. Burgess JO, McCartney JG. Anterior retainer design for resin-bonded acid-etched fixed partied dentures. J PROSTHET DENT 1989;61:433-6. 9. Lacy AM. Conservative restoration of fractured cusps with posterior composite resins. Quintessence Int 1985;12:867-11.

AND

14.

15. 16.

17.

18. 19.

FH. Polymerization shrinkage of posterior composite resins and its possible in6uence on postoperative sensitivity. Quintessence Int 1986;17:103-11. Hansen EK. Visible light-cured composite resins: Polymerization contraction, contraction pattern and hygroscopic expansion. Stand J Dent Ftes 1982;90:329-35. Atta MO, Smith BGN, Brown D. Bond strengths of three chemical adhesive cements adhered to a nickel-chromium alloy for direct bonded retainers. J PROSTHET DENT 1990;63:137-43. Thompson VP, Grolman KM, Limo R. Bonding of adhesive resins to various non-precious ahoys [Abstract]. J Dent Res 1985;64(specieI issue):314. Pegoraro LF, Barrack G. A comparison of bond strengths of adhesive cast restorations using different designs, bonding agents, and luting resins. J PROSTHET DENT 1987;57:133-8. Watanabe F, Powers JM, Lorey RE. In vitro bonding of prosthodontic adhesives to dental alloys. J Dent Res 1988;67:479-83. Kohh S, Levine WA, Grisius J, Fenster RK. The effect of three different surface treatments on the tensile strength of the resin bond to nickel-chromium-beryllium alloy. J PROSTHET DENT 1990;63:4-8. Kurosaki N, Kubota M, Yamamoto Y, Fusayama T. The effect of etching on the dentin of the clinical cavity floor. Quintessence Int 1990;21:8792. Fusayama A, Kohno A. Marginal closure of composite restorations with the gingivai wah in cementum/dentin. J PROSTHET DENT 1989;61:293-6. Inokoshi S, Iwaku M, Fusayama T. Pulpal response to a new adhesive restorative resin. J Dent Res 1982;61:1014-9.

Reprint

requests

to:

DR. DAVID MADJAR 6 HAGAON ELIAHU ST. RAMAT GAN 52364 ISRAEL

JULY

1992

VOLUME

6s

NUMBER

1

Resin-bonded cast coverage for fractured posterior teeth.

Enamel-dentin fracture without pulpal involvement of intact posterior teeth demands restoration of form and function while preserving as much sound to...
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