108 THE JOURNAL OF PROSTHETIC DENTISTRY VOLUME 84 NUMBER 1

The precise transfer of the spatial relationships ofimplants from the mouth to the master cast is a criticalstep for ensuring the accuracy of fit of implant-retainedprostheses. Distortion that occurs during the impres-sion-making procedure ultimately results in a prosthe-sis that does not seat passively onto the implant abut-ments. Absence of a passive fit may cause loosening ofretaining screws and screw fracture. Distortion mayresult from dimensional changes of the impressionmaterial, as well as movement of impression copingswithin the impression during tightening of the labora-tory abutment analogs.

Intraoral splinting of transfer copings has been rec-ommended to preserve their spatial relationship andminimize the effects of the aforementioned factors thatmay cause distortion. Suggested methods of splintingtransfer copings include the use of acrylic resin on amatrix of dental floss,1 orthodontic wire,1,2 and prefab-ricated acrylic resin rings around gold copings.3 Relyingsolely on the impression material to preserve the3-dimensional relationship between multiple implantshas been shown to be less accurate than when transfercopings are splinted with acrylic resin.4 However, whena large volume of acrylic resin is used to splint transfercopings intraorally, distortion may result from polymer-ization shrinkage. It has been reported that the totalshrinkage of acrylic resin is between 6.5% and 7.9% inthe first 24 hours, with 80% of the shrinkage occurringin the first 17 minutes after mixing.5 The greater themass of the acrylic resin used, the less accurate the rela-tionship between 2 segments splinted.6

To minimize the mass of acrylic resin used duringthe splinting of transfer copings, prefabricated acrylicresin rings are made by placing resin around gold cop-ings before the final impression appointment.3 In thismanner, polymerization shrinkage of the bulk of theacrylic resin would have taken place before the resinrings are splinted intraorally. This procedure is usefulin situations where the distance between implants is

relatively short. However, longer distances betweenimplants, such as that encountered in implant-retainedoverdentures, may require a greater bulk of acrylicresin to splint the gold copings. In addition, the labo-ratory procedures involved with this technique is time-consuming. Another technique that has been suggest-ed involves splinting the transfer copings with acrylicresin in a matrix of dental floss and performing anadditional step of sectioning and rejoining the resin toreduce the effects of polymerization shrinkage.7 Withthis procedure, however, clinic and laboratory time isincreased.

This article describes a simple and time-savingmethod of intraoral splinting of implant transfer cop-ings for the final impression procedure. The objectiveof this technique is to minimize the effects of acrylicresin polymerization shrinkage by prefabricatingacrylic resin bars that will be used to splint implanttransfer copings. The advantages of this methodinclude ease of fabrication of the resin bars and ease ofintraoral application for splinting transfer copings. Theacrylic resin bars can be sectioned chair side to accom-modate varying distances between transfer copings.Intraoral splinting of transfer copings can be accom-plished without the need for excessive bulk of acrylicresin at the time of final impression, minimizing theeffects of acrylic resin polymerization shrinkage.

PROCEDURE

1. Mix acrylic resin (Pattern resin, GC Corp, Tokyo,Japan) and load into a disposable syringe.

2. Immediately inject the resin into a drinking strawwith a cross-sectional diameter of approximately 3mm (Fig. 1).

3. After allowing the resin pattern to set for at least17 minutes, release the resin bar from the straw bycutting along one side of the straw. For optimalresults, allow the resin bar to set for 24 hours.5(The resin bar can be stored for later use.)

4. At the time of the final impression appointment,place transfer copings onto the abutments andtighten the guide screws according to manufac-turer’s recommendations (Fig. 2). Verify correct

Prefabricated acrylic resin bars for splinting implant transfer copings

Herman B. Dumbrigue, DDM,a Dincer C. Gurun, DMD,b and Nikzad S. Javid, DMD, MS, MEdc

University of Florida College of Dentistry, Gainesville, Fla.

Splinting of implant transfer copings with acrylic resin during impression procedures is performedto accurately transfer the spatial relationships of implants to the master cast. However, distortionmay occur during the splinting procedure because of resin polymerization shrinkage. This articledescribes a simple technique for minimizing this effect by fabrication of resin bars. (J ProsthetDent 2000;84:108-10.)

aAssistant Professor, Department of Prosthodontics.bClinical Assistant Professor, Department of Prosthodontics.cProfessor, Department of Prosthodontics.

DUMBRIGUE, GURUN, AND JAVID THE JOURNAL OF PROSTHETIC DENTISTRY

JULY 2000 109

seating of the transfer copings visually and/orradiographically.

5. Section appropriate lengths of the resin bar with acutting disk to bridge the spaces between the adja-cent transfer copings (Fig. 3).

6. Using a bead brush technique, lute the ends ofthe resin bar to the transfer copings with acrylicresin (Fig. 4). (For adjacent implants that are sit-uated relatively close to each other, preapplicationof acrylic resin around the transfer copings maybe used instead of the resin bar. The modifiedtransfer copings can then be splinted directlyintraorally.)

7. Make the final impression using a custom tray andimpression material of choice. Impression materi-al should be syringed around the transfer copingsand underneath the resin bar to ensure that softtissue topography around the implants and under-neath the resin bar is captured accurately.

8. Allow the applied resin to set for at least 17 min-utes from the time the transfer copings are

splinted to the resin bars to before the finalimpression is removed from the mouth.

DISCUSSION

Accuracy of fit of screw-retained prosthesis is theresult of processes that are affected by material consid-erations and technical manipulations. Distortion mayoccur during the impression procedure and fabricationof the metal framework, which will ultimately affectthe final fit of the prosthesis. The goal is to minimizepotential sources of error in the series of steps leadingto the fabrication of the prosthesis.

An accurate master cast requires an impression pro-cedure that transfers the intraoral position betweenimplants precisely in all dimensions. Achieving a rigidconnection between transfer copings allow preserva-tion of implant spatial relationships independent ofimpression material considerations. A procedure forprefabricating a resin bar that can rigidly connecttransfer copings was presented to minimize the effectof resin polymerization shrinkage.

Fig. 2. Implant transfer copings in place.

Fig. 3. Sectioned resin bar positioned between adjacenttransfer copings.

Fig. 4. Transfer copings splinted with acrylic resin.

Fig. 1. Acrylic resin injected into straw to fabricate resin bar.

THE JOURNAL OF PROSTHETIC DENTISTRY DUMBRIGUE, GURUN, AND JAVID

110 VOLUME 84 NUMBER 1

REFERENCES

1. Brånemark PI, Zarb GA, Albrektsson T. Tissue-integrated prostheses.Osseointegration in clinical dentistry. Chicago: Quintessence PublishingCo; 1985. p. 117-28.

2. Loos LG. A fixed prosthodontic technique for mandibular osseointegrat-ed titanium implants. J Prosthet Dent 1986;55:232-42.

3. Rasmussen EJ. Alternative prosthodontic technique for tissue-integratedprostheses. J Prosthet Dent 1987;57:198-204.

4. Assif D, Marshak B, Schmidt A. Accuracy of implant impression tech-niques. Int J Oral Maxillofac Implants 1996;11:216-22.

5. Mojon P, Oberholzer JP, Meyer JM, Belser UC. Polymerization shrinkageof index and pattern acrylic resins. J Prosthet Dent 1990;64:684-8.

6. Moon PC, Eshleman JR, Douglas HB, Garrett SG. Comparison of accu-racy of soldering indices for fixed prostheses. J Prosthet Dent 1978;40:35-8.

7. Hussaini S, Wong T. One clinical visit for a multiple implant restorationmaster cast fabrication. J Prosthet Dent 1997;78:550-3.

Reprint requests to: DR HERMAN B. DUMBRIGUE

DEPARTMENT OF PROSTHODONTICS

PO BOX 100435COLLEGE OF DENTISTRY

UNIVERSITY OF FLORIDA

GAINESVILLE, FL 32610FAX: (352) 846-0248E-MAIL: hdumbrigue@dental.ufl.edu

Copyright © 2000 by The Editorial Council of The Journal of ProstheticDentistry.

0022-3913/2000/$12.00 + 0. 10/1/107914doi:10.1067/mpr.2000.107914

Receive Table of Contents by E-mail

To receive the table of contents by e-mail, sign up through our Web site at http://www.mosby.com/prosdentChoose E-mail Notification.Simply type your e-mail address in the box and click the Subscribe button.Alternatively, you may send an e-mail message to majordomo@mosby.com. Leave the subject line blank and typethe following as the body of your message:

subscribe prosdent_tocYou will receive an e-mail to confirm that you have been added to the mailing list. Note that table of contents e-mails will be sent out when a new issue is posted to the Web site.