Support for tooth-mucosa–supported removablepartial dentures (RPD) is derived from structures withmarkedly different viscoelastic responses to loading.Abutments and tissues over the residual ridge will dis-tort approximately 20 µm and 500 µm, respectively,under 4 N of force.1 Recognition of this disparity hasled to use of impression procedures that attempt toaccommodate the difference in resiliency between hardand soft tissue support. No single impression materialcan record the anatomic form of teeth and functionalform of the residual ridge simultaneously.1

Clinical studies on a limited number of patients sug-gest that different impression procedures result in vary-ing amounts of denture base movement under simulat-ed occlusal load, with the altered cast impression pro-viding the least amount of tissueward movement.2,3

The purpose of the altered cast impression is 2-fold: (1)to obtain maximum tissue coverage for support withinthe physiologic tolerance of limiting border tissues and(2) to capture the spatial relationship of residual ridgesto the teeth. Two philosophies exist on the residualridge form that is best obtained in impressions forfavorable denture base support. Some clinicians4,5

advocate making impressions with no pressure appliedto the residual ridge, whereas others advocate loadingthe residual ridge during the impression procedure.1,6-8

The altered cast impression, as described by Leupoldand Kratochvil,5 displaces residual ridge mucosa.9

Although the altered cast impression fulfills therequirements of relating the anatomic form of teeth tothe functional form of the residual ridge, there are dis-advantages to this procedure. Making an altered castimpression requires additional treatment time and lab-oratory procedures involved are difficult. Errors may beintroduced in orienting and stabilizing the frameworkon the sectioned cast and an additional appointment isneeded for making interocclusal records. To simplifythe laboratory phase of the altered cast procedure, sev-eral clinicians advocate making a fullarch irreversible

hydrocolloid pick-up impression over the remainingteeth, framework, and altered cast impression to gener-ate a new master cast.7,10,11 However, 2-stage impres-sion procedures may introduce other errors.12 Prefabri-cating custom impression trays that attach to the frame-work has also been suggested to minimize laboratorytime necessary between framework try-in and alteredcast impression.13,14

An impression procedure for tooth-mucosa–supported RPD is presented that relates the anatomicform of teeth to the functional form of the residualridges with a single impression.

PROCEDURE

1. Place two layers of baseplate wax relief over theteeth and residual ridges of the diagnostic cast.Burnish aluminum foil over the wax with either anegg burnisher or the back of a wax spatula No. 7.Place occlusal stops on the teeth by making defi-nite boxes through the aluminum foil and wax to

Selective-pressure single impression procedure for tooth-mucosa–supportedremovable partial dentures

Herman B. Dumbrigue, DDM,a and Josephine F. Esquivel, DDM, MSa

University of Florida College of Dentistry. Gainesville, Fla.

This article describes a method of making impressions for tooth-mucosa–supported removable par-tial dentures using a single impression procedure. Through the use of border-molded custom trays,selectively relieved, and application of pressure on residual ridge areas, the objectives of maximumtissue coverage and selective tissue placement of primary stress-bearing areas are fulfilled. With a sin-gle impression procedure, treatment time is reduced and laboratory errors commonly encounteredwith the altered cast impression technique can be minimized or eliminated. (J Prosthet Dent1998;80:259-61.)

aAssistant Professor, Department of Prosthodontics.

AUGUST 1998 THE JOURNAL OF PROSTHETIC DENTISTRY 259

Fig. 1. Aluminum foil and two sheets of baseplate wax overdiagnostic cast before tray fabrication.

ensure proper reseating of the tray during bordermolding procedures (Fig. 1).

2. Fabricate custom tray with either Triad VLC cus-tom tray material (Dentsply, York, Pa.) or autopoly-

Fig. 3. A, Custom tray with softened modeling compoundreseated on diagnostic cast. B, Modeling compound overresidual ridges shaped appropriately before intraoral place-ment.

merizing tray resin with borders 2 mm short of thefunctional vestibule (Fig. 2). Check intraorally foroverextension and reduce as necessary.

3. Remove wax relief and wet surface of cast. Placesoftened thermoplastic modeling compound (KerrMfg. Co., Romulus, Mich.) on the tissue surface ofthe custom tray overlying residual ridges. Reseatcustom tray on the diagnostic cast (Fig. 3). (Thisprocedure shapes the modeling compound appro-priately before intraoral placement.)

4. Reheat compound and place intraorally, placingfinger pressure on the area of the residual ridges.Apply modeling compound to lingual borders ofcustom tray and any modification spaces and com-plete border molding procedure (Fig. 4).

5. Reduce modeling compound contacting the tissuesurface by 1 mm except at the pear-shaped pad andbuccal shelf areas. (This selectively places pressureover the primary stress-bearing areas during theimpression procedure.)

6. Make the impression with low viscosity polysulfiderubber impression material (Light-bodied Perm-lastic, Kerr Mfg. Co.). Apply finger pressure overresidual ridge areas during subsequent bordermolding steps and while impression material is set-ting.

7. Inspect impression for accuracy (Fig. 5) and pourin type IV dental stone.

DISCUSSION

Alternative methods of relating the anatomic formof teeth to the functional form of the residual ridgeshave been advocated because of inherent problemsassociated with the altered cast impression proce-dure.8,15-17 These methods include making a relineimpression after wax denture try-in15 or at the time of

THE JOURNAL OF PROSTHETIC DENTISTRY DUMBRIGUE AND ESQUIVEL

260 VOLUME 80 NUMBER 2

Fig. 2. Custom tray fabricated with extensions reduced 2 mmshort of vestibule.

Fig. 4. Border molding procedure completed.

A

B

denture insertion,8 and single-tray impression proce-dures that use different impression materials for teethand residual ridges.16,17 Single-tray dual-impressionprocedures for tooth-mucosa–supported RPDdescribed in the literature16,17 are complicated. Othersingle-tray impression procedures advocated do notallow for selective placement of primary stress-bearingareas.18,19 Areas on the mandible considered primarystress-bearing include the pear-shaped pad and buccalshelf.20

SUMMARY

A simple and efficient impression procedure forobtaining maximum tissue coverage, for denture basesupport, that allows selective placement of tissues overprimary stress-bearing areas is presented. The anatom-ic form of teeth and functional form of the residualridges is obtained with a single impression procedure.Other advantages of this impression procedure includereduced treatment time, simplification of the laborato-ry phase, and reduction of errors that may be incorpo-rated in the RPD. The alveolar lingual sulcus is alsocaptured in its functional form, permitting placementof a sublingual bar when indicated.18,19

REFERENCES

1. McGivney GP, Castleberry DJ. McCracken’s removable partial prostho-dontics. 8th ed. St Louis: CV Mosby; 1989. p. 163-7, 327-37.

2. Holmes JB. Influence of impression procedures and occlusal loading onpartial denture movement. J Prosthet Dent 1965;15:474-81.

3. Leupold RJ, Flinton RJ, Pfeifer DL. Comparison of vertical movement occur-ring during loading of distal-extension removable partial denture basesmade by three impression techniques. J Prosthet Dent 1992;68:290-3.

4. Applegate OC. The partial denture base. J Prosthet Dent 1955;5:636-48.5. Leupold RJ, Kratochvil FJ. An altered-cast procedure to improve tissue

support for removable partial dentures. J Prosthet Dent 1965;15:672-8.6. Hindels GW. Load distribution in extension saddle partial dentures. J

Prosthet Dent 1952;2:92-100.

7. Bauman R, DeBoer J. A modification of the altered cast technique. J Pros-thet Dent 1982;47:212-3.

8. Krol AJ, Jacobson TE, Finzen FC. Removable partial denture design, out-line syllabus. 4th ed. San Rafael: Indent; 1990. p. 155-65.

9. Stuart LN, Elliot RW Jr. A comparative study of the tissue surface contourson casts fabricated by using two impression techniques for mandibulardistal extension removable partial dentures. Am Coll ProsthodontistsNewsletter 1983:13-6.

10. James JS. A simplified alternative to the altered-cast impression techniquefor removable partial dentures. J Prosthet Dent 1985;53:598.

11. Chen MS, Eichhold WA, Chien CC, Curtis DA. An altered-cast impressiontechnique that eliminates conventional cast dissecting and impressionboxing. J Prosthet Dent 1987;57:471-4.

12. Sykora O. An altered-cast impression technique that eliminates conven-tional cast dissecting and impression boxing (letter). J Prosthet Dent1988;59:388.

13. Lund PS, Aquilino SA. Prefabricated custom impression trays for thealtered cast technique. J Prosthet Dent 1991;66:782-3.

14. Lynde TA, Baker PS, Brandt RL, Berte JJ. Simplifying the altered castimpression technique for distal-extension removable partial dentures. JProsthet Dent 1992;67:891.

15. Hoffman JM. An alternative to the altered cast procedure. J Prosthodont1994;3:13-5.

16. Rapuano JA. Single-tray dual-impression technique for distal extensionpartial dentures. J Prosthet Dent 1970;24:41-6.

17. Von Krammer R. A two-stage impression technique for distal-extensionremovable partial dentures. J Prosthet Dent 1988;60:199-201.

18. Cecconi BT. Lingual bar design. J Prosthet Dent 1973;29:635-9.19. Hansen CA, Campbell DJ. Clinical comparison of two mandibular major

connector designs: the sublingual bar and the lingual plate. J ProsthetDent 1985;54:805-9.

20. Jacobson TE, Krol AJ. A contemporary review of the factors involved incomplete dentures. Part III: support. J Prosthet Dent 1983;49:306-13.

Reprint requests to: DR. HERMAN B. DUMBRIGUE

DEPARTMENT OF PROSTHODONTICS

COLLEGE OF DENTISTRY

UNIVERSITY OF FLORIDA

PO BOX 100435GAINESVILLE, FL 32610

Copyright © 1998 by The Editorial Council of The Journal of ProstheticDentistry.

0022-3913/98/$5.00 + 0. 10/1/90907

Fig. 5. A, Final impression made with light-bodied polysulfide material. B, Areas of com-pound visible through wash impression over buccal shelf and pear-shaped pad, indicatingselective tissue placement.

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AUGUST 1998 261

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