Double band rubber impressions

DOUBLE BAND RUBBER IMPRESSIONS SAUL

M. HIRSHBERG, D.M.D."

Tufts University, School of Dentistry, Boston, Mass.

BASE impression material offers convenience and simplicity of handling when partial coverage retainers are to be the abutments.l However, dentists use a variety of techniques when making impressions for full crowns. Histologic studies indicate that both pressure and heat cause damage to dental p~lps.~,~ Despite this, warm waxes under pressure are still used for impressions because : (1) the rubber base impression material could not be successfully pressed subgingivally around full crown preparations, (2) the retraction of the gingival tissue around a complete crown preparation is exceedingly difficult and on occasion impossible, and (3) electrosurgery of buccal and lingual tissue leaves much to be desired esthetically and physiologically.

R

UBBER

TECHNIQUE

OF DOUBLE

BAND

IMPRESSIONS

The use of mercaptan rubber and copper bands satisfies both the clinical and histological requirements of impressions for full crowns. Mercaptan rubbers are .dependable when they are used with mixes of light and heavy material in combination.4 Therefore, these features were incorporated into an impression technique for full,crown preparations. The crown is prepared (Fig. l), and a tight-fitting nonannealed copper band is adapted slightly below the cervical margins of the preparation (Fig. 2). The band must be snug so that it will maintain its position on the tooth. Then a copper band two sizes larger than the first band is sealed with modeling compound, and the larger band is seated over the smaller one on the prepared tooth (Figs. 3 to 5). Four holes are drilled through both copper bands in the contact area with a No. 6 round bur so that the impression material will lock both bands together. The smaller copper band is replaced on the preparation, and .mixes of the heavy and light rubber base impression materials are made simultaneously. The light rubber base impression is placed inside the smaller copper band with a syringe so as to cover the entire preparation. The heavy rubber base impression material is placed inside the larger copper band which is then placed over the smaller copper band. The hydraulic force that is produced will force the light rubber base impression material under the free margin of the gingiva around the cervical limits of the preparation. The impression material will be forced through the openings in the copper tubes and will lock the two bands together (Fig. 6). *Postgraduate

student

in Prosthetics.

DOUBLE

BAND

RUBBER

IMPRESSIONS

705

‘iy. 1

Fig. I.-A cast core with a shoulder preparation is ready for an impression copper band. Fig. Z.-The copper band is adapted to fit snugly over the preparation.

to be made in a

Countersunk

Fig. 3.-A

schematic drawing

of the design of the larger band that fits over the smaller band.

After the rubber base impression material has cured, an alginate (irreversible hydrocolloid) impression or another rubber base impression is made over the top of the two bands to relate the impression of the prepared tooth to the other teeth (Fig. 7). A cast is poured in this impression and the resulting master cast contains an accurate die that is correctly related to the surrounding teeth (Figs. 8 and 9).

706

HIRSHBERG

J. Pros. Den. July-August, 1965

Fig. 4

Fig. 5

Fig. 4.-The larger band fits over the smaller one and acts as a plunger. There mlust be some space between the smaller band and the contact areas to permit the passage of the larger outside band. Fig. B.-The outside band is in the correct trial position.

Fig. &-The light around the preparation copper band.

rubber base impression material in the small copper band is forced by the heavy rubber base impression material in the larger 1outside

DOUBLE

BAND

RUBBER

Fig. 7.-The impression of the preparation pression. Both copper bands should be in their

707

IMPRESSIONS

is contained in an irreversible hydrocolloid correct relationship to the other teeth.

im-

Fig. 8

Fig. 9

Fig. S.-The die pin is held in position in the impression of the prepared of straight pins and sticky wax. Fig. 9.-The master cast contains the removable die in its proper relation teeth.

tooth by rn~tans to the adja cent

708

J. Pros. Den. July-August, 19G5

HIRSHBERG

Fig. lO.-The

Fig. 11,The

veneer

completed

crown

is fabricated

on the stone die.

veneer crown is in place in the mouth.

The veneer crown is then fabricated and cemented to place on the abutment tooth (Figs. 10 and 11). SUMMARY

A technique has been described which uses telescoping copper bands and rubber base elastic impression materials for making impressions of preparations for full crowns. The impression material is forced into the gingival regions by hydraulic action. Many kinds of impression materials can be used to make this technique valuable for making impressions for fixed restorations. REFERENCES 1. Miller,

L. L.: Partial Coverage in Crown and Bridge Prosthesis With the Use of Elastic Impression Materials, J. PROS.DEN. 13:905, 1963. Changes in Dental Pulps of 2. Seltzer, S., Bender, I. B., and Kaufman, I. J. : Histologic Dogs and Monkeys Following Application of Pressure, Drugs, and Microorganisms on Prepared Cavities, Oral Surg., Oral Med. & Oral Path. 14:327, 1961.

Volume 15 Number 4

DOUBLE

BAND

RUBBER

IMPRESSIONS

709

3. Seltzer, S., Bender, I. B., and Kaufman, I. J.: Part II. Changes Observable More Than One Month After Application of Traumatic Agents, Oral Surg., Oral Med. & Oral Path. 14:856,.1961. 4. Johnston, J. F., Phdlips, R. W., and Dykema, R. W.: Modern Practice in Crown and Bridge Prosthodontics, Philadelphia, 1960, W. B. Saunders Company, p. 205. 907 PARK SQUARE BUILDING BOSTON, MASS. 02116