A simple procedure for boxing elastomeric impressions

Daniel Galindo, DDS, a and Gerald N. Graser, DDS, MS b University of Rochester, Eastman Dental Center, Rochester, N.Y.

Boxing an impression is defined as the enclosure of an impression to produce the desired size and form of the base of the cast and to preserve desired details. 1 The benefits of boxing an impression before pouring are (l) to preserve border contour and extension; (2) to con- trol size, form, and thickness of casts; (3) to facilitate pouring of cast materials; and (4) to improve quality, of cast material against impression surfaces.

The article describes a simple and inexpensive proce- dure for boxing dentate and edentulous impressions made with elastomeric materials using Mortite weather putty strips (Mortite Inc., Kankakee, Ill.) available at most hardware stores, and Boxing Wax X-Thin strips (Heraeus Kulzer Inc., South Bend, Ind.).

aResident, Department of Prosthodontics. bprogram Director, Department of Prosthodontics. J Prosthet Dent 1997;78:531-32.

P R O C E D U R E

1. Examine impression and determine its accuracy. 2. Follow adequate disinfection procedures. 3. Air dry the borders of the impression. 4. Adapt a strip of Mort_ire material around the im-

pression, leaving 3 mm of the borders exposed. For lower impressions, follow contour of the lingual borders. The Mort_ire strip will adhere to the elasto- meric impression material (Fig. 1).

5. Adapt a strip of boxing wax over the Mortite mate- rial. The boxing wax will stick firmly to the Mortite material (Fig. 2).

6. Test that water does not leak through the sealed borders. (This will favor a clean pouring procedure [Fig. 3].)

Fig. 1. Strip of Mortite material adapted to borders of elasto- meric impression,.leaving 3 mm of border exposed.

Fig. 3. Water poured into boxed impression. There is no leak- age which favors clean procedure.

Fig. 2. Boxing wax adapted over Mortite strip.

NOVEMBER 1997

Fig. 4. Working cast with adequate border contour and ex- tension. Mortite strip has been easily removed from cast and can be used again.

THE JOURNAL OF PROSTHETIC DENTISTRY 531

THE JOURNAL OF PROSTHETIC DENTISTRY GALINDO AND GRASER

7. Mix a proper amount of cast material in accordance with the manufacturer's instructions.

8. Pour the cast material into the impression. 9. Remove boxing wax and Mortite after the cast has

set. 10. Separate the cast from the impression. 11. Remove the remaining boxing wax and Mortite

strips from the cast (Fig. 4). Mortite strips can be reshaped and used again.

REFERENCE 1. The Academy of Prosthodontics. The glossary of prosthodontic terms. 6th

ed. J Prosthet Dent 1994;71:57.

Reprint requests to: DR. DANIEL GALINDO DEPARTMENT OF PROSTHODONTICS UNIVERSITY OF ROCHESTER EASTMAN DENTAL CENTER 625 ELMWOOD AVE. ROCHESTER, NY 14620

Copyright © 1997 by The Editorial Council of The Journal of Prosthetic Den- tistry.

0022-3913/97/$5.00 ÷ 0. 10/4/85547

The effect o f resin desensitizing agents on crown retention Swift EJ, Lloyd AH, Felton DA. J A m DentAssoc ] 997,'128:195-200.

Purpose. This study examined the effect of two dentin desensitizing agents on the retention of crowns cemented with three luting agents. Material and Methods. Thirty extracted human molars were secured in 1-inch phenolic tings with autopolymerizing acrylic resin. Standardized crown preparations were completed on each tooth to provide an axial wall height of 4 ram, and a 2.4-degree of taper. Specimens were assigned to a control group and two experimental groups (n = 10 each). A silver palladium alloy full-coverage casting (Ney-Oro 76, Ney Dental Intl.) was fabricated for each specimen. All fitted castings were air abraded with 50 lam A1203. Ten of the prepared teeth were treated with One-Step (Bisco Dental Products) cement and 10 were treated with gluma desensitizer (Heraeus Kulzer) cement, accord- ing to manufacturers' instructions. The 10 specimens in the control group were not treated. Imme- diately after dentin preparation, the castings were cemented onto each specimen with zinc phos- phate cement (Hy-Bond, Shofu Inc.). The specimens were stored in room temperature tap water for 24 hours, and then each was mounted in testing machine and subjected to a tensile force until cement bond failure occurred. The tooth surfaces were cleaned, the crowns were cleaned and air abraded with A1203, and the dentin surfaces were treated as described previously. The crowns were cemented again with a conventional glass ionomer luting agent (Fuji I, GC America). Tensile testing was again performed. Finally, after cleaning the castings and teeth, crowns were cemented with a resin-modified glass ionomer luting agent (Vitremer). Tensile testing was also accomplished with these specimens. A two-way analysis of variance and Tukey's Honestly Significant Difference test were used to analyze the gathered data. Results. It was found that the conventional glass ionomer luting agent exhibited the highest mean tensile bond strength to untreated dentin, and the zinc phosphate luting agent exhibited the low- est. Application of both resins decreased retention of the zinc phosphate luting agent, and in- creased retention of resin-modified luting agent. The type of luting agent used was found to have a significant effect on casting retention, with two glass ionomer products showing significantly greater retention than the zinc phosphate luting agent. However, dentin surface treatment was not found to have a significant effect on retention. Conclusion. Use of a resin adhesive system or resin primer (before cementation of a full-coverage casting) has no effect onthe retentive properties of the three luting agents tested in this study. 21 References.--DL DIXON

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