Boxing impressions Ali Bolouri, D.M.D.,* Terence C. Hilger, D.D.S.,** and Maynard D. Gowrylok, C.D.T.***

The University o~ Tennessee, College o/Dentistry, Memphis, Tenn.

A

technique applicable for boxing impressions of almost any type of impression material is presented. "Impressions are boxed in order to condense the stone by vibration and to preserve a record of the denture border width. ''1 Boxing of impressions has been a seemingly difficult, time-consuming procedure for students, and accuracy may be" lost by too much handling of the impression. The technique to be described consumes minireal time and lessens handling of the impression itself.

TECHNIQUE 1. Pour a ~laster base, and lightly seat the impression into the plaster, leaving the peripheral Iturn of the impression at least 4 ram. above the level of plaster (Figs. 1 and 2). 2. Before the plaster sets, mold it to develop an area at least 5 ram. wide around the denture border and 4 ram. below and parallel to it. This area needs to be somewhat wider beyond the retromolar-pad region of an edentulous mandibular final impression. Also, the interlingual flange (tongue) space of a mandibular impression is filled with plaster. N O T E : The setting expansion of plaster can be reduced, within practical limits, by increasing the water/powder ratio and lessening the mixing time.'-" 3. Trim the plaster base to an area 5 ram. wide around the impression borders. Leave a slightly wider area beyond the retromolar pad of a n)andibular impression (Figs. 3 and 4). Any small amounts of plaster on the outside of the impression's peripheral turn may be gently washed off at this time. If necessary, trim the bottom of tile plaster base to a 5 to 6 ram. thickness. For a mandibular impression, block out any undercuts created in tile plaster, especially distal to the lingual border. This is important for recovering the master cast. *Instructor, Department of Prosthetics. ***Assistant Professor, Departments of Prosthetics and Crown and Bridge. ***Demonstrator, Department of Prostheties.

692

Volume 33 Number 6

Boxing impressions

693

Fig. 1. Master impressions ready for boxing. Fig. 2. Master impressions are set in plaster bases.

Fig. 3. The impression-plaster maxillary base is trimmed and ready for Plasticine.

Fig. 4. The impression-plaster mandibular base is trimmed and ready for Plasticine.

4. Adapt modeling clay or Plasticine to the plaster base to a level 3 mm. below the impression border and parallel to it (Figs. 5 to 7). 5. Wrap and seal a piece of boxing wax around the prepared base in the usual manner, leaving the border to the boxing wax approximately 1 3 m m . above the highest point of the impression (Fig. 8). 6. T h e boxed impression is ready to be poured (Fig. 9). 7. After setting, strip away the boxing wax (Fig. 10). The master cast may now be carefully separated from its impression. If necessary, the plaster base can be easily cut and broken away from the impression before recovering the master cast. 8. The master cast is ready for trimming as needed (Fig. 11). SUMMARY

This technique is reliable for different types of impression materials and consumes minimal time. Accuracy is not sacrificed. Heat produced by tile setting plaster is not a significant disadvantage. An alternate procedure is to eliminate step No. 4. The unset plaster is molded and smoothed to a level 3 ram. below tile impression border. Undercuts are noted

694

J' P"°stJlu':/eDe"t' 1975

Botouri, Hilger~ and Gowrylok

Fig. 5. Maxillary impression-plaster base with Plasticine applied. Fig. 6. Mandibular impression-plaster base with Plasticine applied.

•

,&,

c-

• :i!~

~

,

.';

.~'

". •

'..... •

. ~ '

".......

"

_

Fig. 7. Mandibular impression-plaster base with Plasticine applied, showing retromolar-pad region with no undercut. Fig. 8. Boxed maxillary and mandibular impressions.

Fig. 9. Maxillary impression boxed and poured in stone. Fig. 10. Boxing wax is stripped away from the maxillary impression, set plaster base, Plasticine, and set stone.

VohLmc :13 Number 6

Boxing impressions

695

Fig. 11. Maxillary master cast is given final trim. Fig. 12. Maxillary and mandibular impressions boxed and ready to add the petroleum-jelly separating medium. a r o u n d the outside of the impression border a n d suitably blocked out to facilitate cast recovery. Instead of a d a p t i n g Plasticine to the plaster base, p e t r o l e u m jelly is used as a s e p a r a t i n g m e d i u m (Fig. 12). We wish to thank Mrs. Lucille Harrison for her assistance in the preparation of the manuscript.

References 1. Boucher, C. O.: Swenson's Complete Dentures, ed. 6, St. Louis, 1970, The C. V. Mosby Company, p. 351. 2. Skinner, E. W., and Phillips, R. W.: The Science of Dental Materials, ed. 7, Philadelphia, 1973, W. B. Saunders Company, p. 66. 3. The Nomenclature Committee of the Academy of Denture Prosthetics: Glossary of Prosthodontic Terms, ed. 3, St. Louis, 1968, The C. V. Mosby Company. 4. Boucher, C. O.: Swenson's Complete Dentures, ed. 6, St. Louis, 1970, The C. V. Mosby Cdmpany, pp. 351-353. 5. Lecture Series of Department of Removable Prosthodontics, Emory University School of Dentistry, Atlanta, Ga., 1971. T H E UNIVERSITY OF TENNESSEE COLLEGE OF DENTrSTRY

MEMPHrS, TENN. 38163