Applied plaster impressions for maxillary complete dentures

Complete dentures

Applied piuster impressions complete dentures

for rnaxikary

Robert G. Vig, D.D.S.,* and Roland C. Smith, D.D.S.** Uniuersity of California School of Dentistry, Los Angeles, Calif.

V

arious theories and materials have been adapted to specific philosophies of impression making. The technique described in this article will produce a passive impression of the maxillary denture-bearing area (basal seat) regardless of the physical characteristics of the soft tissues. Lytlel demonstrated that dentures cause deformed tissues. Excessive pressures from denture bases, poor occlusion, or trauma can cause distortion of the mucoperiostium. These soft tissues will re-assume normal shape when relieved of the trauma. The basal-seat tissues should be permitted to attain a normal thickness and configuration prior to impression-making procedures to avoid perpetuation of the conditions ordinarily found under dentures which have been worn for some time. Tissue treatment or conditioning materials have made it possible to reduce hypertrophic tissue under ill-fitting dentures without requiring the patient to remove his dentures for unreasonable lengths of time. Occasionally, the bone loss and hyperplastic tissue cannot be corrected without surgical intervention. If replaced, this amount of tissue loss may require an excessively thick, heavy denture. In such instances, the soft, freely movable tissue must be maintained and accepted. This condition is frequently present in mouths in which a maxillary complete denture has been worn opposing mandibular natural anterior teeth without replacement of the posterior teeth or opposing a removable partial denture that has not been adequately maintained, The soft tissue covering the anterior part of the maxillary ridge is often as soft and movable as an earlobe. The mere act of moving the upper lip distorts it. The shapes of these freely movable tissues should be recorded in their undistorted state. Since placing an impression tray in the mouth causes distortion of such mobile tissues, a tray is not used to carry the impression material to place. Instead, impression plaster is applied directly to the tissues without a tray. *Associate Clinical Professor. **Associate Clinical Professor, College of the Pacific, San Francisco, Calif. 586

Volume Number

27 6

Plaster

Fig. 1. The armamentarium fast-setting plaster, (3) indelible pencil, and (7)

for applied plaster wooden tongue blades, cellophane cones.

impressions

for

complete

dentures

587

impressions (4) cotton

includes forceps,

(I) (5)

the paper cups gauze squares,

(2) (6)

ARMAMENTARIUM The armamentarium for making an applied plaster impression consists of (1) paper cups containing 20 c.c. of water, (2) fast-setting impression plaster,* (3) wooden tongue blades, (4) cotton forceps, (5) gauze squares, (6) indelible pencil, and (7) cellophane cones or confectioner’s cones (Fig. 1) .

TECHNIQUE FOR APPLIED PLASTER IMPRESSIONS Place 20 C.C. of water in each of the 6 cups. Split the tongue blades in halves to use as disposable spatulas. Cut a few squares of gauze of postage-stamp size. Seat the patient in a comfortable, semireclining position. Raise the chair to place the maxillae at the level of the dentist’s chin. Insert a comfortable saliva ejector in the mouth. Identify the pterygomaxillary (hamular) notches, and mark them with an indelible pencil. Mark the vibrating line from notch to notch. Place 6 to 8 pieces of gauze in one of the paper cups and add plaster to form a thin mix. Have your assistant hold the cup a foot or so from the patient’s mouth at shoulder level. Use a mouth mirror for access and to help in patting the plastersoaked gauze to place. Work as rapidly as possible, because the plaster sets in just one minute. Pick up a piece (or pieces) of plaster-soaked gauze with a cotton plier. Lay the pieces of gauze along the pencil line across the vibrating line and into the buccal vestibules (Fig. 2). Prepare another mix of plaster about one half minute after the first is mixed, again incorporating 6 to 8 pieces of gauze. Be certain that the posterior part of the buccal vestibules, the pterygomaxillary notches, and the posterior part of *Impression

Plaster

No.

2, Kerr

Mfg.

Company,

Romulus,

Mich.

588

Vig

J. Prosthet. Dent. June, 1972

and Smith

Fig. 2. Plaster-soaked gauze is placed line and into the buccal vestibules. Fig.

3. The

plaster-soaked

gauze

over

the

is in position

posterior

border

of the

palate

at the

vibrating

on the palate.

/

Fig.

4. Fast-setting

Fig.

5. Plaster

plaster is carried

is applied into

the labial

to the anterior vestibular

half space

of the palate by means

by means

of a cone.

of a cone.

the palate are covered by the gauze soaked in plaster. Tell the patient to relax as much as possible with the mouth opened just wide enough for access. When the posterior third of the palate is covered (Fig. 3)) make another mix of soft plaster and pour it into a confectioner’s cone. (Cellophane can be used to make cones and has the advantage of being transparent.) Fold the open end of the cone to seal it, and snip off the point of the cone. Squeeze plaster over the remainder of the palate up to the crest of the residual ridge (Fig. 4). Distribute the plaster systematically so as not to trap air and to prevent voids encountered when new plaster is added to set plaster. Build up a layer of plaster approximately 5 mm. in thickness to gain adequate strength. Stop for one minute to allow the plaster covering the palate to set compIetely. Make a fourth mix of plaster, and again load a cone. Use the mouth mirror to

Volume 27 Number

Plaster

6

Fig.

6. A second

Fig. tion

7. A reinforcing layer to serve as a handle.

layer

of plaster

is added

of plaster

impressions

to the vestibular

is applied

to the

for

complete

The

tongue

dentures

SS9

space. palate.

blade

is left

in posi-

Fig. 8. (A) The cross section of a cast poured in a standard minimum-pressure impression indicates the forward displacement of the anterior segment of soft tissue. (B) The cross section of a cast poured in an applied plaster impression indicates the more erect, nondisplaced anterior segment of soft tissue.

expose the vestibular space, and squirt plaster from one posterior (buccal) vestibular space around the labial vestibular space and into the opposite posterior vestibular space (Fig. 5). Permit the patient to close his mouth as much as possible and to relax his facial musculature. Allow this plaster to set for one full minute. Make a fifth mix of plaster, again load a cone, and squirt a ribbon of plaster systematically from one posterior vestibular space around to the opposite side (Fig. 6). The first layer of plaster will cause the second to dehydrate slightly resulting in a material that is somewhat heavier bodied. Gently massage the border in a horizontal direction with your fingers. When the plaster has set, reflect the lips and cheeks to examine the border roll for deficiencies. Add more plaster where needed. Reinforce the palatal portion of the impression with the last mix of plaster. Place a generous patty of plaster on the end of a piece of tongue blade, and attach the blade to the palatal portion to act as a handle in removing the impression (Fig. 7). Blast air into the vestibular spaces to aid in removing the impression when it has completely set. The entire procedure should be completed in 10 to 15 minutes. Apply a separating medium, such as foil substitute or green soap to the impression, box, and pour the cast in a hard artificial stone. Identify and remove blebs or fins of artificial stone which represent minor voids or discontinuities in the impression.

590

J. Pro&et. Dent. Junr, 1972

Vig and Smith

ACCURACY

OF APPLIED

PLASTER

IMPRESSIONS

Numerous pairs of casts poured from orthodox minimum-pressure impressions and the applied plaster impressions have been compared. In addition, many pairs of casts have been sectioned to produce profiles of the cast surfaces in order to evaluate the impression techniques. The lack of distortion with the applied plaster impression technique is significant (Fig. 8). The positive reactions of patients in regard to improved comfort and denture stability are gratifying. SUMMARY A technique has been described for making maxillary impressions using fastsetting plaster that is applied directly to the soft tissues without a tray. The technique produces an accurate impression of movable soft tissues without distortion. References 1. 2.

Lytle, R. B.: The Management of Abused Oral Tissues J. PROSTHET. DENT. 7: 27-42, 1957. Boucher, C. O., editor: Swenson’s Complete Dentures, Mosby Company, p. 136. UNIVERSITY OF CALIFORNIA SCHOOL OF DENTISTRY CENTER FOR THE HEALTEI SCIENCES Los ANGELES, CALIF. 90024

in Complete ed.

Denture

5, St. Louis,

Construction, 1964,

The

C. V.