The porcelain press technique

The porcelain G. G. J. DrSge,

press technique D.D.S.

Tilb,urg, Holland

A

lthough porcelain has proved to be excellent for crown and bridge work for almost a century, this material is used less frequently than acrylic resin, because the possibilities for use of the porcelain technique are limited. To utilize the favorable qualities of ceramic material, a new technique was developed, the “porcelain press technique.” Using this simplified supplementary technique in which alumina-strengthened ceramic material is first vacuum fired and then compressed in the furnace, any type of inlay, crown or bridge (fixed partial denture), can be reproduced enhancing the qualities, denseness strength, and accuracy. This technique is applicable to making ( 1) inlays and onlays, (2) jacket crowns. dowel crowns, porcelain veneer facings, (3) alumina porcelain bridges (fixed partial dentures) ? (4) pontic bridges (fixed partial dentures), and (5) gold-bond porcelain bridges. TECHMtQUE

1. Shape the restoration in wax. 2. Invest the wax pattern in a flask in the same manner as that used for acrylic: resin. 3. Eliminate the wax with boiling water (Fig. 1) . 4. Apply aluminous porcelain or gold-bond porcelain to the cavity, and condense it until the desired shape is obtained. 5. Reduce the mesial, distal, and incisal parts of the porcelain to make space for the addition of transparent and enamel porcelain, and shape and mold the new porcelain material with instruments and brushes. Porcelain contracts about 25 per cent during heating in the furnace, so the modeled piece of porcelain should be built a little thicker and longer than the finished prosthesis is to be. 6. Place both halves of the flask on the guide posts of a flask holder (Fig. 2). 7. Preheat the investment and the porcelain to about 400’ C. in a preheating furnace, or on the platform of an open furnace, to evaporate moisture from the binders (Fig. 3 ) . 8. Fire the preheated mold under vacuum.

210

Fig. die.

J. Prosthet. Dent. August, 1972

Driige

1. The

FIRING

wax

pattern

has been

eliminated

from

the flask

exposing

the die and

the counter

TECHNIQUE

Two procedures are possible. In the first method, the flask is placed on the firing platform of the furnace (P.O.C. vacuum, * Fig. 4, A), inserted in the heating zone of this furnace, and fired under vacuum to a low glaze. The vacuum is then released, and the firing is continued till the porcelain shows a high glaze. The lower half of the flask is pressed against the upper half (Fig. 4, B) , thus the soft porcelain is pressed with precision into the hollow form or onto the metal frame. While many laboratories have vacuum furnaces made by Jelenko,? Stern,$ de Trey§ or Vita,11 I also designed an atmospheric furnace (P.O.C.A.jT) which I use as an auxiliary item of equipment. ALTERNATE

FIRING

TECHNIQUE

1. Introduce the flask into the firing chamber of a vacuum furnace, and fire the porcelain to a low glaze. 2. Simultaneously, heat the P.O.C.A. furnace. 3. Release the vacuum as soon as the porcelain in the vacuum furnace attains a low glaze. Remove the flask from this furnace, and place it on the firing platform of the P.O.C.A. furnace (Fig. 5). 4. Continue the firing in the atmospheric furnace for several minutes until the porcelain shows a high glaze. 5. Press the two halves of the flask together. 6. Remove the pressed crown or fixed partial denture from the investment after cooling. *P.O.C.V.,

Keram

+J. F. Jelenko

Ind.,

BED.

and Company

$Stern, Mt. Vernon, §de Trey, Wiesbaden,

Berlin, New

N .Y. Germany.

/IVita,

Sackingen,

Germany.

IKeram

Ind.,

KG,

BED.

KG, Inc.,

Berlin,

Germany.

Germany.

Rochelle,

N. Y.

The porcelain

Fig.

2. The

Fig.

3. Preheating

flask placed

Fig. 4. (A) The flask flask is pressed against

7. to the 8. stones, 9.

on the guide

the investment

posts

preparatory

and porcelain

on the firing platform the upper half.

to 400”

press techn.iqus

211

to firing. C.

of the vacuum

furnace.

(B)

The

lower

half

of the

Remove the thin flash from around the crow11 with stones, and fit the crown die to check the occlusion and contour (Fig. 6). Grind horizontal and vertical grooves in the porcelain surface with diamond and clean the crown with a stiff brush under running water. Fill the crown with soldering investment (no expansion), and place it on a

212

J. Prosthet. Dent. August, 1972

Drijge

Fig.

Fig. 6. The flash a fin Ial restoration Figs .‘I

5. The

P.O.C.A.

present upon removal of the porcelain after being trimmed (right).

to 9. Restorations

made

by the pressure

technique.

furnace.

restoration

from

the flask

(le

and

Fig. 10. Restoration

made

by pressure

technique.

Fig. 11. An alumina porcelain bridge. Figs. 12 and 13. The ALO profile permits the construction Fig. 14. Metal posts are accurately fitted to the restoration.

of an MOD

inlay

crown stand. This step is done when the crown or inlay is baked investment die and not on platinum foil or a special gold alloy. 10. Characterize the crown with stains. 11. Preheat for a few minutes.

and

pontici

on a rrfractoxy

214

J. Prosthet. Dent. August. 1972

Driige

.~.Figs.

15 and

16. The

- precise

-“--marginal

.~”,.

seal is made

possible

by the technique.

12. Make the final glaze without vacuum. The desired glaze can be seen through the observation lenses of the P.O.C.V. and P.O.C.A. furnaces. ADVANTAGES 1. The possibilities are unlimited (Figs. 7 to 10). 2. Platinum foil is not necessary. Alumina profiles (Figs. 11 to 13)) metal posts (Fig. 14)) and attachments can be accurately inserted. 3. An exact marginal seal is possible, and the technique for making a fixed partial denture is simple (Figs. 15 and 16). 4. Compressed porcelain units are very strong, and repairs can be made intraorally. SPOORLAAN TILBURG HOLLAND

326