US2432820A - Apparatus for making dentures - Google Patents

Description

Dec. 16, 1947. J SCHWARTZ 2,432,820

APPARATUS FOR MAKING DENTURES Filed April 17 1945 3 Sheets-Sheet 1 INVENTOR ATTORNEY Dec. 16, 1947. J S H 2,432,820

\ APPARATUS FOR MAKING DENTURES WITNESSES: INVENTORI ATTORNEY Dec. 16, 1947. J, D. SCHWA'RTZ 2,432,820

APPARATUS FOR MAKING DENTURE S Filed April 1'7, 1945 3 Sheets-Sheet 3 WITNESSES: INVENTOR BY I Wad. A)

ATTORNEY Patented Dec. 16, 1947 UNITED STATES PATENT OFFICE APPARATUS FOR MAKING DENIURES Jacob D. Schwartz, Pittsburgh, Pa.

Application April 17, 1945, Serial No. 588,837

Claims.

This invention relates to new and useful improvements in a method of and apparatus for making dentures, and it is among the objects thereof to provide a method of making partial or full dentures which shall maintain the proper relationship of the cast of the jaw, teeth and anchorage members during the steps of investing the waxed-up models and the opening and closing of the molds preliminary to the finish denture molding step: The present application is a continuation-in-part of my application Serial No. 491,303. filed June 18, 1943.

Another object of the invention is the provision of a method of forming dentures which shall compensate for shrinkage of the plastic material to produce a sound non-porous denture of the exact size of the waxed-up model.

It is a further object of the invention to provide flask structures suitable for the preparation of. forming molds especially suited to carry out the method steps in an expedient manner.

It is still a further object of this invention to provide a flask structure which is especially adapted to eject the investment material and finished denture.

These and other objects of the invention will become more apparent from a consideration of the accompanying drawings constituting a part hereof in which like reference characters designate like parts and in which Fig. 1 is a cross-sectional view of a mold flask and Waxed-up model partially invested in the bottom of the flask;

Fig. 2 a top plan view thereof Fig. 3 an exploded view of a pair of flask sections separated for the purpose of illustration to show the investment of the waxed-up model and the finished mold section for shaping the palatal surface of the denture;

Fig. 4 an exploded view of a three-section flask for molding full dentures utilizing a hard base plate in the waxed-up model;

Fig. 5 a partial vertical sectional View illustrating the investment of the front teeth of a waxed-up model;

Fig. 6 a bottom plan view of a partial denture made in accordance with this invention;

Fig. 7 a top plan view of a modified form of mold suitable for practicing the invention; and

Fig. 8 a vertical section partially in elevation taken along the line 8-8, Fig. 7.

With reference to Figs. 1 to 3 inclusive of the drawings, the structure therein illustrated comprises a mold having a bottom flask I and an upper flask 2, respectively. provided with holes 3 and pins 4 for maintaining registered alignment of the sections when assembled,

The bottom section I is provided with abase 5 and the upper section 2 with a COVer 6 which may be secured by fillister head screws or otherw1se.

The bottom flask section I is provided with an inner conical shaped wall I terminating in a shoulder at the top formed by a radially extending flange 8 which constitutes an abutment for the investment material, as will be hereinafter explained. V

The upper flask 2 is provided with a conical inner wall 9 converging with a conical wall III which looks the molding material, as will be hereinafter explained. The wall I of the bottom flask is cut away, as shown by dotted lines, at I I to form key slots that are filled with investment material to prevent movement of the investment material in the flask section. Also the bottom flask is provided with slidable abutments I2 which may be secured in adjusted position by screws I3, the slides I2 being provided with slots I4 to allow movement of the slides for adjusting purposes.

Partial dentures and in some cases full dentures are made by means of the above-described molding equipment as follows.

A waxed-up model which consists of the cast of a jaw I5 having teeth I Ii and anchorage membars I! built up thereon by wax I8 is set in investing material I 9 and adjusted with reference to the U-shaped opening 20, Fig. 2.

The waxed-up model is moved to the position shown in Fig. 2 in which position the front teeth designated by the numeral I Ba are brought in alignment with a portion of the flask 8 as is shown in Fig. 5.

The side teeth are then adjusted to be equally spaced from the U-shaped edge 20 of the flange 8 and the movable slides I2 are then adjusted to the position shown with the edges in substantial register with the center of the occlusal surface of the teeth I6.

In this position the slides I2 are secured by screws I3 and nuts l3a to hold them in place. The flask I is then completely filled with investment material I9 extending completely over the occlusal surface of the teeth so that only the palatal surface of the model is exposed. The top section 2 of the flask is then placed on the bottom section I with the dowel pins 4 inserted in the openings 3 and the upper section is filled with an investment material such as plaster of Paris to form an upper mold section having a matrix portion 2 I complementary in shape to the exposed surface of the waxed-up model. The upper and lower flask sections are then separated and the wax I8 is removed by melting.

The mold is then charged with a plastic material, of which the denture is to be made, in an amount in excess of that needed to form the denture. The upper and lower flask sections are then reassembled and inserted in press to bring pressure to bear on-the upper flask section while the plastic material is subjected to heat to cure the same to form the finished denture. The flask sections are then separated and because of the tapered inner Wall 1 the completed denture and investment material is bodily pushed out at the bottom of the flask after removal of the bottom plate 5.

The investment material in the upper flask section is then removed after removing the cover plate 6. By cutting out the portion of the material around the upper conical wall lll, the molding material may be pushed out of the upper section 2 and the equipment is then available for making another denture.

Because of the use of an excess amount of plastic material, the finished denture will be smooth and non-porous with the inner surface [801. shaped to exactly the size of the jaw cast.

If as is the customary practice only sufficient material to secure the matrix portion of the mold is used, the shrinkage in molding will cause the plastic material to shrink away from the surface l8a of the jaw cast, resulting in an ill-fitting denture. Because of the available pressure on the plastic material applied through the upper mold section on the surface of the plastic material, the latter will flow into all of the space that had previously been filled with wax and will exert uniform fluid pressureon all portions of the investment material and against the invested teeth and anchorages. Consequently, if the investment material were not supported by the adjustable abutments or plates l2. the teeth or anchorages l6 and II. respectively, may be accidentally displaced. By extending the edge of the movable abutments l2 to substantially the center of the occlusal surface of the teeth, such displacement is impossible. While as previously stated the mold equipment of Figs. 1 to 3 may in some instances be employed to make full dentures, in most cases a full denture requires the use of a relatively hard base plate Zla, Fig. 4, on which the teeth are waxed up similar to the structure of Figs. 1 and 3. For this purpose I have provided a three-section mold, as shown in Fig. 4.

For the sake of simplicity, the two-part bottom flask may be designated by reference characters a and b which when assembled would constitute the bottom flask or mold section I of Fig. 3, these sections being joined by dowel pins 22 and pin holes 23 to maintain registered alignment and are secured by screws. The upper section is also provided with dowel pins 4 for maintaining alignment of the pressure platen with the flask, and the base 5 and cover 6 are employed as in Fig. 3.

It is to be noted that the inner walls of the bottom and top flasks are tapered as shown at I so that after the denture is completed the entire investment material of all the sections may be simply pressed downward to remove it from the mold after the material has been cut away at the chamfer ID.

The three-section mold differs from the twosection mold of Figs. 1 to 3 in that the upper section a of the bottom mold is not provided with a radial flange like the flange 8 of Figs. 1 to 3.

Instead, a flanged ring 24 is secured to the inner Wall of section a by screws 25, the member 24 being provided with adjustable abutting plates 26, like the plates [2 of Figs. 1 to 3. In making full dentures by the three-section flask or mold of Fig. 4, the cast of the jaw is made, such as the cast 21, and a base plate am is placed thereon, the base plate consisting of a material such as shellac of about 1% inch thickness which is pliable when heated to conform it to the shape of the cast 21. Soft wax iii of horseshoe shape is then placed on the base plate and the teeth lfib are inserted in the wax. The jaw cast is then invested in the bottom flask section b as shown and the middle flask section A is placed on the bottom flask with dowels 22 inserted in the holes 23 to maintain registered alignment of the flask sections.

The abutment plates 26 are then properly set as previously stated with their inner edges in substantial register with the center of the occlusal surface of the teeth, and secured in that position by the screws as shown. Investment material is then poured into this section leaving the palatal surface exposed. The upper flask section 2 is then placed on dowel pins 4 and investment material 28 is charged in the assembled flask. When the investment material is set the flask section 2 is removed and its investment material constitutes a pressure platen of the mold for the final molding operation. The wax I8 is then melted out leaving teeth lfib invested as shown in Fig. 4, and sections a and b are separated for the purpose of removing the base plate Zia. Sections a and b are then again assembled and charged with the plastic material in an amount in excess of that required to form the plate of proper thickness. The upper flask section 2 is then again placed on section a and the assembled mold and plastic material is subjected to heat and pressure in the usual manner.

On the final assembly of the flask sections a and b after the base plate 2 la has been removed and before charging the plastic material therein, the sections a and b are closed completely. When, however, the top section 2 is placed on the section a, the excess material will not permit the mold 2 to close on section a. By maintaining pressure on the upper section 2 the plastic material will flll the matrix formed by the invested teeth and jaw cast, numbered I62) and 21 respectively, and continuing pressure should be exerted on the upper section 2 so that there is always pressure available on the plastic material during the setting stage. Some of the excess material may be caused to escape from between the upper and middle mold sections by increasing the pressure so long as the pressure is limited to prevent complete closing of the top and center mold sections.

In the modified form of mold shown in Figs. 7 and 8, a lower and upper flask section 30 and 3|, respectively, are provided with lugs 32 and 33 by which the sections are fastened by bolts 34. The bottom flask section is provided with countersunk openings 35 which act as interlocks for the investment material. and the upper flask section 3| is provided with a central opening 36, the size of which is controllable by adjustable plates 31 that are anchored by a link 38 held by screws 39. link 38 constituting a clamping ring for the adjustment plate 31, the latter having the same function as plate i2 in Figs. 1, 2 and 3, and plate 26 in Fig. 4, to constitute a pressure abutment for the investment material above the occlusal surface of the denture.

The upper flask section 3| is provided with a hollow pressure platen 46 having dowel pins 4| that extend in openings 42 in the flask section 3| to maintain proper alignment. The hollow platent 49 is provided with a conical inner wall 4,3 which is the receptacle for the investment material that constitutes the pressure matrix such as that shown at 2! in Fig. 3 of the drawings and at 28 in Fig. 4, countersunk openings 44 being provided in the upper wall of the pressure platen for interlocking investment material with the platen. After the denture has been molded and cured it is usually very difficult to separate the plaster of Paris filled hollow platen from the mold because the hardened excess plastic material fills the irregularities in the surface 2| and thereby forms a mechanical lock with the denture. It is therefore ejected in its locked position with the rest of the contents of the flask, after the metal platen has been removed by cutting out the plaster of Paris in the interlocks M.

The opening in the platen is therefore specifically always made smaller than the central opening 36 in the upper flask section 3| to make possible this easy ejectment.

After the metal platen has been removed access is obtained to screws 39 which are removed, thereby freeing the adjustable pressure abutments and the clamping ring which in turn frees the contents from the upper flask section 3|. The bolts 34 are then removed and the lower flask section 3!] is removed by cutting out the plaster in the interlocks 35 therein. This leaves the entire contents in the upper flask section 3| from which it is easily ejected because of the smooth tapering inner wall.

Another advantage of the type of flask of Figs. 7 and 8 is its relatively light weight and the ready handling of the pressure platen All which by means of the dowel pins 4| always fits in the same place with proper registration of the matrix portion 2| and the built-up model invested in the sectional flask. The clamping of the abutment plate 3! by the ring 38 through the use of a pair of screws 39 facilitates adjustment of the abutment plate, and the entire structure is particularly designed to facilitate my new meth- 0d of molding dentures as disclosed in my application Serial No. 491,303 hereinbefore referred to.

I have found that as much as 30% in excess of the required plastic material will form a sound and dense denture and any excess material that would render the denture cross-sectional area greater than that needed does in no manner interfere with the fitting of the denture, and such excess material can be readily removed by scraping or in any other suitable manner. In the molding operation,m0st of the excess material will flow out between the closing mold sections.

By means of the above-described method, the teeth, anchorages and jaw cast maintain their proper relationship at all times and are never separated or disturbed in the method employing the two-section mold of Figs. 1 to 3 for making partial dentures and some full dentures.

Where, as described in connection with the use of the three-section mold of Fig. 4, a hard base plate is utilized for mounting the teeth, the mold sections are not separated until the wax has been removed and the teeth and jaw cast have been solidly invested in their respective flask sections.

In eitherlrcase the molding process of charge ing through the center of the bottom mold and applying the molding pressure to the palatal region of the denture permits the employment of excess plastic material to insure sound and solid dentures.

Also in either. the use of the two or three section molds by the present method the occlusal surface of the denture is firmly secured against displacement by the upper abutments that support the investment material above and around the entire periphery of the occlusal surface.-

The conical walls of the flask sections which, as shown in Fig. 4., would constitute a, continuing uniformly tapering wall if the molds were closed, is to provide a draft angle for the removal or the dentureand inve tme ia after m nletion by displacing the same in the direction of the larger diameter of the tapered wall.

Although several embodiments of the invention have been herein illustrated and described, it will be evident to those skilled in the art that various'medificatlons may be made in the details of construction without departing from the prinnles herein set truth- I claim:

1. In a mold for making dentures a sectional flask, th bottom section of which is provided with recesses for receiving investment material to be interlocked therewith and the upper section of which is provided with a central opening for exposing a waxed-up model, a plurality of abutment plates sufficiently rigid to resist molding pressure relatively adjustable and secured to the upper flask section in position for supporting the investment material around the occlusal surface of the Waxed-up model, and a pressure platen having dowel pins disposed in slots in said flask section for maintaining alignment therewith, said pressure platen having a recess for investment material constituting a portion of the matrix and having means for interlocking the same with the wall of the recess.

2. In a mold for making dentures, a hollow flask consisting of a plurality of sections having means for aligning and locking said sections, the top section having an opening, means adjustable on the top section for regulating the size and contour of said opening and being sufficiently rigid to resist molding pressure, and a pressure platen above said flask having means coacting with said flask for maintaining fixed alignment with the top opening in said flask, said platen being chambered to receive investment material which forms a portion of the matrix surface of the denture mold and extends through the upper flask opening in the molding operation.

3. In a mold for making dentures, a flask consisting of a plurality of sections having means for aligning and locking said sections, the top section having an opening, plates adjustably secured to the top flask section in position to vary the size and shape of said opening, said plates being sufilciently rigid to resist molding pressure, and'a pressure platen above said flask having means coacting with said flask for maintaining fixed alignment with said opening in said flask, said platen being chambered to receiv investment material which forms a portion of the matrix surface of the denture mold and extends through the upper flask opening in the molding operation.

4. In a mold for making dentures, a hollow flask consisting of a plurality of sections having means for aligning and locking said sections, the

top section having an opening, an abutment plate sufliciently rigid to resist molding pressure disposed beneath said opening, a clamping ring for rigidly securing said abutment plate in desired position, and a pressure platen above said flask having means coacting with said flask for maintaining fixed alignment with the top opening in said flask, said platen being chambered to receive investment material which forms a portion of the matrix surface of the denture mold and extends through the upper flask opening in the molding operation.

5. In a mold for making dentures, a hollow flask having an opening in the top thereof, means adjustable on the top sufficiently rigid to resist molding pressure for regulating the size and contour of said opening and a pressure platen above said flask having means coacting with said flask for maintaining fixed alignment 'with the opening in said flask, said platen being chambered to receive investment material which forms a portion of the matrix surface of the denture mold and extends through the flask opening in the molding operation.

JACOB DQSCHWARTZ. 25

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,502,377 Davies July 22, 1924 1,796,597 Fritzenwallner Mar. 17, 1931 1,926,508 Ballard Sept. 12, 1933 2,087,014 Beeker July 13, 1937 2,171,736 Ballard Sept. 5, 1939 2,171,759 E Meyer Sept. 5, 1939 2,233,295 Miller Feb. 24, 1941 2,279,952 Pryor Apr. 14, 1942 2,367,767 Gale Jan. 23, 1945 FOREIGN PATENTS Number Country Date 444,533 Germany May 24, 1927 463,544 Germany 1928

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