US2858568A

US2858568A - Means for processing dentures

Info

Publication number: US2858568A
Application number: US388494A
Authority: US
Inventors: Myerson Simon
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-10-27
Filing date: 1953-10-27
Publication date: 1958-11-04
Anticipated expiration: 1975-11-04

Description

Nov. 4, 1958 vs. MYERsoN MEANS FOR PROCESSING DENTURES Filed Oct. 27. 1955 BY 2.( 4M;

MEANS FOR PROCESSING DENTURES I Simon Myerson, Waban, Mass.

Application October 27, 1953, Serial No. 388,494 1 Claim. (ci. 1st- 33) The present invention relates to a means for accurately reproducing original models or trial dentures.

In the practice of prosthetic dentistry when preparing dentures, the dentist first prepares a trial plate consisting of wax or other similar components in which various teeth are set in their proper positions. When this trial denture has been made and fitted to the mouth of the patient and found satisfactory to esthetics, fit and articulation, it is then subjected to a process hereinafter more fully described in which a permanent plastic material is substituted for the wax.

The reproduction of the trial wax denture into a permanent plastic denture has llong been a recognized problem particularly with respect to proper articulation. In the ordinary process of producing a denture, the trial dentures are attached by wax to a cast which is then placed in one-half of a container known as a flask, and after this portion of the investment has set, the top surface or land is painted with a film of soap or other separating medium to the edge of the trial denture which projects above the investment. The upper half of the flask is then secured over the first mentioned half and a second section of plaster is poured into the flask covering the trial denture. When this upper part of the investment has hardened, the flask containing the investment, cast and trial denture is placed in warm or hot Water until the wax has softened enough to be removed. The two halves of the investment thereby form a cavity mould already containing the artificial teeth in proper position in which a permanent plastic material, such as a resin of methyl methacrylate, is packed after first placing a thin sheet of cellophane or the like over the cast.

Ordinarily much more plastic material is placed in the cavity than is needed. The two halves of the investment are then fitted together and the halves of the flask containing them are then forced together in a press device. As the two halves of the flask are forced together, excess plastic material will ooze out between the two opposite faces or lands of the investment. The flask is then removed from the press and excess plastic material is removed. This process, which is called trial packing, is repeated several times until the operator believes just enough plastic material has been removed for the flask to completely close. Ordinarily he determines the ask is closed when he can no longer detect plastic material being forced onto the land. This method of determining whether the flask is properly closed is, however, inaccurate as the ask is not necessarily completely closed merely because there ,is no more plastic material being forced onto the land. In fact when trial packing, the two halves of the ask do not ordinarily approximate each other within .015 of an inch, as the acrylic resins which are used to form the denture tend not to ow through gaps of such narrow dimensions. vThe present invention overcomes these difliculties by providing a method and equipment by means of which a technician forming a denture may readily and properly close the t United StatesI Patent O Patented Nov. 4i, 1958 fit:

more accurately reproduced in the finished product than heretofore. Moreover, this considerable improvement in accuracy will be accompanied by a substantial saving of time.

In this invention, I have provided a press for forcing the two halves of the flask together which has a measuring means which may be used to determine accurately whether or not the ask is properly closed.

A further object and advantage of the present invention is that it enables the technician or operator to use efciently the plastic material which forms the dentures, and to compensate for any known shrinkage or expansion of this material while it is being used. In my method of preparing dentures, a trial denture is first formed and secured to a cast and is then invested into one-half of the flask as is ordinarily done. A melted layer of Wax, preferably very soft, is then painted onto the land to a thickness of between .005 and .020 of an inch. The upper half of the flask is then placed in the correct position and in Contact with the lower half, and plaster is poured into the second half of the flask, forming a ycomplete investment. The flask is then placed in a screw press. The screw thereof is provided with a member which contacts the upper member of the flask by means of which the ask members are pressed together.

In this invention, I provide a press having means for measuring the particular position of the pressing member when the flask is properly closed. After noting or setting the particular reading on the measuring element at which the two halves of the flask are held firmly together in position, the flask is removed and opened. The wax is then removed in the usual manner and the investment is painted with an alginate or a type of tin foil substitute. The denture resin is then packed in the ordinary fashion into the cavity of the investment containing the teeth with more than enough material to form the denture. The flask is closed and placed in the press and the screw is turnedto force the two halves of the ask together until the reading on the measuring device is the same as it was previously. When the sections of the flask are forced together, the excess denture resin is forced out of the investment cavity into the space between the lands formed by the application of the soft waX. This space is of the same magnitude as the thickness of the layer of wax applied. The thickness of the space required between the lands will depend on the flowability of the particular resin being used, The denture is then cured in the usual manner.

One of the important merits -of the present invention is the preservation of thev correct articulation of the artificial teeth as established lby the dentist. If the flask containing the denture has not been properly closed, the increased thickness of the denture in the area of the posterior teeth will be increased, resulting in what is usually termed as opening of the bite.

These and other advantages and objects of the present invention will be more fully understood when considered in connection with the drawings 4in which:

Figure 1 is a plan view of a press containing a ask.

Figure 2 is a fragmentary sectional view of the measuring elements of Figure. 1.

Figure 3 is a cross sectional view of the flask containing an investment and denture.

Figure 4 is a fragmentary view of a modification of the elements of Figure 2.

Referring to Figure l, there is shown a press embodying my invention in which an .accurate and full closure of the ask may beachieved ruring the processing of the denture. The press is provided with a base 1 preferably flat, fixed to a frame 2. The frame 2 is provided with two upwardly extending

opposite legs

3 and 4 and a transverse span 5. The span 5 has acentrally located threaded hole 6 extending perpendicularly through it. This hole 6 may be provided at its upper end with a concentric hardened steel bearing plate 7. Through this hole is threaded a crew -8 which is free to be moved .up and down. At the lower end of this screw Ais secured Va freely movable press element generally designated 9 which Acomprises an inner barrel 10 and an outer barrel 11, said barrel 11 having an outwardly extending circular base 12. Suitably secured to this base is a plate 13 of hardened steel. The upper end of the screw is provided with a head 14 having ya hole through which a bar or lever 15 is secured by a set screw 16. Instead of the rigid lever herein illustrated, a torque wrench lever capable of `being set to exert a pre-determined force may be employed.

A cylinder 17 having a central threaded aperture through it is fitted onto the screw 8 in a position at the upper end of the screw. This cylinder, although it is threaded on the screw 8, has sufliciently tight a fit so that it may not readily change its position relative to the screw 8 unless intentionally turned. Normally it will turn with the screw 8. In order to facilitate the moving of this cylinder when desired, a marginal section 18 near the top of the side wall may be knurled. Also fitted on the screw is a nut 19 which is threaded to lit onto the screw 8. At the upper end of this nut 19 is an annular upwardly extending peripheral flange 20 which forms an inner recess 21 at the center of the nut. The upper edge 25 of this llange is beveled inwardly towards the outer face of the cylinder 17.

The recess 21 has a sufliciently wide diameter as to permit the lower end of the cylinder 17 to fit within it as the nut 19 and cylinder 17 are screwed towards each other.

yOn the surface of the cylinder 17 is provided calibrations comprising a series of horizontal parallel lines each at an equal distance apart, preferably J/10 of an inch apart. A vertical line divides these horizontal lines in equal sections. On the edge 25 of the nut 19 is provided a series of twenty-five vertical equi-distant lines. -If the screw 8 has ten threads to the inch, each calibration on nut 19 will indicate a relative change in the positions between cylinder 17 and nut 19 of .004 of an inch. There may also be positioned on the screw 8 a case hardened locknut 22.

In the operation of this press after the trial denture 50 has been placed in `a flask 23 and with au investment 52 surrounding it, in the manner briefly mentioned above, with a layer of soft wax 53 separating the opposite lands 54 of the investment, the flask is then placed upon the base 1 and the screw is turned down until the platey 13 comes into contact with the top of the flask 23. The operator then tightens the screw so that the edges of the two parts of the flask meet firmly as shown at 49, Figure 1. To properly position this flask each time, the base 1 of the press m-ay be provided with a series of upwardly extending pins 24 which may be used to center the flask at lall times. Having closed the flask firmly, the operator then turns the locknut 22 until it comes into contact with the hardened bearing plate 7. He then screws the nut 19 downward until it contacts the locknut 22. He may take the reading at this point, or he may rotate the cylinder 17 downward until it reaches a point at which the horizontal calibration marked zero on the cylinder 17 registers with the zero on the upper edge of the calibrated nut 19. This establishes the position at which the flask was closed. The screw 8 is then loosened and the flask is removed and opened. The wax forming the trial denture and the soft wax which was placed on the lower portion of the investment before the upper part of the investment was formed in then removed by boiling water or warm water. If boiling water is used, the wax may be removed in about four minutes, after which any remaining traces of wax are cleaned out by flushing.

The denture resin in a flowable state is then packed over the teeth and surrounding cavity in the investment. Enough material is pressed into position to insure that when the lflask is closed there will be more than enough resin to occupy the denture cavity. The flask is then closed and any excess resin will be squeezed out in a thin ribbon between the lands lof the two parts of the investment, which because of the coating of soft wax placed there during the forming of this investment are spaced apart between .O05 and .020 of an inch. When the flask is thus forced into a closed position in the press, the operator can be certain that the flask is properly closed if he turns the screw down to a point at which the nut 19 comes into contact with the locknut 22 when the locknut 22 is in contact with the bearing plate 7. This is the same position established by the original setting. `If the operator can rotate the nut 19 he will know the llask is still open. By means of the micrometer cylinder 17 and nut 19, he can determine to what extent it is open and make correction accordingly. When the flask is closed, the denture is cured and then removed from the investment; any excess plastic material in the form of a ribbon may then readily be removed.

In the modification .as illustrated in Figure 4, the screw 41 is threaded through the bridge member 42 corresponding respectively to the screw S and the bridge member 5 of Figure l. Secured to the bridge member 42 is a bracket 43 supporting yan indicator device having a scale member 44 and an indicator 45, pivoted at 46. The indicator has one end positioned to point to the scale member 49 and the other end adapted to contact the lower lsurface of the nut 47 whereby the longitudinal movement' of the nut 47 may readily be registered 'on the scale Imember 44.l

Alternatively, the indicator 45 may be used as an actuator for a microswitch, which may be connected to a light circuit which will signal the` closing of the flask.

Although I have illustrated my invention using screw pressure means because this type of press is most commonly used, it is obvious that the pressing member may be operated `by a lever, air, or hydraulic pressure. Other modifications may be made without departing from this invention.

Having now described my invention, I claim:

A press for closing a dental flask comprising a base, a bridge member arching over and supported from said base, said bridge member having a threaded hole ftherethrough, a screw threaded through said hole and extending downwardly toward said base, a plate supportedion the lower end of the screw for closing a flask supported on the base, a nut threaded on the screw above the bridge member and having a recess formed on its upper surface, a cylinder threaded on the screw above the 4nut and adapted to move in and out of the recess when the nut and cylinder are moved relative to one another on the screw, said nut and cylinder each being movable on the screw, and calibrations formed on the adjacent portions of the nut and the cylinder indicating relative positions of the nut and cylinder and the condition of the flask.

References Cited in the le of this patent UNITED STATES PATENTS 1,424,383 Schleicher Aug. 1, 1922 1,941,780 Angell Jan. 2, 1934 2,006,903 Roelofs July 2, 1935 2,320,826 Mandel June 1, 1943 2,358,730 Nelson et al. Sept .19, 1944 2,491,147 Zahn Dec. 13, 1949 2,666,263 Laserson Jan. 19, 1954 2,761,175 Myerson Sept. 4, 1956 FOREIGN PATENTS 46,874 Sweden Apr. 1, 1909 429,486 Germany May 29, 1926 1,045,870 France July 1, 1953