US2025344A - Blank for artificial teeth - Google Patents

Description

Dec. 24, 1935. v. FISCHER 2,@25,s44.

BLANK FOR ARTIFICIAL TEETH Filed Dec. 27, 1932 Patented Dec. 24, 1935 UNITED STATES BLANK FOR, ARTIFICIAL TEETH Victor Fischer, Beziers,.France Application December 27, 1932, Serial No. 649,025 In France December 31, 1931 2 Claims.

The invention relates to a process for the manufacture of blanks for casting artificial teeth including a core.

Previous knowledge covers the manufacture of blanks provided with a core for casting artificial teeth through depositing at will, by means of a spatula, liquid wax upon an artificial tooth which has been. dressed for this purpose, that is to say, an already prepared artificial tooth, and then in conforming to the required shape of tooth, the layer or coating of wax after the same has been solidified, as by scraping ofi the excess of wax from some parts of the tooth and by applying wax to some other parts of same. In this case, the same operation has to be repeated for every succeeding tooth, even when the shape of the tooth remains the same.

Furthermore, provision has been made to prevent as nearly as possible the displacement of the tooth used as a core after the wax cover thereof has been burnt off, as by putting around the same a wire which is capable of resisting the casting heat and the end of which is allowed to project freely from the layer of wax. Various metal wedges have also been proposed which are not fusible and which cross the layer of wax, which support the tooth at one end and which are maintained in their position by the solidified embedding body of the mold.

According to this invention, it is possible not only to avoid the previous preparation of the artificial tooth used as a core, but also to more easily control the thickness of the layer or coating of wax and to cause the same to conform more accurately to the future unequal wear of the metal tooth and, furthermore, to multiply or reproduce as many times as desired the same blank or model of tooth. Moreover, all necessity of the known fastening wires and metal wedges and their inconveniences are avoided.

According to the invention, the blanks are manufactured so that a core, which is held in a pending position in a divided casting mold by means of pins, is provided with a layer of wax corresponding to the desired metal coating of the tooth and this being done by casting or running the wax into the cavity existing between the core and the casting mold.

An embodiment of the object of the invention is represented by way of example in the accompanying drawing, in which:-

Figure 1 shows a cross section of a casting mold used for making a blank and holding a core in the required position for casting the wax.

Figure 2 is a longitudinal section of the blank of a molar tooth adapted to be used for bridge work and firmly secured by means of a molding Wall to the alveolar comb of the jaw.

Figure 3 is a longitudinal section of the blank of a molar tooth adapted to be used for the lower 5 bridge work.

Figure 4 is a longitudinal section made through the blank of a molar for a removable set of teeth.

Figure 5 shows, in longitudinal section made along the pin, a core which is held pending by 10 means of a pin in the mold for casting the metal.

According to this invention, molar teeth designed for use in connection with a removable set of teeth have improved hygienical properties due to the fact that the core a. is provided with a 5 plane palatal or tongue surface connecting the internal edge of the masticating surface along a straight line with its alveolar edge. In order to cast with a sufiicient thickness the masticating protuberances or inequalities which are the 20 most subject to wear, the core is flattened at the corresponding points. i

The core is provided with one or several pins 1) capable of holding the same pending in a casting mold, The pins are arranged to disturb as little 25 as possible the setting or application of the blank upon the casting of the jaw and the hinging in the articulator, although still firmly maintaining the core. In the case of molar teeth for bridge work, the pins are preferably secured to the plane: sura0 face in the vicinity of the inner edge of the masticating surface. In the case of molar teeth adapted to be used in connection with a non-removable set, the pins are also located on the inner face so that their cut and polished ends 35 are concealed. The pins are made of metal, for instance stainless steel, capable of withstanding the casting heat of the precious metal. The pins are preferably duplicated and can be made of equal or unequal shape. One of the pins can be 40 thinner than the other and may also be provided with a pointed or tapered free end.

In order to make a blank by means of the described core a. provided with one or several pins b and consisting of a fire-proof material, use is 45 made of the divided casting mold shown by way of example in Figure 1, whose parts I and 2 surround a cavity-3, the shape of which corresponds to that of the body of the artificial teeth and which can be opened in displacing the part 2 from thepart I. The part I of the mold is provided with a channel 4 used for directing the liquid casting material into the cavity 3. In the embodiment of the divided casting mold, the removable part 2 is provided with a hole 5 into which a pin b of the core a is introduced. As shown in this figure, the pin 2) is notched and provided with wedge-shaped surfaces which join the notch and on which a bolt 6, movably mounted in the part 2 and loaded by a spring I, can slide before the same engages the notch in order to firmly secure the pin. The part 2 of the mold can also be provided, besides the hole 5, with one or several holes in which the pins of the core may be introduced. The said pins may be smooth and be provided with pointed ends. The parts I and 2 are prevented from moving by means of projections I2 provided on the one part engaging grooves l3 formed in the other part, and connected by means of suitable fasteners or securing means, such as hooks 9, for example.

In order to make the layer or coating of wax, the core a is to be suspended or placed in the pending position in the cavity 3 of the casting mold I, 2. To permit this, the part 2 is removed from the part I, the pins of the core are introduced into the hole of the core so that the pin b is engaged and held by the locking bolt 6, whereby the pin 17 is secured inthe required position. The part 2 is then secured upon the part I. A wax mixture is run or cast into the cavity 3 containing the core. A given metal casting mold does not correspond merely to a determined sort of teeth, but also to a determined size of the tooth cores. In order to prevent any confusion between the parts of one mold and those of other molds, the difierent parts of the molds may be provided with distinguishing marks.

When several blanks are to be cast in a single casting mold, the latter is provided with several cavities for the cores a to be coated with wax and with a channel or duct connecting the said cavities, which channel is capable of leading the liquid wax from a common inlet orifice or port 4 to the cavities. The last cavity is connected to a vertical channelthrough which air may escape from the cavities when the latter-are filled with wax.

Y When the wax has set, the mold is opened and the cast blank is removed. In order to relieve the blanks from the part 2 of the mold, the pro- J'e'ctingend of the core pin 1) is pressed back into the hole 5 until the bolt 6 has moved from the notch. Y

The blank is then ready to be used for casting a tooth. The blanks are, as usual, embedded in a metal cylinder (Figure 5) containing a soft mass II which can be solidified. After the same is solidified, the wax mixture is melted out of the embedding body by heating the metal cylinder. The core a then assumes in the mold the position shown in Figure 5, wherein it is secured against any displacement by means of the pin 1) or by means of further pins. The cavity left between the core a, and the mold wall of the embedding body H is filled with molten precious metal supplied in the way which is usually adopted for casting plain or solid metal teeth without cores. The core a thus passes automatically into the cast artificial tooth. The said blanks savei'or the dentist a large number of minute operations and allow him to make the metal teeth in a more accurate manner than heretofore, because his work consists merely in selecting a blank suitably adapted to the present case, while the thickness of the layer of precious metal has been calculated and determined beforehand. A general improvement of the tooth prosthesis is the result, not only of the improved shape of the core, but also of the fact that the same weight of precious metal allows to obtain a more hygienical form of the bridge prosthesis, without involving the technical difficulties which were to be overcome up to now.

I claim:--

1. A blank for the manufacture of metal coated artificial teeth, comprising a core, a layer of wax surrounding the core, the thickness of the wax layer being greatest at that point where the maximum wear of the formed tooth will occur, and a pin fixed in said core and projecting outwardly through the layer of wax, said pin being formed with a wedge-shaped end and with a notch adjacent to said end, said notch comprising means whereby the pin may be secured in the wall of the casting mold receiving said core with the pin holding the core immovably in a freely suspended position within the mold.

2. A blank for the manufacture of artificial teeth coated with a precious metal, comprising a heat resisting core, a layer of wax surrounding the core, the thickness of the wax layer being at the maximum at the area providing the masticating surface of the finished tooth, a heat resisting pin fixed in the core and projecting outwardly through the layer of wax at the side of the blank, said pin being formed with a wedge shaped end, and a laterally arranged notch adjacent said end, the notch serving to permit the pin to be firmly locked in the Wall of a casting mold receiving the blank to permit the blank to be freely suspended within the casting space of the mold.

VICTOR FISCHER.

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