US2792628A

US2792628A - Prosthetic tooth simulating a natural tooth having a filling and method of making the same

Info

Publication number: US2792628A
Application number: US483937A
Authority: US
Inventors: Neumayer Wilhelm
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-01-29
Filing date: 1955-01-25
Publication date: 1957-05-21
Anticipated expiration: 1974-05-21

Description

May 21, 1957 w. NEUMAYER 2,792,628 PROSTHETIC TOOTH SIMULATING A NATURAL TOOTH HAVING A FILLING AND METHOD OF MAKING THE SAME Jan. 25, 1955 Filed 1 mmvrozc WIH'IQIM Neum MueJM Unite Sttes Patent PROSTHETIC TOOTH SIIVIULATING A NATURAL TOOTH HAVING A FILLING AND METHOD OF MAKING THE SAME Wilhelm Neumayer, Heilbronn, Germany Application January 25, 1955, Serial No. 483,937 Claims priority, application Germany January 29, 1954 8 Claims. (Cl. 32-8) The present invention relates to a prosthetic tooth simulating a natural tooth having a filling, and to a method of making the same. More particularly, the present invention relates to a prosthetic tooth appearing to have a filling, such as gold or amalgam fillings which are customarily applied to a natural tooth, so as to more closely simulate a natural tooth.

It is known to put fillings into prosthetic teeth which do not only simulate the fillings made in natural teeth but which are actually made by the same method which is used for the filling of natural teeth. According to the customary procedure, a hole is bored into the prosthetic tooth at the desired spot which will be potentially visible when the prosthetic tooth is placed in a persons mouth, and the hole is filled just like cavities in natural teeth are filled. It is a disadvantage of this process that relatively large quantities of filling material have to be used, thus increasing the cost when precious metals or their alloys are applied. Furthermore, the filling of the prosthetic tooth made by these customary methods comes in contact with the contents of the oral cavity and thereby is exposed to attack by chemically active substances.

It is an object of the present invention to overcome the aforementioned disadvantages.

It is a further object of the present invention to provide a prosthetic tooth closely simulating a natural tooth having a filing, thereby using considerably smaller quantities of filling material than were heretofore needed for this purpose.

It is still another object of the present invention to join the filling simulating material to the prosthetic tooth so as to prevent its exposure to the oral cavity and thereby avoiding chemical reactions which might damage the material. 7

With the above objects in view, the present invention mainly consists in a false tooth comprising, in combination, a prosthetic tooth of artificial tooth-simulating material, a thin metal body joined to the prosthetic tooth on a portion of the tooth visible when the prosthetic tooth is in a persons mouth so that the false tooth in a persons mouth appears to have a filling and thereby more closely simulates a natural tooth having a filling, and a layer of transparent plastic covering at least the metal body portion of the false tooth and protecting the metal body.

The present invention also comprises in a method of making a false tooth, the steps of joining to the surface of a prosthetic tooth of artificial tooth-simulating material a thin metal body, and covering the surface of at least the thin metal body with a thin layer of solidifiable transparent plastic material.

In accordance with the present invention, a thin metal body is joined to a prosthetic tooth made of porcelain or plastic synthetic material and covered with a transparent layer of synthetic plastic material. The porcelain or the synthetic plastic material of which the prosthetic tooth is formed may contain coloring materials so as to closely resemble the color of a natural tooth. The surface of the thin metal body in accordance with the present invention simulates the surface appearance of a Patented May 21, 1957 filling in a natural tooth both as to color and shape. The synthetic plastic layer covering the surface of the metal body may also cover adjoining surface portions or the entire surface of the prosthetic tooth. This covering layer is preferably made of colorless, transparent material so as not to be visible when the false tooth is in a persons mouth.

Various methods for the making of a false tooth can be used in accordance with the present invention, depending on whether the metal body is to be joined to a finished prosthetic tooth of either porcelain or synthetic plastic material, or whether the metal body is to 'be joined to a prosthetic tooth of synthetic plastic material during the making of the same.

According to a method of the present invention a false tooth may be molded by first covering at least a portion of the inner surface of a tooth-forming mold with a synthetic material adapted to form upon heating a hard transparent layer, placing a thin metal body in the mold on the portion thereof which iscovered by the synthetic material, filling the mold with artificial tooth-simulating material which is adapted to harden upon heating under pressure, heating the mold with these materials and the metal body therein under pressure so as to form a hard body having the shape and appearance of a tooth, and removing the thus formed false tooth from the mold, the false tooth simulating a natural tooth having a filling.

In order to join a thin metal body to a previously formed prosthetic tooth in accordance with the present invention so as to simulate a tooth-filling, a shallow indentation of desired dimensions is formed in the surface of a plastic tooth, preferably by abrasive methods, and a thin metal body of such dimensions as to substantially fill the indentation is placed therein.

When it is desired to join a thin metal body to a prosthetic tooth made of porcelain, the method of the present invention also includes the step of forming a shallow indentation in the surface of the porcelain tooth. In a preferred execution of the method of the present invention the surface of the indentation in a porcelain tooth is roughened and thereafter moistened with a syrupy synthetic plastic material, preferably belonging to the group of ethylene oxides or polyurethanes. The thin metal body is then fitted into the indentation and adhered to the surface thereof by the adhesive qualities of the synthetic syrupy material. Again, the dimensions 'of themetal body approximate the dimensions of the indentation. At least the surface of the metal body and, if desired, also adjoining portions of the surface of the porcelain tooth are then covered with a thin layer 'of transparent plastic synthetic material. Preferably ethylene oxides or polyurethanes are used for this purpose. The synthetic plastic layer adhering the thin metal body to the surface of the indentation and the synthetic plastic layer covering the free surface of the metal body are then polymerized, for instance by heating the false tooth for about 15 minutes to a temperature of about 200 C. It is most preferred to use a plastic synthetic material in connection with a porcelain tooth a synthetic resin belonging to the group of ethylene oxide resins since these resins possess a glass-like transparency, have affinity to porcelain and polymerize without contraction in volume. These resins penetrate the microscopic and capillary apertures in the surface of the porcelain tooth and thereby form an extremely intimate connection. Furthermore, the resins to which the present invention is applicable are insoluble, non-poisonous and possess great strength, all of which qualities are very desirable in a transparent layer according to the present invention.

In accordance with another preferred embodiment of the present invention the false tooth having the layer of transparent material thereon is polished at least on that portion of its surface which is covered by the transparent plastic material. It is therefore advisable to provide for a small surplus thickness ofthe plastic layer which will be removed during thepolishing process.

It will be apparent from the forgoing that a large percentage of the precious metal or precious metal alloy customarily used for fillings of false teeth is saved by replacing the conventionalfilling with the thin metal body of the present invention. It will also beapparent that the simulated filling provided by the present invention is not exposed to chemical or mechanical injury because it is protected by the transparent synthetic layer.

The synthetic plastic tooth-simulating material from ch. h Pr he c tooth o he p e n n t on s formed canbe any synthetic plastie material customarily ssdi r he. m nufac ure o pro t e i s o quently it is composed of polyacrylj and polymethacryl acid methyl esters. The prosthetic tooth may also be formed from the monomer compoundina dry process by heating to about 170C. under high pressures, or it may be formed from powder and liquid by heating to about 100 C; Acrylates which are commercially available for the purpose of forming prosthetic teeth are sold under a variety of trademarks such as for instance Paladon, Palapont, or Lucite. Customarily they are colored so as tomore closely simulate the color of natural teeth.

Porcelain teeth consist of porcelain compositions well known in the art and contain as coloring agents preferably metal oxides so as to closely simulate the color of natural teeth.

The transparent layer with which the metal body joined to a synthetic plastic tooth is covered, consists preferably ofsynthetic plastic material belonging to the groups of polyacryl and polymethacryl acid methyl esters, such as are also used for forming the synthetic plastic tooth. However, other synthetic plastics having similar physical and chemical characteristics may also be used.

The synthetic plastic materialsused' for adhering the metal body to a porcelain tooth and for covering the metal body joined to a porcelain tooth preferably belong to the groups of ethylene oxides or polyurethanes.

The thin metal bodies are preferably made of precious metals or alloys of the same and most preferably of gold 'or gold alloys.

The thickness of the thin metal bodies is preferably kept to between 0.1 mm. and 0.02 mm. and most preferably to approximately 0.05 mm.

The thickness of the transparent layer which covers atleast the free surface of the metal body in accordance with the present inventionis preferably kept at between 0.3 and 0.1 mm. and most preferably at approximately 0.2mm.

The previously mentioned ethylene oxides andtransparent, polyurethanes are only used in connection with porcelain teeth and not in connection with teeth made of synthetic plastic materials since tempertures of at least between 150 C. and 160 C. are required for their polymerization. A prosthetic tooth made of porcelain can easily'withstand these temperatures while prosthetic teeth made of synthetic plastic materials incur structural damage when exposed to such high temperatures without con; current considerable increase in pressure. To the extent to which it becomes possible to polymerize and harden the polyurethane resins and ethylene oxides at lower temperatures, it will also be possible to use these resins as transparent layer on synthetic plastic teeth.

The following examples are given to further. illustrate the process of the present invention, the scope of the invention not however being limited to the specific details of the examples.

EXAMPLE 1 Making of a prosthetic tooth with a simulated filling from monomeric acrylate A thin layer of colorless acrylatepowder such as Lucite a tooth mold, corresponding to the surface portion of the prosthetic tooth on which the simulated filling is to be located. This corresponds to the layer covering metal body 3 of Pig. 1 of the drawing, as will be more clear from the specific description, ofthe drawing.

A small circular gold plate having a thickness of 0.05 mm., and a diameter of 2 mm. is positioned on the acrylate powder.

Thereafter the mold is filled with acrylate powder suitably colored so as to simulate the color of natural tooth.

The mold is closed and heated for about 10 minutes to about 170 C. at a pressure of 10 atmospheres.

The mold remains in the press until it is cooled, thereafter it is opened, the prosthetic tooth is taken from the mold, the mold-flash removed, and the thus formed false tooth is polished.

EXAMPLE 2 Making of a prosthetic tooth with a simulated filling from polymeric acrylate A thin layer of-colorless polymeric acrylate such asfon instance Palapont of dough-like consistency isplaced on a portion of the inner surface of a tooth mold.

A small rectangular goldalloy. plate having a gold content of athickness of 0.07 mm., a length of 2 /2 mm. and a width of 1 /2 mm. is positioned on the doughlike polymeric acrylate mass.

Thereafter the mold is filled with polymeric acrylate of dough-like consistency which has been suitably colored so as to simulate the-color of a natural tooth.

The surplus is squeezed out of the mold, the mold is closed and heated for 1 hour to C. under an excess pressure of betweenS and 5 atmospheres.

After cooling of the mold, the tooth is finished as-described in Example 1.

EXAMPLE 3 Making of a simulated filling on a prosthetic tooth con sisling of synthetic plastic material EXAMPLE 4 Making of'a;,simulated filling on,a pr0sthetic tooth c0nsisting of. porcelain Ashallow indentation is ground in the chosen portion of the surface of the prosthetictooth. This indentation is 0.05 mm deep, of approximately circular shape, having a diameter of 2 /2 mm.

The surface of the indentation is moistened with a colorless, transparent polyurethane resin.

A gold alloy plate containing 90% of gold and dimensioned so as'to fit into the indentation is placed therein.

The free surface of the plate and the surroundingsurface-area-of the porcelain tooth are covered with a polyurethane layer having a thickness'of 0.15 mm.

The polyurethane is polymerized by heating of the prosthetic tooth on a hot plate to 200 C. keeping it at that temperature for 15 minutes.

After grinding 01% any excess of the transparent plastic material, the plastic covered area of the prosthetic tooth is polished.

The novel features-which are considered as characteristic forthe invention are set forth in particularin the appended claims. The invention itself, however, both' as to itsconstruction and its method of operation, togethenwith additional objects and advantages thereof, will be bestunderstoodfrom thefollowingdescription of spe-- cific embodiments when read in connection with the accompanying drawings, in which:

Fig. 1 is a cross section through tooth-forming mold and a prosthetic tooth according to the present invention; and

Fig. 2 is a perspective view of a false tooth according to the present invention.

Referring now to the figures, and more particularly to Fig. 1, a prosthetic tooth of synthetic plastic material is made in accordance with the present inv n ion by placing a thin layer 2 of colorless transparent p re material into the lower half 1 of the mold, thereafter placing a thin metal body 3 on a portion of the lower par-t l of the mold corresponding to the surface portion of the prosthetic tooth on which the simulated filling is to In the illustrated embodiment the colorless plastic layer 2 has also been applied to the inner surfs e of the upper portion 5 of the mold. lower part 1 of Thereafter the the mold and the upper part 5 of the mold are completely filled with a colored plastic 4. The two parts of the mold are put together and the false tooth is formed by application of heat and pressure as previously described.

The false tooth shown in Fi ure 2 comprises a prosthetic tooth 7 made of porcelain, a thin metal body 8 simulating a filling, and a thin colorless transparent layer 9 covering the metal body. This plastic layer 9, due to its being transparent and colorless, while indicated in the drawing cannot actually be seen when the false tooth is in a persons mouth.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of false teeth differing from the types described above.

While the invention has been illustrated and described as embodied in prosthetic teeth, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A false tooth comprising, in combination, a prosthetic tooth of porcelain tooth-simulating material; a thin metal body joined to said prosthetic tooth on a portion of said tooth visible when said prosthetic tooth is in a persons mouth so that said false tooth in a persons mouth appears to have a filling and thereby more closely simulates a natural tooth having a filling; and a transparent layer made of transparent synthetic plastic material selected from the group consisting of transparent water insoluble polymerized ethylene oxides and transparent polyurethanes covering at least said metal body portion of said false tooth and protecting said metal body.

2. A false tooth comprising, in combination, a prosthetic tooth of porcelain tooth-simulating material; a thin metal body joined to said prosthetic tooth on a portion of said tooth visible when said prosthetic tooth is in a persons mouth so that said false tooth in a person's mouth appears to have a filling and thereby more closely simulates a natural tooth having a filling; a layer of synthetic plastic material selected from the group consisting of water insoluble polymerized ethylene oxides and polyurethanes adhering said thin metal body to said portion of said tooth; and a transparent layer made of transparent synthetic plastic material selected from the group consisting of transparent water insoluble polymerized ethylene oxides and transparent polyurethanes covering at least said metal body portion of said false tooth and protecting said metal body.

3. In a method of making a false tooth, the steps of forming a shallow indentation in a portion of the surface of a prosthetic tooth said portion being visible when said prosthetic tooth is in a persons mouth; placing into said indentation a thin metal body being so dimensioned as to substantially fill said indentation; and covering the surface of at least said thin metal body with a thin layer of solidifiable transparent plastic material.

4. In a method of making a false tooth, the steps of forming a shallow indentation in a portion of the surface of a prosthetic tooth said portion being visible when said prosthetic tooth is in a persons mouth; covering the surface of said indentation with an adhesive latently hardenable synthetic material; placing into said indentation and adhering to the surface thereof by means of said ad- 'hesive material a thin metal body being so dimensioned as to substantially fill said indentation; and covering the surface of at least said thin metal body with a thin layer of solidifiab'le transparent plastic material.

5. In a method of making a false tooth, the steps of forming a shallow indentation in a portion of the surface of a prosthetic tooth said portion being visible when said prosthetic tooth is in a persons mouth; roughening the surface of said indentation; covering the surface of said indentation with an adhesive latently hardenable synthetic material; placing into said indentation and adhering to the surface thereof by means of said adhesive material a thin metal body being so dimensioned as to substantially fill said indentation; and covering the surface of at least said thin metal body with a thin layer of solidifiable trans parent plastic material.

6. In a method of making a false tooth, the steps of joining to the surface of a prosthetic tooth of artificial tooth-simulating material a thin metal body; covering the surface of at least said thin metal body with a thin layer of solidifiable transparent plastic material; and polishing at least the portion of the surface of said false tooth having said layer of transparent plastic material thereon.

7. A false tooth comprising, in combination, a prosthetic tooth of porcelain tooth-simulating material; a thin metal body joined to said prosthetic tooth on a portion of said tooth visible when said prosthetic tooth is in a persons mouth so that said false tooth in a persons mouth appears to have a filling and thereby more closely simulates a natural tooth having a filling; and a transparent layer made of transparent polyurethane covering at least said metal body portion of said false tooth and protecting said metal body.

8. A false tooth comprising, in combination, a prosthetic tooth of porcelain tooth-simulating material; a thin metal body joined to said prosthetic tooth on a portion of said tooth visible when said prosthetic tooth is in a persons mouth so that said false tooth in a persons mouth appears to have a filling and thereby more closely simulates a natural tooth having a filling; a layer of polyurethane adhering said thin metal body to said portion of said tooth; and a transparent layer made of transparent polyurethane covering at least said metal body portion of said false tooth and protecting said metal body.

References Cited in the file of this patent UNITED STATES PATENTS 325,626 Phillips Sept. 1, 1885 2,302,375 Myerson Nov. 17, 1942 2,393,817 Schlosser et a1. Jan. 29, 1946 2,677,150 Rydin May 4, 1954

Claims

1. A FALSE TOOTH COMPRISING, IN COMBINATION, A PROSTHETIC TOOTH OF PORCELAIN TOOTH-SIMULATING MATERIAL; A THIN METAL BODY JOINED TO SAID PROSTHETIC TOOTH ON A PORTION OF SAID TOOTH VISIBLE WHEN SAID PROSTHETIC TOOTH IS IN A PERSON''S MOUTH SO THAT SAID FALSE TOOTH IN A PERSON''S MOUTH APPEARS TO HAVE A FILLING AND THEREBY MORE CLOSELY SIMULATES A NATURAL TOOTH HAVING A FILLING; AND A TRANSPARENT LAYER MADE OF TRANSPARENT SYNTHETIC PLASTIC MATERIAL SELECTED FROM THE GROUP CONSISTING OF TRANSPARENT WATER INSOLUBLE POLYMERIZED ETHYLENE OXIDES AND TRANSPARENT POLYURETHANES COVERING AT LEAST SAID METAL BODY PORTION OF SAID FALSE TOOTH AND PROTECTING SAID METAL BODY.