United States Patent: 3601895

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United States Patent	3,601,895
Zollner	August 31, 1971

METHOD OF MAKING A DENTAL CROWN WITH GOLD APRON

Abstract

In a method of making a dental crown, a die is made from an impression of a tooth. A ringlike apron which is preformed is swaged on the die. Alternatively, the apron is formed as a casting made from an impression of the die. A porcelain jacket is then formed on the apron and die. The jacket is then bonded to the apron. The assembly of apron and jacket are then installed on the tooth by cementing both the jacket and apron to the tooth.

Inventors:	Zollner; Frank L. (Long Island City, NY)
Appl. No.:	05/006,170
Filed:	January 27, 1970

Current U.S. Class: 433/223 ; 433/218

Current International Class: A61C 5/08 (20060101); A61C 5/10 (20060101); A61c 005/08 ()

Field of Search: 32/12,2,8 264/16,21

References Cited [Referenced By]

U.S. Patent Documents


2770040	April 1956	Moyer
2930125	March 1960	Pos

Primary Examiner: Peshock; Robert

Claims

What is claimed is:

1. A method of making a dental crown for a tooth, comprising the steps of making a die from an impression of the tooth, said die having a smaller upper portion and larger lower portion with an annular shoulder between the upper and lower portions; applying a ringlike apron to the shoulder of the die, said upper portion of the die extending through the apron; forming a porcelain jacket on the apron and upper portion of the die; bonding the jacket to the apron; removing the bonded assembly of jacket and apron from the die; and polishing the assembly.

2. A method as defined in claim 1, comprising the further step of mounting said assembly on said tooth, and cementing both said jacket and said apron to the tooth simultaneously.

3. A method as defined in claim 1, comprising the further steps of forming dovetailed grooves in the apron and applying a settable cement to the apron prior to bonding the jacket to the apron.

4. A method as defined in claim 1, comprising the further step of swaging the apron on the die prior to forming the porcelain jacket on the apron.

5. A method as defined in claim 4 comprising the further steps of forming dovetailed grooves in the apron and applying settable cement to the apron prior to bonding the jacket to the apron.

6. A method as defined in claim 4, comprising the further step of mounting said assembly on said tooth, and cementing both said jacket and said apron to the tooth simultaneously.

7. A method as defined in claim 1, comprising the further steps of taking a plastic impression of the shoulder and adjacent parts of the die, and casting said ringlike apron from said plastic impression of the die prior to applying the apron to the die.

8. A method as defined in claim 7 comprising the further steps of forming dovetailed grooves in the apron and applying settable cement to the apron prior to bonding the jacket to the apron.

9. A method as defined in claim 8, comprising the further step of mounting said assembly on said tooth, and cementing both said jacket and said apron to the tooth.

Description

This invention relates to the art of dental crown manufacture, and more particularly concerns a method of making a dental crown with a metal apron.

Heretofore the generally practiced way of making a dental crown involved the following basic steps. A die was made from an impression of a tooth or group of teeth in a denture to be crowned. A porcelain jacket was then formed on the die. The jacket was removed and a thin gold thimble was then hammered on the die to form a cup-shaped base for a crown. The cup-shaped thimble was then cemented on the tooth. Then the jacket was cemented on the gold thimble.

The above procedure was not entirely satisfactory for several reasons. The formation of the jacket without the thimble resulted in a crown which had to be ground down by the thickness of the thimble. The complete separation of the jacket from the tooth by the interposition of the thimble made it impossible to bond the jacket to the tooth directly. Often the jacket came loose from the thin thimble due to poor bonding. The consumption of god where a large member of crowns were made proved to be very costly. The separate attachment of thimble and jacket to the tooth was also objectionable.

The present invention is directed at overcoming the above and other objections, difficulties and disadvantages of the prior methods of making dental crowns.

According to one method of practicing the invention a preformed gold apron is swaged on a die cost from a tooth. Then a porcelain jacket is formed on the apron while it is on the die. The jacket and apron are removed and undercuts are made in the apron and jacket. The die is oiled. The apron is replaced on the die. Cement is applied and the jacket is fitted on the apron. The cement bonds the jacket and apron. The center of the apron is open so that the jacket will fit precisely on the tooth and can be cemented directly to the tooth.

In another method or process according to the invention, a die is cast from an impression of the tooth to be crowned. Then a second impression is made of a margin or shoulder of the die. A ringlike metal apron is then cast from the impression of the die shoulder. The method then proceeds as previously outlined. A porcelain jacket is made on the apron while it is on the die. Then the jacket and apron are removed and undercuts are made. The die is oiled, the apron is replaced. Cement is applied and the jacket fitted on the apron. The cement bonds the jacket and apron. In both methods or processes described the result is a crown assembly consisting of a porcelain jacket with precious metal apron bonded to it. The assembly of jacket and apron can then be cemented directly to the tooth to be crowned.

The invention will be explained in further detail in connection with the drawings wherein:

FIG. 1 is a perspective view of a die and ring at a stage of the process where the apron ring is about to be mounted on the die.

FIG. 2 is a perspective view of a die with apron thereon.

FIG. 3 is a cross-sectional view of a die, apron and porcelain jacket.

FIG. 4 is a perspective view of an apron with undercut grooves for receiving cement.

FIG. 5 is an exploded sectional view of the die, apron, cement and jacket.

FIG. 6 is a cross-sectional view of a crown assembly comprising apron and jacket bonded together.

FIG. 7 is a side elevation of the crown assembly of jacket and apron.

FIG. 8 is a sectional view partially in side elevation of the crown assembly cemented to a tooth.

FIG. 9 and FIG. 10 are flow charts setting forth and principal steps in two processed for making the crown assembly.

Referring first to FIG. 1 there is shown a die 10 made from a plastic impression of a tooth T. The tooth is shown in FIG. 8. The die has a generally tapered smaller top portion 12 and larger tapered bottom portion 14. An annular shoulder 16 is formed between the top and bottom portions of the die. The top portion 12 and shoulder 16 are duplicates of top portion 12a and shoulder 16a of the tooth T. A post 18 is secured in the bottom end of the die for supporting the die in a suitable fixture (not shown). A preformed tapered apron ring 20 is being mounted on top of the die as shown in FIG. 1. The smaller upper opening 22 of the ring is approximately equal to the circumference of inner edge 23 of shoulder 16. The outer periphery 21 of the ring is larger than the periphery 24 of shoulder 16.

FIG. 2 shows apron 20a on the die. The apron is formed by swaging ring 20 on the die as stated in step I of the method or process A outlined in FIG. 9.

A porcelain jacket 25 is then cast on the assembly of die and apron as shown in fig. 3 and as set forth in step II of method A. Then the jacket and apron are removed. The jacket will be trial fitted by a dentist on the tooth T and will be checked for proper shade. Undercuts 27 may be made in the bottom of the jacket as shown in FIG. 5. A plurality of dovetailed, undercut grooves 26 will be formed in the upper side of the apron 20a as shown in FIG. 4 and stated in step III of method A. Thereafter the die is oiled and the apron is refitted on die 10. A quantity of a suitable cement 30 is applied to the apron as shown in FIG. 5; see step IV of method A. Then the jacket 25 is fitted on the die and lightly pressed. The cement is allowed to set; see method A step V. Setting may be done by baking if the cement is of a thermosetting type. FIG. 6 and FIG. 7 show crown assembly 50 comprising apron 20a and jacket 25 bonded together by cement 30. Excess cement has been removed; edges of the apron have been filed smooth; and the assembly has been externally polished; see method A step VI. The crown assembly can now be fitted on the tooth T and secured in place by cement 32 as shown in FIG. 8; see method A step VII. This completes the process. It will be noted that the upper portion 12a of the tooth extends through the opening in the apron ring 20a and is bonded directly to the jacket. This makes a stronger bond than the prior known method where a gold thimble is cemented to the tooth and the jacket is cemented to the thimble.

FIG. 10 sets forth another method B according to the invention part of which is identical to the method of FIG. 9. In FIG. 10, as stated, the first step Ia involves making a plastic impression of the die 10 including the shoulder 16 and adjacent portions of the upper and lower die portions 12, 14 shown in FIG. 1. A precious metal apron ring 20a is then cast from this plastic impression. This is step IIa stated in FIG. 10. The cast apron ring is then fitted on the die 10. FIG. 2 applied equally well to both methods at this step since apron 20a is shown fitted on the die. Thereafter all succeeding steps III through VII in method B are the same as in method A, and the above description of these steps in connection with method A applied equally well to method B.

It will be noted that the crown assembly process effects a saving in gold or other precious metal since the apron is ring-shaped rather than thimble-shaped. Furthermore a better bond to the tooth T is made. Assembly work by the dentist is minimized. The process is performed almost entirely at the dental laboratory and a completed crown assembly is delivered to the dentist. This contrasts with the prior procedure where a thimble and separate jacket was delivered to the dentist for separate fittings, adjustments and mounting on the tooth. As a result of the present invention more satisfactory, less expensive dental crowns are fabricated and installed. Dentists time is saved and work on the patient is minimized.

* * * * *

Current U.S. Class:	433/223 ; 433/218
Current International Class:	A61C 5/08 (20060101); A61C 5/10 (20060101); A61c 005/08 ()
Field of Search:	32/12,2,8 264/16,21