US2253222A - Pontic insert and dental bridge - Google Patents

Description

Aug. 19, 1941. I JQBE TRAM. 2,253,222

PONTIC INSERT AND DENTAL BRIDGE Filed Jag. 50, 1939 Patented Aug. 19, 1941 UNITED STATES PATENT OFFICE 2,253,222 I A PONTIC INSERT AND DENTAL BRIDGE Joseph Bertram, Chicago, Ill. Application January 30, 1939, Serial No. 253,577

2 Claims.

This invention relates to pontic inserts in dental bridges for decreasing the Weights of the bridges as well as the amount of noble metal used in the bridge construction.

More specifically this invention relates to hollow base metal pontic inserts adapted to interchangeable backings and covered with the material forming the construction of a dental pontic. i

it According to this invention, hollow metal inserts are provided to conform in shape with i the desired exterior contour of a bridge pontic behind the interchangeable backing. The members, however, are somewhat smaller than the exterior size of the bridge pontic so that they can be uniformly covered with the construction material and encased in this material.

In posterior bridges, the hollow metal memhere can be provided with lingual, mesial, distal and occlusal surfaces conforming with the corresponding surfaces of a particular tooth but of smaller dimensions than said tooth. Such'members can have open front faces adapted to be secured to the interchangeable backings of pontics carried by the bridge abutments. Since uniform-layer of the noble metal.

the bridge construction is usually made from 3 noble metal and since the insert members of this invention can be formed from base metal, a considerable saving in noble metal is obtained. Furthermore, since the inserts of this invention are hollow, the weight of the resulting bridge is materially decreased.

- According to this invention the interchangeable backing for a pontic has one of the pontic inserts tacked thereon with a dab of solder. The selected insert should conform with the desired contour for the bridge suspension or pontic area behind the porcelain facing (false tooth). A molded wax cap is then slipped over the pontic insert and the suspension of the bridge is built up with additional wax worked onto the molded cap and shaped for occlusion with the opposing tooth of the articulated model. The use of a premolded wax cap or cover for the pontic insert of this invention serves to cover the insert with walls of uniform thickness and at the same time facilitates a shaping of the bridge with the added wax.

The wax assembly and the pontic backing. is removed from the model and invested in a suitable heat resisting material after which the Wax is burned out and the resultant mold filled with gold or other noble metal.

The resulting bridge therefore has the metal insert in the bridge suspension covered with a V The insert itself is smaller than the pontic backing and is centered onthe backing so that the noble metal can securely unite directly with the backing plate and with the insert.

It is, then, an object of this invention to provide a preformed pontic insert for dental bridges.

Another object of the invention is to provide hollow base metal pontic inserts for dental bridges.

A specific object of the invention is to provide hollow metal inserts for posterior dental bridgeshaving lingual, mesial; distal and occlusal surfaces shaped to conform generally with the corresponding surfaces of a particular tooth & but of smaller dimensions than said tooth surfaces.

A further object of the invention is to provide prefabricated hollow metal pontic inserts and matingpremolded wax caps for said inserts.

Another object of the invention is to provide dental bridges of light weight and great strength. A further object of the invention is to provide a new process'of casting or soldering dental bridges for the purpose of decreasing the weight of the resulting bridge with a resultant decrease in amount of noble metal necessary for the bridge.

A further object of the invention is to provide prefabricated hollow metal pontic inserts for pontic backings.

Other and further object of the invention will become apparent to those skilled in the art from the following description of the annexed sheet of drawings which discloses the invention in a preferred form.

' shown in Figure 1';

t Figure 3 is a vertical cross-sectional view taken along the line III-III of Figure 2;

Figure 4 is a horizontal cross-sectional view taken along the line IV--IV of Figure 3;

Figure 5 is a longitudinal cross-sectional view taken along the line V-V of Figure 2;

Figure 6 is a rear elevational view of ,a pontic backing illustrating the manner in which a l pontic insert of this invention is tacked onto the plate prior to a casting of the bridge;

Figure 7 is a front elevational view of the pontic backing and insert assembly shown in Figure 6;

Figure 8 is an isometric view of a hollow metal pontic insert according to this invention;

Figure 9 is an isometric view of a premolded wax cap for the insert as shown in Figure 5; and

Figure 10 is a rear elevational view of a modified form of metal pontic insert according to this invention.

As shown on the drawing:

In Figures 1 and 2, the reference numeral I designates a portion of a human gum having spaced posterior teeth II and I2 projecting therefrom. A dental bridge designated generally by the reference numeral [3 carries a porcelain facing or false tooth M in the space between the teeth ll and I2.

The bridge I3 is composed of a crown l5 covering the tooth ll, cast or soldered noble metal I6 forming the bridge pontic and a disto-occlusal noble metal inlay lfia. placed in tooth I2. The pontic I6 is soldered to the crown l5 and to the inlay l6a in tooth [2. A backing IT for the facing M is carried by and forms part of the pontic I6.

As best shown in Figures 3 and 4, the backing H has the usual attachment pin I8 secured on the front face thereof. The facing M has a recessed groove along the back face thereof adapted to receive the pin l8, As is customary, the facing i4 is cemented onto the backing I! in addition to being held thereon by the pin l3.

According to this invention a hollow metal pontic insert 20 is included in the bridge suspension l6 behind the backing N. This insert 20 is permanently secured to the backing H and to the suspension metal l6 during the casting or soldering operation.

As best shown in Figure 8, the pontic insert 20 comprises a prefabricated hollow metal member having an occlusal wall 2|, a mesial wall 22, a distal wall 23 and a lingual wall 24. The front face of the pontic insert 20 is open as shown in Figure 8 and presents a rim 25 for abutting against the backing [1.

The pontic inserts of this invention can be made from base metal, such as steel, having a melting point above the melting point of the metal used in casting or soldering the bridge. Since gold alloy is commonly used in casting the bridge, the melting point of the insert metal should be above the melting point of the gold alloy. Metals having melting points above 1800" F. are satisfactory to form the pontic inserts. The pontic inserts can be prefabricated by a simple stamping operation and are formed to conform with a particular tooth so that the walls of the insert will carry out the general contour of the tooth which the pontic is replacing. The pontic inserts, however, are smaller than the desired exterior dimensions for the finished bridge suspensions so that they can be uniformly covered with the cast metal or solder forming the bridge pontic I6.

Pontic inserts, according to this invention, therefore, can be supplied in shapes and sizes conforming with every tooth in the mouth.

As shown in Figures 6 and '7, the inserts 20 of this invention are temporarily centered on the pontic backing l by means of a dab of solder 26 after the backing has been cut to size. The inserts 2B are of smaller exterior dimensions than the cut or trimmed backing I! and are centered on the back of the plate so as to provide an even margin 21 therearound.

As shown in Figure 9, premolded Wax caps such as 30 can be provided for covering the inserts 20. The wax cap 30 has walls conforming with the particular insert 20 and is slipped over the insert after the same is applied to the backing as shown in Figures 6 and '7. The wax cap insures an even covering of the cast metal forming the bridge pontic l6 around the entire insert.

This invention simplifies and reduces the cost of making dental bridges. Thus the bridge l3 can be formed using the crown I5 as an abutment and building up additional wax between the cap 30 on the insert 20 so as to shape the pontic and form a connection between the crown and the pontic. Similar procedure is carried out to make contact between the pontic and the distoocclusal inlay lfia in tooth I2. The wax assembly is formed after the insert is temporarily centered on the pontic backing as shown in Figures 6- and 7.

After the proper Wax form has been made and trimmed the assembly is set into an inlay investment to form its own mold. When the investment is set the mold is heated to melt out the wax and a noble metal such as gold is forced into the mold to take the place of the removed wax. The resulting bridge suspension I6 is thus formed in integral relation with the crown 15, the insert 20, and the backing H.

This invention also accomplishes identical results with identical saving of weight and amount of noble metal used when the pontic is constructed with a swaged metal occlusal surface and the remaining portion of the body of said pontic filled with a precious metal solder. According to the swaging and soldering method of making the bridges, the hollow metal insert is centered on a pontic backing and secured thereon in centered position. A thin sheet of gold is swaged to the shape of the desired occlusal surface and the swaged sheet is then tacked on the occlusal edge of the pontic backing. The remaining spaces are thereafter filled in with gold solder to totally encase the insert.

The technique in forming the bridges of this invention is simple and the light weight and reduced cost of construction made possible by the hollow base metal inserts of this invention has many decided advantages over the heretoforeknown solid bridge suspensions.

In Figure 10 there is illustrated a modified hollow metal insert 28a according to this invention. The insert 20a is prefabricated with projections 3| on the lingual, mesial, distal and occlusal walls thereof. These projections can be in the form of pinheads, fingers or the like so as to increase the gripping surface for the noble metal cast or soldered therearound. The projections will give an added bond between the insert and the noble metal but are ordinarily not necessary.

While the invention has been described in connection with a single tooth posterior bridge having a crown abutment and a disto-occlusal inlay abutment, it should be understood that the bridges of this invention can vary widely from the illustrated form. The invention broadly includes bridges of all types having hollow pontic inserts in the suspensions thereof.

It will, of course, be understood that various details of construction may be varied through a wide range without departing from the principles of this invention and it is, therefore, not the purpose to limit the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. A pontic insert comprising a hollow metal member of the general shape of a triangular prism, said member having solid occlusal and lingual walls and a hollow buccal face forming the faces of the prism, and mesial and distal Walls comprising the bases of the prism.

2. In a dental bridge including at least one 10 abutment and at least one backing plate for a facing, the improvement which comprises a hollow pontic insert having an open buccal face abutting the plate in spaced relation inwardly from the periphery thereof to provide an exposed margin on the plate, and noble metal covering said insert and brazed to the margin of the plate, whereby said plate and. said noble metal completely encase the insert.

JOSEPH BERTRAM.

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