JPH0588682B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to materials and methods for reinforcing dental metal structures in forming, repairing or reinforcing dental restorations.

BACKGROUND OF THE INVENTION In crown and bridge prosthetics, a wide variety of retainers and pontectures can be used in various combinations for bridge assembly. Ceramic-metal restorations use a metal framework as reinforcement for crowns and bridges with a fired coating of ceramic material, such as porcelain. The metal framework is cast or formed from prefabricated units of preformed copings or ponteics. According to current practice, the framework can be modified by soldering, but cannot otherwise be modified without investment and casting operations. Current practice is limited by the unavailability of commercially available materials for constructing or expanding the framework. To strengthen the framework without investment and casting, it is necessary to add material to the framework that becomes an integral part of the framework by heat treatment. The material must be capable of being molded into the desired shape and must be free standing in the molded shape as well as capable of retaining the molded shape under heat treatment. In order to shape the material into the desired shape, the material should be relatively flexible and workable. Under heat treatment, the material should solidify into a solid mass of metal without losing the shape formed before heat treatment. The material should be compatible with the metal framework and have hardness properties at least equal to, or preferably greater than, the hardness of the material before heat treatment.

Such materials can be used, for example, to create a cervical shoulder around the support member at the gingival end without investment or casting. For example, a finishing shoulder can be formed around a preformed prefabricated metal coping without a shoulder edge. Similarly, the material can be used to create a metal cusp on a metal coping before adding porcelain to reinforce the oral and/or lingual cusp.
The material may be used to strengthen seams in place in the framework or for general bridgework repairs. Currently, the latter is relatively impossible. Heretofore, dentists and dental technicians have been fundamentally limited in the use of materials useful as casting dental structures and solders or fluxes. Conventional solder or flux cannot be formed into free-standing shapes or retain their shape under heat treatment. In reality, solder alloys are designed to melt under the heat of soldering, flow freely, and perform the function of fusing and joining metals.
Flux is a non-oxidizing agent. Currently, dental materials are not commercially available for reinforcing dental restorations, although there have been attempts in the past to create such materials. All such attempts are based on the use of compositions that solidify into a solid mass and undergo substantial shrinkage upon heat treatment.

SUMMARY OF THE INVENTION The method of the invention and its materials form a mass that retains its shape but is not subject to any shrinkage upon heat treatment and is therefore ideal for use in dental procedures where shrinkage is not tolerated. . Moreover, the method according to the invention results in very little waste of precious metals and is therefore cost-effective.

The method of the invention is particularly useful for reinforcing metal structures in dental restorations and is comprised of metal particles consisting essentially of a high melting temperature metal component and a low melting temperature metal component, the low melting temperature component forming a material composition in which the material composition has a small proportion compared to the high melting temperature component; adding the material composition to a reinforcing dental structure; molding the material composition into a predetermined shape; a temperature below the melting temperature of the component, but sufficiently high to cause substantial melting of the low melting temperature component so as to form a porous spongy mass suitable for fusing with the dental structure; heat treating the material composition at a selected temperature; adding low melting temperature filler particles to the porous spongy mass;
The method then consists of heat treating the filler particles to dissolve the filler particles into a spongy mass, thereby forming a solid reinforcing structure. The solid mass may be further shaped if desired.

According to the method of the invention, the porous spongy mass is
As a result of a first heat treatment step filled with a low melting temperature filler or ceramic, an intermediate product is formed;
Heat treated again to form a solid mass. This two-step process of melting the low melting temperature component and then melting the filler is an important feature of the invention. In the second melt, the added fillers bond together to form an integral solid mass.

The ceramic material is applied in a conventional manner onto the solid reinforcing structure to form a ceramic to metal dental restoration.

The reinforcing materials of the present invention preferably consist of a metal composition comprising a substantial proportion of a high melting temperature metal having a melting temperature of about 1300° C. or higher, such high melting temperature metal particles having a particle size of 100 microns or less; The composition has a minor proportion of low melting temperature metals suitable for melting during heat treatment at temperatures below the high melting temperature, preferably below 1200°C.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Broadly, the dental materials of the present invention are compositions of metal particles that can be molded into a desired free-standing shape for forming a dental reinforcement during heat treatment in the formation or repair of a dental restoration. The dental material of the present invention allows the dental material to be formed into a solid mass without undergoing any shrinkage. The dental material is composed of a composition of metal particles containing a high melting temperature noble metal component consisting of a single metal or a metal alloy. The high melting temperature noble metal particles preferably have a particle size of about 100 microns or less and are a major component of the overall composition of the dental material.
The dental material preferably contains a high melting temperature noble metal and a small proportion of a low melting temperature noble metal component, consisting of a single metal or a metal alloy, in the form of particles or cladding. The melting temperature of the high melting temperature metal component is substantially higher than the melting temperature of the low melting temperature metal component and substantially higher than the temperature at which the material is heat treated. Under heat treatment, the low melting temperature metal component melts and becomes fused with the high melting temperature particles at their contact points, retaining the shape given to it before the heat treatment. Forms a porous sponge-like structure.

During the formation of the dental material of the present invention, the composition of metal particles may have a binder or carrier vehicle added to give the material a paste or putty-like structure. This makes the material easier to process. The binding agent is
One is selected that evaporates without leaving any residue during the heat treatment. For example, any suitable organic or synthetic resinous material is acceptable, such as ethylene or polyethylene glycol. In addition to binders, fluxes such as borax may be added to form the dental materials of the present invention. The flux eliminates oxide formation.

The metal composition formed into the dental material should be biocompatible since it will be used in the mouth. Therefore, noble metals or noble metal alloys are preferred, but not essential. Noble metals may be used in combination with non-noble metals. In said embodiments of the invention, the high melting temperature metal composition is comprised primarily of 0-100% platinum, 100-0% palladium and/or other components such as gold. Gold may be added to the high melting temperature metal component to increase the affinity of the high melting temperature metal component particles for the low melting temperature component. The low melting temperature metal particles are preferably composed of a gold alloy containing gold as a main constituent or pure gold. The selection of gold as the main component of the low melting component is based on its known processing properties, non-oxidizing properties, and color.

The particle size of the high melting temperature component is an important characteristic of the present invention. Best results are achieved when the maximum particle size of the high melting temperature component is less than about 100 microns, preferably less than 74 microns. The high melt temperature component particles are also larger than the particle size of the low melt component. The high melt temperature component is at least equal to the particle size of the low melt component, but preferably is about 5-10 times larger than the particle size of the low melt component. When cladding a low melting component to particles of a high melting component, the latter is larger than the particle size based on the relative thickness between the cladding components. The particle shape of the high melting component is believed to be important to the invention, but is not a critical characteristic. Flaky, irregularly shaped particles appear to work best. The irregular shape causes the particles to form a reticulated or open-particle chain network. Under heat treatment, the low melting components dissolve with the high melting temperature particles at the contact points of the open network. Any shape is acceptable, including spherical shapes, but strips and irregular contour shapes (particularly crescent shapes) are preferred.

Although the material of the present invention is a composition of metal particles, the method of forming the particles is not critical to the present invention; as described above, low melting component particles are clad with high melting component particles to form a high melting temperature component and A composite consisting of low melting temperature components may also be formed. Clad particles are
It may have one component that completely embeds the other component or only partially covers the other component. Clad particles may be formed, for example, from laminated multilayer sheets. Various other known deposition methods can be used to form layered sheets or embed particles, such as by electrodeposition or cathodic sputtering. When metal particles are clad together, the proportion of high melting to low melting components in the total composition is based on the difference in thickness between the clad metals. Preferably, the thickness of the low melt component is in the range of 8 to 15 microns for reasons discussed below.

The method of the invention comprises a high melting temperature component as defined above,
Preferably it consists of forming a dental material having in combination the low melting temperature components as defined above. The low melting temperature component is intended to function solely as a soldering agent to fuse with the particles of the high melting temperature metal at the point of contact upon heat treatment. The high melting temperature component therefore constitutes a major proportion of the combination of particles of high melting temperature component and low melting temperature component, up to about 100%, preferably 50-98%
%, optimally between 50 and 75%. in fact,
If the heat treatment is combined with the application of pressure and the particles of the high melting temperature component self-fuse into each other at their points of contact, 100% of the composition will be the high melting temperature component.
Binding and/or fluxing agents are added to the dental material prior to application to the dental structure. As mentioned above, binders may be added to provide the dental material with a pasty viscosity component that makes the material easier to process. Dental materials are added to dental structures, such as metal copings or bridges, to reinforce or expand the structure at desired specific locations. The dental material is applied to the structure with a brush or spatula and burnished or molded into the desired shape by hand. The dental structure containing the dental material is then heat treated by exposing it to the flame of a Bunsen burner or by sintering it in a furnace at a temperature below the melting temperature of the high melting temperature component. The melting temperature of the high melting temperature component is about 1300°C or higher, while the heat treatment temperature is about 1200°C or less, preferably about 1075-1175°C. Upon heat treatment, the dental material forms a porous mass of metal in the form of a chain network of bonded metal particles having a generally spongy appearance that blends into the dental structure. The porous spongy mass made of metal retains its given shape before heat treatment,
It does not undergo any shrinkage during heat treatment.

After heat treatment, filler particles having a low melting temperature are added to the metal porous mass and heat treated to dissolve the filler particles into the spongy porous mass to form a solid reinforcing structure. The filler particles are preferably gold metal particles. The heat treatment of the filler particles can be carried out at the same temperature as the heat treatment initially carried out to form the porous mass. The low melting temperature components in the porous mass are melted by heat treatment,
The lower melting component forms an alloy with the higher melting temperature metal at the point of contact where it solidifies. The metal alloy has a melting temperature higher than that of the original low melting component and therefore does not remelt upon repeated heat treatments at the same temperature. Alternatively, the filler particles can be selected to have a different melting temperature than the original melting temperature of the low melting temperature component. For example, the filler particles are gold and a gold alloy of a low melting metal, or both may be pure gold or a gold alloy. Other metals can also be used. Additionally, for repair of chipped porcelain restorations where strength is not required, porous sponges are filled with filler particles of ceramic compositions such as porcelain.

The low melting metal component may be a single metal such as pure gold, an alloy thereof, or a combination of one or more metal alloys. When coating a low melting component onto a high melting component to form clad particles, it is important that the thickness of the low melting component is small compared to the thickness of the high melting component. The preferred thickness is 8-15 microns. The high melting temperature component may be a composition consisting of gold, platinum and palladium with the addition of small amounts of other component elements, a combination in which palladium and/or platinum are the main components.

This invention should not be construed as being limited to any dental application provided for the material. For example, the material may be added to the dental framework after the porcelain is fired. For example, if the crown is insufficient at the ends, material may be used to expand the crown. Therefore, the term "reinforcement" should not be interpreted narrowly but should be given a broader definition.
It specifically encompasses the concept of increasing the dimensions and physical scale of the framework simply by adding to or expanding the framework. Similarly,
The materials of the present invention can be used to fill interproximal spaces to which fired ceramic veneers are applied and, if desired, to form dental restorative copings.

Claims (1)

[Scope of Claims] 1. A composition of metal particles that is heat treated at a selected temperature of 1300° C. or less to perform the function of forming, repairing or reinforcing a dental restoration, the composition comprising: metal particles of a first high melting temperature metal component having a melting temperature equal to or higher than the selected heat treatment temperature; and metal particles of a second low melting temperature metal component that substantially melt during the heat treatment. including the first
The metal particles of the ingredients have a particle size of about 100 microns or less,
and a particle size larger than that of the second component, and the heat treatment causes the formation of a porous sponge-like structure from the high melting temperature metal particles interconnected by the molten low temperature metal particles. A dental material for forming, repairing or reinforcing dental restorations. 2. The dental material of claim 1, wherein the high melting temperature metal comprises noble metal particles selected from the group consisting of platinum and palladium. 3. The dental material of claim 2, wherein the low melting temperature component comprises gold. 4. The high melting temperature metal component accounts for 50% or more of the dental material.
The dental material of claim 3 containing 75%. 5. The dental material of claim 3, wherein the particle size of said high melting temperature metal particles is about 5 to 10 times larger than the particle size of said low melting temperature metal particles. 6. The dental material of claim 5, wherein the high melting temperature metal component is irregularly shaped particles. 7. The dental material of claim 6, further comprising a binder to hold the metal particles before heat treatment. 8. The dental material according to claim 5, wherein at least a portion to 100% of the low melting temperature metal component particles are clad with particles of the high melting temperature metal component. 9 The thickness of the clad low melting metal particles is 8
9. The dental material of claim 8 which is ~15 microns. 10 forming a material composition consisting of metal particles substantially of a high melting temperature metal component and a low melting temperature component; adding the material to a dental structure; shaping the material composition into a predetermined shape; ; causing substantial melting of the low melting temperature component below the melting temperature of the high melting temperature metal component and causing the high melting temperature metal component to form a porous spongy mass of interconnected particles; heat treating the material composition at a temperature level sufficient to produce; adding particles of a low melting temperature filler to the porous metal sponge mass; and then heat treating the filler particles to form filler particles; 1. A method for forming, reinforcing or repairing a dental structure, characterized in that the solid reinforcing structure is formed by melting into a spongy mass. 11. The method of claim 10, wherein the material composition of the metal particles comprises a noble metal and a binder. 12. The method of claim 11, wherein said high melting temperature metal component comprises particles selected from the group consisting of platinum and palladium. 13. The method of claim 12, wherein the melting temperature of the high melting temperature component is about 1300°C or higher and the heat treatment temperature is about 1200°C or lower. 14. The method of claim 13, wherein said low melting temperature component comprises gold. 15. The method of claim 14, wherein the high melting temperature metal particles have a particle size of about 100 microns or less. 16. The method of claim 15, wherein the filler comprises particles of metal or metal alloy. 17. The method of claim 16, wherein the filler particles are comprised of gold. 18. The method of claim 10, wherein said filler comprises a ceramic composition. 19. The method of claim 18, wherein the ceramic is porcelain. 20. The method of claim 14, wherein the high melting component comprises a combination of up to about 50 to 75 volume percent of a high melting metal component and a low melting metal component.