Plastic and nonmetallic article shaping or treating: processes – Dental shaping type – Denture forming
Reexamination Certificate
2000-11-06
2003-12-09
Heitbrink, Jill L. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
Dental shaping type
Denture forming
C264S016000, C264S019000, C425S002000, C425S175000
Reexamination Certificate
active
06660194
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for preparing a dental prosthesis from a composite resin.
2. Description of the Conventional Art
As the restoration of teeth are generally carried out by a restoration method using a dental prosthesis, in which, after preparation of a cavity, or after core construction of an abutment tooth, an impression (counterdie of tooth) is taken, a gypsum model (duplicate of tooth) is prepared based on the impression by using a gypsum or the like, a dental prosthesis is prepared based on the cast in a manner as described later, and the dental prosthesis is cemented to a tooth by using an adhesive such as a dental cement; and by a method of filling restoration, in which a dental composite resin is directly filled in a cavity and then polymerized and cured by chemical polymerization or light-polymerization to effect restoration.
In the case of dental prostheses such as inlays and crowns, there is widely employed a method called as a lost wax casting process, in which a dental wax is applied on a gypsum model to prepare a wax pattern having the same shape as an objective dental prosthesis; the wax pattern is invested in a refractory investment; after setting the investment, the wax pattern is heated and burnt in an electric furnace; a dental alloy is cast using a cast molding thus obtained; and the resulting cast material is excavated from the investment, followed by triming and polishing to prepare a metallic dental prosthesis.
In cases of inlays, crowns, etc., particularly in cases where aesthetics in, for example, restoration of anterior teeth, are required, restoration by means of dental prostheses such as ceramic inlays, resin facing crowns, porcelain facing metal crowns, and all ceramic crowns is carried out.
Specifically, in the case of dental prostheses such as ceramic inlays and all ceramic crowns, a refractory duplicated model is prepared by using a refractory material, a dental ceramics powder is built up and formed on the refractory duplicated model through manual works by a dental technician, and after firing, the refractory duplicated model is removed, followed by forming the surface characterization and polishing to prepare a dental prosthesis. Further, in the case of resin facing crowns or porcelain facing metal crowns, a resin having a tooth crown color is built up and polymerized for application on a labial surface of a metal crown prepared by the lost wax casting process, or a porcelain having a tooth crown color is built up and fired and then subjected to forming the surface characterization and polishing, to prepare a dental prosthesis.
However, in the case of dental filling restoration using composite resins, since the dental composite resin is filled in a cavity and immediately thereafter polymerized and cured, the strength is often insufficient. Further, since the unpolymerized monomer likely remains, a problem of pulp irritation is also pointed out. In addition, in the case of metallic dental prostheses, since a metal color is exposed on a surface of the dental prosthesis, a problem of aesthetics arises. Moreover, in the case of dental prostheses such as ceramic inlays, all ceramic crowns, resin facing crowns, and porcelain facing metal crowns, since a high-level technique is required for building up and forming through porcelain works, there is a defect that not only a lot of skill by a dental technician but also a long period of time and much expenses are required.
On the other hand, Japanese Patent Laid-Open No. 227400/1995 discloses a process for preparing a denture base by charging under a high pressure a thermoplastic resin, a thermosetting resin, etc. into in a mold, in which a process for preparing a dental prosthesis such as an inlay and a crown is also described. This process is a process in which a denture base is subjective and is formed by charging under a high pressure a thermoplastic resin into a mold, with thermoplastic resins having good fluidity, such as polycarbonates, polysulfones, polyethersuflones, and acrylic resins, being used. However, even when these thermoplastic resins are compounded and reinforced with glass fibers, etc., the strength is still insufficient. Accordingly, it was hard to say that these thermoplastic resins have a performance sufficient for utilizations of the preparation of dental prostheses such as crowns, which are required to have a mechanical strength and wearing durability.
SUMMARY OF THE INVENTION
The invention is aimed to provide a process for preparing a dental prosthesis, particularly suitable for an inlay, a crown, etc., which is not only superior in aesthetics and mechanical properties but also is free from any fear of pulp irritation by unpolymerized monomers.
We, the present inventors, investigated that when, by applying a technique of injection molding or pressure injection, which has hitherto been employed for the preparation of dentures, artificial teeth, etc., a composite resin having a superior strength as compared with thermoplastic resins such as polysulfones and being, superior in esthetics to metal materials, is charged under pressure into a mold and subjected to polymerization under heat and pressure, a dental prosthesis that is free from the remaining of unpolymerized monomers and superior in mechanical properties can be prepared, leading to the accomplishment of a process for preparing a dental prosthesis according to the invention.
Specifically, the invention is to provide a process for preparing a dental prosthesis comprising preparation of a wax pattern of an objective dental prosthesis based on a duplicated model having an intraoral shape, investment of the wax pattern in an investment material, and removal of the wax pattern to prepare a mold, wherein a composite resin is charged under pressure into the mold, and the composite resin is cured under heat and pressure.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
In carrying out the process for preparing a dental prosthesis according to the invention, first of all, a tooth on which an objective dental prosthesis is applied subjected to preparation of a cavity or core construction of the tooth, and an impression of its shape is then taken by using a dental impression material, etc. At this time, any materials can be used without particular limitations as the impression material to be used, so far as they can preciously reproduce the shape of the tooth. However, impression materials that are popularly used in the dentistry field are preferred because they are superior in precision and handling, with dental silicone impression materials being particularly preferred.
Subsequently, a dental gypsum, a dental investment or the like is poured into the taken impression and set to prepare a duplicated model having an intraoral shape. Then, a wax such as a dental wax is applied on the duplicated model to prepare a wax pattern of an objective dental prosthesis, and the thus completed wax pattern is attached to a sprue made of a wax or a metal in a usual manner.
Subsequently, the wax pattern is invested, either alone or together with a duplicated model, in a heat-resistant vessel such as a casting ring, by using an investment material. As the investment material, in the case where the viscosity of the composite resin to be charged under pressure is low, and the maximum charging pressure is low as 0.5 to 5 MPa, casting investment materials that are used in the dentistry can be used. Further, when a dental gypsum or the like is used, it is possible to apply a higher pressure. Moreover, in the case where a charging pressure exceeding 5 MPa is required, it is preferred to use a dental improved stone that is durable to a higher pressure.
After setting of the investment material, the whole of the heat-resistant vessel is heated according to a customary manner, and the internal wax pattern is removed to prepare a mold. When the wax pattern cannot be burnt and removed by burning as in the case where a gypsum is used as the investment material, the wax is removed by using hot
Fontaine Monica A
GC Corporation
Heitbrink Jill L.
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