JPH0542172A - Artificial tooth root - Google Patents

Abstract

PURPOSE:To facilitate production by forming the artificial tooth root by using a powder sintered body of a shape memory alloy of a Ti-Ni alloy system. CONSTITUTION:Ti powder and Ni powder are mixed and the mixture is made into, for example, a pellet form by molding; thereafter, the moldings are subjected to a heating treatment in a vacuum or inert gaseous atmosphere at <=900 deg.C temp., by which the Ti-Ni alloy is formed. The sintered molding consisting of the resulted Ti-Ni alloy is pulverized to form Ti-Ni alloy powder. A binder is added to the Ti-Ni alloy powder and after the mixture is kneaded, the kneaded mixture is molded to a shape approximately equal to the shape of the desired tooth root by press forming, casting, injection molding, etc. The resulted molding is degreased at about 500 deg.C after machining or without machining and is then sintered in a vacuum or an inert gaseous atmosphere of gaseous argon, gaseous helium or gaseous nitrogen for about one hour at about 950 to 1250 deg.C. The easy molding to the precise shape is possible in this way.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an artificial tooth root having shape memory characteristics.

[0002]

2. Description of the Related Art Recently, artificial tooth roots made of materials having shape memory characteristics have been provided. An artificial tooth root having such shape memory characteristics should be inserted into a hole opened in the tooth bed and heated to a temperature equal to or higher than the transformation point of the artificial tooth root material to recover the shape and form an undercut portion or the like. To temporarily fix the artificial tooth root to the tooth base. As such an artificial tooth root material, a material which is harmless to the human body and has a high corrosion resistance is desirable. For example, a Ti-Ni-based shape memory alloy satisfies such requirements. Conventionally, in order to manufacture an artificial tooth root using a Ti-Ni-based shape memory alloy, a method has been adopted in which the alloy block is melted, and then the block is subjected to plastic working and mechanical processing and then heat treatment.

[0003]

However, in the above-mentioned conventional method, since the Ti-Ni type shape memory alloy is inferior in plastic workability and machinability, it takes a lot of time and labor to reach a product having a predetermined shape. It was expensive and costly.

[0004]

As a means for solving the above-mentioned conventional problems, the present invention is to manufacture an artificial tooth root using a powder sintered body having a shape memory characteristic as a material.

[Ti-Ni Alloy Powder] In the present invention, a Ti-Ni-based shape memory alloy powder sintered body is mainly used as an artificial tooth root material. As a method of manufacturing the above-mentioned powder sintered body, there are a method of molding and sintering Ti-Ni based shape memory alloy powder, and a method of mixing a predetermined amount of Ti powder and Ni powder and molding and sintering. However, since the method of mixing Ti powder and Ni powder causes a large deformation during sintering, it is desirable to powder the Ti-Ni alloy. However, since the Ti-Ni alloy has a high viscosity and is difficult to pulverize, it is desirable to produce the Ti-Ni alloy powder by either of the following two methods.

(1) Ti powder and Ni powder are mixed and press-molded into pellets, for example, and the molded body is heated to 900 ° C.
A Ti-Ni alloy is formed by heat treatment in vacuum or in an inert gas atmosphere at the following temperature. The Ti-Ni alloyed sintered compact thus obtained is crushed to obtain a Ti-Ni alloy powder. By reducing the density of the compact by controlling the press pressure during press molding, Ti-
The crushing of the Ni alloyed sintered compact is facilitated. Further, when the compact is made to absorb hydrogen to hydrogenate the Ti-Ni alloy, the compact is remarkably embrittled and pulverization becomes easier. Since the molded body has a large surface area, hydrogenation is easy. The Ti-Ni alloy powder obtained by crushing is used as it is or after dehydrogenation. In the above method, Ti
As the powder, a Ti hydrogen compound powder may be used. Ti
By hydrogenating the powder, contamination such as oxidation of Ti is prevented. The Ti hydrogen compound is dehydrogenated during sintering to become Ti. As the Ni powder, carbonyl nickel or a powder produced by a spraying method is used. (2) A Ti-Ni alloy wire rod is manufactured by a melting method, the wire rod is cut into pellets, the pellets are hydrogenated to be embrittled, and then ground.

[Molding of Ti-Ni alloy powder] To the Ti-Ni alloy powder or hydrogenated Ti-Ni alloy powder obtained as described above, a binder is added and kneaded so that it has a substantially same root shape. Molded, but the binder used is acrylic resin, polyethylene, polypropylene, ethylene-vinyl acetate copolymer, wood wax, beeswax,
There are one or more kinds of mixed binders such as paraffin wax. The amount of binder added is usually about 5 to 15% by weight.

The kneaded product of the Ti-Ni alloy powder and the binder is molded into a shape substantially equal to the target root shape by, for example, press molding, cast molding, injection molding or the like. Of the above molding methods, the most suitable method for obtaining a molded body having a complicated shape such as a tooth root is an injection molding method. Also Ti-
When Ni mixed powder is used, injection molding gives good dispersibility and a homogenous compact can be obtained. The green body obtained by injection molding has a relatively high strength of 2 to 3 Kgf / cm ² even in the state of the green body before sintering, so that it can be machined even in the state of the green body.

[Sintering] The molded body (green body) obtained by the above method is subjected to degreasing at a temperature of about 500 ° C. with or without machining, and then sintered. Sintering conditions are 950 to 1 for Ti-Ni system sintered body
It is carried out at 250 ° C. for about 1 hour in vacuum or in an atmosphere of an inert gas such as argon gas, helium gas or nitrogen gas. In addition, before the above-mentioned main firing, at a temperature of around 800 to 900 ° C.
You may perform calcination which heats for 4 hours. Then, the calcined body obtained by the calcining may be machined before the main calcining. In the case of a Ti-Ni based sintered body, Ti is active, so it is necessary to sinter in a high vacuum and a non-polluting atmosphere. Since equipment is expensive to form such an atmosphere, a method for preventing Ti contamination is to put the molded body in a box made of an active metal such as Ti or an alloy containing the active metal. It is desirable to sinter. Sintering the compact in such a box allows the use of a normal vacuum furnace. In this way, an artificial tooth root made of a powder sintered body having shape memory characteristics can be obtained, and if desired, the sintered body is further machined to correct it into a predetermined shape.

In the artificial tooth root of the present invention, the desired relative density of the sintered body is 40 to 97%. That is, the relative density is 9
When the porosity is 7% or less and the porosity is 3% or more, bone grows and adheres around the embedded artificial tooth root to firmly fix the tooth root.
However, when the relative density is 40% or less and the porosity is 60% or more, the mechanical strength decreases.

In the artificial tooth root of the present invention, it is desirable that the transformation point of the powdery sintered body having a shape memory property is about 40 to 60 ° C. What is required is that the artificial tooth root of the present invention is inserted into a hole opened in the tooth base and sprayed with a saline solution or the like heated to a predetermined temperature to recover the shape and fix it.
At the following transformation points, body temperature may cause shape recovery, and at transformation points of 60 ° C or higher, burns may occur.

[0012]

In the present invention, the powder of the material having the shape memory characteristic is kneaded with the binder or the like to form a kneaded product, and the kneaded product is molded by a molding method such as injection molding, press molding, or cast molding. Even if the material is poor in workability and machinability, a precise shape can be formed extremely easily. Particularly in injection molding, it is possible to easily obtain a molded product having a precise shape and a uniform shape. Ti-N
In the case of the i-based shape memory alloy, it is difficult to directly pulverize the Ti-Ni alloy. Therefore, a mixed powder sintered body of Ti powder and Ni powder is first manufactured and then pulverized to obtain Ti-Ni alloy powder. The mixed powder sintered body becomes brittle by hydrogenation and becomes easier to grind. Further, Ti-Ni alloy powder can be easily manufactured even if the Ti-Ni alloy pellets are embrittled by hydrogenation and then crushed. Since such an artificial tooth root is a sintered body, it can be easily straightened by machining, and after straightening, it is inserted into a hole opened in the tooth bed and heated to a temperature above the transformation point to recover the shape and fix it. The artificial tooth root of the present invention is porous and easily fits in the tooth bone.

[0013]

【Example】

[Example 1] Ti powder having an average particle diameter of 1 to 2 µm and carbonyl nickel powder having an average particle diameter of 4 µm were mixed in a weight ratio of 44:56, and a binder for injection molding (acrylic resin-
Polypropylene-paraffin wax mixture) 9.1
0 parts by weight was added and kneaded to prepare a kneaded product. This kneaded product was injection-molded under the conditions of 180 ° C. and 1 t / cm ^{2 into} the root shape shown in FIGS. The molded body (1)
The (green body) was heated and degreased in an argon stream at a rate of 6 ° C / hour to 500 ° C, then placed in a Ti box and heated in vacuum to 850 ° C at a rate of 50 ° C / hour. After heating and heating, and holding at 850 ° C. for 3 hours to perform calcination, the temperature is raised to a predetermined temperature shown in Table 1 at a rate of 100 ° C./hour, and then the temperature is maintained for 1 hour to perform main firing. After that, it was cooled in the furnace. The shape of the obtained sintered body was corrected by machining, and heat treatment was performed at 500 ° C. for 0.5 hour to obtain a sample. The properties of the obtained sample are shown in Table 1.

[0014]

[Table 1] As shown in Table 1, the porosity of each sample is in the range of 3 to 60%, which is well compatible with tooth bones, and the shape is recovered by spraying a saline solution at a temperature of about 45 ° C. at which there is no risk of burns.

Example 2 Ti powder (average particle size ≤44 μ
m) and carbonyl Ni powder (average particle size 4 μm) are mixed in a hexane solvent by a ball mill and dried, and then 11φ
It is molded into pellets of × 10 mm under the pressure conditions shown in Table 2. Each of the obtained pellets was placed in a Ti box and heated to 850 ° C. at a rate of 100 ° C./hour→25° C./hour in vacuum and heat-treated at that temperature for 3 hours to synthesize a Ti—Ni alloy. .. Further, a part of the sample is taken and 50 in H ₂ 30atm.
It was gradually cooled from 0 ° C. at a rate of 10 ° C./hour for hydrogenation. Put these samples in a ball mill with an inner diameter of 160φ, and
After treating at 80 rpm for 96 hours, the sample was weighed to determine the crushability. The results are shown in Table 2.

[0016]

[Table 2] According to Table 2, it was found that the low-pressure molded sample and the hydrogenated sample were easy to pulverize, and it was found that fine pulverization was possible.

[Example 3] A Ti-Ni alloy wire rod having a diameter of 2 mm was manufactured by a melting method, and the wire rod was cut into about 2-3 mm to obtain pellets. This is pickled with hydrofluoric nitric acid solution,
The hydrogenation treatment was carried out at a temperature of 130 ° C. and H ₂ pressure. The hydrogen absorption amount in this case was about 70 cc / g. The hydrogenated pellets were subjected to an attritor treatment in a Diflon solution and pulverized to obtain fine powder having an average particle size of 13 μm.

[Embodiment 4] A raw material powder having an average particle diameter of about 13 μm produced by the method of Embodiments 2 and 3 is used in Embodiment 1
Molding, degreasing, and sintering were performed under the same conditions as above. However, the sintering temperature was 1200 ° C. As a result, the shrinkage rate is 11.8.
%, And an artificial tooth root composed of a sintered body having a porosity of 37% was obtained.

[0019]

Therefore, in the present invention, an artificial tooth root having shape memory characteristics can be manufactured very easily.

[0020]

[Brief description of drawings]

1 is a side view of an artificial tooth root B: A-A sectional view of B. C: A-BB sectional view of B

[Explanation of symbols]

 1 artificial tooth root

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[Procedure amendment]

[Submission date] July 10, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Delete

Claims (5)

[Claims] 1. An artificial tooth root comprising a powder sintered body having shape memory characteristics. 2. The artificial tooth root according to claim 1, wherein the powder sintered body is a mixed powder sintered body of Ti powder or Ti hydrogen compound powder and Ni powder. 3. The powder-sintered body is a Ti-Ni alloy powder sintered body obtained by pulverizing a powder mixture of Ti powder or Ti hydrogen compound powder and Ni powder. Artificial tooth root 4. The Ti powder or the Ti hydrogen compound powder,
The powder of the mixed powder sintered body with Ni powder is obtained by pulverizing the sintered body after absorbing hydrogen.
Artificial tooth root 5. The artificial tooth root according to claim 1, wherein the powder sintered body is a Ti-Ni powder sintered body obtained by hydrogenating Ti-Ni alloy pellets and then pulverizing the hydrogenated Ti-Ni alloy pellets.