JPH02161941A - Artificial tooth root and production thereof - Google Patents

Abstract

PURPOSE:To provide both characteristics of mechanical strength and affinity to the living body by using a material having excellent mechanical strength in the inner cap part to be mounted with an upper structure and using a material having the excellent affinity to the living body in the tooth root part. CONSTITUTION:Porous HAP is used for the tooth root part to be implanted into the living body. The good affinity to the alveolar bone is, therefore, obtd. and the secure bond by the preparation and infiltration of the neonatal bond into the pores is possible. Dense alumina is used in the inner cap part. The mechanical strength is, therefore, high and the easy bonding to the upper structure is executed. The production is executed by a method consisting in adding the distilled water of ethanol dilution and acetic acid to a soln. mixture composed of a soln. prepd. by dissolving calcium diethoide in 2-methoxyethanol and triethyl phosphite diluted with ethanol and subjecting the soln. mixture to hydrolysis to prepare a sol. Fine alumina powder and polystyrene of a foaming agent are added to this sol. The sol is gelatinized by pH adjustment, etc., in the stage when the soln. begins to separate by a sp. gr. difference and the alumina and polystyrene in the sol exhibits a suitable concn. distribution. The gel is dried to form a dry gel. The artificial tooth root is produced by sintering this gel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an artificial tooth root made of porous HAP and alumina, and a method for manufacturing the same.

[Prior Art] There is a treatment method in which an artificial material is implanted into the alveolar bone after a tooth has fallen out, and the upper part of the material is made to function as a tooth. This artificial material is called an artificial tooth root, and research is progressing on various materials such as metals, ceramics, and polymers.

The two conditions required for this artificial tooth root are: 1. It must be smaller than a natural tooth but have high strength; 2. It must be able to be firmly fixed in the bone for a long period of time. In order to satisfy this condition, the most research has been carried out in the past on artificial tooth roots made of metal, mainly titanium.

However, artificial tooth roots made of metal, including artificial tooth roots made of titanium, always have the problem of corrosion resistance, so research is currently underway on artificial tooth roots made of ceramics, which do not have to worry about corrosion resistance and have excellent strength. .

[Problems to be Solved by the Invention] Research is underway on two types of materials, high-strength alumina and biocompatible apatite, and porous materials for ceramic artificial tooth roots.

Alumina has excellent mechanical properties and long-term stability, making it a promising material for artificial tooth roots. However, although alumina does not harm adjacent bone tissue, it has the problem that it does not blend in with the surrounding alveolar bone tissue because it cannot bind to bone at the molecular level.

Apatite has excellent biocompatibility and can chemically bond with bone tissue. For this reason, two months after apatite is embedded in bone tissue, a portion where the boundary line between the two is not clear appears. Although apatite has the property of blending well with the surrounding alveolar bone tissue, it has problems with its mechanical properties and cannot be used alone as an artificial tooth root.

In addition, in the case of a porous material, new bone can easily proliferate and invade into the pores, so that a strong bond with the alveolar bone is maintained for a long period of time. However, the mechanical strength of porous ceramics is extremely low, and there is also the problem that it is impossible to attach a superstructure such as a dental crown.

The present invention aims to solve these problems, and its purpose is to use a material with excellent mechanical strength for the inner crown part to which the upper structure is attached, and to use the most biocompatible material for the root part of the tooth. By using materials with excellent properties,
An object of the present invention is to provide an artificial tooth root having both mechanical strength and biocompatibility, and a method for manufacturing the same.

[Means for Solving the Problems] The artificial tooth root of the present invention has the following characteristics:
The inner crown, which is made of porous HAP and is exposed outside the living body, is characterized by being made of alumina.

Furthermore, in the production method of the present invention, fine powder consisting of the remaining components and a foaming agent are added to the sol of either alumina or HAP, and the difference in specific gravity between the sol, fine powder, and foaming agent causes the alumina to It is characterized in that gelation, foaming treatment, and sintering are performed at stages in which the composition ratio of HAP and foaming agent is continuously changed.

[Effect] FIG. 3 shows an external view of the artificial tooth root of the present invention.

Since porous HAP is used in the tooth root part embedded in the living body, it is compatible with the alveolar bone, and a strong bond is made possible by the growth and invasion of new bone into the pores. Furthermore, since dense alumina is used for the inner crown, it has high mechanical strength and can be easily connected to the upper structure.

The manufacturing method of the present invention involves mixing the remaining component fine powder and a foaming agent in a sol, and at the stage when the fine powder and foaming agent exhibit a certain concentration distribution, gelling, foaming, and sintering. Accordingly, the artificial tooth root described above can be created.

[Example] (Example-1) Triethyl phosphite diluted with ethanol was mixed into a solution of calcium jetoxide dissolved in 2-methoxyethanol so that the atomic ratio of Ca/P was 1.67. Distilled water diluted with ethanol and acetic acid are added to this mixed solution to perform hydrolysis to create a sol. This sol contains fine alumina powder with a particle size of 0.05 to 0.1 (μm) and 0.03 (wt%) polystyrene as a blowing agent.
) Add i and store in a designated container in a sealed state to prevent gelation. The amount of alumina added was adjusted so that the composition after gelation was alumina/HAP=1/1.

The sol, alumina, and polystyrene in the container begin to separate due to the difference in specific gravity. When the alumina and polystyrene in the sol exhibit an appropriate concentration distribution, gelation is caused by adjusting the pH and heating. The prepared wet gel is taken out of the container and dried for about two weeks to form a dry gel.

Next, this dry gel was placed in a sintering furnace and heated for 20 minutes in a vacuum.
It is heated to 300°C at a heating rate of ('C/hour) and held at the same temperature for 8 hours to completely decompose and remove polystyrene, and to perform desorption water treatment.
Sintering is carried out by heating to 1200 ('C) at a temperature increase rate of 24 hours) and holding at the same temperature for 24 hours.

Sintering is performed in a nitrogen atmosphere or in vacuum, but it is desirable to perform the foaming and degassing steps in vacuum until the foaming agent is completely decomposed and removed.

The shape of the artificial tooth root created in this example was φ10Xt20.
(mm) cylindrical shape. This sintered body is 10 mm thick in the thickness direction.
The samples were divided into equal parts, and each sample was subjected to compositional analysis and porosity measurement using mercury intrusion method. The obtained results are shown in FIG.

Alumina with heavy specific gravity settles to the bottom side, and alumina and H
The ratio of AP is changing continuously. Since polystyrene has a light specific gravity, it is contained in large amounts on the HAP side, and as a result, HA
The porosity on the P side is high.

Normally, when ceramics made of multiple compositions are sintered at the same time, large stresses are applied to the bonded surfaces due to differences in shrinkage rates, coefficients of thermal expansion, etc., often resulting in breakage.

However, since the present invention uses a sol-gel method, it becomes possible to easily gradient the composition at the sol stage. Therefore, by continuously changing the composition distribution of alumina and HAP in the sintered body, it is possible to eliminate so-called bonding surfaces and relieve stress, thereby producing artificial tooth roots that have the characteristics of two types of ceramics. is now possible. Furthermore, since polystyrene is concentrated on the HAP sol side, porous HAP with excellent biocompatibility can be produced.

Furthermore, the sol-gel method has a large degree of freedom in shape, and by selecting the shape of the container in which the gel is made, it can be controlled to a shape close to the final shape desired at the end of sintering. This eliminates the need for secondary processing, making it possible to significantly reduce costs.

(Example 2) A mixed solution of aluminum isopropoxide and isopropanol is hydrolyzed under acidic conditions to create a sol. To this sol were added HAP fine powder with a particle size of 0.05 to 0.2 (μm) and 0.2 (ili amount %) of N,N''-dinitrosopentamethylenetetramine as a blowing agent. 1
Store in the same container and keep it tightly closed to prevent gelation. The amount of HAP was adjusted so that the composition after gelation was alumina/HAP=674.

The sol, HAP, and N,N'-dinitrosopentamethylenetetramine in the container begin to separate due to the difference in their specific gravity. At the stage when alumina and polystyrene in the sol exhibit an appropriate concentration distribution, gelation is caused by means such as pH adjustment and heating. The prepared wet gel is taken out of the container and dried for about two weeks to form a dry gel.

Next, this dry gel was placed in a sintering furnace and heated for 20 minutes in a vacuum.
Heating to 300°C at a heating rate of (C/hour) and holding at the same temperature for 5 hours, then heating to 600°C at the same heating rate and holding at the same temperature for 5 hours to completely remove polystyrene. Along with decomposition and removal, desorption water treatment is performed.After that,
Sintering is performed by heating to 1200 ("C) at a temperature increase rate of 30 ("C/hour) and holding at the same temperature for 24 hours.

The obtained sintered body was subjected to compositional analysis and porosity measurement in the same manner as in Example 1, and the results are shown in FIG. The HAP fine powder and N,N'-dinitrosopentamethylenetetramine, which have a heavy specific gravity, settle to the bottom, and the composition ratio of alumina and HAP changes continuously, and the pores are concentrated on the HAP side. . In this way, even if the compositions of the sol and the fine powder are alternated, a similar artificial tooth root can be created.

When fine alumina powder is added to the foaming agent, a blowing agent whose specific gravity is lighter than that of the sol is used, and when fine HAP powder is added, a blowing agent whose specific gravity is heavier than that of the sol is used.

The blowing agents used are typified by N-nitroso-based agents such as N,N'-dinitrosopentamethylenetetramine, azo-based agents such as azodicarbonamide, and hydrazine-based agents such as diphenylsulfone-3,3'disulfohydrazine. Any of organic foaming agents, organic resins such as polystyrene and polyethylene, and inorganic materials such as carbon and CaCO3 may be used.

[Effects of the Invention] As described above, according to the present invention, alumina with excellent mechanical strength is placed in the internal crown part protruding from the living body, and biocompatible alumina is placed in the tooth root part inside the living body. Because excellent porous HAP is arranged and the composition ratio of each is continuously changed, one artificial tooth root has the effect of having two properties of mechanical strength and biocompatibility. In addition, fine powder of the remaining composition and a foaming agent are added to the sol of either alumina or HAP, and after these fine powders have a certain concentration distribution due to the difference in specific gravity, they are gelled and sintered. This has the effect that the artificial tooth root described above can be easily created.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the composition distribution and porosity distribution inside the tooth root, created in Example-1. FIG. 2 is a diagram showing the composition distribution and porosity distribution inside the tooth root, created in Example-2. FIG. 3 is an external view of the artificial tooth root of the present invention. The numbers on the horizontal axis in Figures 1 and 2 indicate the number of each sample when the sintered body is divided into 10 equal parts. Smaller numbers indicate the bottom side of the container used for gelation. (Mo, Ruzu・) (Ninobon 7” W look at fJ2 figure Bun Anon meet figure 3

Claims (2)

[Claims] (1) Alumina and hydroxyapatite (hereinafter referred to as HAP)
An artificial tooth root whose main component is a tooth root embedded in a living body is made of porous HAP, and the inner crown part that is exposed outside the living body is made of alumina. tooth root. (2) Add fine powder consisting of the remaining ingredients and a foaming agent to the sol of either alumina or HAP, and this sol,
Due to the difference in specific gravity between fine powder and blowing agent, alumina and HAP
Claim 1 characterized in that gelation, foaming treatment and sintering are performed at the stage where the composition ratio of the foaming agent is continuously changed.
The method for manufacturing the artificial tooth root described.