JPH0153211B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a high-strength crystallized glass useful as an implant material for artificial tooth roots, artificial bones, etc., and a method for producing the same. In recent years, artificial materials such as artificial tooth roots and artificial bones have been used as substitutes for tooth roots and bones that no longer function. As such artificial materials, corrosion-resistant alloys such as stainless steel or cobalt chromium alloys, and polymeric materials such as polymethyl methacrylate or high-density polyethylene have conventionally been used. However, these materials tend to elute metal ions and monomers into the body when used for a long period of time, and may be harmful to the human body. In comparison, ceramic materials generally have excellent biocompatibility and are stable in vivo, so they are attracting attention as future materials. Examples of such ceramic materials include single-crystal and polycrystalline alumina, which are characterized by extremely high strength. However, since alumina ceramics do not form chemical bonds with bones, in order to fix them in vivo, it is necessary to physically fix them within the bones by cutting screws or drilling holes in the alumina ceramics itself. It won't happen. In this case, if the shape of the material is inappropriate, stress concentration will occur in the bone or part of the material, causing bone resorption, or collagen fibers will form at the interface between the bone and the material, causing the fixed part of the material to Loosening or falling off may occur. In order to solve this problem, progress has been made in recent years in the development of ceramics that can chemically bond with bone and firmly anchor it within the bone. Typical examples of this type of ceramics include sintered hydroxyapatite, Na ₂ O−CaO−P ₂ O ₅ −SiO ₂ based bioglass, and Na ₂ O−K ₂ O−MgO−CaO−
Apatite-containing crystallized glass is known, in which apatite crystals are precipitated from _{P2O5 - SiO2-} based glass. However, when hydroxide apatite crystals are sintered at high temperatures, they change to tricalcium phosphate.
It is difficult to produce a strong sintered body with a dense structure. On the other hand, bioglass and apatite-containing crystallized glass have the disadvantage that they have low mechanical strength and can only be used as bone replacement materials in areas where little stress is applied. Therefore, recently, crystallized glass that forms chemical bonds with bones and is relatively strong has been developed. Such conventional crystallized glass is made by crushing MgO−CaO−P ₂ O ₅ −SiO ₂ glass with an MgO content of 7% or less into 200 meshes or less, and press-forming it. ,
Some are made by heat treatment in the sintering temperature range of glass powder and the formation temperature range of apatite crystals and wollastonite crystals. The bending strength of the crystallized glass thus obtained is 1200 to 1400 Kg/ ^cm2 ,
It is the strongest material to date that forms a chemical bond with bone. However, in this crystallized glass, the sintering temperature range of the glass powder and the precipitation temperature range of the crystals are close to each other, so crystallization progresses before the pores disappear due to sintering, resulting in the crystallization of a dense structure. It is difficult to produce glass stably. For this reason, there is a drawback that the strength varies depending on the production lot. Further, in order to use this crystallized glass for an artificial tooth root, it is desired that the mechanical strength is even higher. This invention was made in view of the above-mentioned conventional problems, and aims to provide a crystallized glass containing apatite crystals with excellent biocompatibility and high strength, and a method for producing the same. There is. That is, the crystallized glass of this invention has a
MgO8~34%, CaO12~43%, _SiO2 25~40%,
_{P2O5 10-25 %} , and MgO, CaO, _SiO2 , _P2O5
The total content of Li ₂ O, Na ₂ O, K ₂ O,
It has a composition in which one or more additives of SrO, B ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and F ₂ are 10% or less, and a large amount of apatite (Ca ₁₀ (PO ₄ ) ₆ O)
and alkaline earth silicate crystals such as diopside (MgO・CaO・2SiO ₂ ), forsterite (2MgO・SiO ₂ ), and acamanite (2CaO・MgO・2SiO ₂ ) coexist, and these crystals are uniformly distributed in the glass. It is characterized by having a dispersed structure. Regarding the composition, MgO8 to 34% by weight,
CaO12~43%, _SiO2 25~40%, _{P2O5 10} ~25%,
Al ₂ O ₃ 1-10%, and MgO, CaO, SiO ₂ ,
The total content of P ₂ O ₅ , Al ₂ O ₃ is 90% or more, Li ₂ O,
_Na2O , _{K2O ,} SrO, _B2O3 , _TiO2 , _{Nb2O5 ,}
Another feature is that the content of one or more additives of Ta ₂ O ₅ and F ₂ is 10% or less. Furthermore, the method for producing crystallized glass of the present invention includes:
After molding a glass powder of 200 mesh or less of each composition above, it is heat-treated in the sintering temperature range of the glass powder, and then the temperature at which apatite crystals and alkaline earth silicate crystals such as diopside, forsterite, and acamanite crystals are formed. It is characterized by being heat-treated at a temperature range. Next, the reason why each component of the crystallized glass according to the present invention is quantitatively limited as described above will be described. When MgO is less than 8%, the sintering temperature range of the glass powder and the crystal formation temperature range are close to each other, so crystallization occurs before pores disappear due to sintering, making it difficult to obtain crystallized glass with a dense structure. . Also, MgO
If it exceeds 34%, the amount of apatite crystals produced will decrease, which is not preferable. Therefore, the MgO content is limited to 8 to 34%. If CaO is less than 12%, the amount of apatite crystals produced is small, which is not preferable. Moreover, if it exceeds 43%, the glass tends to have a significant tendency to devitrify, making it difficult to manufacture. Therefore, the content of CaO is 12
Limited to ~43%. If the SiO ₂ content is less than 25%, the glass tends to devitrify, making it difficult to manufacture and producing fewer calcium and magnesium (alkaline earth) silicate crystals, making it difficult to obtain a glass with high strength. Moreover, if it exceeds 40%, the glass tends to undergo phase separation, making it impossible to obtain a uniform glass. Sideways
The content of _SiO2 is limited to 25-40%. If P ₂ O ₅ is less than 10%, the amount of apatite crystals produced is small, and if it is more than 25%, a uniform glass cannot be obtained due to phase separation. Therefore, the content of P ₂ O ₅ is
Limited to 10-25%. As for glass containing Al ₂ O ₃ , the details of the effect when added will be described in detail later, but when glass with a composition containing Al ₂ O 3 is heat-treated at a temperature of about 900 to 1000°C, the amount of apatite crystals produced increases It increases significantly compared to the one that does not contain O ₃ . If Al ₂ O ₃ is less than 1%, it has little effect on promoting the precipitation of apatite crystals, and if it is more than 10%, it reduces the amount of alkaline earth silicate crystals formed.
Limited to: In addition to the above-mentioned components, the crystallized glass of the present invention contains Li ₂ O, Na ₂ O, K ₂ O, SrO, which is not harmful to the human body.
One or more of components such as B ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , F ₂ and the like can be contained as an additive within 10%. The total amount of these ingredients is 10
%, the amount of alkaline earth silicate crystals such as apatite crystals and diopside crystals will decrease, so the total amount of these components is limited to 10% or less. Therefore, MgO, CaO, SiO ₂ ,
The total amount of P ₂ O ₅ or Al ₂ O ₃ added thereto is limited to 90% or more. Among the above additives, if Na ₂ O exceeds 5%,
Since the amount of apatite crystals produced is significantly reduced,
The content of Na ₂ O is preferably within 5%. If the amount of F ₂ exceeds 3%, the glass tends to devitrify significantly, so the content of F ₂ is preferably within 3%. The crystallized glass having each of the above compositions is manufactured by the following method. First, in any of the above-mentioned composition glasses,
After pulverizing this to a particle size of 200 mesh or less,
Mold into a predetermined shape. When the glass used in this invention is directly formed into a predetermined shape from a molten state and then heat-treated, apatite crystals are uniformly dispersed and precipitated, but alkaline earth silicate crystals such as diopside, acamanite, and forsterite are precipitated. teeth,
It precipitates from the glass surface and causes cracks inside the glass. Therefore, crystallized glass with high strength cannot be obtained. The fact that the glass is a fine powder is an extremely important condition for obtaining crystallized glass with few pores and uniformly dispersed crystals. If the glass powder has a mesh size of 200 or more, large pores tend to remain in the crystallized glass obtained by sintering, making it impossible to obtain a crystallized glass with high mechanical strength. Therefore, the glass powder is limited to 200 mesh or less. Further, in order to produce the crystallized glass of the present invention, it is necessary to perform heat treatment in the sintering temperature range of glass powder and the formation temperature range of alkaline earth silicate crystals such as apatite crystals and diopside. Heat treatment of glass powder in the sintering temperature range is important for obtaining crystallized glass with no pores and high mechanical strength. The sintering temperature range of the glass powder is determined by heating a molded body of glass powder at a constant temperature increase rate and measuring the thermal shrinkage due to sintering of the molded body. The sintering temperature range is from the start temperature of heat shrinkage to the end temperature of heat shrinkage. Furthermore, heat treatment in the apatite crystal formation temperature range is important in order to precipitate a large amount of apatite crystals necessary for chemically bonding to bone. Furthermore, heat treatment in the temperature range for forming alkaline earth silicate crystals such as diopside is important in order to precipitate a large amount of alkaline earth silicate crystals and increase the mechanical strength of the crystallized glass. The temperature range in which each crystal forms is determined by differential thermal analysis of glass powder. By analyzing the X-ray diffraction data of glass powder heat-treated at the temperature of the exothermic peak in the differential thermal analysis curve, the precipitated crystals corresponding to each exothermic peak were identified, and the temperature from the exothermic start temperature to the exothermic end temperature was determined respectively. This is the crystal formation temperature range. Next, the effect of adding Al ₂ O ₃ is shown in Figures 1 and 2.
This will be explained with reference to the figures. Both figures show the intensity of X-ray diffraction lines of crystals contained in these samples and the heat treatment for both samples manufactured with glass A that does not contain Al ₂ O ₃ and glass B that contains Al ₂ O ₃ . The relationship between the temperature and the holding temperature is shown. In these figures, A indicates the main X-ray diffraction peak of apatite crystal (d = 2.81 Å), B indicates the main X-ray diffraction peak of diopside crystal (d =
2.99 Å), C shows the relationship between each X-ray diffraction intensity of the main X-ray diffraction peak (d=3.88 Å) of the forsterite crystal and the holding temperature of heat treatment. Glass A also has MgO20.8, CaO29.2,
It has a composition of 33.4% SiO ₂ , 16.1% P ₂ O ₅ , and 0.5% by weight of F ₂ , and Glass B has a composition to which 4% by weight of Al ₂ O ₃ is added. These glasses were crushed to 200 mesh or less and heated in an electric furnace at a rate of 10°C/min from room temperature to 850°C.
It was kept at a constant temperature in the range of 1150°C for 30 minutes and then cooled to room temperature. Crystals precipitated from Glass A and Glass B after heat treatment were identified by powder X-ray diffraction, and the main precipitated crystals in each sample were apatite, diopside, and forsterite. Figures 1 and 2
As is clear from the figure, the X-ray diffraction intensity of apatite crystals at temperatures below 1015°C is approximately 23% higher in glass B to which Al ₂ O ₃ is added than in glass A to which Al ₂ O ₃ is not added. It can be seen that the amount produced is large. 1015 for this
The amount of diopside crystals formed below ℃ is Al ₂ O ₃
It is slightly less than Glass A which does not contain.
However, the amount of forsterite crystals produced tends to increase slightly, and the total amount of diopside and forsterite produced is not much different from Glass A. In this way, the addition of Al ₂ O ₃ has the effect of significantly increasing the amount of apatite crystals produced, and glass to which Al ₂ O ₃ is added, such as glass B, is
Crystallized glass obtained by heat treatment at temperatures below 1015°C contains a large amount of apatite crystals, and therefore has excellent biocompatibility. The effect of adding Al ₂ O ₃ above was described for glass with a certain composition, but when Al ₂ O ₃
The effect of increasing the amount of apatite crystal precipitation due to the addition of is not limited to the above composition.
The type of alkaline earth silicate crystals precipitated by heat treatment differs depending on the glass composition. Forstellite (2MgO・SiO ₂ ) is obtained from glass with a high MgO content, and diopside (MgO・CaO・2SiO ₂ ) is obtained from glass with a high CaO content.
Acamanite (2CaO・MgO・2SiO ₂ ) is precipitated from glass with a composition with a low SiO ₂ content and glass with a composition with a low P ₂ O ₅ content. In these intermediate range compositions, two or more types of the above-mentioned crystals are precipitated. Furthermore, when components such as Na ₂ O, K ₂ O, and Li ₂ O are added, crystals other than the above crystals may be precipitated. Therefore, the crystallized glass according to the present invention uses oxides, phosphates, carbonates, fluorides, etc. as raw materials, and is manufactured using a refractory crucible or a platinum crucible in the same manner as general glass. Can be melted at ℃. The molten glass is rapidly cooled by pouring it onto a mold, passing it between chilled rolls, or submerging it in water. The glass thus obtained is pulverized into 200 meshes or less using a common pulverizer such as a pot mill or a jet mill. If necessary, the glass powder is classified according to particle size, and the particle size is appropriately blended. Glass powder can be prepared using common methods used for molding ceramics, such as pressure molding with a mold, slurry casting,
Molded by extrusion molding method, hydrostatic pressing method, etc. In order to improve the rheological properties such as the flowability of the powder during molding, it is effective to add common molding aids such as paraffin and stearate to the glass powder. Furthermore, in order to improve the fluidity of the glass powder, it is also effective to use granulated glass powder. The sintering and crystallization of the glass powder compact is carried out at a temperature within the sintering temperature range of the glass powder, the formation temperature range of apatite crystals, and the formation temperature range of alkaline earth silicate crystals such as diopside. This can be carried out by a method in which the powder is held, or by a method in which it is gradually heated to a temperature range from the sintering temperature range of glass powder to the formation temperature range of alkaline earth silicate crystals such as diopside. Furthermore, sintering and crystallizing glass powder by high temperature pressing, hot isostatic pressing, or the like is effective for obtaining dense crystallized glass. Next, embodiments of this invention will be described. A batch of glass corresponding to the composition shown in the table was prepared from oxides, carbonates, phosphates, fluorides, etc., placed in a platinum crucible, and melted at 1400-1500°C for 1 hour. The molten glass is poured into water and rapidly cooled.
After drying, it was placed in a pot mill and pulverized to a particle size of 350 mesh or less. A mixture of this glass powder and 5% paraffin as a binder was placed in a mold, and a pressure of 600 kg/cm ² was applied to press-form it into a predetermined shape. Place the molded body in an electric furnace and heat it from room temperature for 3
It was heated to a constant temperature within the range of 950 to 1050°C at a constant heating rate of °C/min and held at this temperature for 2 hours to perform sintering and crystallization. Thereafter, it was slowly cooled to room temperature in a furnace. Break this crystallized glass,
When the fracture surfaces were observed using SEM, they all had dense structures with almost no pores. The samples were crushed and the precipitated crystals were identified by X-ray diffraction. As a result, it was found that a large amount of alkaline earth silicate crystals such as diopside, forsterite, and acamanite were precipitated in both samples along with a large amount of apatite crystals. was recognized. The table also shows the types of crystals precipitated in each sample. For some samples, the bending strength was measured using a 5 x 5 x 25 mm square column whose surface was polished with No. 1000 alumina abrasive grains. The results are also listed in the table. As shown in this table, the crystallized glass of the present invention has a high bending strength of 1500 to 1800 Kg/cm ² . As described above, the crystallized glass according to the present invention contains a large amount of apatite crystals necessary for chemical bonding with bone, and has an extremely high bending strength of 1500 to 1800 Kg/cm ² . The value of this bending strength is
Conventional sintered bodies of hydroxyapatite and Na ₂ O−CaO
−P ₂ O ₅ −SiO ₂ -based bioglass and Na ₂ O−K ₂ O−MgO−CaO− containing only apatite crystals
The bending strength of P ₂ O ₅ -SiO ₂ -based crystallized glass, as well as crystallized glass containing apatite crystals and wollastonite crystals, is 700 to 1400 Kg/cm ² , but this value is extremely large. have. In addition, since the bending strength of the crystallized glass of the present invention hardly varies depending on production lots, it is extremely useful as a material for artificial bones and artificial tooth roots.

【table】

【table】 [Brief explanation of drawings]

1 and 2 are relationship curve diagrams showing the relationship between the heat treatment temperature of the high-strength crystallized glass according to the present invention and the X-ray diffraction line intensity of the contained crystals, and FIG. 1 is a relationship curve diagram for apatite crystals. , FIG. 2 is a relationship curve diagram for diopside crystals and forsterite crystals. A...Glass that does not contain Al ₂ O ₃ , B... Al ₂ O ₃
Glass containing 4wt%.

Claims (1)

[Claims] 1% by weight: MgO8-34%, CaO12-43%,
_SiO2 25-40%, _{P2O5 10-25} %, and MgO,
The total content of CaO, SiO ₂ and P ₂ O ₅ is 90% or more,
_{Li2O , Na2O} , _K2O , SrO, _B2O3 , _TiO2 ,
Alkaline earth silicate crystals such as diopside, forsterite, acamanite, etc., with a composition in which one or more additives of Nb ₂ O ₅ , Ta ₂ O ₅ , and F ₂ are 10% or less with one or more types of
A high-strength crystallized glass characterized by containing apatite crystals. 2. MgO8-34%, CaO12-43% by weight,
_SiO2 25-40%, _{P2O5 10-25} %, _{Al2O3 1-10} %,
and the total content of MgO, CaO, SiO ₂ , P ₂ O ₅ , Al ₂ O ₃ is 90% or more, Li ₂ O, Na ₂ O, K ₂ O, SrO,
It has a composition in which one or more additives of B ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and F ₂ is 10% or less, such as diopside, forsterite, acamanite, etc. A high-strength crystallized glass characterized by containing one or more types of alkaline earth silicate crystals and apatite crystals. 3 MgO8-34%, CaO12-43% by weight,
_SiO2 25-40%, _{P2O5 10-25} %, and MgO,
The total content of CaO, SiO ₂ and P ₂ O ₅ is 90% or more,
_Li2O , _Na2O , _K2O , SrO, _{B2O3 , TiO2} ,
After molding a glass powder of 200 mesh or less with a composition containing 10% or less of one or more additives of Nb ₂ O ₅ , Ta ₂ O ₅ , and F ₂ , the sintering temperature range of the glass powder 1. A method for producing high-strength crystallized glass, which comprises heat-treating at a temperature range for forming apatite crystals and alkaline earth silicate crystals such as diopside, forsterite, and acamanite. 4 MgO8-34%, CaO12-43% by weight,
_SiO2 25-40%, _{P2O5 10-25} %, _{Al2O3 1-10} %,
and the total content of MgO, CaO, SiO ₂ , P ₂ O ₅ , Al ₂ O ₃ is 90% or more, Li ₂ O, Na ₂ O, K ₂ O, SrO,
A composition containing 10% or less of one or more additives of B ₂ O ₃ , TiO ₂ , Nb ₂ O ₅ , Ta ₂ O ₅ , and F ₂ .
After molding a glass powder of 200 mesh or less, it is heat-treated in the sintering temperature range of the glass powder, and then heat-treated in the temperature range for forming apatite crystals and alkaline earth silicate crystals such as diopside, forsterite, and acamanite. A method for producing high-strength crystallized glass, characterized by: