JP5097354B2 - Biological member and method for producing the same - Google Patents

Description

  The present invention relates to a biomedical member made of a zirconia sintered body of a biomaterial and a method for producing the same, and more particularly to a biomedical member having high resistance to low temperature degradation in a humid environment and a method for producing the same.

  As a ceramic having excellent mechanical properties, a partially stabilized zirconia sintered body to which yttria is added is known. Since this zirconia sintered body is excellent in wear resistance in addition to mechanical properties of high strength and high toughness, it is used as a sliding member used under high load. Further, since the zirconia sintered body is a chemically very stable substance and excellent in biological safety, it is also used as a biological material such as a sliding member of an artificial joint.

  A partially stabilized zirconia sintered body is obtained by adding yttria (usually adding about 3 mol%) to convert a tetragonal crystal that is a high-temperature stable phase into a metastable phase at room temperature, that is, after sintering to room temperature. It is a zirconia sintered body that can maintain a tetragonal crystal even when returned. It is known that such tetragonal zirconia undergoes a phase transition to monoclinic zirconia, which is a room temperature stable phase, when subjected to stress. For example, when cracks enter the sintered body and stress concentrates on the crack tip, the surrounding structure of the crack tip changes from tetragonal to monoclinic. This phase transition from tetragonal to monoclinic crystal is accompanied by a volume expansion of about 4%, and this volume expansion works to compress the crack tip from the periphery, thereby effectively preventing the crack from progressing. it can. That is, the zirconia sintered body has characteristics of high strength and high toughness because it is composed of metastable tetragonal zirconia.

  A zirconia sintered body is a material that is chemically stable enough to be used as a biomaterial, but under conditions where moisture is present, the surface of the sintered body reacts with water to form a monoclinic crystal from tetragonal zirconia. There may be a phase transition to zirconia (this is generally called degradation). This deterioration starts from the surface of the sintered body, but with the time, it undergoes a monoclinic phase transition to the internal structure. As a result, the amount of monoclinic zirconia increases, and the strength and toughness of the zirconia sintered body decreases. Therefore, techniques for suppressing deterioration in the presence of moisture have been developed.

For example, a technique for suppressing deterioration in the presence of moisture by adding a compound such as Al ₂ O ₃ , TiO ₂ , and / or SiO _{2 to} zirconia and sintering is known (for example, Patent Document 1). ~ 3). Moreover, in order to protect the surface of a zirconia sintered body from a water | moisture content, it coats with a silica (for example, patent document 4), or forms a protective layer by making a solid solution of nitride on the surface of a zirconia sintered body (for example, Patent document 5) is known.
Japanese Patent Laid-Open No. 11-240757 JP 11-116328 A JP 2001-302345 A JP 2000-63175 A JP-A-9-227228

  The demand for the mechanical strength of the zirconia sintered body has been higher in recent years, and accordingly, the demand for deterioration resistance has become stricter. For this reason, even in the past, even a material that was previously considered to have sufficient deterioration resistance may be judged to have insufficient deterioration resistance in recent years. The deterioration resistance is judged by the monoclinic zirconia fraction (mol%) existing on the surface of the zirconia sintered body after the deterioration test, but in recent years the value is extremely suppressed to 10 mol% or less. There is a need for a zirconia sintered body that does not easily deteriorate.

  Further, it is known that a zirconia sintered body deteriorates over a long time in a low temperature range of room temperature to 300 ° C. (this is called low temperature deterioration). When using a zirconia sintered body as a biomaterial, this low temperature deterioration becomes a problem. For example, when a zirconia sintered body is used as a biomaterial such as a sliding member of an artificial joint, the zirconia sintered body is maintained at a temperature of 36 to 37 ° C. in a wet state always in contact with a body fluid, and for a long time. It is highly likely that low temperature degradation will proceed. Therefore, it is desired to use a zirconia sintered body having a property that does not deteriorate over a long period of time in a living body, that is, a low temperature deterioration resistant zirconia sintered body as a biomaterial.

  A zirconia sintered body to which a compound as described in Patent Documents 1 to 3 has been added has a conventional standard of deterioration resistance, but it cannot be said that it satisfies the recent severe requirements. Moreover, it may be possible to improve the degradation resistance by changing the compound to be added, but when used as a biomaterial, the usable compounds are significantly limited from the viewpoint of biosafety. There is a problem. Moreover, although the zirconia sintered body which gave surface coating or surface modification like patent document 4 or 5 is anticipated to show sufficient performance in terms of biosafety and low-temperature deterioration, it takes processing. Issues remain such as high cost and the need for strict control of surface modification conditions.

  In addition, since low-temperature degradation is caused by the reaction between the material surface and water, even if the zirconia sintered body has the same composition, the resistance to low-temperature degradation can be different if the surface properties differ depending on the degree of surface processing. There is enough sex. Most of the zirconia sintered body biomaterials that are actually commercialized are appropriately surface-treated after sintering. For example, in an artificial bone head for an artificial joint, the sliding surface of the bone head is mirror-finished, and the inner surface of the fitting hole into which the stem shaft is fitted is ground. As described above, the surface processing often varies depending on the location of one biomedical member, but it is desired that any surface does not deteriorate at low temperature or hardly deteriorates at low temperature even when it comes into contact with moisture. However, it is not known at all what surface processing is likely to cause low temperature deterioration and how to improve the low temperature deterioration resistance of any processed surface. In Patent Documents 1 to 5, there is no example in which the relationship between the surface property and the low temperature deterioration resistance is examined, and at present, the correlation between the surface property and the low temperature deterioration is not considered.

  Accordingly, an object of the present invention is to provide a biomedical member of a zirconia sintered body that suppresses low-temperature deterioration while taking into consideration the relationship between surface properties and low-temperature deterioration. Another object of the present invention is to provide a method for producing a biological member of a zirconia sintered body that suppresses low-temperature deterioration by performing a simple and low-cost treatment.

  The present invention is a biomedical member made of a zirconia sintered body of a biomaterial and used in a living body, and the inside of the biomedical member is mainly made of tetragonal zirconia and is included in the surface of the biomedical member. The monoclinic zirconia fraction is 1 mol% or less.

The biomedical member of the present invention may be any bioprocessed member that has been subjected to any surface treatment, or any biomaterial that has been subjected to surface treatment that varies depending on the location. The monoclinic zirconia fraction is low. That is, the biomedical member of the present invention has a low monoclinic zirconia fraction on the surface and a low starting point for low temperature deterioration, and is therefore excellent in low temperature deterioration resistance.
The biomedical member of the present invention does not require an additive for improving low-temperature degradation resistance, so that the composition of the zirconia sintered body whose biosafety has been confirmed can be used as it is. There is also.

  The present invention also relates to a method for producing a biomedical member used in a living body, comprising a zirconia sintered body of a biomaterial, wherein the method processes a powder raw material containing zirconia and yttria into a molded body. A forming step, a firing step of firing the formed body to obtain a sintered body, a surface processing step of processing the surface of the sintered body, and heat treating the processed sintered body to obtain a monoclinic crystal And a heat treatment step of phase transition of zirconia to tetragonal zirconia.

  The manufacturing method of the present invention is a method for manufacturing the above-described biomedical member, and after the surface processing, a post-processing biomaterial member surface is obtained by performing a heat treatment step for phase transition of monoclinic zirconia to tetragonal zirconia. Made it possible to lower the monoclinic zirconia fraction. As a result, any surface processed or biomedical member that has been subjected to surface processing that differs depending on the location can be treated with heat treatment after processing. Even if it exists, a monoclinic zirconia fraction can be reduced.

Since this heat treatment process is a process that can be performed relatively easily in the atmosphere using an apparatus usually used for manufacturing a zirconia sintered body, a special apparatus, a complicated process, or complicated conditions are required. There is an advantage of not.
Thus, the production method of the present invention can produce a biomedical member with improved low-temperature degradation resistance by suppressing the monoclinic zirconia fraction on the surface.
And since the manufacturing method of this invention does not require the additive for improving low temperature-proof deterioration property to the biomedical member, it uses for the living body which utilized the composition of the zirconia sintered compact by which biosafety was confirmed as it is. Suitable for manufacturing parts

  The biomedical member of the present invention can have high low temperature deterioration resistance regardless of the surface properties by setting the monoclinic zirconia fraction to 1 mol% or less on all surfaces. Moreover, the manufacturing method of this invention can manufacture the biological member excellent in low temperature deterioration-proof property by adding the simple and low-cost process called the heat processing in air | atmosphere to the conventional manufacturing method.

<Embodiment 1>
The biomedical member of the zirconia sintered body of the present invention is suitable for the artificial bone head 22 constituting the total replacement artificial hip joint 100 as shown in FIG.
The artificial hip joint 100 is composed of a femoral stem 20 that is fixed to the femur 91 and a cup 10 that is fixed to an acetabular acetabulum 93. The femoral stem 20 further includes a bone marrow of the femur 91. The stem body 21 is inserted into the stem body 21, and the artificial bone head 22 is fitted into one end of the stem body 21. The artificial hip joint 100 is configured by fitting an artificial bone head 22 into a concave portion of the cup 10 and sliding the artificial bone head 22 so as to be able to turn.

  In the artificial bone head 22 of the zirconia sintered body of the present embodiment shown in FIG. 1 (B), the sliding surface 23a is mirror-finished to reduce friction, and the hole into which the end portion 21a of the stem body 21 is fitted. The inner diameter 23b of the part 222 is cut so that the end 21a of the stem body 21 fits accurately, and the hole diameter is adjusted. The outer peripheral surface 23c of the hole 222 does not need to be machined such as grinding or blasting, and may be in a sintered state.

The artificial bone head 22 of the present embodiment can be formed from a sintered body of so-called yttria partially stabilized zirconia (PSZ) containing ₂ to 6 mol% of Y ₂ O ₃ . In particular, a zirconia sintered body containing ₃ mol% of Y ₂ O ₃ is known as a 3 mol% yttria-containing tetragonal zirconia polycrystal (3Y-TZP), and is widely used as a biomaterial.

  The inside and the surface of the artificial bone head 22 are mainly composed of tetragonal zirconia. The artificial bone head 22 often has a monoclinic zirconia fraction on the surface higher than the inside. This is presumably because the surface region was stressed during the surface processing performed after sintering, and tetragonal zirconia was phase-transformed to monoclinic zirconia. The biomedical member of the present invention is characterized in that the monoclinic zirconia fraction of the member surface that has been raised after the surface processing is finally reduced to 1 mol% or less.

In a product made of a zirconia sintered body, the low temperature deterioration starts from the product surface. If monoclinic zirconia is present on the product surface at this time, the deterioration tends to be promoted by acting as a starting point of the low temperature deterioration. However, the biomedical member of the present invention (artificial bone head 22) has a monoclinic zirconia fraction on the surface as extremely low as 1 mol% or less, so that there is little monoclinic zirconia as a starting point for low temperature degradation, and low temperature degradation. Can be suppressed.
If the monoclinic zirconia fraction on the surface of the living body member is 1 mol% or less, the living body member is excellent in low temperature deterioration resistance, but is more preferably 0.5 mol% or less, further reducing low temperature deterioration resistance. Can be improved.

By forming a living body member such as the artificial bone head 22 from a dense sintered body, it can be expected that not only the mechanical properties can be improved, but also the low temperature deterioration resistance can be improved. If the living body member has a large number of voids communicating with the external environment, moisture from the external environment comes into contact with the inner wall of the void and is placed in an environment in which low temperature degradation is likely to occur. Moreover, since the apparent Young's modulus decreases, the binding force of the particles decreases. For these reasons, there is a possibility that the deterioration resistance of the biomedical member may be lowered, which is not preferable.
As a sintered body particularly suitable for a biomaterial, a zirconia sintered body having a relative density (measured bulk density / theoretical density) calculated with a theoretical density of 6.09 g / cm ³ of 99% or more, This is preferable because the effect of the relative density on the deterioration becomes remarkable. In this specification, the “mass density” is measured per unit volume including both open pores (empty walls leading to the outside air) and closed pores (empty walls isolated inside) measured by the Archimedes method. It is the mass of.

  In addition, the average particle diameter of the zirconia sintered body constituting the biomedical member affects the stability of tetragonal zirconia that is a metastable layer at room temperature. The smaller the particle size, the larger the phase transition energy from tetragonal zirconia to monoclinic zirconia, that is, the crystals of tetragonal zirconia are likely to be stable. Therefore, a biological member having a small average particle diameter is preferable because it is less likely to deteriorate at low temperatures. In particular, the average particle size is preferably 0.3 μm or less, and with the advantage that the crystal stability of tetragonal zirconia can be increased, it is suitable for obtaining a dense sintered body having a suitable relative density as described above. Yes.

  The surface of a biomedical member is often processed by grinding, polishing or blasting, but the surface roughness after these processes is quite different. In general, the surface roughness increases as the surface roughness increases, since the surface area per unit area increases. However, in the present invention, by setting the monoclinic zirconia fraction to 1 mol% or less, low-temperature deterioration can be suppressed on the surface by any processing method such as grinding, polishing or blasting. That is, it can be said that the living body member of the present invention is excellent in low temperature deterioration resistance regardless of the surface roughness. Here, the polishing process means the entire polishing including mirror finishing.

The manufacturing method of the biomedical member of the present invention will be described below.
The zirconia sintered body of the present embodiment can be manufactured from four steps as shown in FIG. That is, a molding step S20 for processing a powder raw material containing zirconia and yttria into a molded body, a firing step S30 for firing the molded body to obtain a sintered body, and a surface processing step S40 for processing the surface of the sintered body. And the processed sintered body is heat-treated, and the four steps of heat treatment step S50 in which monoclinic zirconia is phase-transformed to tetragonal zirconia.
These steps will be described in detail below.

<Molding step S20>
The prepared powder raw material is formed into a desired shape. As the molding method, for example, pressure molding such as cold isostatic pressing (CIP) or uniaxial pressure molding, potter's wheel method or casting method, tape molding, pressure casting, extrusion molding, injection molding, etc. It can be carried out. If the molded product obtained by molding is a near net shape close to the shape of the final product, it is preferable because it does not require significant cutting after firing. Further, it can be compression-molded larger than the desired shape, and then formed into a desired shape by cutting or the like. In the present invention, a molded product obtained by compression molding and a molded product obtained by processing the molded product are referred to as a molded body.

<Baking step S30>
The molded body is fired under predetermined conditions to obtain a zirconia sintered body. The firing step is preferably performed in two stages.
The first stage is a process of sintering the molded body in the atmosphere (referred to as an atmospheric firing process). By this atmospheric firing, the powder raw material is sufficiently baked and solidified to form a pre-sintered body having a relative density of about 95% to 99%. Although the appropriate range varies depending on the composition of the material, the sintering temperature is preferably at least the temperature at which the relative density is 95% or more and lower than the temperature at which the growth of crystal grains is promoted.
If the sintering temperature is too low and the relative density is less than 95%, the sintered body has open pores, which is not preferable because sufficient densification is not achieved in the hot isostatic pressing method (HIP) in the next step. . Further, regarding the relationship between crystal grains and crystal stability, when crystal grains become large, the phase transition energy from tetragonal crystal to monoclinic crystal at room temperature decreases, and the stability of tetragonal crystals decreases. Therefore, if the sintering temperature is too high and crystal grain growth is promoted, it can be said that the stability of tetragonal crystals at room temperature is lowered, which is not preferable. In the zirconia sintered body suitable for the present invention, the relative density of the sintered body can be made 99% even at a sintering temperature or lower at which crystal grains grow.

The second stage of the firing process is a process of densifying the pre-sintered body by a hot isostatic pressing method (HIP) (referred to as HIP process). In the HIP process, pores remaining in the pre-sintered body can be removed, and the pre-sintered body becomes a sintered body densified to a relative density of 99.5% or more. The processing temperature of the HIP process varies depending on the composition of the material, but is at least the temperature at which the relative density is 99.5% or higher and lower than the temperature at which the growth of crystal grains is promoted. Is preferred.
If the treatment temperature is too low and the relative density is less than 99.5%, it cannot be said that the treatment member is sufficiently dense as a living body member, and the strength and proof stress are lowered. Further, if the treatment temperature is too high and the growth of crystal grains is promoted, the stability of tetragonal crystals at room temperature is lowered, which is not preferable. In the zirconia sintered body suitable for the present invention, the relative density of the sintered body can be 99.5% even at a processing temperature or lower at which crystal grains grow.

  In addition to the two-step firing as described above, a one-step firing or a multi-step firing with three or more steps can be applied as the firing step. The relative density of the body is preferably 99% or more. For example, in the case of one-stage baking, when the baking is performed by hot pressing, a dense product can be obtained by adjusting the conditions.

<Surface processing step S40>
The obtained sintered body is subjected to mechanical surface processing in order to obtain a desired surface property. As the surface processing, general mechanical surface processing such as grinding, polishing and blasting can be used.
Examples of the grinding process include a process using a diamond or a SiC grindstone. For polishing, there is a method of using a paste or slurry containing diamond, or a suspension of silica or alumina, and finishing it to a mirror surface using a buffing machine or a copper or brass lapping machine. In blasting, the surface properties can be increased by spraying hard fine particles (media) such as alumina fine particles on the surface.

<Heat treatment step S50>
In the sintered body after the surface processing, monoclinic zirconia increases on the surface of the sintered body due to the stress applied during the processing. In particular, the increase rate of monoclinic zirconia is high in blasting and cutting. Therefore, the material is subjected to heat treatment in order to cause the increased monoclinic zirconia to undergo phase transition to tetragonal zirconia so that the monoclinic zirconia fraction on the surface falls within a predetermined range (for example, 1 mol% or less). This heat treatment can be performed in the atmosphere. The processing temperature varies depending on the composition of the material, but the amount of monoclinic zirconia on the surface is 1 mol% or less, and of course the temperature at which no crystal grain movement (thermal grooving) occurs inside the sintered body. It is desirable to process with a range. When thermal grooving occurs, the grain boundary appears remarkably and the stability of the tetragonal crystal is lowered, so that the phase transition to the monoclinic crystal tends to occur, that is, it tends to deteriorate, which is not preferable.

  The zirconia sintered body thus obtained has a predetermined surface property and excellent low temperature deterioration resistance. Moreover, since it can form only from a yttria and a zirconia, it can utilize suitably as a biomaterial which comprises an artificial joint etc. as a biosafety ceramic material.

<Embodiment 2>
The biomedical member of the zirconia sintered body of the present invention is suitable for the artificial bone head 27 constituting the total replacement artificial shoulder joint 70 as shown in FIG.
The artificial shoulder joint 70 shown in FIG. 3 includes a sliding member (glenoid cup 15) fixed to the glenoid of the scapula and a humeral stem 25 fixed to the proximal end of the humerus.
The humeral stem 25 includes a stem body 26 inserted into the bone marrow of the humerus, and an artificial bone head 27 made of a substantially hemispherical zirconia sintered body fixed to the proximal end of the stem body 26. ing.

The sliding surface 23a of the artificial bone head 27 is mirror-finished to reduce friction, and the inner surface 23b of the hole 222 into which the end portion 26a of the stem body 26 is fitted fits the end portion 21a of the stem body 21 accurately. The hole diameter is adjusted by cutting. And the outer peripheral surface 23c of the hole 222 does not need to be machined in particular, and may be in a sintered state.
The artificial bone head 27 made of the biomedical member of the present invention is safe to maintain the initial mechanical strength over a long period of time in the body because all the surfaces of the sliding surface 23a, the inner surface 23b and the outer peripheral surface 23c are not easily deteriorated at low temperatures. Can be used.

  The glenoid cup 15 includes a scapula stem 19 that is buried in the glenoid of the scapula and a sliding surface 16 that is recessed in a shallow dish shape. The artificial shoulder joint 70 functions as a shoulder joint capable of performing a back-and-forth movement and a turning movement by bringing the head 27 of the humeral stem 25 into contact with the sliding surface 16 of the glenoid cup 15 and sliding it.

<Embodiment 3>
The biomedical member of the zirconia sintered body of the present invention is suitable for the femoral component 52 constituting the artificial knee joint 72 as shown in FIG.
FIG. 4 shows a non-hinge type knee prosthesis 72, a tibial component 50 fixed to the proximal portion of the tibia, and an articulation member made of a zirconia sintered body fixed to the distal portion of the femur. (Femoral component 52) and these are fixed to each bone end in a separated state.

The femoral component 52 has, on its lower surface side, two curved projecting surfaces 53 and 53 (inner condyles and 53A) extending in an arc from the anterior direction (the kneecap direction, arrow A) to the posterior direction (the back of the knee, arrow P). With lateral condyles).
The sliding surfaces 23a and 23a of the femoral component 52 are mirror-finished to reduce friction, and the inner surface 23b of the recess 223 into which the distal end of the femur is fitted is a bone cut into a predetermined size. The dimensions are adjusted by cutting so that the ends fit correctly. And the outer peripheral surface 23c of the recessed part 223 does not need to be machined in particular, and may be in a sintered state.
The femoral component 52 comprising the biomedical member of the present invention is safe because all surfaces of the sliding surface 23a, the inner surface 23b, and the outer peripheral surface 23c are not easily deteriorated at low temperatures, and the initial mechanical strength is maintained for a long period in the body. Can be used for

The tibial component 50 of the knee prosthesis 72 includes a sliding member (tibial tray 48) that constitutes the joint surface, and a tibial stem 51 that fixes the tibial tray 48 to the tibia. The tibial tray 48 has a curved recess formed on the upper surface thereof extending from the front direction A to the rear direction P. The slide surface is in contact with the two projecting surfaces 53, 53 of the femoral component 52. 16 and 16.
The artificial knee joint 72 of the fifth embodiment can bend and stretch in the front-rear direction by sliding the projecting surfaces 53 and 53 of the femoral component 52 and the sliding surfaces 16 and 16 of the tibial tray 48. .

<Embodiment 4>
The biomedical member of the zirconia sintered body of the present invention is suitable for the humerus component 62 constituting the artificial elbow joint 74 as shown in FIG.
FIG. 5 shows a non-hinge type artificial elbow joint 74, which is composed of an ulnar component 58 fixed to the proximal portion of the ulna and a zirconia sintered body fixed to the distal portion of the humerus. (Humeral component 62), and these are fixed to each bone end in a separated state.
The ulna component 58 includes a sliding member (ulna tray 54) that constitutes the joint surface, and an ulna stem 60 that fixes the ulna tray 54 to the ulna.

The humeral component 62 of the artificial elbow joint 74 is a cylindrical body having a through hole 224 therein, and a part of the cylindrical body is opened in a C-shaped cross section by a notch 225 extending in the axial direction. Further, the outer surface of the humeral component 62 is slightly constricted in the vicinity of the center in the axial direction to form a pulley 63.
The sliding surface 23a of the humeral component 62 is mirror-finished to reduce friction, and the inner side 225b of the notch 225 for fitting the distal end of the humerus and the inner surface 23b of the through hole 224 of the cylindrical body. The size is adjusted by cutting so that the end of the bone cut into a predetermined size fits precisely. The end face 23c of the cylindrical body does not need to be machined in particular and may be in a sintered state.
The humeral component 62 made of the biomedical member of the present invention has a sliding surface 23a, an inner side 225b of the notch, an inner surface 23b of the through-hole, and an end surface 23c that are all resistant to low temperature deterioration, It can be used safely while maintaining its mechanical strength.

The ulna tray 54 has a shape obtained by cutting off a part of the annular member in the radial direction, and the inner surface is the sliding surface 16. The sliding surface 16 of the ulna tray 54 swells from the edges on both sides in the width direction toward the central direction, and forms a ridge portion 55 extending in the circumferential direction.
By fitting the pulley 63 of the humerus component 62 and the protruding portion 55 of the ulna tray 54, an artificial elbow joint that can bend and stretch forward and backward is formed.

  Since the artificial bone head 27, the femoral component 52, and the humerus component 62 of the second to fourth embodiments use the biomedical member of the present invention, any surfaces are not easily deteriorated at low temperatures, and are safe for a long period in the body. In addition, the initial mechanical strength can be maintained.

  In order to investigate the relationship between the monoclinic zirconia fraction present on the surface of the zirconia sintered body and the low temperature degradation, tests were conducted using samples prepared under various processing conditions.

<Preparation of sample>
A 3Y-TZP raw material powder obtained by adding a binder to primary particles having a BED specific surface area of 7 m ² / g and spray drying was molded at 294 MPa by the CIP method to obtain a cylindrical molded body having a diameter of 20 mm. This molded body was cut into a disk shape having a thickness of 5 mm to obtain a sintered molded body. The disk-shaped molded body was fired in the atmosphere at 1325 ° C. to 1485 ° C. for 2 hours, and then subjected to HIP treatment at 1350 ° C. for 1 hour. Three types of surface treatments (cutting, mirror finishing and blasting) were applied to the fired disc-shaped fired body. The sintered body that had been subjected to the surface treatment was subjected to a heat treatment in the temperature range of 600 ° C. to 1300 ° C. or was used as a measurement sample without heat treatment.
The three types of surface treatment methods are as follows. The cutting was performed using a # 400 grinding wheel to a depth of about 200 μm. The mirror finish was lapped with a diamond paste having a particle size of 1 μm. The blasting was performed by using alumina fine particle media (SA # 180) and spraying the sintered body at a pressure of 3 kgf / cm ² .

<Acceleration test>
An accelerated test was conducted to examine resistance to low temperature degradation. The sample was exposed to hydrothermal conditions at 121 ° C. for 150 hours, and the change in the monoclinic zirconia fraction on the sample surface was examined. The monoclinic zirconia fraction was measured by X-ray diffraction, and the Garvie and Nicolson formula (J. Am. Ceram. Soc., 55 [6], 303-305 (1972)) shown in Formula 1 was used. Used to calculate.
[Formula 1]
X (mol%) = (I _m (111) + I _m (11-1) / (I _m (111) + I _m (11-1) + I _{t + c} (111))
here,
X is the monoclinic zirconia fraction,
I _m (111) is the X-ray diffraction peak intensity of the monoclinic (111) plane,
I _m (11-1) is the X-ray diffraction peak intensity of the monoclinic (11-1) plane,
I _{t + c} (111) is the sum of the X-ray diffraction peak intensities of tetragonal (111) and cubic (111) planes.

<Experimental result>
The experimental conditions and the results are shown in Tables 1 and 2. The item “monoclinic fraction” in the table indicates the monoclinic zirconia fraction present on the surface before and after the acceleration experiment.
The item “Evaluation” evaluates the experimental results in four stages based on the following criteria. In this example, the index of monoclinic zirconia after the acceleration test was 10 mol% as an index of low temperature deterioration resistance.
The symbol ◎ means that the sample is within the scope of the present invention and is an excellent sample. (Monoclinic zirconia fraction: 0.5 mol% or less before the acceleration experiment and 10 mol% or less after the acceleration experiment).
The mark “◯” is within the scope of the present invention and is a good sample (monoclinic zirconia fraction: 1 mol% or less before the acceleration experiment and 10 mol% or less after the acceleration experiment).
The Δ mark is outside the scope of the present invention, but is a good sample with respect to low temperature deterioration resistance (monoclinic zirconia fraction: more than 1 mol% before the acceleration experiment and 10 mol% or less after the acceleration experiment).
A cross indicates a sample having low low temperature degradation resistance (monoclinic zirconia fraction: after the acceleration experiment exceeds 10 mol%).

(Relationship between heat treatment temperature and low temperature resistance)
Table 1 summarizes the results of experiments conducted by changing the surface treatment and the heat treatment temperature for samples fired at a constant firing temperature (1370 ° C.) in order to investigate the relationship between the heat treatment temperature and the low temperature degradation resistance.

The graph which plotted the monoclinic zirconia fraction before and behind the acceleration experiment of Table 1 with respect to the heat processing temperature is shown in FIG.6 and FIG.7.
From FIG. 6, the monoclinic zirconia fraction before the acceleration experiment is 1 mol% or less when the heat treatment temperature is about 810 ° C. or higher in the cut sample (sample No. 1 to 9). In the processed sample (sample Nos. 19 to 27), the heat treatment temperature was about 900 ° C. or higher. Therefore, in the sample used in the present embodiment, the monoclinic zirconia on the sample surface increased by the stress of cutting and blasting is reduced to 1 mol% or less by firing at 900 ° C. or higher. I was able to. In the mirror-finished samples (Sample Nos. 10 to 18), the monoclinic zirconia fraction was lower than 1 mol% regardless of the presence or absence of heat treatment. This suggests that the stress applied during processing is small and the monoclinic zirconia fraction did not increase.

FIG. 7 shows that the monoclinic zirconia fraction tends to decrease with increasing processing temperature in the cutting and blasting samples after the acceleration test. In the cut sample, the monoclinic zirconia fraction after the test can be suppressed to a reference value of 10 mol% or less by heat treatment at about 420 ° C. or higher, and in the blasted sample by heat treatment at about 550 ° C. or higher. did it.
In the sample of mirror polishing, although sample No. 10 that is not heat-treated (untreated) is excellent in low temperature deterioration resistance, sample No. 13 having a heat treatment temperature of 800 ° C. exceeds the allowable range of the present invention. Deteriorated at low temperature. Sample No. 14 having a heat treatment temperature of 900 ° C. exhibited excellent low temperature deterioration resistance. Further, when the treatment temperature exceeded 1210 ° C., the low temperature deterioration resistance tended to deteriorate rapidly. The reason why the mirror-polished sample exhibits such low temperature deterioration resistance behavior with respect to the heat treatment temperature is not clear.

  From the experimental results, in a biological member having a combination of different surface properties, from a smooth surface by mirror polishing to a rough surface by blasting, the treatment temperature at which all surfaces are 1 mol% or less (in this example, It was found that all surfaces exhibited excellent low-temperature deterioration resistance (monoclinic zirconia fraction after the acceleration test was 2 mol%) by performing heat treatment by selecting (900 ° C.). Further, when the processing temperature is too high, the surface of mirror polishing tends to rapidly deteriorate at a low temperature. Therefore, it was found that by treating in an appropriate treatment temperature range (900 to 1200 ° C. in this example), high surface-temperature deterioration resistance is exhibited in any surface properties.

  In addition, in samples that have been subjected to stressed surface treatment that increases monoclinic zirconia on the surface, such as cutting and blasting, low-temperature degradation significantly proceeds unless heat treatment is performed after processing, Conversely, it has been found that if heat treatment is carried out at an appropriate treatment temperature, the low temperature degradation resistance is greatly improved and may exhibit better low temperature degradation resistance than an unprocessed material.

(Relationship between firing temperature and low temperature resistance)
Table 2 summarizes the results of experiments conducted by changing the surface treatment and the heat treatment temperature for samples prepared at a constant heat treatment temperature in order to investigate the relationship between the firing temperature and the low-temperature degradation resistance in air firing.

As is clear from Table 2, the monoclinic zirconia fraction before the acceleration test shows a low value of 0.1 to 0.2 mol%. This is considered to be due to heat treatment at an appropriate treatment temperature.
FIG. 8 shows a graph in which the monoclinic zirconia fraction after the acceleration experiment in Table 2 is plotted against the firing temperature. In FIG. 8, two graphs for the mirror-finished sample and one graph for the cutting sample are depicted.

One of the graphs of the mirror-finished sample is a sample having a processing temperature of 800 ° C. at the time of heat treatment, and it is considered that the processing temperature is too low according to the results of Table 1, FIGS. This treatment temperature was found to impart good low temperature deterioration resistance to a sintered body sintered at a firing temperature of 1365 ° C. or lower.
The other graph is a sample having a heat treatment temperature of 1100 ° C. in mirror finishing, and is considered to be an appropriate treatment temperature. At this treatment temperature, the sintered body sintered at a firing temperature of 1383 ° C. or lower shows good low-temperature deterioration resistance, and the range of the appropriate firing temperature is broader than that at the above-mentioned treatment temperature of 800 ° C. ing.
From these facts, it can be seen that the low temperature deterioration resistance is influenced by both the sintering temperature and the heat treatment temperature.

  The cut sample was heat-treated at 1100 ° C., which is an appropriate processing temperature, and it can be seen that if the firing temperature is 1426 ° C. or less, a good low-temperature deterioration resistant zirconia sintered body can be obtained. As a result, it can be said that the range of the appropriate firing temperature is wider than that of the mirror-finished sample having the same processing temperature. That is, as inferred from the results of Table 1, FIG. 7 and FIG. 8, when appropriate heat treatment is performed after applying stress by cutting or the like, the low temperature deterioration resistance is greatly improved and the unprocessed material is improved. Supports the possibility of exhibiting good low temperature degradation resistance.

From this example, it is possible to improve the low temperature deterioration resistance by performing heat treatment at an appropriate temperature in any surface processing, and the appropriate temperature range varies depending on the type of surface processing. However, it was found that there were overlapping temperature ranges. Further, the temperature range suitable for the heat treatment approximately coincided with the temperature at which the monoclinic zirconia fraction after the heat treatment becomes 1 mol% or less.
Furthermore, since the low temperature deterioration resistance is influenced not only by the heat treatment temperature but also by the sintering temperature during sintering, the low temperature deterioration resistance can be further improved by adjusting the sintering temperature.

The effect of heat treatment after surface processing of the sintered body was investigated. Sample No. 1 of Example 1 Similar to 31, two samples that were fired, surface-treated, and heat-treated were prepared. Indentations were formed on the surfaces of these two samples by holding them for 49 N-15 seconds with a micro Vickers apparatus, and monoclinic zirconia was intentionally generated on the surfaces. One sample was heat-treated at 1100 ° C. for 2 hours after forming the indentation, and the produced monoclinic zirconia was phase-transformed to tetragonal zirconia. The other sample was not heat-treated as a comparative example.
FIG. 9 is an image obtained by observing the indentation 3 of two samples with a eutectic point laser microscope. FIG. 9A is a schematic diagram of a microscopic image of a sample heat-treated after formation of an indentation, and FIG. 9B is a microscopic image of a sample of a comparative example with the formation of the indentation. In any sample, the indentation 3 remains clearly, and it can be confirmed that cracks 11 are generated from the center 9 of the indentation 9 to the four apexes 7 of the indentation 3.

An acceleration experiment was performed using two samples, and the distribution of monoclinic zirconia present on the sample surface was measured by Raman spectroscopy to investigate the progress of deterioration. The acceleration experiment was performed by exposing the sample to a hydrothermal condition of 121 ° C. for 150 hours. When the exposure time was 0 hours, 50 hours, 100 hours, and 150 hours, the distribution state of monoclinic zirconia on the sample surface was measured.
Determination of the monoclinic zirconia fraction using Raman spectroscopy was determined from the 460 cm ⁻¹ peak among the zirconia Raman peaks. The 460 cm ⁻¹ peak shifts to the higher wavenumber side by about 10 cm ⁻¹ when the phase transition from tetragonal to monoclinic. When tetragonal crystals and monoclinic crystals are mixed on the material surface, the peak near 460 cm ⁻¹ is the result of overlapping each peak (referred to as a mixed peak). The mixed peak shifts to the high wave number side when the monoclinic zirconia fraction increases, and conversely shifts to the low wave number side when the monoclinic zirconia fraction decreases. Using this fact, the monoclinic zirconia fraction and its distribution were investigated from the position of the mixed peak.
In the Raman spectroscopic analysis, a micro-Raman spectroscope was used, and a laser beam having a diameter of about 1 μm was moved in 1 μm increments to measure the entire measurement region. As a result, the monoclinic zirconia fraction existing on the zirconia surface could be understood as a planar distribution.

FIGS. 10 and 11 are schematic images of the results of Raman spectra of two samples having indentations formed as a shift amount distribution of 460 cm ⁻¹ peak. In these figures, the shift amount is roughly classified into four stages. Almost all are tetragonal zirconia, and there is a peak at 460 cm ⁻¹ (that is, the shift amount from 460 cm ⁻¹ is 0 cm ⁻¹ ), and almost all is monoclinic zirconia, which is 470 cm ⁻¹ . a peak (i.e., the shift amount is 10 cm ^-1 from 460 cm ^-1) large shift, between 0 shift and the large shift, provided the middle shift and small shifts. Then, the areas classified into the four stages are designated as 0 shift area a, small shift area b, medium shift area c, and large shift area d in order of increasing shift amount. That is, it can be said that the monoclinic zirconia increases from the region a to the region d, and the deterioration progresses.
10 and 11 are measured in the measurement region 5 shown in FIG. 12, and this measurement region includes a part of the indentation 3.

  FIG. 10 shows a peak shift distribution when an accelerated test (0 hour, 50 hours, 100 hours, and 150 hours) is performed on a sample heat-treated after forming an indentation. Referring to FIG. 10, at the start of the acceleration experiment (FIG. 10A), it is only the region a regardless of the presence or absence of the indentation, indicating that no monoclinic zirconia is detected. Further, even when the acceleration test (FIGS. 10B to 10D) is performed, it can be seen that the region b is slightly distributed in the region a, and monoclinic zirconia is slightly generated. Further, the distribution range of the region b appears at a position unrelated to the indentation 3.

  FIG. 11 shows a peak shift distribution when an acceleration test is similarly performed on a sample that has not been heat-treated after forming an indentation. At the start of the acceleration experiment (FIG. 10A), the region d was distributed along the shape of the indentation 3, and the phase transition from tetragonal zirconia to monoclinic zirconia was caused by the stress received by the indentation of the diamond indenter. I understand that. However, single crystal zirconia is not generated in the portion where the crack 11 is generated. Then, by the acceleration test (FIGS. 10B to 10D), the region b, the region c, and the region d expand so as to spread from the indentation 3, and in particular, cracks extending from the center 9 to the top 7 of the indentation 3. It can be seen that the area c and the area d are remarkably enlarged along the line 11. From this, it became clear that the deterioration proceeds from the indentation 3 as a base point, and also proceeds from a defect portion such as the crack 11 as a base point.

From the results of FIGS. 10 and 11, the zirconia sintered body is subject to local stress on the surface and phase transition to monoclinic zirconia, and low temperature deterioration tends to proceed from that point. By re-transforming zirconia to tetragonal zirconia, there is an effect of preventing low temperature deterioration. In addition, a defect portion such as a crack becomes a base point of low-temperature deterioration even when monoclinic zirconia is not formed, but low-temperature deterioration based on the crack can also be suppressed by heat treatment.
As described above, when stress is applied to the surface of the zirconia sintered body, the low temperature deterioration resistance is remarkably reduced by transferring to monoclinic zirconia or by generating defects such as cracks. However, by subsequently heat-treating the zirconia sintered body, the low temperature deterioration resistance can be improved reliably and efficiently.

(A) is the schematic of the artificial hip joint concerning Embodiment 1, (B) is a schematic sectional drawing of an artificial bone head. FIG. 3 is a block diagram showing a manufacturing method according to the first exemplary embodiment. It is the schematic of the artificial shoulder joint concerning Embodiment 2. FIG. It is the schematic of the artificial knee joint concerning Embodiment 3. FIG. It is the schematic of the artificial elbow joint concerning Embodiment 4. FIG. 2 is a graph plotting the results of a deterioration experiment of Example 1. FIG. 2 is a graph plotting the results of a deterioration experiment of Example 1. FIG. 2 is a graph plotting the results of a deterioration experiment of Example 1. FIG. It is a eutectic point laser microscope image of two samples used for the deterioration experiment of Example 2 (A, B). In the deterioration experiment of Example 2, it is a schematic diagram which shows the Raman shift distribution of a sample (AD). In the deterioration experiment of Example 2, it is a schematic diagram which shows the Raman shift distribution of the sample of a comparative example (AD). FIG. 8 is a schematic diagram of an indentation showing the degradation measurement portion of FIGS. 6 and 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Zirconia sintered compact 3 Indentation 20 Femoral stem 22 Artificial head 23a Sliding surface 23b Inner surface 23c Outer peripheral surface 25 Humeral stem 27 Artificial head 52 Femoral component 62 Humeral component 70 Artificial shoulder joint 72 Artificial knee joint 74 Artificial elbow joint 100 Artificial Hip Joint S20 Molding Process S30 Firing Process S40 Surface Processing Process S50 Heat Treatment Process

Claims (8)

A biomaterial composed of a zirconia sintered body of a biomaterial, used in vivo,
The inside of the biomedical member is mainly composed of tetragonal zirconia,
The surface of the biomedical member is subjected to cutting and / or blast machining, and the processed zirconia sintered body is heat-treated at 900 ° C. to 1200 ° C. to convert monoclinic zirconia into tetragonal zirconia. A biological member, wherein a monoclinic zirconia fraction contained in the surface of the biological member is reduced to 1 mol% or less by a heat treatment step for phase transition. Biological member according to claim 1, wherein the surface of the living body member, characterized in further comprising a polishing Men及 beauty / or raw surface. The biomedical member according to claim 1 or 2 , wherein a monoclinic zirconia fraction contained in the surface is 0.5 mol% or less. The biological member according to any one of claims 1 to 3 , wherein a relative density (measured density / theoretical density) calculated with a theoretical density of 6.09 g / cm ³ is 99% or more. . The biological member according to any one of claims 1 to 4 , wherein the zirconia sintered body has an average particle diameter of 0.3 µm or less. A method for producing a biomedical member comprising a zirconia sintered body of a biomaterial and used in a living body, the method comprising:
A molding step of processing a powder raw material containing zirconia and yttria into a molded body;
A firing step of firing the molded body to obtain a sintered body;
A surface processing step of processing the surface of the sintered body by cutting and / or blasting ;
A heat treatment step of heat-treating the processed sintered body at 900 ° C. to 1200 ° C. to cause phase transition of monoclinic zirconia to tetragonal zirconia, and a method for producing a biomedical member. The said baking process is a manufacturing method of the member for biological bodies of Claim 6 including carrying out air baking at 1325 degreeC-1400 degreeC. An artificial joint comprising the biological member according to any one of claims 1 to 5 .

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