JPH0534986B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a manufacturing method for forming a hydroxyapatite coating on a core material as an implant.

In recent years, implants used for artificial joints, artificial bones, artificial tooth roots, etc. have been sought to have greater biocompatibility and higher mechanical strength, and as a result, calcium phosphate compounds such as hydroxyapatite, which have excellent biocompatibility, have been developed. By spraying this on a core material made of a metal material, an implant with excellent biocompatibility on the outside and mechanical strength has been provided.

However, conventionally, when hydroxyapatite powder is thermally sprayed, the hydroxyapatite decomposes due to thermal metamorphosis, resulting in a decrease in affinity for living organisms and metals that may be leached. The bonding material provided to increase the bonding force with hydroxyapatite has no affinity for living organisms, and as a result, it is difficult to manufacture and use, and it is still difficult to put it to practical use. I can't say it's expensive.

In view of the above, the present inventors thermally spray coated a powder mainly composed of calcium phosphate, which is the starting material for hydroxyapatite, and further performed a process to convert it into hydroxyapatite, thereby shortening the manufacturing process. The present invention was achieved by discovering that a hydroxyapatite sprayed layer with stronger and more reliable bonding force with metal can be formed as the outermost layer.

Hereinafter, the composition of the starting materials of the present invention and Examples will be described in detail.

The material composition in the present invention is based on the starting material.
It is a powder containing calcium phosphates with a Ca/P molar ratio set to 1.0 to 2.0. Calcium is CaO, Ca(OH) ₂ , CaCO ₃ , and phosphate is CaHPO ₄ 2H ₂ O, ( _NH4 ) _{3PO4 ,}
Examples include Ca ₂ P ₂ O ₇ and Ca ₃ (PO ₄ ) ₂ .

Further, the base material for thermal spray coating may be appropriately selected depending on the application, such as metal, ceramics, glass, or plastic.

Further, the treatment for converting it into hydroxyapatite involves immersing the coated base material in water or hot water for several hours. Alternatively, it is immersed in a steam atmosphere with high temperature and pressure. Alternatively, immersion in a phosphoric acid aqueous solution or a CaCl ₂ aqueous solution is exemplified. In particular, when immersing in a steam atmosphere, about 2 hours at 120° C. and 2.2 atm is preferable.

Examples The method for forming a hydroxyapatite thermal spray layer from the material composition is as follows: (1) A single or mixed material powder with a Ca/P molar ratio of 1.0 to 2.0 is thermally sprayed onto the surface of a substrate using high-temperature plasma. do.

That is, a single or mixed material with a Ca/P molar ratio of 1.0 to 2.0 undergoes a reaction in high-temperature plasma, and the mixed material powder is injected with the high-temperature plasma by a plasma spray gun, and is sprayed onto the metal surface. Collision join. The heat and collision force of this high-temperature plasma not only promote the production reaction of tricalcium phosphate or hydroxyapatite as much as possible, but also form a temporary sintered body layer using this energy. The plasma atmosphere at this time uses commonly used ones such as argon, helium, hydrogen, and nitrogen, and the gas ratio of the atmosphere is, for example, a mixture of H ₂ /Ar at a ratio of 0 to 25/60 to 150. When using a plasma spray gun (9MB manufactured by Metco), the current is 300 to 500 (A),
It supplies electricity with a voltage of 70 to 80 (V).

After being spray coated, it is converted into hydroxyapatite through a specific treatment.

That is, as shown above, after the core material is coated with the mixed powder, it is immersed in water for several hours or left in high-pressure steam (approximately 120° C., 2.2 atmospheres) for about 2 hours. Alternatively, the surface can be reliably converted to hydroxyapatite by immersion in an aqueous phosphoric acid solution or an aqueous CaCl ₂ solution.

(2) Mix powder with a Ca/P molar ratio of around 1.67 and hydroxyapatite powder, and spray coat the mixed powder under the above conditions. At this time, glassy apatite is generated between the core material and the coating layer, increasing their bonding strength, and in addition, by performing the treatment described above, the outermost layer can be converted to hydroxyapatite. It is.

(3) Hydroxyapatite powder synthesized in advance by a wet method or the like is thermally sprayed onto a base material under the same conditions as above. Next, this spray-coated base material is immersed in a water or high-temperature steam atmosphere under predetermined temperature and pressure conditions to ensure that the surface layer is converted into hydroxyapatite.

As described above, the thermal spray coating method of the present invention can be easily carried out using a commonly used plasma spray gun, etc., and can not only produce implants with high adhesive strength, but also thermally spray hydroxyapatite. Since it is generated during the manufacturing process, the manufacturing process can be significantly shortened, and the effects are tremendous.

The present invention will be explained in detail below using experimental examples.

Experimental Example 1 A mixed powder of Ca ₃ (PO ₄ ) ₂ and CaCO ₃ was thermally sprayed onto a flat plate (SUS316) that had been sandblasted with alumina grit using the plasma gun described above. This flat plate, on which a coating layer with a thickness of about 50 μm was formed, was immersed in a steam atmosphere of about 120° C. and 2.2 atm for about 2 hours to convert it into hydroxyapatite. After 2 hours, the coating layer was subjected to powder X-ray diffraction, and the formation of hydroxyapatite was certainly observed.

Experimental Example 2 Synthesize the same mixed powder as in Experimental Example 1 using a wet method,
Spray-dried hydroxyapatite powder having a particle size of 20 to 40 μm was further added and mixed to produce a mixed powder. Next, this mixed powder was applied to the surface of the artificial bone (SUS316L) at a hydrogen gas to argon gas ratio of 25:150 and a current and voltage value of 500 (A) and 80 (V).
Thermal spray coating was performed using the above plasma gun set so that After immersing the artificial bone with this coating layer in a water vapor atmosphere of about 120°C and 2.2 atm for about 12 hours, we performed X-ray diffraction and found that the surface layer was hydroxyapatite. Sandblasting is applied to the surface of the layer, approx.
After removing about microns, the surface was subjected to powder X-ray diffraction. As a result, it was confirmed that the removed surface was glassy hydroxyapatite.

Experimental example 3 CaHPO ₄ 2H ₂ O powder or CaCO ₃ to this
The mixed powder was thermally sprayed onto a flat plate (Ti) that had been sandblasted with alumina grit using the plasma gun described above. A coating layer having a thickness of about 50 μm was formed. When this coating layer was identified by powder X-ray diffraction, the formation of tricalcium phosphate was observed. Add this to 1 to 5 mol 1
When it was immersed in a Cacl ₂ aqueous solution and allowed to stand for one day in a constant temperature bath at 80°C, it was confirmed that hydroxyapatite was generated on the surface of the coating layer.

Experimental example 4 A flat plate (SUS316L) made of hydroxyapatite powder (particle size 20 to 100 μm) synthesized by a wet method and sandblasted with alumina powder.
Plasma spraying was applied to the top using a plasma gun (9MB manufactured by Metco). The gas used at this time was a mixture of hydrogen and argon at a ratio of 5:70, and the current and voltage values of the power supply to the plasma gun were
It was 400(A) and 80(V). After thermal spraying, surface analysis was performed using powder X-ray diffraction, and it was found that most of the hydroxyapatite had been decomposed and transformed into tricalcium phosphate, tetracalcium phosphate, calcium oxide, calcium carbonate, etc. After that, 0 to 10 ^-3 mol/
The sample was immersed in an aqueous phosphoric acid solution and left at room temperature and pressure for about one day. When we performed powder X-ray diffraction on this again,
It was observed that the surface of the sprayed layer had been converted to hydroxyapatite.

Animal experiment An implant manufactured in the same manner as in Experimental Example 3 was placed in the lower limb bone of an adult dog and observed over time. As a result, no abnormal findings such as inflammatory reactions or peeling of the thermal spray coating layer were observed even 3 months after implantation. It wasn't something.

Claims (1)

[Claims] 1. A method for producing a hydroxyapatite coating material, which comprises spraying a powder mainly composed of calcium and phosphate onto the surface of a base material, and then subjecting the surface of the coating layer to a hydroxyapatite conversion treatment in an aqueous atmosphere.