RU2158189C1 - Method of applying hydroxyapatite coatings - Google Patents

Abstract

FIELD: prosthetics. SUBSTANCE: hydroxyapatite powder is mixed with phosphate binding agent at ratio (1-1.5):(1.5-2). Mixture is dried and baked at temperature 250 to 600 C to give material useful as coating on metallic endoprostheses. EFFECT: reduce percentage of invalid produce due to eliminated crack and detachment of coating. 1 tbl, 6 ex

Description

 The invention relates to methods for applying hydroxyapatite coatings (HA) and can be used in medicine as a coating on metal endoprostheses.

 A known method of applying HA coatings by plasma spraying [1], the technology of this method is that HA powder is passed through a plasmatron, followed by adhesion to a metal substrate.

The closest method of applying HA coatings in essence and the achieved results is a method comprising mixing HA powder with a binder, drying, firing at 900 -1000 ^o C [2].

 The main disadvantage of this method is the high sintering temperature, which may be the main reason for the marriage of products: cake and rebound coating.

 The aim of the invention is to reduce the marriage of products due to the exclusion of the cake and rebound coating.

This goal is achieved by mixing HA powder with a binder, with phosphate bonds being used as a binder, and HA powder and a phosphate bond being taken in a ratio of 1-1.5: 1.5-2.0; firing is carried out at a temperature of 250 - 600 ^o C.

The difference of the proposed method from the known one is that phosphate bonds are used as a binder, and hydroxyapatite powder and phosphate bond are taken in a ratio of 1-1.5: 1.5-2.0; firing is carried out at a temperature of 250 - 600 ^o C.

 Changing the HA / phosphate bond ratios is not possible, since with an increase in the amount of the liquid bond, a suspension with a minimum viscosity is formed, as a result of which the suspension is not retained on the substrate, an increase in the amount of the solid component leads to the formation of thick solutions.

Heat treatment at temperatures below 250 ^o C is impossible, since the resulting coating is prone to rehydration, and firing at temperatures above 600 ^o C leads to a decrease in the strength of the resulting coating.

 Example 1

A calcium phosphate binder is prepared. To prepare it, they take a 65% solution of H ₃ PO ₃ 99.1%, to which 0.99% CaO powder is added, completing the reaction by boiling in a water bath for 20 minutes.

The prepared binder is mixed with HA powder in a ratio of 1.2: 1.8 (see table), the resulting suspension is applied to the substrate with a brush, burned at 450 ^o .

Example 2. Prepare a calcium phosphate binder. To prepare it, they take a 65% solution of H ₃ PO ₄ 98.04%, to which 1.96% CaO powder is added, completing the reaction by boiling in a water bath for 20 minutes.

The prepared binder is mixed with HA powder in a ratio of 1.5: 1.5 (see table.), The resulting suspension is applied to the substrate with a brush, burned at 450 ^o C.

Example 3. Prepare a calcium phosphate binder. To prepare it, a 65% solution of H ₃ PO ₄ 97.09% is taken, to which 2.91% CaO powder is added, completing the reaction by boiling in a water bath for 20 minutes.

The prepared binder is mixed with HA powder in a ratio of 1: 2 (see table.), The resulting suspension is applied to the substrate with a brush, burned at 450 ^o C.

Example 4. Prepare a calcium phosphate binder. To prepare it, they take a 65% solution of H ₃ PO ₄ 96.15%, to which 3.85% CaO powder is added, completing the reaction by boiling in a water bath for 20 minutes.

The prepared mixture is mixed with HA powder in a ratio of 1.2: 1.8 (see table.), The resulting suspension is applied to the substrate with a brush, burned at 450 ^o C.

Example 5. Prepare a magnesium phosphate binder. To prepare it, they take a 65% solution of H ₃ PO ₄ 98.30%, to which 1.70% MgO powder is added, completing the reaction by boiling in a water bath for 20 minutes.

The prepared binder is mixed with HA powder in a ratio of 1.2: 1.8 (see table.), The resulting suspension is applied to the substrate with a brush, burned at 405 ^o C.

Example 6. A solution of 65% H ₃ PO _{4 is} mixed with HA powder in a ratio of 1: 2 (see table), after which this mixture is applied to a substrate and fired at 600 ^o C.

 The test results of the coatings are presented in table.

This method compared with the prototype has several advantages:
1. The ability to control the viscosity of the suspension allows you to select the viscosity favorable for the selected method of coating (watering, spraying, dipping).

 2. The ability to obtain coatings of various thicknesses.

 3. The ability to control the coefficient of thermal expansion over a wide range.

 4. Lower firing temperature.

 Metal endoprostheses coated with the proposed method, when used in medicine, provide the best clinical results, since the method allows you to adjust the ratio of amorphous and crystalline phases of HA and, as a result, regulate the bioactivity of the coating depending on the type and purpose of the implant.

Literature
1. Yanke SJ, Pletka B. J., Luckey HA, Jonson WA Process for fabrication HA coatings for biomedical aplications. Sprey Conference. May 2 - 25, 1990; Long beac, CA: 433-438.

 2. Ducheyene P., Radin S., Healy K., Cuckler J. M. The effect of plasma-spreying on the stracture and properties of calcium phospate ceramics. 34th Annual miting, Orthopedic Reasearch Sociaty. Februry 1-4, 1988, Atlanta, GA: 50.

Claims (1)

The method of applying hydroxyapatite coatings, including mixing the hydroxyapatite powder with a binder, drying, firing, characterized in that phosphate binder is used as the binder, and the hydroxyapatite powder and phosphate binder are taken in a ratio of 1 - 1.5: 1.5 - 2, firing is carried out at 250 - 600 ^o C.

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