Environmental Stability of Calcium Phosphate Granules & Coatings - Test Method

Overview

This method, based on ASTM F1926, covers the measurement of the stability, and dissolution rate, of calcium phosphate and hydroxyapatite (HA) in buffer and un-buffered preparations by Calcium ion selective electrode analysis. The result is a measure of the rate of dissolution of calcium and phosphorous from the solid material into the buffer solutions.

Applications and Benefits

The dissolution rate provides an indication, of the rate at which the calcium phosphate and hydroxyapatite may dissolve if coated onto a medical device implanted into the human body. It provides an indication to medical device manufacturers, who coat their medical devices with hydroxyapatite to aid strengthening after implantation, of how quickly the coating will breakdown. The aim is to produce a hydroxyapatite material that is resorbed at a rate not faster than the rate of the lay down of new bone material. The dissolution is measured in a buffer system with a background of sodium chloride and calcium much like the concentrations in blood. Different buffers can be used for different applications.

The method can also provide confirmation that the hydroxyapatite is not changed after coating of the medical device.

Form of Results

An initial rate of dissolution and a final, equilibrated, rate of dissolution is reported in mg of calcium dissolved per ml of buffer per mg HA per hour.

Similar Tests for other Applications

ASTM F1926/F 1926M - 08 Standard test method for Evaluation of the environmental stability of calcium phosphate granules, fabricated forms and coatings.