Properties of hydroxyapatite prepared by the hydrolysis of tricalcium phosphate

Abstract

Non-stoichiometric hydroxyapatite was prepared by the hydrolysis of a-tricalcium phosphate. The apatite was obtained as a powder and hardened with and without stirring during the hydrolysis. The apatite had a general formula, characteristic dehydration and pyrolysis behaviour similar to that of precipitated non-stoichiometric hydroxyapatite. In addition, it exhibited some new phenomena (i.e. thermal reaction between lattice HzO and Po43-above 473 K, formation of ESR centres above 473 K and disappearance at 873-973 K, and a slight weight loss at 873-973 K). Apatite particles were composed of aggregates of cylindrical rods or thin blades grown along the c-axis or (100) faces of apatite structure. Hardened apatite materials with various porosities above 5 5 % and bulk densities below 1.4 g c w 3 were obtained by using different water-soluble additives. The strength of the hardened materials was 20-500 kg cm-2 in compression and 10-1 20 kg cm-2 in bending. The strengths were improved at least two to three times by impregnating the hardened materials with methyl methacrylate polymer.

Bone-like Layer Growth and Adhesion of Osteoblast-like Cells on Calcium-deficient Hydroxyapatite Synthesized at Different pH

“…Ca/P ratio of stoichiometric HAp is known to be 1.67, 1) while the Ca/P ratio of DAp is lower than 1.67 and increases with increasing pH during the synthesis. From the DAp formula (Ca 10Àz (HPO 4 …”

“…4) Both Ca/P ratio and the morphology of DAp depended on pH during the synthesis. So, one can say that the potential of DAp as a bone substitute is higher than that of stoichiometric HAp.…”

Preparation of Porous Hydroxyapatite/α-Tricalcium Phosphate Composites by a Colloidal Process

“…2(d)), since the temperature of the slurries exceeded 353 K due to ultrasonic dispersion. 11) But the volume fraction of DAp seems to be too small to influence the solubility of the specimen. Yuan et al reported that porous α-TCP implanted to dogs exhibit fast dissolution, but is not hydrated to DAp.…”

Texture Control in Hydroxyapatite by Hot Forging

“…This means that partial reverse transformation of DAp occurred at 1273 K and above. 4) Ca 10Àz (HPO 4 …”

“…3) Similarly, calcium-deficient hydroxyapatite (DAp: Ca 10Àz -(HPO 4 ) z (PO 4 ) 6Àz (OH) 2Àz ÁnH 2 O (Ca/P = 1.50-1.67) which is synthesized by hydrolysis of -tricalcium phosphate (-TCP), 4) has been expected to be bone substitutes because of its superior biocompatibility and bone inductivity. 2) Recently, a crystallographic texture of biological apatite in bone has attracted much attention since it is believed to be closely related to bone function.…”