Hydroxyapatite from limestone?

2004

YEAR BOOK

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Limerick Institute of Technology

James Ring & Fergal Barry

The capacity of the human body to regenerate bony components that are lost or damaged is limited. For this reason, materials need to be developed that can adequately replace bone tissue, especially mineralised tissue such as bone and teeth. Only a few materials have been shown to be practical as a bone substitute. Full integration of the living bone with the non-living implant is the ultimate goal. With the advancement in ceramic technology, the application of calcium phosphate materials as bone substitutes has recently received considerable attention.

Calcium phosphates make up approximately 90% of our teeth and bones. These, along with other constituents that are not yet fully identified and quantified, give our teeth and bones their characteristic strength and porosity. Attempts are constantly being made to artificially stimulate these characteristics. Hydroxyapatite Ca10(PO4)6(OH)2 is particularly attractive for use for human tissue implantation, as it has similar chemical composition and crystal structure to apatite in the human skeletal system, and therefore suitable for bone substitution and reconstruction. HA has a calcium phosphate ratio of 1.67 and has an excellent affinity for the living body due to its favourable osteoconductive and bioactive properties. It is estimated that synthetic surgery only accounts for 8% of all bone surgeries currently undertaken.

The purpose of this research is to determine a method of producing pure Hydroxyapatite (HA), from waste Blue Irish Limestone. Hydroxyapatite is easily made from calcium carbonate and, as limestone is about 90% calcium carbonate, it is thought that, with proper chemical modification, the impurities of the limestone can be removed after conversion to Hydroxyapatite to leave a pure substance. It is proposed to employ one-pot thermo mechanical synthesis to HA preparation from the waste material under conditions that may also work as a purification step.

Investigation of reaction conditions for yield, effect of catalysts, removal of impurities, purification of product, chemical and elemental analysis, will be carried out. Materials analysis will require surface, particle size, crystallinity, phase and morphological analysis of by-product by X-ray diffraction, scanning electron microscopy, BET, Auger spectroscopy, Fourier Transform Infra Red & TGA. Composting of the HA with materials such as titanium dioxide, titanium alloys or polymer sols with subsequent examination of biocompatibility of these bioceramics will also be investigated.

Contact: Mr James Ring or Dr Fergal Barry,
Centre for Research in Electrochemically Novel Technologies, Limerick Institute of Technology;
Tel: +35361208286; E-mail: [email protected]