CHARACTERIZATION OF HYDROXYAPATITE COATINGS FOR BIOMEDICAL APPLICATIONS

Abstract

Calcium phosphates are used extensively as biomaterials for promoting bone growth and improving the fixation of bone to dental and orthopaedic devices. Calcium phosphates were introduced in the early 1980's, and are used as implants today, however more work is being conducted to produce a higher quality coating. Due to the low mechanical strength, it has been used as a filler material or a coating. Initially, hydroxyapatite was the desired material for application in coatings due to its compositional similarity to the inorganic phase of bone, but thermal decomposition during processing has produced various unexpected chemical phases. It has become necessary to expand the collection of characterization techniques to fully describe the nature of the coating and ensure a good quality coating.A transfer of analysis techniques from thermal spray science, minerology and chemistry have been necessary to achieve a more detailed description of the coating. Characterisation is necessary for powder synthesis and preparation, coating production, and analysis of histological sections and retrieved prostheses. The latter mentioned stages require more analysis techniques for a full characterization. Techniques incorporate structural, compositional, chemical phase, microstructural, strength and dissolution assessment methods. This paper will outline the characteristics that are addressed at each characterisation stage and list the different techniques that are presently used in industry. The additional analysis requirements that still need to be developed to completely describe the coating will be described.