New coating systems for biomedical implants

摘要

The pearl, a biomaterial of animal origin, is a bone consisting of a mineral phase deposited on an organic skeleton. The mineral phase of the pearl consists of crystallised calcium carbonate in form of aragonite while the human bone is made out of the hydroxyapatite form of calcium carbonate. The use of this material in orthopaedic surgery allows the complement of defect bone and also an intimate connection between a metallic implant and bone receiver. The extracted pearl of giant pinctada maxima oysters used as a coating for implants leads to some difficulties. Characteristics of coatings obtained from this product show obviously a decomposition of aragonite into two components: Calcium carbonate (basis) and calcium oxide. This transformation can be explained by process temperatures. Due to the plasma flame the particles reach temperatures which are above the transformation temperatures. Two peaks of the thermogravimetric analysis attract attention: The first corresponds to the change of aragonite phase of CaCO_3 into calcite, the second corresponds to the decomposition of the calcite in oxide of calcium.