ISSN 0204-3548. Mineral. Journ. (Ukraine). — 2001. — 23, N 5/6 65 UDK 549.903:538.955:539.219.3 L. F. Sukhodub, C. Moseke, A. B. Brik, O. Boelling, B. Sulkio-Cleff Properties of Hydroxylapatite Coatings for Biological Implants Deduced from Complementary Instrumental Methods Characteristics of coatings produced on the basis of hydroxylapatite, tricalcium phosphate and other minerals for biological implants manufactured using titanium and its alloys have been studied. Mineral composition of the coatings includes synthetic analogues of minerals of boiological origin that substantially influence the application effectiveness of the implants. Influence of peculiarities of different manufacturing techniques, magnetron sputtering technique in particular, on the characteristics of the coatings, has been analyzed. It has been shown that the behavior of biological implants in living bone tissue is determined by physical and chemical characteristics of the coatings and by their interaction with bone tissue and implant material. Use of complementary physical methods such as X-ray diffraction, desorption mass spectrometry, infrared, electron paramagnetic resonance spectroscopy etc., for studies of the calcium phosphate coatings is a necessary step for creation of physical models that describe the interaction mechanisms and mass transfer processes in the system "bone tissue — coating — metal implant". The possibilities of the aforementioned complementary methods for determining of structure, chemical composition, impurity crystal phases and mechanical characteristics of the coatings have been described. The properties of synthetic hydroxylapatite produced in the presen- ce of titanium ions have been studied. It has been shown that substitution of calcium ions by titanium ions takes place in the samples of hydroxylapatite. 1. Introduction It is well known that the mineral component of bone tissue and other biominerals is represented mainly by hydroxylapatite (HA). This is the cause why this material is an ideal candidate for coating onto metal implants, which are used for the treatment of bone diseases. Coatings on the base of hydroxylapatite have very high biocompatibility, no toxicity and serve for assimilation of the implants by living bone tissue. The characteristics of the coatings depend essentially from peculiarities of surface deposition technique. So it is very important to study the correlation between surface deposition techniques and characteristics of the coatings. Osteointegration of surgical implants starts with adhesion of cells. Different approaches are used for preparing bioinert or bioactive surfaces, although the processes in the bone- implant interface are still not fully understood. Also, the problem of interaction between organic and inorganic parts of bone although having been investigated thoroughly for a long time before, is still presenting a challenge in the field of complete and unambiguous understanding of the underlying processes. Especially this is true, when these processes are complicated by the influence of external factors, such as metallic artificial limbs and implants, and metal ions released there from. Among the common used implant materials for orthopedic and dental applications, those based on titanium are most interesting. Two kinds are mainly used — commercially pure titanium and titanium alloys. Both are characterized as corrosion resistant material with good biocompatibility. Titanium alloys have the best mechanical properties. It is known that Ti is quickly oxidized into titanium oxide. Although this oxide layer is thermodynamically stable, metal-containing species are still released through passive dissolution mechanisms, and induce a local accumulation of titanium-containing species. In the absence of wear on the implant, the increase of the concentration of titanium in tissue can be observed when the implantation time increases. The behavior of coated implants in bone tissue substantially depends on physical and chemical characteristics of coatings and their interactions as with bone components and with implant material as well. It is known, that apatite-coated implants are very rapidly incorporated in bone. However, at the same time, clinical results with, for example, HA-coatings are not very optimistic because of failure at the HA-Ti interfaces. Ideally, coatings should be biocompatible, displaying no toxicity effect, providing a highly adhesive interface between bone tissue and the bone implant and encouraging bone tissue ingrowth and preventing the release of metal ions from implant material. © L. F. Sukhodub, C. Moseke, A. B. Brik, O. Boelling, B. Sulkio-Cleff, 2001