PubMed · 3858253
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E Dorigo. [Ceramic apatites: comparative microstructure with SEM].. https://pubmed.ncbi.nlm.nih.gov/3858253/
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A novel method to rapidly deposit bone apatite-like coatings on titanium implants in simulated body fluid (SBF) is proposed in this article. The processing was composed of two steps; for example, micro-arc oxidation (MAO) of titanium to form titania films, and UV-light illumination of the titania-coated titanium in SBF. The morphology, crystalline structure, and bond strength of the MAO films were investigated as a function of the applied voltage (in the range of 250-400 V) by using scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectrometry, Fourier transform infrared spectroscopy, adhesion-tensile test, and scratch test. Results showed that the MAO films were porous and nanocrystalline with pore sizes varying from 1 to 3 microm and grain sizes varying from 10-20 to 70-80 nm; the predominant phase in titania films changed from anatase to rutile, and the bond strength of the films decreased from 43.4 to 32.9 MPa as the applied voltage increased from 250 to 400 V. After UV-light illumination of the films in SBF for 2 h, bone apatite-like coating was deposited on the MAO film formed at 250 V. The bond strength of the apatite/titania bilayer was about 44.2 MPa. However, no apatite was observed on the MAO film formed at 400 V after UV-light illumination.
The mineral constituent of bone tissue is a carbonate-substituted apatite (CHA). The thermal stability of the CHA has been revealed to depend on the substitution type and degree, although relatively little is known about this behavior. The aim of this study was to investigate the carbonate loss from synthetic CHAs in equilibrium conditions in a wide temperature range. An approach based on FTIR spectroscopy of condensed gas phase was applied to evaluate the CO and CO2 release with increasing temperature. Four different CHAs were studied, which were prepared by either precipitation from solution or the solid-state interaction. The samples differ from each other by the substitution degree. In one of the samples calcium was partially substituted by magnesium. Decomposition was shown to start at surprisingly low temperature, about 400 degrees C, and the CO content increases monotonously with the increase of temperature. The CO2 content goes through a maximum due to its decomposition into carbon monoxide and oxygen, the temperature of this maximum being strongly dependent on the chemical synthesis route. Therefore, control of the sintering atmosphere with respect to the CO2/CO ratio is needed when preparing the carbonated apatite bioceramics.
Methods of preparing different types of titanium oxide (TiO(2)) and their effects on apatite deposition and adhesion on titanium surfaces were investigated. Forty-eight commercially pure titanium (Ti) discs were divided into four groups (12 per group) and each group was subjected to the following treatments: Group 1, heat treatment at 750 degrees C; Group 2, oxidation in H(2)O(2) solution followed by heat treatment; Group 3, dipping in rutile/gelatin slurry; and Group 4, dipping in anatase/gelatin slurry. Surface-treated Ti discs were immersed in a supersaturated calcium phosphate solution to allow apatite deposition. Results showed that the percentage of area covered by deposited apatite was highest in Group 4 compared to the other groups. Apatite deposited on Ti discs pretreated in H(2)O(2) solution (Group 2) demonstrated the highest adhesion to the titanium substrate. Results from this study indicated that surface treatment method affects the type of TiO(2) layer formed (anatase or rutile) and affects apatite deposition and adhesion on the Ti surface.