ABSTRACT
The alumina and zirconia surfaces were pretreated with chemical etching using alkaline mixtures of ammonia, hydrogen peroxide and sodium hydroxide, and followed with application of the powder layer of Ca-deficient hydroxyapatite (CDH). The influence of etching bath conditions time and concentration on surface development, chemical composition and morphology of medicinal ceramic powders were studied. The following analyses were performed: morphology (scanning electron microscopy), phase composition (X-ray diffraction analysis), changes in binding interactions and chemical composition (FT-Infrared and Energy dispersive spectroscopies). Both types of etchants did not expose the original phase composition changes or newly created phases for both types of ceramics. Subsequent decoration of the surface with hydroxyapatite revealed differences in the morphological appearance of the layer on both ceramic surfaces. The treated zirconia surface accepted CDH as a flowing layer on the surface, while the alumina was decorated with individual CDH aggregates. The goal of this study was to focus further on the ceramic fillers for polymer-ceramic composites used as a biomaterial in dental prosthetics.
ABSTRACT
PURPOSE: This paper is focused on the works concerning preparation of zirconium oxide ceramic blocks recommended for CAD/CAM systems used in prosthetic dentistry for manufacturing fixed prosthetic restorations. METHODS: Zirconium-yttrium-magnesium mixed ceramic oxides were prepared by sol-gel method via hydrolysis and condensation of zirconium alkoxide precursor (zirconium (IV) propoxide) with yttrium and magnesium nitrates diluted in 2-propanol. The aim of this work was to obtain 2% mol yttria-stabilized zirconia ceramic powders with magnesium as an additional tetragonal ZrO2 phase stabilizer in amount between 2÷6% mol (with 2% variable). Prepared gels were dried (24 h at 65 °C). Obtained powders were mixed with binder (carboxymethyl cellulose) and uniaxial pressed into specimens with a dimensions 38 × 22 × 6 mm. Afterwards green bodies were sintered in range of temperature between 1350-1550 °C. Powders and blocks were characterized by Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, Specific Area Measurement. RESULTS: Highly homogeneous powders with a low open porosity were obtained. Prepared blocks after sintering showed numerous cracks. Nevertheless blocks were fine grained and showed quite reproducible chemical composition. CONCLUSION: A sol gel wet chemical route of powder synthesis allow us to obtain high homogenous ceramic materials with inconsiderable amount of pores with low variation in dimensions. In spite of a reproducible synthesis methods of a ceramic powders, applied to prepare green bodies procedure and sintering manner do not allowed to obtain zirconia cermic blocks free from cracks.
Subject(s)
Magnesium Oxide/chemistry , Technology, Dental/methods , Yttrium/chemistry , Zirconium/chemistry , Adsorption , Gels , Microscopy, Electron, Scanning , Nitrogen/chemistry , Powders , Spectroscopy, Fourier Transform Infrared , TemperatureABSTRACT
The aim of the study was to fabricate a biodegradable bio-composite using only natural biological precursors for both composite components, i.e., for a support and for a filler. Bio-composites of biomorphous structure were prepared using monolithic blocks of yucca (Yucca flaccida) carbonised at 550°C as a stiff porous skeleton, and chitosan as a filler that coated the internal surface of the skeleton by a thin film. Highly porous supports and the resultant biomorphous composites were characterized by means of TGA, SEM, low-temperature physical adsorption of nitrogen, as well as electric and ultrasonic measurements. The resultant bio-composites were found to be very light materials with density of about 0.13g/cm3 and very porous (over 90%). They were found to be hierarchically ordered anisotropic structures with a stiff skeleton of dynamic elastic moduli up to 0.8GPa. The specific surface area was found to be 72m2/g giving a surface area of chitosan film equal to about 12m2 for a block sample of a volume of 2cm3. Covering porous support by thin film of chitosan resulted in the increase of electrical conductivity of the resultant composite.
