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Experimental investigation of particle size distribution and morphology of alumina-yttria-ceria-zirconia powders obtained via sol–gel route

Nakonieczny D. S., Antonowicz M., Paszenda Z. K., Radko T., Drewniak S., Bogacz W., Krawczyk C.

Biocybernetics and Biomedical Engineering

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2018

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Vol. 38, no. 3

535--543

EN

Background: Oxide-doped zirconia is currently commonly used ceramics in dental prosthetics. However, its use raises a lot of controversy. This is related to the stability of the zirconia metastable phases in the human mouth environment and it sensitivity for the so-called low-temperature degradation. A key way to avoid this type of negative phenomena is doping ZrO2 with selected metal oxide sand choosing appropriate methods for the synthesis of ceramic powders. Objective: The aim of this paper is to present investigations of modification and to analyse the influence of chemical composition and volume of parent-solvent for the morphology and thermal properties of ceramic powders prepared in a ZrO2-CeO2-Y2O3-Al2O3 system. Methods: The powders were obtained by using the sol–gel method in an inert gas atmosphere and ambient temperature using zirconium n-propoxide for this purpose. Morphology was examined by using scanning electron microscopy (SEM) and particle size distribution (PSD); thermal properties was evaluated using thermogravimetric analysis (TGA/DTA/DTG), and chemical composition was confirmed by using electron probe microanalysis (EPMA). Results: Depending from the volume of the CeO2 precursor solution of and regardless of the volume of the second oxide precursor, was observed difference in morphology of the obtained powders. Overall trend is related to reduce the size of agglomerates with an increase in the volume of the precursor of CeO2. Conclusions: The influence of various chemical compositions for morphology and thermal properties is negligible. In contrast, a clear correlation is observed between the volume of parent alcohol for both morphology and thermal properties. Use of sol–gel method to further research in view of these results appears to be appropriate.

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Wpływ technologii wytwarzania na właściwości materiałowe stopu kobaltu wykorzystywanego w protetyce dentystycznej

Litwinko M., Grądzka-Dahlke M.

Aktualne Problemy Biomechaniki

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2014

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z. 8

99--102

PL

Jednym z etapów w procesie powstawania protetycznego uzupełnienia dentystycznego jest realizacja zaprojektowanego kształtu protezy w tworzywie metalowym. Jest krokiem istotnym a zarazem narażonym na wiele niepowodzeń. W artykule przedstawiono porównanie dwóch metod wykonawstwa techniki dentystycznej: tradycyjnego odlewania oraz nowoczesnej SLM. Badaniom poddano protetyczny stop kobaltu w postaci prostopadłościennych próbek.

EN

One of the stages in the process of restoration of dental prostheses is the shape which was designed to achieve a complement in the metal. It is an important step and exposed to many setbacks. The article gives a comparison of two methods of dental technology: traditional casting and modern SLM. The test was in the form of a cobalt alloy prosthetic square bales samples.

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Characterization of magnesia-doped yttria-stabilized zirconia powders for dental technology applications

Nakonieczny D., Walke W., Majewska J., Paszenda Z.

Acta of Bioengineering and Biomechanics

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2014

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Vol. 16, no. 4

99--106

EN

Purpose: This paper is focused on the works concerning on preparing 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 it 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 in 65°C). Obtained powders were mixed with binder (carboxymethyl cellulose) and uniaxial pressed in to a specimens with diameter 38 x 22 x 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, was obtained. Prepared blocks after sintering showed numerous cracks. Nevertheless blocks was fine grained and show quite reproducible chemical composition. Conclusion: A sol gel wet chemical route of powder synthesis allow to obtain high homogenous ceramic materials with inconsiderable amount of pores with low variation in a diameter. 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 free from cracks zirconia ceramics blocks.

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Ocena stabilności termicznej proszków ZrO2 modyfikowanych tlenkami MgO oraz Y2O3

Nakonieczny D., Paszenda Z., Walke W.

Engineering of Biomaterials

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2013

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Vol. 16, no. 120

8--12

EN

Celem zrealizowanych badań było uzyskanie proszków ZrO2 zmodyfikowanych tlenkami itru i magnezu, które mogłyby być wykorzystane do przygotowania bloczków ceramicznych - półproduktu w procesie wytwarzania tzw. pełnoceramicznych protez stałych w protetyce stomatologicznej. Uzupełnienia pełnoceramiczne (full-ceramic restorations) w porównaniu do konwencjonalnych protez metalowo-ceramicznych (porcelain fused to metal) nie powodują metalozy oraz nie sprzyjają odkładaniu się płytki nazębnej i kamienia nazębnego. Rosnąca popularność protez pełnoceramicznych jest wynikiem upowszechnienia się technologii CAD/CAM, (wprowadzenie bardzo dokładnych frezarek numerycznych oraz oprogramowania dedykowanego dla gabinetów i laboratoriów stomatologicznych), dzięki której można precyzyjnie odwzorować warunki anatomiczne panujące w jamie ustnej pacjenta oraz wykonać funkcjonale uzupełnia protetyczne. Etapem limitującym dalsze stadia procesu wytwórczego oraz właściwości eksploatacyjne ZrO2 jest synteza proszków ceramicznych. Do przygotowania proszków wykorzystano „klasyczną” mokrą metodę zol-żel. Jako prekursor tlenku cyrkonu zastosowano propanolan cyrkonu. Jako prekursory domieszek tlenkowych wykorzystano heksahydraty azotanu itru oraz magnezu. Przydatność przygotowanych do prac proszków oceniono na podstawie analizy termicznej z wykorzystaniem termograwimetrii (TG). Materiały poddano badaniom ze względu na prawdopodobieństwo wystąpienia w składzie chemicznym sporządzonych próbek termolabilnego w zakresie temperatur spiekania wodorotlenku cyrkonu (Zr(OH)4, temperatura rozkładu 823 K) [1]. Przeprowadzona analiza pozwoliła stwierdzić nieznaczny, nie związany z dehydratacją ubytek masy próbek, co świadczy o braku obecności wodorotlenku cyrkonu w przygotowanych proszkach.

PL

The aim of presented study was to obtain zirconia powders modified with magnesium and yttrium oxides addition, which could be used for the preparation of the ceramic blocks - an intermediate product for manufacturing of the full ceramic fixed prosthetic restorations in prosthetic dentistry. Full ceramic restorations compared to so called conventional porcelain fused to metal restorations do not cause metallosis and prevent to the accumulation of plaque and tartar. The growing popularity of all-ceramic restorations is the result of spread of CAD / CAM technology, (introduction of high-precision milling machines and dedicated software for dentist and technicians la¬boratories) which allows to precisely reproduce the anatomical conditions prevailing in the patient's mouth and perform functional prosthetic restorations. Limiting step of the further process stages is the synthesis of ceramic powders. For the preparation of the ceramic powders the "classic" wet sol-gel method was used. As the zirconium oxide precursor zirconium isopropoxide was used. As the dopant oxide precursors were used yttrium and magnesium nitrate hexahydrates. Usefulness of prepared powders was characterized by thermogravimetry (TG). Materials were tested due to the likelihood occurrence of zirconium hydroxide in prepared samples chemical composition which is thermolabile in the range of sintering temperatures (Zr(OH)4, decomposition temperature 823 K) [1]. Results of the analysis led to the conclusion of presence of negligible, not associated with dehydration weight loss of the samples which show the absence of zirconium hydroxide in prepared powders.

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The simulation of mastication efficiency of the mucous-borne complete dentures

Żmudzki J., Chladek G., Malara P., Dobrzański L.A., Zorychta M., Basa K.

Archives of Materials Science and Engineering

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2013

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Vol. 63, nr 2

75--86

EN

Purpose: The aim of this study was to present rules for numerical investigations of mastication efficiency of mucous-borne complete dentures. Design/methodology/approach: Finite element method (FEM) large displacements analysis with denture detaching and sliding at mucous membrane interface was employed. The possibility of a lower denture destabilization under oblique mastication load was modeled. Denture stabilization at balancing contact „at time” and „delayed” was modeled with increasing of a distance to the opposite denture. An unfavorable mucous membrane foundation was assumed. Findings: Pressures beneath dentures during stable vertical occlusal loadings are lower than pain threshold of mucous membrane even when the denture foundation was very unfavorable. Simulation of realistic oblique mastication force results in a denture destabilization. Denture experienced a large slide, completely lost adherence at balancing side and the balancing contact was needed to achieve stabilization. The pressures beneath denture under oblique load increased to values much higher than pain threshold and the „delayed” balancing contact influenced additional increase of pressure values. Research limitations/implications: In the FEM study only characteristic unfavorable denture foundation and conventional denture type were analyzed. Practical implications: Defined values of pressure beneath dentures show that it is necessary to underlay the dentures. The influence of „delayed” balancing contact on significant increase of stress beneath dentures indicates that in case of a problem with stabilization of dentures it is necessary to introduce stabilization on the implants. Originality/value: Universal rules of conducting a numerical experiment and interpreting its results constitute the base and encouragement to complete further practical tasks awaiting engineers and prosthetists.