română ANDREI TIBERIU CUCURUZ, ECATERINA ANDRONESCU, ANDREIA CUCURUZ, GEORGE PELIN
Abstract
The aim of this work was to prepare via in situ radical polymerization polymethacrylic acid/Al2O3 composite materials and to modify the structure of alumina with two silane coupling agents, 3-aminopropyl-trimethoxysilane (APTMS) and dichlorodimethylsilane (DMDCS). Also, the influence of silanization on the physico-mechanical properties of the resulting composite materials was studied. The surface modification of inorganic particles appears as an efficient technique to improve interactions between polymer matrix and nanoparticles.
The modification of alumina was investigated using transmission Fourier transform infrared spectroscopy that confirmed the success of the silanization procedure. The crystalline phase was identified using XRD analysis and the presence of alumina in the composite materials is demonstrated according to ASTM. Scanning electron microscopy revealed in all the analyzed samples alumina particles with spherical morphology that are embedded homogeneously in the organic polymer matrix. Also, the mechanical properties of composites were investigated based on xylene porosimetry and compression testing.
The composite materials synthesized in this study demonstrated a good potential for application in dentistry as dental resins or denture base materials.
Keywords
Alumina, Polymethacrylic acid, Composite materials, Denture base materials
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Year
2019
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Issue
49 (1)
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Pages
3-11
ELISABETA VASILESCU, VLAD GABRIEL VASILESCU, ION PĂTRAȘCU, BOGDAN GĂLBINAȘU
Abstract
The quality of metal - ceramic restorations is closely related to the quality of the metal - ceramic bond, where the rigidity of the metallic structure that prevents the occurrence of the flexural forces in the plating ceramic and in the interface area is an essential condition. Typically cast, the metallic component is made up of various metals and noble alloys or non-noble alloys.
Titanium and titanium alloys are at present an ideal solution due to their exceptional properties such as: corrosion resistance and high mechanical strength, density, thermal conductivity and reduced thermal expansion coefficient.
The research carried out aimed at studying the behavior of a new titanium alloy in metal - ceramic technology (Ti10Zr), a preliminary study on metal - ceramic bonding compared to conventional alloys (Ti6Al4V) and pure titanium (TiCp). The evaluation of the Ti10Zr-ceramic bond T22 Noritake was performed by mechanical tests, namely the shear resistance measurement and the determination of the final value of the force at which the ceramic component of the metal substructure is detached.
Mechanical tests were complemented by indirect, non - destructive methods of assessing the strength of metal - ceramic bonding.
The experimental results obtained confirm some results from the literature on the behavior of non - alloying alloys as substructures in metal - ceramic restorations, and on the other hand they can constitute novelty elements regarding the behavior of a new titanium alloy (Ti10Zr) as a component metallic in metal - ceramic technology.
Keywords
non - noble alloys, Ti10Zr bioalloy, metal - ceramic connection, mechanical tests metal – ceramic (M – C) prosthetic restoration, oxide, layer thickness, SEM analysis
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Year
2019
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Issue
49 (1)
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Pages
12-22
ENIKÖ VOLCEANOV, CRISTINA GEORGIANA POPA, ADRIAN VOLCEANOV, SORIN CIUCA
Abstract
In this study, the effects of simultaneous admixture of CaO and MgO on the crystalline phases, crystallite sizes and sintering properties of coprecipitated zirconia-alumina powder are investigated using complex thermal analysis (TG, DTA, DTG), X-ray diffractometry (XRD), scanning electron microscopy (SEM) coupled with EDS. Correlations among composition - microstructure and properties of the coprecipitated 85ZrO2. 15Al2O3 powder after sintering at 1050 oC, 1350 oC, and 1500o C with 2 hours soaking time at each temperature were performed. The results showed that development of tetragonal phase of zirconia stabilized with Ca2+ and Mg2+ was effective at 1500 oC. In dental applications, dental materials are soaked in saliva, which contains a large number of ions which in turn may accelerate the corrosion of materials. In such context, the chemical stability in modified Fusayama-Meyer type artificial saliva of sintered zirconia- alumina ceramics was also investigated. The ceramic samples sintered at 1500 oC show a better chemical stability, as the pH variation is lower when using a starting immersion solution with pH = 7.4. However, the variation of pH after immersion in artificial saliva is obvious after 216-288 hours due to the ionic transport between ceramic and the solution, even after sintering at 1500o C.
Keywords
Zirconia, Alumina, bioceramic, chemical stability, artificial saliva, corrosion
SIMONA NEAGU, CRINA ANASTASESCU, IOAN BALINT, MARIA ZAHARESCU, IOAN ARDELEAN, MĂDĂLIN ENACHE
Abstract
This study was undertaken as an attempt to assess the effects of ZnSe based materials toward Escherichia coli cells. ZnSe materials with spherical and flower-like morphologies were obtained in hydrothermal conditions. Qualitative and quantitative assays were conducted to evaluate the antibacterial activity. The effect of materials on the bacterial cells was observed by electron microscopy. Repetitive Sequence-Based PCR (rep-PCR) and polymerase chain reaction (PCR) of the 16S rRNA gene analyses were performed after the interaction of the samples with the bacterial cells. The results demonstrate that the antibacterial activity was influenced by concentration, size, time exposure, and shape of the material. Thus, ZnSe with flower-like morphology exhibited higher antibacterial activity on Escherichia coli reference strain compared with the micro-sized ZnSe spheres, related to their different morphology and their higher surface area
Keywords
zinc selenide, antibacterial activity, Escherichia coli
NESE KEKLIKCIOGLU CAKMAK , GULER BENGUSU TEZEL
Abstract
In this study, graphene oxide nanoparticle (NGO) was fabricated via modified Hummers’ method and then modified with amine terminated 4-armed PEG to enhance the biocompatibility and stability of nano drug carrier. In our strategy, Doxorubicin (DOX) was used as a model drug. DOX loading onto NGO–PEG was synthesized by simply mixing with the NGO-PEG solution at pH 7 overnight. NGO, NGO-PEG and NGO-PEG-DOX was characterized by power X-ray diffraction, scanning electron microscopy, and UV spectroscopy. Stability analysis was performed with zeta potential. The experimental results showed that the zeta potential analysis values were above ±40 mV. NGO-PEG-DOX is still had very good dispersion stability even after 45 days. Therefore, this drug loaded product can be good candidate for treatment of cancer.
Keywords
nanographene oxide (NGO) , nanostructured drug carrier, stability, DOX, PEGylated
ADRIAN-IONUȚ NICOARĂ, RUXANDRA- ELENA GEANALIU-NICOLAE, ECATERINA ANDRONESCU, ROXANA TRUȘCĂ
Abstract
The scope of the present study is the synthesis and characterization of mesoporous silica. using two different methods, the classic sol-gel and a novel microwave- hydrothermal process. There were synthesized nanostructured mesoporous silica materials with average particle size dimensions between 87-500 nm presenting a structure with symmetrical hexagonal pores with the average size of 4 nm.
In order to obtain mesoporous silica, the precursor has been characterized using TG-DSC analysis. Nanoporous silica materials, MCM-41, have been characterized using different techniques as X- ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and the Brunauer– Emmett–Teller (BET) analysis.
Keywords
MCM, mesoporous silica, hexagonal, mesostructured, biomaterials