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52. Estimation of the corrosion properties for titanium dental alloys produced by SLMTadeja Kosec, Mirjam Bajt Leban, Maja Ovsenik, Matej Kurnik, Igor Kopač, 2022, original scientific article Abstract: Titanium alloys are known for their excellent biocompatible properties. The development of additive-manufacturing technologies has increased the interest in the use of Ti-6Al-4V, produced by selective laser melting (SLM) method, also in dentistry, i.e., prosthodontics and orthodontics. In the present paper, the effect of laser printing parameters in the selective laser melting (SLM) process on the porosity and corrosion behavior of Ti-6Al-4V dental alloy was metallographically and electrochemically studied. All the tests were performed in artificial saliva at 37 °C. Different forms of Ti-6Al-4V alloy were selected: a reference sample, i.e., pre-fabricated milling disc in wrought condition and four different 3D-printed samples made from Ti-6Al-4V powder using the SLM method, one being heat treated. Electrochemical, spectroscopic and hardness measurements were employed in the study. It was shown that the SLM-produced Ti-6Al-4V samples with different printing parameters have similar microstructural and electrochemical properties, while the electrochemical properties of a reference and thermally treated 3D-printed sample were different, most probably due to the change in the microstructure of the alloys. The corrosion properties were related to the microstructural properties as well as to the pore density.
Keywords: Ti-6Al-4V, dental alloys, artificial saliva, selective laser melting, corrosion
Published in DiRROS: 31.05.2023; Views: 258; Downloads: 115
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53. Differences between 3-D printed and traditionally milled CoCr dental alloy from casted block in oral environmentMirjam Bajt Leban, Matej Kurnik, Igor Kopač, Matic Klug Jovičević, Bojan Podgornik, Tadeja Kosec, 2023, original scientific article Abstract: The aim of this study was to compare corrosion resistance and ion release in CoCr dental alloys with identical chemical compositions produced using different technologies (SLM – selective laser melting and milling from cast blocks) and heat treatment (SLM parts only). The corrosion properties were tested in artificial saliva, artificial saliva with fluoride ions, and artificial saliva with added lactic acid to simulate inflammations. The study included electrochemical tests, microstructural investigation and ion release tests in the three different environments for a total of 42 days. The best performance of CoCr as a result of potentiodynamic polarization was observed in the artificial saliva with added lactic acid, which is in contradiction with the highest ion release measured from all the materials tested and electrochemical impedance spectroscopy that showed a deterioration of the passive layer in an acidic environment. Microstructural investigation revealed that different phases precipitated by heat treatment trigger increased release of Mo and W ions. The printing method does not raise critically ion release from CoCr alloy, while the state of the surface greatly impacts the extent of the ion release. This study demonstrates the importance of an interdisciplinary approach to the study of corrosion and biocompatibility in dental alloys.
Keywords: CoCr dental alloy, selective laser melting, corrosion, ion release, artificial saliva
Published in DiRROS: 29.05.2023; Views: 342; Downloads: 288
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55. Environmental hazard of polypropylene microplastics from disposable medical masks : acute toxicity towards Daphnia magna and current knowledge on other polypropylene microplasticsAnita Jemec Kokalj, Andraž Dolar, Damjana Drobne, Marjan Marinšek, Matej Dolenec, Luka Škrlep, Gregor Strmljan, Branka Mušič, Andrijana Sever Škapin, 2022, original scientific article Abstract: The COVID-19 pandemic has increased the use of disposable plastics, including medical masks, which have become a necessity in our daily lives. As these are often improperly disposed of, they represent an important potential source of microplastics in the environment. We prepared microplastics from polypropylene medical masks and characterised their size, shape, organic chemical leaching, and acute toxicity to the planktonic crustacean Daphnia magna. The three layers of the masks were separately milled and characterised. Each of the inner frontal, middle filtering, and outer layers yielded different types of microplastics: fibres were obtained from the inner and outer layer, but irregular fragments from the middle layer. The shape of the obtained microplastics differed from the initial fibrous structure of the intact medical mask layers, which indicates that the material is deformed during cryo-milling. The chemical compositions of plastics-associated chemicals also varied between the different layers. Typically, the inner layer contained more chemicals related to antimicrobial function and flavouring. The other two layers also contained antioxidants and their degradation products, plasticisers, cross-linking agents, antistatic agents, lubricants, and non-ionic surfactants. An acute study with D. magna showed that these microplastics do not cause immobility but do physically interact with the daphnids. Further long-term studies with these microplastics are needed using a suite of test organisms. Indeed, studies with other polypropylene microplastics have shown numerous adverse effects on other organisms at concentrations that have already been reported in the environment. Further efforts should be made to investigate the environmental hazards of polypropylene microplastics from medical masks and how to handle this new source of environmental burden.
Keywords: COVID-19 pandemic, plastics-associated chemicals, Daphnia magna, fibres, fragments, nanofibres, polypropylene microplastics, single-use plastic
Published in DiRROS: 05.05.2023; Views: 343; Downloads: 214
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56. Analyte-driven clustering of bio-conjugated magnetic nanoparticlesTilen Potisk, Jurij Sablić, Daniel Svenšek, Elena Sanz-de Diego, Francisco J. Teran, Matej Praprotnik, 2023, original scientific article Keywords: biochemistry, nanoparticles, magnetic nanoparticles, proteins, biosensors
Published in DiRROS: 16.03.2023; Views: 524; Downloads: 210
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60. Lower Permian (Artinskian) chondrichthyan tooth remains (Petalodontidae) from Dovje (Karavanke Mts., NW Slovenia)Matija Križnar, 2022, original scientific article Abstract: Fossil remains of chondrichthyan tooth bases (roots) were found in Lower Permian beds exposed along the forest road between Dovje and Plavški Rovt. These layers are part of the clastic development of the Trogkofel Group beds. They are composed of an alternation of dark to light-grey shales, siltstone, and sandstone with rare beds of the conglomerate. Within the clastic succession, layers or lenses of dark-grey to black limestones (biosparitic, biomicritic and oolitic) and limestone breccias occur. The limestone consists remains of algae, fusulinids, brachiopods, and mostly crinoids (Palermocrinus and Entrochus). Detail study has shown that two remains of tooth bases belong to the genus Petalodus, one of them to the species Petalodus ohioensis. The bases are tongue-shaped and come to a rounded point in the distal (base end) edge. On the surface of the base, the typical oval-shaped foramina are visible. In addition, the osteodentine is visible on the cross-section of one specimen. Teeth of Petalodus are often the most common chondrichthyan fossil vertebrate remains reported from the Carboniferous and Permian rocks of the USA, Europe, and Russia. In Slovenia, Petalodus ohioensishas been recorded only from Upper Carboniferous beds. The new record of Lower Permian remains contributes to the knowledge of this cosmopolitan but still common genus of Late Paleozoic chondrichthyans.
Keywords: fossils, Petalodontiformes, Petalodus ohioensis, Upper Paleozoic, Artinskian, Karavanke Mountains, Slovenia
Published in DiRROS: 18.01.2023; Views: 578; Downloads: 259
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