1. Characterization of micro-threaded stem taper surface of cementless hip endoprosthesesDrago Dolinar, Boštjan Kocjančič, Klemen Avsec, Barbara Šetina, Aleksandra Kocijan, Matjaž Godec, Marko Sedlaček, Mojca Debeljak, John T. Grant, Timon Zupanc, Monika Jenko, 2024, izvirni znanstveni članek Povzetek: We investigated micro-threaded stem taper surface and its impact on premature failures, aseptic loosening, and infection in cementless hip endoprostheses. Our study focused on the fretting, and crevice corrosion of micro-threaded tapers, as well as the characterization of the microstructure and surface properties of two new and three retrieved Zweymüller stem tapers. The retrieved samples were selected and examined based on the head–stem taper interface being the sole source of modularity with a metallic component, specifically between the Ti alloy taper stem and the ceramic head. To determine the surface chemistry and microstructures of both new and retrieved hip endoprostheses stem taper titanium alloy, scanning -electron microscopy (SEM) was employed for morphological and microstructural analyses. Energy dispersive spectroscopy (EDS) was utilized for characterizing chemical element distribution, and electron backscattered diffraction (EBSD) was used for phase analysis. The roughness of the micro-threated stem tapers from different manufacturers was investigated using an optical profilometer, with standard roughness parameters Ra (average surface roughness) and Rz (mean peak to valley height of the roughness profile) being measured. Electrochemical studies revealed no fretting corrosion in retrieved stem tapers with ceramic heads. Consequently, three retrieved tapers and two new ones for comparison underwent potentiodynamic measurements in Hank’s solution to determine the corrosion rate of new and retrieved stem taper surfaces. The results showed a low corrosion rate for both new and prematurely failed retrieved samples due to aseptic loosening. However, the corrosion rate was higher in infected and low-grade infected tapers. In conclusion, our study suggests that using ceramic heads reduces taper corrosion and subsequently decreases the incidence of premature failures in total hip arthroplasty.
Ključne besede: total hip arthroplasty, stem micro-threaded taper, taper surface morphology, microstructure, corrosion, Ti implant alloy
Objavljeno v DiRROS: 06.06.2024; Ogledov: 59; Prenosov: 49
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3. Bioresorbability dependence on microstructure of additivelly- manufactured and conventionally-produced Fe-Mn alloysMatjaž Godec, Jakob Kraner, Danijela Anica Skobir Balantič, Irena Paulin, Damjana Drobne, Veno Kononenko, Aleksandra Kocijan, Paul J. McGuiness, Črtomir Donik, 2024, izvirni znanstveni članek Ključne besede: Fe-Mn alloy, laser powder bed fusion, bioresorbable, microstructure, corrosion behaviour, biocompatibility
Objavljeno v DiRROS: 06.05.2024; Ogledov: 188; Prenosov: 124
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4. Processing aluminium EN AW 7075 alloy using selective laser meltingNejc Velikajne, Jože Medved, Matjaž Godec, Irena Paulin, zaključena znanstvena zbirka raziskovalnih podatkov Povzetek: Selective laser melting (SLM) is an additive manufacturing process, forming the desired geometry by selective layer fusion of powder material. Unlike conventional manufacturing processes, highly complex parts can be designed and manufactured with high accuracy and little post processing. Currently, different types of steel, aluminium, titanium and nickel-based alloys have been successfully processed; however, high strength aluminium alloy EN AW 7075 has not been processed with satisfying quality. The main focus of the investigation is to develop a new alloy which is more suitable for the SLM process for the wide used aluminium alloy EN AW 7075. But before that, gas-atomized powder material was characterized in terms of statistical distribution. A wide range of process parameters and different pre-heating temperatures were selected to optimize the process in terms of optimum volume density and reducing the effect of hot cracking. However, all laser-melted parts exhibited hot cracks which typically appear in aluminium alloy EN AW 7075.
Ključne besede: EN AW 7075, aluminium alloy, hot cracks, relative density, selective laser melting (SLM)
Objavljeno v DiRROS: 22.04.2024; Ogledov: 165; Prenosov: 0 |
5. Bioresorbability dependence on microstructure of additivelly- manufactured and conventionally-produced Fe-Mn alloysMatjaž Godec, Jakob Kraner, Danijela Anica Skobir Balantič, Irena Paulin, Damjana Drobne, Veno Kononenko, Aleksandra Kocijan, Paul J. McGuiness, Črtomir Donik, 2024, zaključena znanstvena zbirka raziskovalnih podatkov Povzetek: The dataset supports the results shown in the tables and figures in the article entitled “Bioresorbability Dependence on Microstructure of Additivelly-Manufactured and Conventionally-Produced Fe-Mn Alloys” (doi.org/10.1016/j.jmrt.2024.04.097). It contains measurements of corrosion resistance of Fe-Mn samples, phase analysis of samples A, B and C, surface and depth profiling XPS, EDS measurements of a cross-section of Fe-Mn powder particles and viability measurements results.
Ključne besede: Fe-Mn alloy, laser powder bed fusion, bioresorbable, microstructure, corrosion behaviour, biocompatibility
Objavljeno v DiRROS: 12.04.2024; Ogledov: 288; Prenosov: 151
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7. A critical appraisal of the use and properties of nickel–titanium dental alloysPetra Močnik, Tadeja Kosec, 2021, pregledni znanstveni članek Povzetek: Nickel–titanium (NiTi) archwires are used in dentistry for orthodontic treatment. NiTi alloys have favourable mechanical characteristics, such as superelasticity and shape memory, and are also known as a corrosion-resistant alloy. In specific cases, an archwire could be attacked by certain types of corrosion or wear degradation, which can cause the leaching of metal ions and a hypersensitive response due to increased concentrations of Ni in the human body. A systematic search of the literature retrieved 102 relevant studies. The review paper focuses on three main fields: (i) electrochemical properties of NiTi wires and the effect of different environments on the properties of NiTi wires (fluoride and low pH); (ii) tribocorrosion, a combination of chemical and mechanical wear of the material, and (iii) the biocompatibility of NiTi alloy and its subsequent effect on the human body. The review showed that corrosion properties are affected by microstructure, pH of saliva and the presence of fluorides. A high variation in published results should be, therefore, interpreted with care. The release of nickel ions was assessed using the same unit, showing that the vast majority of metal ions were released in the first few days of exposure, then a stable, steady state was reached. In tribocorrosion studies, the increased concentrations of Ni ions were reported.
Ključne besede: NiTi alloy, archwires, corrosion, NI ion release
Objavljeno v DiRROS: 23.02.2024; Ogledov: 277; Prenosov: 98
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8. Mechanisms of premature fracture in modular neck stems made of CoCrMo/Ti6Al4V and Ti6Al4V/Ti6Al4V alloyDrago Dolinar, Miro Gorenšek, Klemen Avsec, Barbara Šetina, Matej Hočevar, Matjaž Godec, Borut Žužek, Mojca Debeljak, Monika Jenko, John T. Grant, Boštjan Kocjančič, 2023, izvirni znanstveni članek Povzetek: In this paper, we present the mechanisms of premature fracture of modular neck stems in two case studies: (I) when the neck and stem are both made of the same Ti6Al4V alloy, and (II) when the neck and stem are made from two different alloys, CoCrMo and Ti6Al4V alloy. Our study integrates two orthopedic patients who have undergone primary uncemented THA for usual indications in two orthopedic centers (Community Health Centre and University Medical Centre). Both centers are part of the national public health care system. Both surgeries were performed by two skilled orthopedic surgeons with more than 10 years of experience in THA. The survivorship of the modular neck of cast CoCrMo alloy was 24 months. The survivorship of the modular neck from Ti6Al4V alloy was 84 months. Multivariate analyses were performed to assess the differences in the fretting, corrosion, and fatigue of the two prematurely failed modular neck stems: stereo light microscopy (SLM), scanning electron microscopy (SEM), X-ray energy-dispersive spectroscopy (EDS), and electron backscatter diffraction (EBSD). Patient demographic information, including sex, age, body mass index, survivorship of implants, and reason for the revision, was collected from medical records. We found that fretting and fatigue occurred on both neck-stem retrievals due to additional galvanic corrosion, but the CoCrMo/Ti6Al4V alloy system suffered more corrosion due to additional galvanic corrosion and fractured earlier than the Ti6Al4V/Ti6Al4V metal alloy system. Both metallic alloy systems used in this application are known to be highly corrosion-resistant, but the bio-tribo-corrosion processes need to be understood in detail and characterized so that appropriate improvements in design and materials can be made.
Ključne besede: total hip arthroplasty, modular neck, Ti6Al4V alloy, CoCrMo alloy, corrosion
Objavljeno v DiRROS: 07.02.2024; Ogledov: 298; Prenosov: 155
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9. Dispersoids in Al-Mg-Si alloy AA 6086 modified by Sc and YFranc Zupanič, Sandi Žist, Mihaela Albu, Ilse Letofsky-Papst, Jaka Burja, Maja Vončina, Tonica Bončina, 2023, izvirni znanstveni članek Ključne besede: aluminium alloy, heat treatment, microstructure, dispersoids, dilatometry, DSC, hardness
Objavljeno v DiRROS: 02.02.2024; Ogledov: 305; Prenosov: 116
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10. Solidification behavior of Fe-6.5Si alloy powder for AM-SLM processing, as assessed by differential scanning calorimetryDarja Steiner Petrovič, Črtomir Donik, Irena Paulin, Matjaž Godec, Maja Vončina, Martin Petrun, 2023, izvirni znanstveni članek Ključne besede: soft magnetic alloy, differential scanning calorimetry, oxygen, high-temperature phase, microstructure, eutectics
Objavljeno v DiRROS: 02.02.2024; Ogledov: 226; Prenosov: 97
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