Ocena korozijskih lastnosti titanovih dentalnihzlitin, izdelanih s SLM postopkom

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.Titanove zlitine so znane po odličnih biokompatibilnih lastnostih. Razvoj aditivnih tehnologij je povečal zanimanje za uporabo Ti-6Al-4V, proizvedenega z metodo selektivnega laserskega taljenja (SLM) v zobozdravstvu - tako v protetiki kot v ortodontiji. V prispevku smo metalografsko in elektrokemijsko proučili vpliv parametrov laserskega tiska pri procesu selektivnega laserskega taljenja (SLM) na poroznost in korozijsko obnašanje dentalne zlitine Ti-6Al-4V. Vsi testi so bili opravljeni v umetni slini pri telesni temperaturi 37 °C. Izbrane so bile različne oblike zlitine Ti-6Al-4V: referenčni vzorec (v obliki diska za rezkanje v kovanem stanju) in štirje različni 3D natisnjeni vzorci iz prahu Ti-6Al-4V po metodi selektivnega laserskega taljenja (SLM), pri čemer je eden toplotno obdelan. Pri raziskavi so bile uporabljene elektrokemijske, spektroskopske metode in meritve trdote. Pokazalo se je, da imajo vzorci Ti-6Al-4V, izdelani s postopkom SLM, z različnimi parametri, podobne mikrostrukturne in elektrokemijske lastnosti, medtem ko so bile elektrokemijske lastnosti referenčnega in termično obdelanega 3D natisnjenega vzorca različne, najverjetneje zaradi različne mikrostrukture te zlitine. Korozijske lastnosti so bile povezane z mikrostrukturnimi lastnostmi, pa tudi z gostoto por

Differences between 3-D printed and traditionally milled CoCr dental alloy from casted block in oral environment

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

Primerjava korozijskih lastnosti CoCrMo dentalnih zlitin v umetni slini

CoCrMo alloys are known for their biocompatible properties, which, together with their favorable mechanical properties, mean they can be efficiently used in dentistry. With the development of selective laser melting for the fabrication of 3D-printed ob - jects, interest in the corrosion properties of this alloy has risen in the field of prosthodontics. In the study, CoCrMoW dental al - loys were studied in artificial saliva at body temperature, i.e., 37 °C. Different forms of CoCrMoW alloy were selected: a refer - ence sample, i.e., original material as received from the supplier, a cast sample acquired from an ordinary procedure in a dental laboratory, and two 3D-printed samples made from CoCrMoW powder using the selective laser melting (SLM) method. Electro - chemical, spectroscopic and hardness measurements were conducted. It was shown that the reference and cast samples have similar microstructural and electrochemical properties, while the electrochemical properties of the 3D-printed samples differ, most probably due to the effect of the higher micro porosity and chemical composition of the alloys.CoCrMo-zlitine so znane po svojih biokompatibilnih lastnostih, ki jih zaradi ugodnih mehanskih lastnosti vse pogosteje uporabljamo v zobozdravstvu. Z razvojem selektivnega laserskega taljenja (SLT) se je zanimanje za izdelavo 3D tiskanih predmetov in preučevanje korozijskih lastnosti teh zlitin povečalo tudi v stomatološki protetiki. V študiji je bila preučevana CoCrMoW-zlitina v umetni slini pri telesni temperaturi 37 °C. Izbrane so bile različne oblike zlitin CoCrMoW: originalni referenčni vzorec dostavljen od dobavitelja, kovinski ulitek, pridobljen z ustaljenim postopkom v zobotehničnem laboratoriju in dva 3D vzorca iz prahu CoCrMoW, ki sta bila izdelana z uporabo metode selektivnega laserskega taljenja. Izvedene so bile elektrokemijske in metalografske preiskave z merjenjem trdote. Ugotovljeno je bilo, da imata referenčni in ulit material podobne mikrostrukturne in elektrokemijske lastnosti, medtem ko imajo vzorci 3D tiska različne elektrokemijske lastnosti, najverjetneje zaradi učinka večje mikro poroznosti in kemijske sestave zlitin

Pulmonary hypertension at admission predicts ICU mortality in elderly critically ill with severe COVID-19 pneumonia: retrospective cohort study

Abstract Background Point-of-care ultrasound (POCUS) is a useful diagnostic tool for non-invasive assessment of critically ill patients. Mortality of elderly patients with COVID-19 pneumonia is high and there is still scarcity of definitive predictors. Aim of our study was to assess the prediction value of combined lung and heart POCUS data on mortality of elderly critically ill patients with severe COVID-19 pneumonia. Methods This was a retrospective observational study. Data of patients older than 70 years, with severe COVID-19 pneumonia admitted to mixed 25-bed, level 3, intensive care unit (ICU) was analyzed retrospectively. POCUS was performed at admission; our parameters of interest were pulmonary artery systolic pressure (PASP) and presence of diffuse B-line pattern (B-pattern) on lung ultrasound. Results Between October 2020 and March 2021, 117 patients aged 70 years or more (average age 77 ± 5 years) were included. Average length of ICU stay was 10.7 ± 8.9 days. High-flow oxygenation, non-invasive ventilation and invasive mechanical ventilation were at some point used to support 36/117 (31%), 39/117 (33%) and 75/117 (64%) patients respectively. ICU mortality was 50.9%. ICU stay was shorter in survivors (8.8 ± 8.3 vs 12.6 ± 9.3 days, p = 0.02). PASP was lower in ICU survivors (32.5 ± 9.8 vs. 40.4 ± 14.3 mmHg, p = 0.024). B-pattern was more often detected in non-survivors (35/59 (59%) vs. 19/58 (33%), p = 0.005). PASP and B-pattern at admission, and also mechanical ventilation and development of VAP, were univariate predictors of mortality. PASP at admission was an independent predictor of ICU (OR 1.061, 95%CI 1.003–1.124, p = 0.039) and hospital (OR 1.073, 95%CI 1.003–1.146, p = 0.039) mortality. Conclusions Pulmonary artery systolic pressure at admission is an independent predictor of ICU and hospital mortality of elderly patients with severe COVID-19 pneumonia

SepsEast Registry indicates high mortality associated with COVID-19 caused acute respiratory failure in Central-Eastern European intensive care units

Abstract The coronavirus disease (COVID-19) pandemic caused unprecedented research activity all around the world but publications from Central-Eastern European countries remain scarce. Therefore, our aim was to characterise the features of the pandemic in the intensive care units (ICUs) among members of the SepsEast (Central-Eastern European Sepsis Forum) initiative. We conducted a retrospective, international, multicentre study between March 2020 and February 2021. All adult patients admitted to the ICU with pneumonia caused by COVID-19 were enrolled. Data on baseline and treatment characteristics, organ support and mortality were collected. Eleven centres from six countries provided data from 2139 patients. Patient characteristics were: median 68, [IQR 60–75] years of age; males: 67%; body mass index: 30.1 [27.0–34.7]; and 88% comorbidities. Overall mortality was 55%, which increased from 2020 to 2021 (p = 0.004). The major causes of death were respiratory (37%), cardiovascular (26%) and sepsis with multiorgan failure (21%). 1061 patients received invasive mechanical ventilation (mortality: 66%) without extracorporeal membrane oxygenation (n = 54). The rest of the patients received non-invasive ventilation (n = 129), high flow nasal oxygen (n = 317), conventional oxygen therapy (n = 122), as the highest level of ventilatory support, with mortality of 50%, 39% and 22%, respectively. This is the largest COVID-19 dataset from Central-Eastern European ICUs to date. The high mortality observed especially in those receiving invasive mechanical ventilation renders the need of establishing national–international ICU registries and audits in the region that could provide high quality, transparent data, not only during the pandemic, but also on a regular basis