Validation of 3D printed MAYO tubes and stethoscope in simulated medical environment - Tools fabricated with additive manufacturing for emergency care.

Emergency and disaster medical care often face resource or equipment shortages. 3D printing technology has been proven to be effective in cases with insufficient supply chains. MAYO tubes and stethoscopes are essential components of ABCDE patient examinations; however, 3D-printed variants have not been fully tested. These 3D-printed instruments were substituted and validated in a simulated pre-hospital environment. In total, 26 participants were included in this study. Fifteen clinicians or paramedics with at least 3 years of professional experience and 10 medical students. One student was excluded because he had relevant experience with emergency care. As basic tasks, the placement of MAYO tubes and auscultation with stethoscopes were performed using medical simulators. 3D printed instruments were compared with conventional clinical devices by measuring the time required for the intervention, success rate, and user satisfaction. In the study FFF (Fused Filament Fabrication (FFF), SLS (Selective Laser Sintering (SLS), and SLA (stereolithography) 3D printing were used in this study. The times required for implementation and auscultation were examined for each instrument. There was no significant difference between the MAYO tube (p = 0.798) and the stethoscope (p = 0.676). In the case of stethoscopy, the study investigated the correct diagnosis, and no significant difference was found (p = 0.239), although an interesting trend was observed. Regarding the MAYO tube, the study found no significant difference in correct position formation (p = 0.163). The experience levels of the groups did not influence these factors. However, significant differences in user satisfaction were found in both cases in favour of the conventional versions (p < 0.001). Overall, the results of this study suggest that 3D-printed devices could be suitable replacements for clinic-based devices in emergency situations. The 3D-printed devices did not perform inferiorly at any of the indicated points compared to their classical counterparts. However, the practical applicability of the devices used in this study requires further investigation.

The effect of individual drilling sleeves on the precision of coronectomy tooth sections. An in vitro 3D-printed jaw model experiment.

OBJECTIVES: The aim of this in vitro study was to evaluate the effect of a 3D-printed drill sleeve (DS) on the precision and duration of coronectomy sections. MATERIALS AND METHODS: Thirty-six trainees and oral surgeons performed 72 coronectomy cuts in a 3D-printed, entirely symmetric mandible model. Coronectomy was performed freehand (FH) on one side and with a DS on the other side. The occurrence of "too superficial" (≥ 4 mm unprepared lingual tooth tissue) and "too deep" (drilling ≥ 1 mm deeper as tooth contour) cuts and sectioning times were registered. RESULTS: In 7 cases, the sections were "too deep" with FH, while none with DS (OR: 18.56; 95%CI: 1.02-338.5; p = 0.048). The deviation between virtually planned and real cut depths was significantly greater in the FH group (1.91 ± 1.62 mm) than in DS group (1.21 ± 0.72 mm) (p < 0.001). A total of 18 "too superficial" buccolingual sections occurred with FH, while 8 cases with DS (OR: 3.50; 95%CI: 1.26-9.72; p = 0.016). Suboptimal sections did not correlate with experience (p = 0.983; p = 0.697). Shortest, suboptimal drillings were most frequently seen distolingually (OR: 6.76; 95% CI: 1.57-29.07; p = 0.01). In the inexperienced group, sectioning time was significantly longer with FH (158.95 ± 125.61 s vs. 106.92 ± 100.79 s; p = 0.038). CONCLUSIONS: The DS effectively reduced tooth sectioning times by less experienced colleagues. Independently from the level of experience, the use of DS obviated the need for any preparation outside the lingual tooth contour and significantly decreased the occurrence of "too superficial" cuts, leaving thinner unprepared residual tooth tissue lingually. CLINICAL RELEVANCE: Coronectomy sections may result in lingual hard and soft tissue injury with the possibility of damaging the lingual nerve. The precision of the buccolingual depth-control can be improved, while surgical time can be reduced when applying a drilling sleeve.

Biomechanical study on the effect of atherosclerosis on the vulnerability of thoracic aorta, and it's role in the development of traumatic aorta injury.

Traumatic aorta injury (TAI) is the second most common traumatic cause of death preceded only by head injuries, being responsible for 5% to 30% of all mortalities in high-speed deceleration injuries. Multiple external factors might play a role such as impact speed, impact direction, occupant location, and presence or lack of restraining safety mechanism. Apart from these external factors, also human biological factors can influence its development. Based on the data of scientific literature, age clearly plays a role in suffering TAI, but the role of atherosclerosis-as a disease affecting the structure of the aorta-is unknown. Biomechanical properties of tissue samples of 104 aorta specimens removed during the autopsy from the posterior (Group 'A') and lateral wall (Group 'B') of descending aorta were analyzed. Specimens were examined by a Zwick/Roell Z5.0 biaxial tester. The Young's modulus (E (MPa)) was calculated using a linear regression procedure where the base of the elongation was the parallel length of the sample, the achieved maximal force (Fmax (N)), the elongation at the time of Fmax (Lmax (mm)), the force at the beginning of rupture (Fbreak (N)), the elongation at the time of Fbreak (Lbreak (mm)) were registered. Specimens were categorized based on macroscopic and microscopic appearance. In the posterior (A) samples the difference between Lbreak (p<0.001) and Lmax (p<0.001) was significant between the macroscopic group. Lbreak (p = 0.009) and Lmax (p = 0.003) showed similar pattern in the lateral (B) samples. Comparing the histological groups by the measured parameters (Fmax, Lmax, Fbreak, Lbreak) showed a significant difference in the means (p<0.001, p = 0.003, p<0.001 respectively). The study demonstrated that atherosclerosis decreases the resistance of the aorta. The rupture occurs at lower force (Fmax and Fbreak), and at shorter elongation (Lmax and Lbreak) in case of the presence of atherosclerosis. This effect is most substantial if calcification is present: the resistance of aorta affected by calcification is only two-thirds on average compared to aorta affected by the early phase of atherosclerosis. This phenomenon can be clearly explained by the weakening structure of the tunica intima.

Pre-eruptive intracoronal resorption in orthodontic patients: A retrospective analysis of 3,143 patients.

Objectives: The aim of this retrospective study was to analyze the occurrence and characteristics of pre-eruptive intracoronal resorptions in a clinical orthodontic patient population. Materials and methods: Patients treated in an orthodontic department (University of Pécs, Pécs, Hungary) were included. Unerupted teeth on panoramic radiographs were analyzed for intracoronal radiolucent lesions. For each patient, the demographic data, jaw localization, number of unerupted teeth with pre-eruptive intracoronal resorption lesions, number of lesions per tooth, size and localization of pre-eruptive intracoronal resorption defects, affected tooth's surface, pulp involvement and ectopic position of the tooth with defects were recorded. Results: In the 3,143 patients investigated, 55 teeth in 49 patients showed pre-eruptive intracoronal resorption lesions (subject incidence: 1.56%). The incidence on unerupted teeth was 0.25%. Pre-eruptive intracoronal resorption was significantly more common in mandibles (43 mandibular vs. 12 maxillary lesions) with an odds ratio of 12.84 (95% Confidence Interval: 5.19-31.74) and no gender differences were found (p = 0.746). The occurrence of pre-eruptive intracoronal resorption was highest in the youngest (7-10 years) mixed dentition status group (p < 0.001). Most of the lesions (44 of 55, or 80.0%) were localized in the dentin, occupying two-third or less of the dentin thickness. Only 12.73% (7/55) of the lesions were not localized on the occlusal surface. Of the lesions, 89.1% (49/55) showed no obvious size increase over an average follow-up of 36.4 ± 8.1 months. Conclusions: Pre-eruptive intracoronal resorption may occur mainly in the mixed dentition stage in orthodontic patients. Careful and attentive radiographic evaluations may facilitate early detection and follow-up of the lesions' possible dimensional changes, especially when resorption influences orthodontic extraction therapy.

Comparative Evaluation of the Repair Bond Strength of Dental Resin Composite after Sodium Bicarbonate or Aluminum Oxide Air-Abrasion.

The dental prophylactic cleaning of a damaged resin-based composite (RBC) restoration with sodium bicarbonate can change the surface characteristics and influence the repair bond strength. The purpose of this study was to compare the effect of sodium bicarbonate (SB) and aluminum oxide (AO) surface treatments on the microtensile bond strength (µTBS) of repaired, aged RBC. Bar specimens were prepared from microhybrid RBC and aged in deionized water for 8 weeks. Different surface treatments (AO air-abrasion; SB air-polishing), as well as cleaning (phosphoric acid, PA; ethylene-diamine-tetraacetic-acid, EDTA) and adhesive applications (single bottle etch-and-rinse, ER; universal adhesive, UA), were used prior to the application of the repair RBC. Not aged and aged but not surface treated RBCs were used as positive and negative controls, respectively. The repaired blocks were cut into sticks using a precision grinding machine. The specimens were tested for tensile fracture and the µTBS values were calculated. Surface characteristics were assessed using scanning electron microscopy. AO-PA-UA (62.6 MPa) showed a 20% increase in µTBS compared to the NC (50.2 MPa), which proved to be the most significant. This was followed by SB-EDTA-UA (58.9 MPa) with an increase of 15%. In addition to AO-PA-UA, SB-EDTA-UA could also be a viable alternative in the RBC repair protocol.

Mechanical Characterization and Structural Analysis of Latex-Containing and Latex-Free Intermaxillary Orthodontic Elastics.

Class II malocclusion is one of the most common dental anomalies and the use of intermaxillary elastomers is the standard method in its treatment. However, orthodontic elastics cannot exert continuous force over a period of time due to force degradation. Our goal was to mechanically characterize the different types of elastomers during static and cyclic loads, based on uniform methodology and examine the morphological changes after loading. Ten types of latex-containing and four latex-free intermaxillary elastics were examined from six different manufacturers. To determine the mechanical characteristics of the elastomers, tensile tests, cyclical tensile fatigue tests and 24 h relaxation tests were performed, and the elastics were also subjected to scanning electron microscopy (SEM) and Raman spectroscopy. Regardless of the manufacturer, the latex-containing elastomers did not show significant differences in the percentage of elongation at break during the tensile test. Only one type of latex-containing elastomer did not tear during the 24 h cyclical fatigue test. Fatigue was confirmed by electron microscopy images, and the pulling force reduced significantly. During the force relaxation test, only one latex-free ligature was torn; the force degradation was between 7.8% and 20.3% for latex ligatures and between 29.6% and 40.1% for latex-free elastomers. The results showed that dynamic loading was more damaging to ligatures than static loading, latex-containing elastomers were more resistant than latex-free elastics, and which observation could have clinical consequences or a potential effect on patient outcome.

Neck-shaft angle measurement in children: accuracy of the conventional radiography-based (2D) methods compared to 3D reconstructions.

Aim of this study was to examine the accuracy of widely used conventional radiography-based (2D) neck-shaft angle measurements compared to 3D reconstruction. In our retrospective study, EOS 2D/3D images of 156 patients (312 limbs) were selected from our database (4-16 years old: 6 girls and 6 boys/year), where no pathology was revealed. Using the 2D modality of the EOS method neck-shaft angle was measured using the "biggest diameter" and "circle fitting" techniques to define the femoral neck axis and 1/3, 1/2 and full femur to determine the femoral shaft axis. EOS 3D reconstructions of same images were also performed and a comparison of 2D and 3D results was made. We did not find any significant difference between accuracy of the four examined 2D methods, although the deviation between 2 and 3D results was considerable (average difference: 5.11-5.58°, p < 0,001). In 31% of the cases, difference was more than 10°. Only femoral torsion showed significant influence on the difference (correlation coefficient: 0.380, p < 0.001). We did not find a clinically significant difference between the examined 2D methods, although their accuracy was highly questionable compared to 3D results. We suggest using any 3D imaging method for surgical planning and in uncertain cases.

Evaluation and Comparison of Traditional Plaster and Fiberglass Casts with 3D-Printed PLA and PLA-CaCO3 Composite Splints for Bone-Fracture Management.

Bone fractures pose a serious challenge for the healthcare system worldwide. A total of 17.5% of these fractures occur in the distal radius. Traditional cast materials commonly used for treatment have certain disadvantages, including a lack of mechanical and water resistance, poor hygiene, and odors. Three-dimensional printing is a dynamically developing technology which can potentially replace the traditional casts. The aim of the study was to examine and compare the traditional materials (plaster cast and fiberglass cast) with Polylactic Acid (PLA) and PLA-CaCO3 composite materials printed using Fused Filament Fabrication (FFF) technology and to produce a usable cast of each material. The materials were characterized by tensile, flexural, Charpy impact, Shore D hardness, flexural fatigue, and variable load cyclic tests, as well as an absorbed water test. In addition, cost-effectiveness was evaluated and compared. The measured values for tensile strength and flexural strength decreased with the increase in CaCO3 concentration. In the fatigue tests, the plaster cast and the fiberglass cast did not show normal fatigue curves; only the 3D-printed materials did so. Variable load cyclic tests showed that traditional casts cannot hold the same load at the same deflection after a higher load has been used. During these tests, the plaster cast had the biggest relative change (-79.7%), compared with -4.8 % for the 3D-printed materials. The results clearly showed that 3D-printed materials perform better in both static and dynamic mechanical tests; therefore, 3D printing could be a good alternative to customized splints and casts in the near future.

Capacity and kinetics of light-induced cytochrome oxidation in intact cells of photosynthetic bacteria.

Light-induced oxidation of the reaction center dimer and periplasmic cytochromes was detected by fast kinetic difference absorption changes in intact cells of wild type and cytochrome mutants (cycA, cytC4 and pufC) of Rubrivivax gelatinosus and Rhodobacter sphaeroides. Constant illumination from a laser diode or trains of saturating flashes enabled the kinetic separation of acceptor and donor redox processes, and the electron contribution from the cyt bc1 complex via periplasmic cytochromes. Under continuous excitation, concentrations of oxidized cytochromes increased in three phases where light intensity, electron transfer rate and the number of reduced cytochromes were the rate liming steps, respectively. By choosing suitable flash timing, gradual steps of cytochrome oxidation in whole cells were observed; each successive flash resulted in a smaller, damped oxidation. We attribute this damping to lowered availability of reduced cytochromes resulting from both exchange (unbinding/binding) of the cytochromes and electron transfer at the reaction center interface since a similar effect is observed upon deletion of genes encoding periplasmic cytochromes. In addition, we present a simple model to calculate the damping effect; application of this method may contribute to understanding the function of the diverse range of c-type cytochromes in the electron transport chains of anaerobic phototrophic bacteria.

Stereolithography 3D Printing of a Heat Exchanger for Advanced Temperature Control in Wire Myography.

We report the additive manufacturing of a heat-exchange device that can be used as a cooling accessory in a wire myograph. Wire myography is used for measuring vasomotor responses in small resistance arteries; however, the commercially available devices are not capable of active cooling. Here, we critically evaluated a transparent resin material, in terms of mechanical, structural, and thermal behavior. Tensile strength tests (67.66 ± 1.31 MPa), Charpy impact strength test (20.70 ± 2.30 kJ/m2), and Shore D hardness measurements (83.0 ± 0.47) underlined the mechanical stability of the material, supported by digital microscopy, which revealed a glass-like structure. Differential scanning calorimetry with thermogravimetry analysis and thermal conductivity measurements showed heat stability until ~250 °C and effective heat insulation. The 3D-printed heat exchanger was tested in thermophysiology experiments measuring the vasomotor responses of rat tail arteries at different temperatures (13, 16, and 36 °C). The heat-exchange device was successfully used as an accessory of the wire myograph system to cool down the experimental chambers and steadily maintain the targeted temperatures. We observed temperature-dependent differences in the vasoconstriction induced by phenylephrine and KCl. In conclusion, the transparent resin material can be used in additive manufacturing of heat-exchange devices for biomedical research, such as wire myography. Our animal experiments underline the importance of temperature-dependent physiological mechanisms, which should be further studied to understand the background of the thermal changes and their consequences.

Pneumothorax/pneumomediastinum and pre-existing lung pathology in ventilated COVID-19 patients: a cohort study.

Background: There is an increasing number of reports on developing pneumothorax/pneumomediastinum among severe acute respiratory syndrome coronavirus disease 2019 (SARS-COVID-19) patients. The aim of our study was whether pre-existing diffuse lung pathology increases visceral pleural vulnerability resulting in pneumomediastinum and pneumothorax among mechanically ventilated COVID-19 patients? Methods: A total of 138 consecutive COVID-19 patients admitted to the Intensive Care Unit of Petz Aladár University Teaching Hospital between 1st March 2020 and 1st February 2021 were included. Sixty/138 (43.48%) patients had one or more computer tomography scans of the chest. Analysis was focused on the image defined lung conditions during artificial ventilation. Results: Thirteen out of 60 ventilated patients developed pneumothorax or pneumomediastinum proven by computer tomography (9.42%). Three/13 patients suffered from pre-existing lung parenchyma pathology, while 10/13 had only COVID-19 infection-related image abnormality. Forty-three/60 patient had healthy lung pre-COVID. Kruskal-Wallis test, Spearman correlation and Cox regression calculations did not reveal any statistically significant result proving increased vulnerability during pressure support therapy and visceral pleural breakdown in patients with pre-existing lung pathologies. Conclusions: Pre-existing lung pathology does not increase the risk of onset of pneumothorax or pneumomediastinum in comparation with previously healthy lungs of ventilated COVID-19 patients.

Development of a Novel X-ray Compatible 3D-Printed Bone Model to Characterize Different K-Wire Fixation Methods in Support of the Treatment of Pediatric Radius Fractures.

Additive manufacturing technologies are essential in biomedical modeling and prototyping. Polymer-based bone models are widely used in simulating surgical interventions and procedures. Distal forearm fractures are the most common pediatric fractures, in which the Kirschner wire fixation is the most widely used operative method. However, there is still lingering controversy throughout the published literature regarding the number of wires and sites of insertion. This study aims to critically compare the biomechanical stability of different K-wire fixation techniques. Different osteosyntheses were reconstructed on 189 novel standardized bone models, which were created using 3D printing and molding techniques, using PLA and polyurethane materials, and it has been characterized in terms of mechanical behavior and structure. X-ray imaging has also been performed. The validation of the model was successful: the relative standard deviations (RSD = 100 × SD × mean-1, where RSD is relative standard deviation, SD is the standard deviation) of the mechanical parameters varied between 1.1% (10° torsion; 6.52 Nm ± 0.07 Nm) and 5.3% (5° torsion; 4.33 Nm ± 0.23 Nm). The simulated fractures were fixed using two K-wires inserted from radial and dorsal directions (crossed wire fixation) or both from the radial direction, in parallel (parallel wire fixation). Single-wire fixations with shifted exit points were also included. Additionally, three-point bending tests with dorsal and radial load and torsion tests were performed. We measured the maximum force required for a 5 mm displacement of the probe under dorsal and radial loads (means for crossed wire fixation: 249.5 N and 355.9 N; parallel wire fixation: 246.4 N and 308.3 N; single wire fixation: 115.9 N and 166.5 N). We also measured the torque required for 5° and 10° torsion (which varied between 0.15 Nm for 5° and 0.36 Nm for 10° torsion). The crossed wire fixation provided the most stability during the three-point bending tests. Against torsion, both the crossed and parallel wire fixation were superior to the single-wire fixations. The 3D printed model is found to be a reliable, cost-effective tool that can be used to characterize the different fixation methods, and it can be used in further pre-clinical investigations.

Comparison of VividTrac, King Vision and Macintosh laryngoscopes in normal and difficult airways during simulated cardiopulmonary resuscitation among novices.

INTRODUCTION: Early endotracheal intubation improves neurological outcomes in cardiopulmonary resuscitation, although cardiopulmonary resuscitation is initially carried out by personnel with limited experience in a significant proportion of cases. Videolaryngoscopes might decrease the number of attempts and time needed, especially among novices. We sought to compare videolaryngoscopes with direct laryngoscopes in simulated cardiopulmonary resuscitation scenarios. MATERIALS AND METHODS: Forty-four medical students were recruited to serve as novice users. Following brief, standardized training, students executed endotracheal intubation with the King Vision®, Macintosh and VividTrac® laryngoscopes, on a cardiopulmonary resuscitation trainer in normal and difficult airway scenarios. We evaluated the time to and proportion of successful intubation, the best view of the glottis, esophageal intubation, dental trauma and user satisfaction. RESULTS: In the normal airway scenario, significantly shorter intubation times were achieved using the King Vision® than the Macintosh laryngoscope. In the difficult airway scenario, we found that the VividTrac® was superior to the King Vision® and Macintosh laryngoscopes in the laryngoscopy time. In both scenarios, we noted no difference in the first-attempt success rate, but the best view of the glottis and dental trauma, esophageal intubation and bougie use were more frequent with the Macintosh laryngoscope than with the videolaryngoscopes. The shortest tube insertion times were achieved using the King Vision® in both scenarios. CONCLUSION: All providers achieved successful intubation within three attempts, but we found no device superior in any of our scenarios regarding the first-attempt success rate. The King Vision® was superior to the Macintosh laryngoscope in the intubation time in the normal airway scenario and noninferior in the difficult airway scenario for novice users. We noted significantly less esophageal intubation using the videolaryngoscopes than using the Macintosh laryngoscope in both scenarios. Based on our results, the KingVision® might be recommended over the VividTrac® and Macintosh laryngoscopes for further evaluation.

Manufacturing a First Upper Molar Dental Forceps Using Continuous Fiber Reinforcement (CFR) Additive Manufacturing Technology with Carbon-Reinforced Polyamide.

3D printing is an emerging and disruptive technology, supporting the field of medicine over the past decades. In the recent years, the use of additive manufacturing (AM) has had a strong impact on everyday dental applications. Despite remarkable previous results from interdisciplinary research teams, there is no evidence or recommendation about the proper fabrication of handheld medical devices using desktop 3D printers. The aim of this study was to critically examine and compare the mechanical behavior of materials printed with FFF (fused filament fabrication) and CFR (continuous fiber reinforcement) additive manufacturing technologies, and to create and evaluate a massive and practically usable right upper molar forceps. Flexural and torsion fatigue tests, as well as Shore D measurements, were performed. The tensile strength was also measured in the case of the composite material. The flexural tests revealed the measured force values to have a linear correlation with the bending between the 10 mm (17.06 N at 5000th cycle) and 30 mm (37.99 N at 5000th cycle) deflection range. The findings were supported by scanning electron microscopy (SEM) images. Based on the results of the mechanical and structural tests, a dental forceps was designed, 3D printed using CFR technology, and validated by five dentists using a Likert scale. In addition, the vertical force of extraction was measured using a unique molar tooth model, where the reference test was carried out using a standard metal right upper molar forceps. Surprisingly, the tests revealed there to be no significant differences between the standard (84.80 N ± 16.96 N) and 3D-printed devices (70.30 N ± 4.41 N) in terms of extraction force in the tested range. The results also highlighted that desktop CFR technology is potentially suitable for the production of handheld medical devices that have to withstand high forces and perform load-bearing functions.

CMT Additive Manufacturing Parameters Defining Aluminium Alloy Object Geometry and Mechanical Properties.

Additive manufacturing technologies based on metal melting use materials mainly in powder or wire form. This study focuses on developing a metal 3D printing process based on cold metal transfer (CMT) welding technology, in order to achieve enhanced productivity. Aluminium alloy test specimens have been fabricated using a special 3D printing technology. The probes were investigated to find correlation between the welding parameters and geometric quality. Geometric measurements and tensile strength experiments were performed to determine the appropriate welding parameters for reliable printing. The tensile strength of the product does not differ significantly from the raw material. Above 60 mm height, the wall thickness is relatively constant due to the thermal balance of the welding environment. The results suggest that there might be a connection between the welding parameters and the printing accuracy. It is demonstrated that the deviation of ideal geometry will be the smallest at the maximum reliable welding torch movement speed, while printing larger specimens. As a conclusion, it can be stated that CMT-based additive manufacturing can be a reliable, cost-effective and rapid 3D printing technology with enhanced productivity, but without significant decrease in mechanical stability.

Increased serum level of high sensitivity troponin T even prior to surgery can predict adverse events during carotid endarterectomy.

OBJECTIVES: Perioperative stress affects the outcome of carotid endarterectomy performed under regional anesthesia. Here we aimed to explore the temporal profile of the stress marker cortisol and its relationship to high-sensitivity troponin-T, matrix metalloproteinase-9, tissue inhibitor of metalloproteinase-1, and S100B as an indicator of blood-brain barrier alteration in the systemic circulation. METHODS: Prospective part of the study: a total of 31 patients with significant carotid stenosis scheduled for carotid endarterectomy in regional anesthesia were enrolled. Follow-up part of the study and retrospective analysis of the outcome: each patient was followed up to five years and morbidity as well as mortality data were collected from an electronic database. Blood samples from each patient were serially taken; prior to surgery (T1), at the time of reperfusion (T2), 24 h (T3) and 72 h later postoperatively (T4), then the plasma concentration of each biomarker was measured. Besides, the clinical and surgical factors and perioperative adverse events were recorded. RESULTS: More positive correlations were found between: the early change of S100B (T2-T1) and late change in plasma cortisol level (T4-T3) (r = 0.403; p < 0.05); the early change of cortisol (T2-T1) and the early postoperative change of plasma matrix metalloproteinase-9 level (T3-T2) (r = 0.432; p = 0.01); the plasma concentration of tissue inhibitor of metalloproteinase-1 at 24 postoperative hours and the late change in plasma high-sensitivity troponin-T level (T4-T3) (r = 0.705; p < 0.001). Five patients needed an intraoperative shunt in whom the high-sensitivity troponin-T was elevated even prior to surgery, but definitive stroke never occurred. Plasma matrix metalloproteinase-9 concentration at reperfusion independently predicted the five-year mortality with a cut-off value of 456 ng/ml (sensitivity: 86%, specificity: 84%, area 0.887, p = 0.002). CONCLUSIONS: A higher intraoperative change in S100B level reflecting carotid endarterectomy induced acute silent brain ischemia was associated with more pronounced post-operative change of cortisol. An early elevation of cortisol was found to be associated with a delayed increase of matrix metalloproteinase-9. Importantly, an increased high-sensitivity troponin-T even prior to carotid endarterectomy may predict clamp intolerance, and elevated matrix metalloproteinase-9 at reperfusion suggests a poor outcome.

The Effect of Extrinsic Factors on the Mechanical Behavior and Structure of Elastic Dental Ligatures and Chains.

Force provided by elastomers used in orthodontics can be affected by several factors present in the oral cavity. The aim of our study was to investigate the role of mouthwashes, toothbrushing, and smoking in the force decay of such elastomers. Tensile strength, changes in the force continuously exerted, and force decay of elastic chains (Ortho Organizer and Masel Short Power Chain) and elastic ligatures (Dentaurum and Masel) by two separate manufacturers were measured. Measurements were initially made on untreated elastics, followed by exposure to different environmental factors including cigarette smoke, toothbrushing (mechanical plaque control), and two different mouthwashes (chemical plaque control). Changes on the surface of the elastics were studied with scanning electron microscopy (SEM). Untreated Masel elastic ligature showed lower tensile strength than Dentaurum elastic ligature (2339 cN vs. 3660 cN), while significantly higher tensile strength was measured for Ortho Organizer elastic chains than Masel chains (2639 cN vs. 1324 cN). The decrease in the elastic force of Masel ligature was greater in response to all external factors compared to Dentaurum. Although brushing with toothpaste and toothbrush impacted the force of both Masel and Ortho organizer ligatures negatively, force degradation was more apparent in the case of the Ortho organizer. Surface changes were more visible when applying Curasept mouthrinse, however force decay was higher in the Corsodyl group. Mechanical and chemical plaque control can influence the tensile strength and force decay of orthodontic elastomers, which should be considered by selecting the elastomers or determining their changing interval for the practice.

Detailed Thermal Characterization of Acrylonitrile Butadiene Styrene and Polylactic Acid Based Carbon Composites Used in Additive Manufacturing.

Currently, 3D printing is an affordable technology for industry, healthcare, and individuals. Understanding the mechanical properties and thermoplastic behaviour of the composites is critical for the users. Our results give guidance for certain target groups including professionals in the field of additive manufacturing for biomedical components with in-depth characterisation of the examined commercially available ABS and PLA carbon-based composites. The study aimed to characterize these materials in terms of thermal behaviour and structure. The result of the heating-cooling loops is the thermal hysteresis effect of Ohmic resistance with its accommodation property in the temperature range of 20-84 °C for ESD-ABS and 20-72 °C for ESD-PLA. DSC-TGA measurements showed that the carbon content of the examined ESD samples is ~10-20% (m/m) and there is no significant difference in the thermodynamic behaviour of the basic ABS/PLA samples and their ESD compounds within the temperature range typically used for 3D printing. The results support the detailed design process of 3D-printed electrical components and prove that ABS and PLA carbon composites are suitable for prototyping and the production of biomedical sensors.

An Overview on Personal Protective Equipment (PPE) Fabricated with Additive Manufacturing Technologies in the Era of COVID-19 Pandemic.

Different additive manufacturing technologies have proven effective and useful in remote medicine and emergency or disaster situations. The coronavirus disease 2019 (COVID-19) disease, caused by the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) virus, has had a huge impact on our society, including in relation to the continuous supply of personal protective equipment (PPE). The aim of the study is to give a detailed overview of 3D-printed PPE devices and provide practical information regarding the manufacturing and further design process, as well as describing the potential risks of using them. Open-source models of a half-face mask, safety goggles, and a face-protecting shield are evaluated, considering production time, material usage, and cost. Estimations have been performed with fused filament fabrication (FFF) and selective laser sintering (SLS) technology, highlighting the material characteristics of polylactic acid (PLA), polyamide, and a two-compound silicone. Spectrophotometry measurements of transparent PMMA samples were performed to determine their functionality as goggles or face mask parts. All the tests were carried out before and after the tetra-acetyl-ethylene-diamine (TAED)-based disinfection process. The results show that the disinfection has no significant effect on the mechanical and structural stability of the used polymers; therefore, 3D-printed PPE is reusable. For each device, recommendations and possible means of development are explained. The files of the modified models are provided. SLS and FFF additive manufacturing technology can be useful tools in PPE development and small-series production, but open-source models must be used with special care.