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The use of 316L stainless steel as an orthopedic bone plate material or as a substrate for coating implies the need to study its properties in a biological medium simulating human body environment. Therefore, the aim of this work is to investigate the microstructural characteristics, corrosion resistance, and mechanical properties of 316L stainless steel in the culture medium and then to check the cytotoxicity of the stainless steel in the presence of human mesenchymal stem cells. The characteristics of the stainless steel were evaluated by studying the microstructure of the samples in untreated state and after soaking in minimum essential medium‐alpha (α‐MEM) for 7 days. The results indicated the formation on the surface of the 316L stainless steel of goethite and deposits composed of Ca and P with porous and amorphous structures, which led to the decrease in the elastic modulus and the hardness of the soaked stainless steel as shown by nanoindentation test. Nevertheless, the hardness and the elastic modulus of the steel after soaking were influenced only for a surface depth of approximately 0.1% of the thickness of the sample. The potentiodynamic polarization curves exhibited that the corrosion resistance of the soaked stainless steel was reduced because of the higher passive current density. However, it should be noticed that the breakdown potential of the steel after soaking was slightly higher, leading to a wider range of passivation. In addition, microscopy examination showed the mesenchymal stem cell adhesion on the materials after 9 days of culture. [ABSTRACT FROM AUTHOR]

During the decommissioning of nuclear facilities, the tritiated materials must be removed. These operations generate tritiated steel and cement particles that could be accidentally inhaled by workers. Thus, the consequences of human exposure by inhalation to these particles in terms of radiotoxicology were investigated. Their cyto-genotoxicity was studied using two human lung models: the BEAS-2B cell line and the 3D MucilAirTM model. Exposures of the BEAS-2B cell line to particles (2 and 24 h) did not induce significant cytotoxicity. Nevertheless, DNA damage occurred upon exposure to tritiated and non-tritiated particles, as observed by alkaline comet assay. Tritiated particles only induced cytostasis; however, both induced a significant increase in centromere negative micronuclei. Particles were also assessed for their effects on epithelial integrity and metabolic activity using the MucilAirTM model in a 14-day kinetic mode. No effect was noted. Tritium transfer through the epithelium was observed without intracellular accumulation. Overall, tritiated and non-tritiated stainless steel and cement particles were associated with moderate toxicity. However, these particles induce DNA lesions and chromosome breakage to which tritium seems to contribute. These data should help in a better management of the risk related to the inhalation of these types of particles. [ABSTRACT FROM AUTHOR]

Here, a prototypical metallic nanoglass is proposed as a new alloy for balloon expandable stents. Traditionally, the stainless steel SS 316L alloy has been used as a preferred material for this application due to its proper combination of mechanical properties, corrosion resistance, and biocompatibility. Recently, metallic glasses (MGs) have been considered as promising materials for biodevice applications. MGs often display outstanding mechanical properties superior to those of conventional metallic alloys and overcome some of the weaknesses of SS 316L, such as radiopacity, stainless steel allergy, and thrombosis‐induced restenosis. However, commonly used monolithic MGs, which have an amorphous homogeneous microstructure, suffer from lack of ductility that is necessary for deployment of balloon expandable stents. In contrast, nanoglasses, that is, amorphous alloys with heterogeneous microstructure, exhibit enhanced ductility which makes them promising materials for balloon expandable stents. We evaluate the feasibility of a prototypical Zr64Cu36 nanoglass with a grain size of 5 nm for balloon expandable stents by performing finite element method modeling of the stent deployment process in a coronary artery. We consider the BX‐Velocity stent design and the nanoglass mechanical properties calculated from atomistic simulations. The results suggest that nanoglasses are suitable materials for balloon expandable stent applications. © 2019 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 108B:73–79, 2020. [ABSTRACT FROM AUTHOR]

This study investigated the prevalence of bacteraemia on removal of fixed appliances. Venous blood samples were taken before and after debonding and debanding for 30 patients (mean age 17 years 8 months) who had worn fixed appliances for an average of 19 months. Before removal of the fixed appliances, bacteraemia was detected in one of the 30 subjects (3%) and in four subjects (13%) following removal of their fixed appliances. The 95 per cent confidence intervals for the prevalence of post- debanding bacteraemia were 3.8 and 30.7 per cent. No significant relationship was detected between the mean plaque scores (t = -0.65, P = 0.52) or the mean gingival scores (t = 0.75, P = 0.46) and the occurrence of bacteraemia. The prevalence of bacteraemia detected following debanding in this study is considerably lower than reported for dental procedures traditionally covered by antibiotic prophylaxis guidelines. [ABSTRACT FROM AUTHOR]

The aim of the present study was to investigate slot deformation and the equivalent torque capacity of polycarbonate brackets with and without a metal slot in comparison with those of a metal bracket. For this purpose, the expansion characteristics and, in a further investigation, the labial crown torque of an upper central incisor, were measured in a simulated intra oral clinical situation, using the orthodontic measuring and simulation system (OMSS). Three types of bracket with a 0.018 inch slot were tested: polycarbonate Brillant® without a metal slot, Elegance® with a metal slot and the metal bracket, Mini-Mono®. For testing purposes the brackets were torqued with 0.016 x 0.022 inch (0.41 x 0.56 mm) and 0.018 x 0.022 inch (0.46 x 0.56 mm) ideal stainless steel archwires. In the activating experiments, significantly higher torque losses and lower torquing moments were registered with both rectangular archwires with the polycarbonate brackets than with the metal bracket. In the simulation tests, significantly higher torquing moments were registered with the metal bracket than with the polycarbonate brackets. The values for the Elegance® bracket were between those of the Mini-Mono® and Brillant® brackets. The OMSS model approximates the clinical situation, with the torque loss being notably higher than in the in vitro activating experiments. This is due to the adjacent teeth giving the archwire additional play. In addition, the torquing process may twist the archwire, resulting in subsidiary forces. On the basis of the present results, all three brackets can be recommended for torquing. However, in view of the high torque losses, the torques programmed in the straightwire technique must be seen as questionable. Data should be provided by the manufacturer on the bending to be expected in polycarbonate brackets, which has to be offset by additional torque, or the bracket torque should be omitted from the technical specifications. [ABSTRACT FROM AUTHOR]

There have been a number of studies regarding the toxicity of orthodontic archwires, but little is known concerning the mechanism of their toxicity. This investigation used murine cortical cell cultures to examine the in vitro neurotoxicity of commonly used orthodontic metallic archwire alloys. The materials examined included 0,016 inch nickel-titanium (NiTi), copper-nickel-titanium, titanium-molybdenum, Elgiloy, and stainless steel archwire alloys. Standard sized samples of each material were placed on tissue culture inserts suspended above the cell cultures. Neuronal death was determined using the lactate dehydrogenase release assay 24 hours after exposure to the archwires. The results indicated that NiTi, copper-nickel-titanium and titanium molybdenum alloys were not neurotoxic, while stainless steel and Elgiloy were significantly toxic. Washing the archwires for 7 days in a saline solution did not alter the toxicity. However, the free radical scavenger, trolox, blocked the toxicity of both stainless steel and Elgiloy, indicating that the death was free radical mediated. The caspase inhibitor, Z VAI-Ala-Asp fluoromethylketone (zVAD FMK), blocked the toxicity of stainless steel, but not Elgiloy, suggesting that stainless steel induced apoptosis. Further evidence that stainless steel induced apoptosis was provided by propidium staining which showed nuclear chromatin condensation and fragmentation into discrete spherical or irregular shapes, characteristic of apoptosis. The specific metal responsible for the toxicity was not determined; the metals common to each of the toxic archwires were nickel, iron, and chromium. [ABSTRACT FROM AUTHOR]

Mechanical axiography was performed on 49 (37 female, 12 male) patients prior to orthodontic treatment, after removal of the fixed appliance, and at the end of retention. Twenty-five subjects (mean age 12.8 years) underwent orthodontic treatment without premolar extractions (group 1) and 24 subjects (mean age 13.5 years) with premolar extractions (group 2). The axiographic tracings of the protrusive movements were analysed using a digitizer and specially designed software. A statistically significant increase (P< 0.05) in the values for horizontal condylar inclination (HCl) was found for both groups over the entire observation period. Group 1 showed a higher increase (P < 0.05) between the beginning of treatment and removal of the brackets, and group 2 between bracket removal and the end of retention. At the end of retention, a similar increase in HCl values was found for both groups. Over the observation period, the frequency of pathological axiographic findings decreased, which seems to be a positive effect of orthodontic treatment. [ABSTRACT FROM AUTHOR]