RESUMEN
PURPOSE: To compare the influence of two metallic implants in the diagnosis of periprosthetic infection using 99m technetium-labeled ceftizoxime. METHODS: Twenty rats were randomly divided into four groups, which received sterile and contaminated titanium and stainless steel implants. After 3 weeks, scintilographic images were obtained using a gamma chamber. Radioactivity counts were obtained for the region of interest (ROI) on the operated and non-operated paws. RESULTS: Groups A, B, and C showed homogenous distribution of the radiopharmaceutical. Hyper uptake was observed in the operated paw from group D. The ROI target count was higher in the two groups with stainless steel implants. Among the control groups, the count was higher in the stainless steel group. Furthermore, among the contaminated groups, the uptake was higher in the stainless steel group, with a significant difference. The target: non-target ratio was significantly lower in the control and contaminated groups with both titanium and stainless steel, but the comparison between control groups and contaminated groups was only significant in the former. The cpm/g observed after a decay of 48h showed statistically significant differences between groups. CONCLUSION: Different biomaterials used in implants have an influence on the results of scintigraphy with 99mTc-CFT.
Asunto(s)
Ceftizoxima/análogos & derivados , Compuestos de Organotecnecio , Infecciones Relacionadas con Prótesis/diagnóstico por imagen , Radiofármacos , Acero Inoxidable/efectos de la radiación , Titanio/efectos de la radiación , Animales , Materiales Biocompatibles/química , Infecciones Relacionadas con Prótesis/microbiología , Radiactividad , Cintigrafía , Distribución Aleatoria , Ratas Wistar , Valores de Referencia , Reproducibilidad de los Resultados , Acero Inoxidable/química , Factores de Tiempo , Titanio/químicaRESUMEN
Abstract Purpose: To compare the influence of two metallic implants in the diagnosis of periprosthetic infection using 99m technetium-labeled ceftizoxime. Methods: Twenty rats were randomly divided into four groups, which received sterile and contaminated titanium and stainless steel implants. After 3 weeks, scintilographic images were obtained using a gamma chamber. Radioactivity counts were obtained for the region of interest (ROI) on the operated and non-operated paws. Results: Groups A, B, and C showed homogenous distribution of the radiopharmaceutical. Hyper uptake was observed in the operated paw from group D. The ROI target count was higher in the two groups with stainless steel implants. Among the control groups, the count was higher in the stainless steel group. Furthermore, among the contaminated groups, the uptake was higher in the stainless steel group, with a significant difference. The target: non-target ratio was significantly lower in the control and contaminated groups with both titanium and stainless steel, but the comparison between control groups and contaminated groups was only significant in the former. The cpm/g observed after a decay of 48h showed statistically significant differences between groups. Conclusion: Different biomaterials used in implants have an influence on the results of scintigraphy with 99mTc-CFT.
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Animales , Acero Inoxidable/efectos de la radiación , Titanio/efectos de la radiación , Ceftizoxima/análogos & derivados , Compuestos de Organotecnecio , Infecciones Relacionadas con Prótesis/diagnóstico por imagen , Radiofármacos , Radiactividad , Valores de Referencia , Acero Inoxidable/química , Factores de Tiempo , Titanio/química , Materiales Biocompatibles/química , Distribución Aleatoria , Cintigrafía , Reproducibilidad de los Resultados , Infecciones Relacionadas con Prótesis/microbiología , Ratas WistarRESUMEN
BACKGROUND/OBJECTIVES: This study investigated the biomechanical properties and bone-implant intersurface response of machined and laser surface-treated stainless steel (SS) mini-screw implants (MSIs). MATERIAL AND METHODS: Forty-eight 1.3mm in diameter and 6mm long SS MSIs were divided into two groups. The control (machined surface) group received no surface treatment; the laser-treated group received Nd-YAG laser surface treatment. Half in each group was used for examining surface roughness (Sa and Sq), surface texture, and facture resistance. The remaining MSIs were placed in the maxilla of six skeletally mature male beagle dogs in a randomized split-mouth design. A pair with the same surface treatment was placed on the same side and immediately loaded with 200 g nickel-titanium coil springs for 8 weeks. After killing, the bone-implant contact (BIC) for each MSI was calculated using micro computed tomography. Analysis of variance model and two-sample t test were used for statistical analysis with a significance level of P <0.05. RESULTS: The mean values of Sa and Sq were significantly higher in the laser-treated group compared with the machined group (P <0.05). There were no significant differences in fracture resistance and BIC between the two groups. LIMITATION: animal study CONCLUSIONS/IMPLICATIONS: Laser treatment increased surface roughness without compromising fracture resistance. Despite increasing surface roughness, laser treatment did not improve BIC. Overall, it appears that medical grade SS has the potential to be substituted for titanium alloy MSIs.
Asunto(s)
Tornillos Óseos , Interfase Hueso-Implante/anatomía & histología , Aleaciones Dentales/efectos de la radiación , Grabado Dental/métodos , Láseres de Estado Sólido , Métodos de Anclaje en Ortodoncia/instrumentación , Acero Inoxidable/efectos de la radiación , Animales , Interfase Hueso-Implante/diagnóstico por imagen , Aleaciones Dentales/química , Grabado Dental/instrumentación , Perros , Procesamiento de Imagen Asistido por Computador/métodos , Imagenología Tridimensional/métodos , Masculino , Maxilar/cirugía , Níquel/química , Alambres para Ortodoncia , Distribución Aleatoria , Acero Inoxidable/química , Estrés Mecánico , Propiedades de Superficie , Titanio/química , Torque , Microtomografía por Rayos XRESUMEN
RATIONALE AND OBJECTIVES: Neonates are at increased risk for cold stress and hypothermia in cool environments. An infant transport mattress (ITM) is commonly used to increase neonate temperature during transport and has been used during CT scanning. This study determined the impact of an ITM on radiation dose and image artifacts during CT scanning. MATERIALS AND METHODS: CT images from a single clinical patient scanned with an ITM were reviewed, and observations of image artifacts were recorded. A phantom was scanned with and without the ITM while varying tube-current modulation, reconstruction method, slice thickness, metal reduction algorithm, tube voltage, and tube current. The effects of the ITM on computed tomography dose index (CTDIvol), mean Hounsfield unit (HU), and HU standard deviation were recorded. RESULTS: The clinical patient scan demonstrated significantly decreased mean HU and increased HU standard deviation. In the phantom, the ITM increased CTDIvol 27% and induced an artifact that decreased the mean HU by 3.5 HU and increased HU standard deviation by 4.6 HU. Angular tube-current modulation, strong iterative reconstruction, thick slices, metal artifact reduction, and high mA reduced the artifact. CONCLUSIONS: Using ITM during CT scanning is not recommended given the relatively brief scanning time, increased dose, and induced image artifacts. Based on our results, several acquisition parameters may be altered to mitigate the image artifact if an ITM is required during scanning.
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Lechos , Movimiento y Levantamiento de Pacientes/métodos , Dosis de Radiación , Intensificación de Imagen Radiográfica/métodos , Tomografía Computarizada por Rayos X/métodos , Algoritmos , Artefactos , Diseño de Equipo , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Recién Nacido , Masculino , Fantasmas de Imagen , Radiografía Abdominal/métodos , Estudios Retrospectivos , Acero Inoxidable/efectos de la radiaciónRESUMEN
Prevention of implant loosening and infection is crucial to orthopedic and dental surgeries. In this work, the surface of stainless steel (SS) was modified by silver-sourced plasma immersion ion implantation (Ag-PIII). Metallic silver nanoparticles with various diameters and distributions were fabricated on the SS surfaces after treatment with Ag-PIII for 0.5 and 1.5 h, respectively. The osteogenic activity and antimicrobial properties of SS before and after Ag-PIII treatment were evaluated using in vitro and in vivo tests. The results demonstrated that Ag-PIII treatment not only promoted the antibacterial activity of SS but also enhanced the osteogenic differentiation of human bone marrow stromal cells.
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Fenómenos Fisiológicos Bacterianos/efectos de los fármacos , Células Madre Mesenquimatosas/citología , Nanopartículas del Metal/administración & dosificación , Osteoblastos/citología , Plata/farmacología , Acero Inoxidable/química , Antiinfecciosos/administración & dosificación , Antiinfecciosos/química , Diferenciación Celular/efectos de los fármacos , Diferenciación Celular/fisiología , Supervivencia Celular/efectos de los fármacos , Células Cultivadas , Iones Pesados , Humanos , Ensayo de Materiales , Células Madre Mesenquimatosas/efectos de los fármacos , Nanopartículas del Metal/química , Osteoblastos/efectos de los fármacos , Osteogénesis/efectos de los fármacos , Osteogénesis/fisiología , Gases em Plasma/química , Plata/química , Acero Inoxidable/efectos de la radiaciónRESUMEN
Iron chromium oxide microspheres were generated by pulsed laser irradiation on the surface of two commercial samples of stainless steel at room temperature. An Ytterbium pulsed fiber laser was used for this purpose. Raman spectroscopy was used for the characterization of the microspheres, whose size was found to be about 0.2-1.7 µm, as revealed by SEM analysis. The laser irradiation on the surface of the stainless steel modified the composition of the microspheres generated, affecting the concentration of the main elemental components when laser power was increased. Furthermore, the peak ratio of the main bands in the Raman spectra has been associated to the concentration percentage of the main components of the samples, as revealed by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. These experiments showed that it is possible to generate iron chromium oxide microspheres on stainless steel by laser irradiation and that the concentration percentage of their main components is associated with the laser power applied.
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Compuestos de Cromo/química , Hierro/química , Rayos Láser , Microesferas , Espectrometría Raman , Acero Inoxidable/efectos de la radiación , Microscopía Electrónica de Rastreo , Espectrometría por Rayos X , Factores de TiempoRESUMEN
A signal processing methodology is proposed in this paper for effective reconstruction of ultrasonic signals in coarse grained high scattering austenitic stainless steel. The proposed methodology is comprised of the Ensemble Empirical Mode Decomposition (EEMD) processing of ultrasonic signals and application of signal minimisation algorithm on selected Intrinsic Mode Functions (IMFs) obtained by EEMD. The methodology is applied to ultrasonic signals obtained from austenitic stainless steel specimens of different grain size, with and without defects. The influence of probe frequency and data length of a signal on EEMD decomposition is also investigated. For a particular sampling rate and probe frequency, the same range of IMFs can be used to reconstruct the ultrasonic signal, irrespective of the grain size in the range of 30-210 µm investigated in this study. This methodology is successfully employed for detection of defects in a 50mm thick coarse grain austenitic stainless steel specimens. Signal to noise ratio improvement of better than 15 dB is observed for the ultrasonic signal obtained from a 25 mm deep flat bottom hole in 200 µm grain size specimen. For ultrasonic signals obtained from defects at different depths, a minimum of 7 dB extra enhancement in SNR is achieved as compared to the sum of selected IMF approach. The application of minimisation algorithm with EEMD processed signal in the proposed methodology proves to be effective for adaptive signal reconstruction with improved signal to noise ratio. This methodology was further employed for successful imaging of defects in a B-scan.
Asunto(s)
Ensayo de Materiales/métodos , Procesamiento de Señales Asistido por Computador , Acero Inoxidable/química , Acero Inoxidable/efectos de la radiación , Ultrasonido/métodos , Algoritmos , Simulación por Computador , Modelos Teóricos , Tamaño de la PartículaRESUMEN
The influence of sunlight of varying intensity on the performance of UNS S30400 stainless steel (SS) was explored under conditions of natural biofilm development in coastal seawater. In a series of tests performed outdoors under an opaque roof, a range of shades were fashioned to impart varied amounts of diurnal light. These were an ambient level where the underwater illumination was ~ 5% of full sunlight, two intermediate ranges of lighting with ~ 2.5% and ~ 1% of the daylight, and a condition of full darkness. In comparison with the dark, increments of sunlight rendered the SS progressively less aggressive as cathodes in galvanic couples with UNS C70600 alloy. Likewise, welded SS with pre-initiated localized corrosion sites exhibited substantially lower rates of propagation with light. Thus, biofilms and sunlight affected cathodic kinetics in opposite ways. Surface analytical tests showed that the accumulation of manganese (Mn) within the biofilms was small relative to reports from waters of lower salinity. These results not only reveal that extremely low amounts of sunlight are adequate to offset the microbial effect, but also highlight the lack of convincing evidence for Mn cycling as a potent mechanism for enhanced cathodic kinetics in full-strength seawater.
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Fenómenos Fisiológicos Bacterianos , Biopelículas/crecimiento & desarrollo , Manganeso/metabolismo , Agua de Mar/química , Acero Inoxidable/efectos de la radiación , Luz Solar , Corrosión , Oscuridad , Electrodos , India , CinéticaRESUMEN
OBJECTIVES: To evaluate the heating and magnetic field interactions of fixed orthodontic appliances with different wires and ligaments in a 3-T MRI environment and to estimate the safety of these orthodontic materials. METHODS: 40 non-carious extracted human maxillary teeth were embedded in polyvinyl chloride boxes, and orthodontic brackets were bonded. Nickel-titanium and stainless steel arch wires, and elastic and stainless steel ligaments were used to obtain four experimental groups in total. Specimens were evaluated at 3 T for radiofrequency heating and magnetic field interactions. Radiofrequency heating was evaluated by placing specimens in a cylindrical plastic container filled with isotonic solution and measuring changes in temperature after T1 weighted axial sequencing and after completion of all sequences. Translational attraction and torque values of specimens were also evaluated. One-way ANOVA test was used to compare continuous variables of temperature change. Significance was set at p < 0.05. RESULTS: None of the groups exhibited excessive heating (highest temperature change: <3.04 °C), with the maximum increase in temperature observed at the end of the T1 weighted axial sequence. Magnetic field interactions changed depending on the material used. Although the brackets presented minor interactions that would not cause movement in situ, nickel-titanium and stainless steel wires presented great interactions that may pose a risk for the patient. CONCLUSIONS: The temperature changes of the specimens were considered to be within acceptable ranges. With regard to magnetic field interactions, brackets can be considered "MR safe"; however, it would be safe to replace the wires before MRI.
Asunto(s)
Imagen por Resonancia Magnética/métodos , Soportes Ortodóncicos , Alambres para Ortodoncia , Aleaciones Dentales/efectos de la radiación , Elastómeros/efectos de la radiación , Calor , Humanos , Soluciones Isotónicas , Campos Magnéticos , Ensayo de Materiales , Níquel/efectos de la radiación , Ondas de Radio , Seguridad , Acero Inoxidable/efectos de la radiación , Temperatura , Termómetros/clasificación , Titanio/efectos de la radiación , TorqueRESUMEN
This study demonstrated meso/micro/nano-ultraprecision machining through electrochemical reactions using intermittent DC pulses. The experiment focused on two machining methods: (1) pulse electrochemical polishing (PECP) of stainless steel, and (2) pulse electrochemical nano-patterning (PECNP) on a silicon (Si) surface, using atomic force microscopy (AFM) for fabrication. The dissolution reaction at the stainless steel surface following PECP produced a very clean, smooth workpiece. The advantages of the PECP process included improvements in corrosion resistance, deburring of the sample surface, and removal of hydrogen from the stainless steel surface as verified by time-of-flight secondary-ion mass spectrometry (TOF-SIMS). In PECNP, the electrochemical reaction generated within water molecules produced nanoscale oxide textures on a Si surface. Scanning probe microscopy (SPM) was used to evaluate nanoscale-pattern processing on a Si wafer surface produced by AFM-PECNP For both processes using pulse electrochemical reactions, three-dimensional (3-D) measurements and AFM were used to investigate the changes on the machined surfaces. Preliminary results indicated the potential for advancing surface polishing techniques and localized micro/nano-texturing technology using PECP and PECNP processes.
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Cristalización/métodos , Galvanoplastia/métodos , Nanoestructuras/química , Nanoestructuras/ultraestructura , Silicio/química , Acero Inoxidable/química , Campos Electromagnéticos , Sustancias Macromoleculares/química , Sustancias Macromoleculares/efectos de la radiación , Ensayo de Materiales , Conformación Molecular/efectos de la radiación , Nanoestructuras/efectos de la radiación , Tamaño de la Partícula , Silicio/efectos de la radiación , Acero Inoxidable/efectos de la radiación , Propiedades de Superficie/efectos de la radiaciónRESUMEN
PURPOSE: A technique whereby the practitioner could improve the esthetic appearance of anterior stainless steel crowns (SSC) could provide a cost-effective alternative to more expensive commercially available preveneered SSCs, which may not be uniformly available. The purpose of this study was to evaluate the effects of ultraviolet (UV) irradiation of the metal crown surface on the shear bond strength of composite resin adhered to stainless steel crowns. METHODS: Seventy extracted anterior bovine teeth randomly divided into 2 groups (n=35/group), were restored with primary maxillary left central incisor SSCs. Surface roughening with a green stone was performed on the labial surfaces, and the crowns of the experimental group were exposed to UV irradiation for 80 minutes. All samples were treated with metal-composite adhesive, followed by composite opaquer. Standardized composite blocks were bonded on the treated surfaces, and the shear bond strength was tested at 1 mm/minute. The values were recorded in MPa and statistically analyzed. RESULTS: The mean value of shear bond strength was significantly higher for the experimental group (19.7 ± 4.3 MPa) than the control group (16.3 ± 4.5 MPa). CONCLUSION: Ultraviolet irradiation of primary tooth stainless steel crowns significantly increased the shear bond strength of composite resin adhered to the facial surface.
Asunto(s)
Resinas Compuestas/efectos de la radiación , Coronas , Aleaciones Dentales/efectos de la radiación , Recubrimiento Dental Adhesivo , Materiales Dentales/efectos de la radiación , Acero Inoxidable/efectos de la radiación , Rayos Ultravioleta , Adhesividad , Animales , Bovinos , Cementación/métodos , Resinas Compuestas/química , Aleaciones Dentales/química , Materiales Dentales/química , Análisis del Estrés Dental/instrumentación , Estética Dental , Cementos de Ionómero Vítreo/química , Incisivo/patología , Óxido de Magnesio/química , Cemento de Policarboxilato/química , Distribución Aleatoria , Resistencia al Corte , Acero Inoxidable/química , Estrés Mecánico , Propiedades de Superficie , Factores de Tiempo , Óxido de Zinc/químicaRESUMEN
Cell-material surface interaction plays a critical role in osseointegration of prosthetic implants used in orthopedic surgeries and dentistry. Different technical approaches exist to improve surface properties of such implants either by coating or by modification of their topography. Femtosecond laser treatment was used in this study to generate microspotted lines separated by 75, 125, or 175µm wide nanostructured interlines on stainless steel (316L) plates. The hydrophobicity and carbon content of the metallic surface were improved simultaneously through this method. In vitro testing of the laser treated plates revealed a significant improvement in adhesion of human endothelial cells and human bone marrow mesenchymal stem cells (hBM MSCs), the cells involved in microvessel and bone formation, respectively, and a significant decrease in fibroblast adhesion, which is implicated in osteolysis and aseptic loosening of prostheses. The hBM MSCs showed an increased bone formation rate on the laser treated plates under osteogenic conditions; the highest mineral deposition was obtained on the surface with 125µm interline distance (292±18mg/cm(2) vs. 228±43mg/cm(2) on untreated surface). Further in vivo testing of these laser treated surfaces in the native prosthetic implant niche would give a real insight into their effectiveness in improving osseointegration and their potential use in clinical applications.
Asunto(s)
Osteoblastos/efectos de los fármacos , Acero Inoxidable/efectos de la radiación , Calcificación Fisiológica , Carbono/química , Adhesión Celular/efectos de los fármacos , Diferenciación Celular , Proliferación Celular/efectos de los fármacos , Células Cultivadas , Fibroblastos/citología , Fibroblastos/efectos de los fármacos , Células Endoteliales de la Vena Umbilical Humana/citología , Células Endoteliales de la Vena Umbilical Humana/efectos de los fármacos , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Rayos Láser , Ensayo de Materiales , Células Madre Mesenquimatosas/citología , Células Madre Mesenquimatosas/efectos de los fármacos , Osteoblastos/citología , Prótesis e Implantes , Acero Inoxidable/farmacología , Propiedades de Superficie/efectos de la radiaciónRESUMEN
In replicate series of experiments in natural seawater, one in full darkness and the other in a 1:1 diurnal cycle with as little as ~5% of natural solar illumination, sunlight promoted calcareous deposition on cathodic stainless steel surfaces. As exemplified by scanning electron microscopy, the deposit that formed under the natural diurnal cycle, in the presence of photosynthetic biofilms, was composed of finer calcareous crystals that provided more compact and more uniform surface coverage than the one formed in the dark. The light-enhanced deposit also possessed better scale properties, as suggested by X-ray analysis and electrochemical measurements. Sunlight enhancement of calcareous deposition looked all the more conspicuous when day and night regimes were examined independently. These results not only bear important implications for cathodic protection in marine waters, but also provide an intriguing analogy to coral reef calcification.
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Carbonato de Calcio/química , Agua de Mar , Acero Inoxidable/efectos de la radiación , Luz Solar , Biopelículas , Cristalización , Cristalografía por Rayos X , Oscuridad , Diatomeas/química , Diatomeas/fisiología , Técnicas Electroquímicas , Electrodos , India , Magnesio/química , Biología Marina/métodos , Microscopía Electrónica de Rastreo , Fotosíntesis , Acero Inoxidable/química , Propiedades de Superficie , TemperaturaRESUMEN
The purpose of the present study is to explore topographical patterns produced with femtosecond laser pulses as a means of controlling the behaviour of living human cells (U2OS) on stainless steel surfaces and on negative plastic imprints (polycarbonate). The results show that the patterns on both types of material strongly affect cell behaviour and are particularly powerful in controlling cell spreading/elongation, localization and orientation. Analysis by fluorescence and scanning electron microscopy shows that on periodic 1D grating structures, cells and cell nuclei are highly elongated and aligned, whereas on periodic 2D grid structures, cell spreading and shape is affected. The results also show that the density and morphology of the cells can be affected. This was observed particularly on pseudo-periodic, coral-like structures which clearly inhibited cell growth. The results suggest that these patterns could be used in a variety of applications among the fields of clinical research and implant design, as well as in diagnosis and in cell and drug research. Furthermore, this article highlights the noteworthy aspects and the unique strengths of the technique and proposes directions for further research.
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Separación Celular/métodos , Rayos Láser , Impresión Molecular/métodos , Osteosarcoma/patología , Osteosarcoma/fisiopatología , Cemento de Policarboxilato/química , Acero Inoxidable/química , Recuento de Células , Línea Celular Tumoral , Proliferación Celular , Tamaño de la Célula , Células Cultivadas , Humanos , Ensayo de Materiales , Cemento de Policarboxilato/efectos de la radiación , Acero Inoxidable/efectos de la radiación , Propiedades de SuperficieRESUMEN
We observe sample morphology changes in real time (24 kHz) during and between percussion drilling pulses by integrating a low-coherence microscope into a laser micromachining platform. Nonuniform cut speed and sidewall evolution in stainless steel are observed to strongly depend on assist gas. Interpulse morphology relaxation such as hole refill is directly imaged, showing dramatic differences in the material removal process dependent on pulse duration/peak power (micros/0.1 kW, ps/20 MW) and material (steel, lead zirconate titanate PZT). Blind hole depth precision is improved by over 1 order of magnitude using in situ feedback from the imaging system.
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Rayos Láser , Ensayo de Materiales/métodos , Microscopía/métodos , Acero Inoxidable/química , Acero Inoxidable/efectos de la radiación , Tomografía de Coherencia Óptica/métodos , Propiedades de SuperficieRESUMEN
Control rods are activated by neutron reactions into the reactor. The activation is produced mainly in stainless steel and its impurities. The dose produced by this activity is not important inside the reactor, but it has to be taken into account when the rod is withdrawn from the reactor. Activation reactions produced have been modelled by the MCNP5 code based on the Monte Carlo method. The code gives the number of reactions that can be converted into activity.
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Modelos Estadísticos , Reactores Nucleares/instrumentación , Radiometría/métodos , Acero Inoxidable/efectos de la radiación , Simulación por Computador , Diseño de Equipo , Análisis de Falla de Equipo , Método de Montecarlo , Neutrones , Dosis de Radiación , Dispersión de RadiaciónRESUMEN
The changes of the stainless-steel electrode surface morphology occurring due to dissolution of the anode under the action of electric pulses which are commonly utilized in cell electromanipulation procedures, have been studied by using atomic force microscopy. The surface of the polished electrode was rather smooth--the average roughness was 13-17 nm and the total roughness 140-180 nm. After the treatment of the chamber filled with 154 mM NaCl solution to a series of short (about 20 mus), high-voltage (4 kV) pulses, the roughness of the surface of the anode has increased, depending on the total amount of the electric charge that has passed through the unit area of the electrode, and exceeded 400 nm for the dissolution charge of 0.24 A s/cm(2). No changes of the cathode surface were detected. Well-defined peaks with the width of 1-2 mum and the height of over 400 nm have appeared. These peaks create local enhancements of the electric field at the interface between the solution and the electrode surface which can lead to the non-homogeneity treatment of cells by electric pulses and can facilitate the occurrence of the electrical breakdown of the liquid samples.
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Electrodos , Electrólisis/instrumentación , Campos Electromagnéticos , Electroporación/instrumentación , Acero Inoxidable/química , Acero Inoxidable/efectos de la radiación , Relación Dosis-Respuesta en la Radiación , Electrólisis/métodos , Electroporación/métodos , Diseño de Equipo , Análisis de Falla de Equipo , Microscopía de Fuerza Atómica , Dosis de Radiación , Propiedades de SuperficieRESUMEN
OBJECTIVE: To test the effects of curing time and light intensity on the shear bond strength of adhesive composites for stainless-steel orthodontic brackets. MATERIALS AND METHODS: An argon laser at four different power settings (100, 150, 200, and 250 mW) and four different exposure times (5, 10, 15, and 20 seconds) was used to bond adhesive-precoated (APC) stainless-steel incisor brackets to the facial surfaces of 154 bovine incisors. The shear bond strength of each specimen in 16 randomly divided groups was randomly tested to failure using an Instron universal testing machine. Each mode of failure was described using the adhesive remnant index (ARI). RESULTS: The ARI scoring system showed that the location of bond failure did not differ significantly in relation to exposure time (P = .40). However, the location of bond failure was significantly different in relation to light power (P = .03). CONCLUSIONS: A short exposure time and a low power setting produce shear bond strengths equivalent to those produced by longer exposure times and higher power settings.
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Recubrimiento Dental Adhesivo , Rayos Láser , Soportes Ortodóncicos , Grabado Ácido Dental , Adhesividad , Animales , Argón , Bovinos , Resinas Compuestas/química , Resinas Compuestas/efectos de la radiación , Análisis del Estrés Dental/instrumentación , Ensayo de Materiales , Microscopía Electrónica de Rastreo , Dosis de Radiación , Distribución Aleatoria , Cementos de Resina/química , Cementos de Resina/efectos de la radiación , Resistencia al Corte , Acero Inoxidable/química , Acero Inoxidable/efectos de la radiación , Estrés Mecánico , Propiedades de Superficie , Factores de TiempoRESUMEN
The surface properties of a biomaterial play an essential role in protein adsorption, which in turn determines the cellular response to the adsorbed surface. In order to obtain a surface that would yield favourable protein adsorption for successful cellular response, the surface properties of a biograde stainless steel were modified by CO2 laser treatment. An investigation of the CO2-laser-modified surface properties and the effects thereof on the adsorption of human serum albumin (no-cell adhesive) and human plasma fibronectin (cell adhesive) was conducted. It was found that the thickness of the adsorbed fibronectin layer increased with increasing CO2 laser power density, while the thickness of the adsorbed albumin layer decreased with increasing CO2 laser power density. The surface roughness and wettability characteristics contributed to the observed changes in protein adsorption. The wettability characteristics of the biograde stainless steel were found to be the predominant mechanism governing the observed change in protein adsorption. Since the wettability characteristics of the biograde stainless steel can be modified in an efficient and controllable way with the CO2 laser, it is believed that this work presents a demonstrable alternative to the techniques currently available for enhancing the biocompatibility of biograde stainless steels.
Asunto(s)
Materiales Biocompatibles Revestidos/química , Fibronectinas/química , Albúmina Sérica/química , Acero Inoxidable/química , Adsorción , Materiales Biocompatibles Revestidos/análisis , Fibronectinas/análisis , Humanos , Rayos Láser , Ensayo de Materiales , Unión Proteica , Albúmina Sérica/análisis , Acero Inoxidable/análisis , Acero Inoxidable/efectos de la radiación , Propiedades de SuperficieRESUMEN
OBJECTIVE: To investigate the effect of laser shock peening on the fatigue life and surface characteristics of 3.5-mm-diameter cortical bone screws. SAMPLE POPULATION: 32 stainless steel, 3.5-mm-diameter cortical bone screws. PROCEDURE: Screws were randomly assigned to an untreated control group or 2 power-density treatment groups, 6 gigawatts (GW)/cm2 and 8.5 GW/cm2, for laser shock peening. Number of cycles to failure and findings on scanning electron microscopy-assisted morphometric evaluation, including the mode of failure, surface debris, surface damage, and thread deformation, were compared between control and treated screws. RESULTS: The 6 GW/cm2 treated screws had a significant (11%) improvement in fatigue life, compared with untreated control screws. The 8.5 GW/cm2 treated screws had a significant (20%) decrease in fatigue life, compared with control screws. A mild but significant increase in thread deformation was evident in all treated screws, compared with control screws. The 8.5 GW/cm2 treated screws had significantly more surface irregularities (elevations and pits), compared with control or 6 GW/cm2 treated screws. CONCLUSION AND CLINICAL RELEVANCE: A modest positive increase in fatigue strength was produced by this design of laser shock peening on the midshaft of cortical bone screws. High laser shock peening power densities were detrimental, decreasing screw fatigue strength probably resulting from structural damage. Greater fatigue life of cortical bone screws can be generated with laser shock peening and could reduce screw breakage as a cause of implant failure; however, future studies will be necessary to address biocompatibility, alternative cleaning techniques, alterations in screw strength and pullout characteristics, and effects on susceptibility to corrosion.