Prevalencia de cristales de colesterol en granulomas perirradiculares de origen endodóntico / Prevalence of cholesterol crystals in periradicular granulomas of endodontic origin

Resumen Objetivo Comparar dos procedimientos de soldadura convencionales empleando una aleación de Cr-Co, para conectar barras coladas seccionadas a ser fijadas sobre implantes. Materiales y métodos A partir de un modelo maestro que representa un maxilar desdentado con cuatro implantes, se confeccionaron veinte (n=20) probetas seccionadas en tres partes. Se conformaron dos grupos, cada uno con diez (n=10) ejemplares. Una vez acondicionadas, fueron atornilladas al modelo maestro. Su desajuste inicial se analizó utilizando una lupa estereoscópica, con una cámara incorporada y un software. Las partes fueron soldadas empleando un procedimiento diferente para cada grupo. Las correspondientes al Grupo I se invistieron en un block refractario a base de sílico-fosfato. Las del Grupo II se montaron en una estructura metálica Clever Spider. El desajuste fue mensurado y los resultados procesados estadísticamente. El nivel de significación fue establecido en p<0,05. Resultados El Grupo I tuvo un desajuste inicial de 97,30±13,81μm y el Grupo II de 98,53±11,24μm. Luego de la soldadura, el Grupo I registró 98,53±17,17μm, 1,23μm mayor respecto al inicial. En el Grupo II se observó 103,13±17,61μm, 4,60μm por encima del original. Se analizaron mediante prueba t de Student; en ambos casos el resultado fue de p>0,05. Al comparar entre sí los grupos I y II, por medio de la prueba t y de comprobación no paramétrica de Mann-Whitney, se observaron diferencias no significativas, p=0,41 y p=0,38 respectivamente. Conclusiones Bajo las condiciones de este estudio, se observó que los dos métodos de soldadura analizados fueron confiables para unir supraestructurasos metálicas sin que se afecte su ajuste final.

Abstract Aim Compare two conventional welding procedures using a Cr-Co alloy, to connect sectioned cast bars to be fixed on implants. Materials and methods From a master model representing a toothless jaw with four implants, twenty (n=20) specimens sectioned into three parts were made. Two groups were formed, each with ten (n=10) specimens. Once conditioned, they were screwed to the master model. Its initial mismatch was analyzed using a stereoscopic magnifier, with a built-in camera and a software. The parts were welded using a different procedure for each group. Those corresponding to Group I were invested in a refractory block based on silyl-phosphate. Those of Group II were mounted on a Clever Spider metal structure. The mismatch was measured, and the results processed statistically. The level of significance was established at p<0.05. Results Group I had an initial mismatch of 97.30 ±13.81μm, and Group II of 98.53±11.24μm. After welding, Group I registered 98.53±17.17μm, 1.23μm higher than the initial one. In Group II, 103.13±17.61μm was observed, 4.60μm above the original. They were analyzed using Student's t test; in both cases the result was p>0.05. When comparing groups I and II, using the t-test and the Mann-Whitney nonparametric verification, non-significant differences were observed, p=0.41 and p=0.38 respectively. Conclusions Under the conditions of this study, it was observed that the two welding methods analyzed were reliable for joining metallic superstructures without affecting their final fit.

Estudio in vitro del ajuste de supraestructuras pasivadas sobre implantes múltiples / In vitro study of the adjustment of passivated suprastructures on multiple implants

Resumen Objetivo Comparar dos procedimientos de soldadura convencionales empleando una aleación de Cr-Co, para conectar barras coladas seccionadas a ser fijadas sobre implantes. Materiales y métodos A partir de un modelo maestro que representa un maxilar desdentado con cuatro implantes, se confeccionaron veinte (n=20) probetas seccionadas en tres partes. Se conformaron dos grupos, cada uno con diez (n=10) ejemplares. Una vez acondicionadas, fueron atornilladas al modelo maestro. Su desajuste inicial se analizó utilizando una lupa estereoscópica, con una cámara incorporada y un software. Las partes fueron soldadas empleando un procedimiento diferente para cada grupo. Las correspondientes al Grupo I se invistieron en un block refractario a base de sílico-fosfato. Las del Grupo II se montaron en una estructura metálica Clever Spider. El desajuste fue mensurado y los resultados procesados estadísticamente. El nivel de significación fue establecido en p<0,05. Resultados El Grupo I tuvo un desajuste inicial de 97,30±13,81μm y el Grupo II de 98,53±11,24μm. Luego de la soldadura, el Grupo I registró 98,53±17,17μm, 1,23μm mayor respecto al inicial. En el Grupo II se observó 103,13±17,61μm, 4,60μm por encima del original. Se analizaron mediante prueba t de Student; en ambos casos el resultado fue de p>0,05. Al comparar entre sí los grupos I y II, por medio de la prueba t y de comprobación no paramétrica de Mann-Whitney, se observaron diferencias no significativas, p=0,41 y p=0,38 respectivamente. Conclusiones Bajo las condiciones de este estudio, se observó que los dos métodos de soldadura analizados fueron confiables para unir supraestructurasos metálicas sin que se afecte su ajuste final.

Abstract Aim Compare two conventional welding procedures using a Cr-Co alloy, to connect sectioned cast bars to be fixed on implants. Materials and methods From a master model representing a toothless jaw with four implants, twenty (n=20) specimens sectioned into three parts were made. Two groups were formed, each with ten (n=10) specimens. Once conditioned, they were screwed to the master model. Its initial mismatch was analyzed using a stereoscopic magnifier, with a built-in camera and a software. The parts were welded using a different procedure for each group. Those corresponding to Group I were invested in a refractory block based on silyl-phosphate. Those of Group II were mounted on a Clever Spider metal structure. The mismatch was measured, and the results processed statistically. The level of significance was established at p<0.05. Results Group I had an initial mismatch of 97.30 ±13.81μm, and Group II of 98.53±11.24μm. After welding, Group I registered 98.53±17.17μm, 1.23μm higher than the initial one. In Group II, 103.13±17.61μm was observed, 4.60μm above the original. They were analyzed using Student's t test; in both cases the result was p>0.05. When comparing groups I and II, using the t-test and the Mann-Whitney nonparametric verification, non-significant differences were observed, p=0.41 and p=0.38 respectively. Conclusions Under the conditions of this study, it was observed that the two welding methods analyzed were reliable for joining metallic superstructures without affecting their final fit.

Current status and research progress of occupational health monitoring in welding fume operations / 中华劳动卫生职业病杂志

Welding operations are widely present in the manufacturing production process, involving a large number of occupational groups, and are the key occupations where work injuries and occupational diseases occur in China. For different welding processes and welding materials, the content and focus of occupational health monitoring are different. At present, the item of occupational health examination in welding operation is in poor consistency with the on-site exposure of occupational hazard factors, and it is mainly concentrated in the stage of disease development, which can not reflect the early health damage caused by welding dust exposure in time. The emergence of biomarkers of welding dust can make up for this defect. Therefore, it is of great significance to describe the current situation of occupational health monitoring of welding dust and summarize the research progress of related biomarkers for the early prevention of diseases caused by welding dust and the practice of occupational health monitoring.

Comparative analysis on occupational hazards of three welding operations / 中华劳动卫生职业病杂志

Objective: To explore the occupational hazards caused by three kinds of welding operations, and to provide data support for individual protection. Methods: In October 2020, the welding fumes, metal elements and welding arc generated by three welding operations of argon gas shielded welding (JS80 welding wire) , manual welding (ZS60A welding rod) and carbon dioxide shielded welding (907A flux cored wire) were collected and measured in the welding laboratory. The samples were analyze and compare in the laboratory, and the differences of the occupational hazard factors of the three welding operations were judged. Results: The concentration of welding fume produced by carbon dioxide shielded welding, manual welding (ZS60A electrode) , and argon gas shielded welding (JS80 welding wires) were 6.80 mg/m(3), 6.17 mg/m(3), and 3.13 mg/m(3), respectively. The effective irradiance of the welding arc outside the welding mask from high to low is manual welding (ZS60A electrode) , carbon dioxide shielded welding (907A flux-cored welding wire) , and argon shielded welding (JS80 welding wire) , respectively 1 010.7, 740.9, 589.5 μW/cm(2). The long-wave ultraviolet UVA intensity generated by argon shielded welding (JS80 welding wire) is the largest, which is 1 500 μW/cm(2). The content of Mn in the three welding operations is the highest, and JS80 welding wire has the highest Mn content of 128493.2 mg/kg. 907A flux cored wire has the highest Ti content, which is 24355.5mg/kg. The electrode ZS60A has the highest Cu content, which is 24422.12 mg/kg. Conclusion: The intensity of occupational hazards is different in the three kinds of welding operations, so the methods of personal protective equipment, field exposure assessment and health monitoring should be more targeted.

Morphological assessment of vascular anastomoses performed using high frequency electric welding / Evaluación morfológica de anastomosis vasculares realizada mediante soldadura eléctrica de alta frecuencia

SUMMARY: The studies of the properties of vascular structures and tissues during electric welding, in particular direct morphological changes in the blood vessel walls in the areas of welding processes, are of interest. Perforating veins, femoral veins, abdominal aorta, vena cava and porcine perforating veins of the limbs were used in this study. We performed end-to-end electric welding of the aorta, venous end-to-side electric welding, vein end-to-artery side arterial and venous welding, venous end-to-end electric welding, as well as arterial and venous lumen sealing.The results of histological studies showed the formation of a coagulated acellular protein matrix, represented by unorganized denatured protein fibrous structures. In the area of vascular tissue coagulation, lacunes were formed as a result of water evaporation from the biological tissue. In the perifocal area of the welded junction, cell reduction occurred without necrosis or charring. The data obtained confirm the safety of high frequency electric welding of the main vessels and the prospectfor clinical use of the studied techniques.

RESUMEN: Los estudios de las propiedades de las estructuras y tejidos vasculares durante la soldadura eléctrica son relevantes, en particular los cambios morfológicos directos en las paredes de los vasos sanguíneos en las áreas de los procesos de soldadura. En este estudio se utilizaron venas perforantes, venas femorales, parte abdominal de la aorta, vena cava y venas perforantes porcinas de los miembros. Realizamos soldadura eléctrica de extremo a extremo de la parte abdominal de la aorta, soldadura eléctrica de extremo a lado venosa, soldadura arterial y venosa de extremo a arteria del lado venoso, soldadura eléctrica de extremo a extremo venoso, así como lumen arterial y venoso. Los resultados de los estudios histológicos mostraron la formación de una matriz de proteína acelular coagulada, representada por estructuras fibrosas de proteínas desnaturalizadas no organizadas. Se formaron lagunas como resultado de la evaporación del agua del tejido biológico en el área de la coagulación del tejido vascular, En el área perifocal de la unión soldada, la reducción celular ocurrió sin necrosis ni carbonización. Los datos obtenidos confirman la seguridad de la soldadura eléctrica de alta frecuencia de los vasos principales y la perspectiva de uso clínico de estas técnicas.

Finite element method simulating bursting process of multi-chamber flexible package infusion bag / 生物医学工程学杂志

This study aims to overcome the shortcomings such as low efficiency, high cost and difficult to carry out multi-parameter research, which limited the optimization of infusion bag configuration and manufacture technique by experiment method. We put forward a fluid cavity based finite element method, and it could be used to simulate the stress distribution and deformation process of infusion bag under external load. In this paper, numerical models of infusion bag with different sizes was built, and the fluid-solid coupling deformation process was calculated using the fluid cavity method in software ABAQUS subject to the same boundary conditions with the burst test. The peeling strength which was obtained from the peeling adhesion test was used as failure criterion. The calculated resultant force which makes the computed peeling stress reach the peeling strength was compared with experiment data, and the stress distribution was analyzed compared with the rupture process of burst test. The results showed that considering the errors caused by the difference of weak welding and eccentric load, the flow cavity based finite element method can accurately model the stress distribution and deformation process of infusion bag. It could be useful for the optimization of multi chamber infusion bag configuration and manufacture technique, leading to cost reduction and study efficiency improvement.

Results analysis of occupational physical examination for major occupational hazards exposed laborer in 2018 in Guangzhou / 中华劳动卫生职业病杂志

Objective@#To analyze the results of occupational physical examination for major occupational hazard exposed laborer in 2018 in Guangzhou, to provide scientific basis for occupational health supervise.@*Methods@#In January 2019, descriptive epidemiological methods were used as the data sources of the Occupational Disease and Occupational Health Information Surveillance System and the report data of Guangzhou Occupational Health Inspection Agency, collecting 2733 employers from 28 Occupational Health Inspection Organizations in 11 administrative regions of Guangzhou from January to December 2018, as well as the occupational health examination data of 97688 workers exposed to the occupational-disease-risk factors, to analyze the inspection of suspected occupational diseases and contraindications during the period of work of the workers who were monitored for the occupational hazard factors (silicon dust, welding fume, benzene, lead, Ethylene Dichloride, N-hexane, high temperature and hand-transmitted vibration) .@*Results@#Total 128 cases of suspected occupational disease were detected, including 3 suspected silicosis, 8 suspected welder＇s pneumoconiosis, 17 suspected other pneumoconiosis, 10 suspected benzene poisoning, 1 suspected lead poisoning and 89 suspected noise deafness. There were 2061 cases of occupational contraindication, among which 550 cases were contraindication of high temperature, 261 cases were benzene and 1089 cases were noise.@*Conclusion@#The Occupational Health Inspection Institution of this city should continuously monitor the occupational health status of the harmful workers during their work, do a good job of prevention, and strengthen the labor protection.

Effect of welding operations on the health status of workers with low working age / 中华劳动卫生职业病杂志

Objective@#To explore the impact of welding operations on the health status of workers with low working age, and provide a basis for occupational health risk assessment for workers of low working age.@*Methods@#Used the method of cluster sampling to randomly selected workers from an automobile manufacturing plant in Guangzhou as research subjects: 982 workers with welding posts of 1 year ≤working age ≤5 years were welding groups, 707 workers with simple exposure noise of 1 year ≤working age ≤5 years were assembly groups, and 717 workers in pre-job medical examinations were pre-job groups from June 2017 to September 2018. Then conducted occupational health checks on all subjects, investigated and detected the occupational hazards in welding posts and assembly posts.@*Results@#There was no statistical difference between the noise over-standard rate of welding posts' (59.3%, 16/27) and the assembly posts' (47.4%, 9/19) (P>0.05) . The over-standard rate of welding fume, manganese and its inorganic compounds in welding posts was 11.11% (3/27) . The results of occupational health examination showed that the detection rate of disease or abnormal of the welding group was 78.4% (770/982) higher than 70.2% (496/707) in the assembly group and 53.0% (380/717) in the pre-job group (the value of 2 were 14.92 and 122.37, respectively, P<0.05) . The rate of hearing loss of the assembly group and the welding group were 14.7% (104/707) and 19.3% (190/982) , respectively, which was higher than that of the pre-job group (10.5%, 75/717) , and the hearing loss rate gradually increased with the increase of working age (the value of linear-by-linear association were 12.04 and 44.67, respectively, P<0.01) . Compared with the hearing loss rate of each working age of the assembly group, the hearing loss rate of each working age of the welding group was higher, and when the working age was 3 years, the risk of hearing loss in the welding group was 2.70 times that of the assembly group (P<0.01) . The rate of pulmonary dysfunction in the welding group was 19.2% (189/982) higher than that in the pre-job group (12.6%, 90/717) , and it increased with the increase of working age (the value of linear-by-linear association was 15.97, P<0.01) .@*Conclusion@#Welding work seriously damages the health of workers with low working age, increases the hearing loss of workers and the occurrence of pulmonary dysfunction; manganese and its compounds increases noise-induced damage to the hearing system.

Investigation and analysis of 7 cases of acute lung injury caused by a welding operation / 中华劳动卫生职业病杂志

Objective@#Throughing the investigation and analysis of seven cases of acute lung injury caused by a welding operation, the hazards and production pathways of harmful gases such as phosgene and nitrogen oxides are understood, which will serve as a reference for preventing similar events in the future.@*Methods@#Throughing the accident scene environment investigation and clinical case analysis, combined with the laboratory test results, carried on the comprehensive analysis.@*Results@#The accident caused a total of 7 people to suffer from acute lung injury to varying degrees. Three of them were sent to the ICU ward for treatment due to acute respiratory failure. After active treatment, 7 people were discharged from the hospital with obvious relief.@*Conclusion@#Welding is also a kind of profession that causes the high incidence of acute lung injury accidents. It is necessary to strengthen the knowledge training and protection awareness education of welding workers to avoid the occurrence of acute harmful gas poisoning accidents.

An investigation of occupational exposure to welding fume, manganese, and manganese compounds in a large container manufacturing enterprise / 中华劳动卫生职业病杂志

Objective@#To investigate the current status of the occupational hazards of welding fume, manganese, and manganese compounds in the welding environment of a large container manufacturing enterprise, as well as the status of occupational health examination of workers, and to provide a basis for improving the welding environment of this enterprise.@*Methods@#In August 2016, July 2017, and August 2018, convenience sampling was used to perform an on-site occupational hygiene survey of the welding workshop for three consecutive years, and welding fume, manganese and, manganese compounds (counted as manganese dioxide) were measured for their workplace exposure concentrations and exposure levels in workers. A comprehensive analysis was performed for the results of occupational health examination.@*Results@#Welding fume, manganese, and manganese compounds in the welding environment gradually increased from 2016 to 2018 (χ2trend=5.14 and 5.54, P<0.05). The maximum over-standard rate of concentration-short term exposure limit was 43.3% (13/30) for welding fume and 40.0% (12/30) for manganese and its compounds, and the maximum over-standard rate of time-weighted average concentration was 26.7% (8/30) for welding fume and 23.3% (7/30) for manganese and its compounds. Abnormalities were observed in the occupational health examination of welding workers in 2016-2018, among which respiratory system abnormalities (cough, expectoration, and wheezing), nervous system abnormalities (dizziness, fatigue, sleep disorders, amnesia, hyperhidrosis, and palpitations), and electrocardiogram abnormalities (bundle conduction block) had an incidence rate of above 10.0%, and the incidence rate of abnormalities on posterior-anterior X-ray high-kV chest radiograph was close to 8.9% (30/336) .@*Conclusion@#There is severe exposure to welding fume, manganese, and manganese compounds among workers in this enterprise, which cause great hazards to the health of workers. It is necessary to strengthen occupational health management, take measures to improve the welding environment, and enhance occupational disease prevention.

Combined effect of noise and other occupational hazards on hearing impairment and electrocardiograph / 中国职业医学

OBJECTIVE: To explore the combined effect of noise and other occupational hazards on hearing impairment and electrocardiograph(ECG) of workers in automobile manufacturing enterprises. METHODS: A judgment sampling method was used to select 3 434 workers as study subjects from an automobile manufacture enterprise. According to the exposure to different types of occupational hazardous factors, they were divided into noise series group, noise dust group, noise welding dust group, noise benzene series group, noise nitrogen oxide group and control group, with 716, 693, 1 540, 45, 195 and 245 cases in each group, respectively. The subjects were examined with pure-tone hearing test and ECG. RESULTS: The total rate of high frequency hearing loss was 11.2%(385/3 434), and high frequency hearing loss was the main type of hearing loss among workers in each group. The simple high-frequency hearing loss rates of noise group, noise dust group, noise welding dust group, noise benzene series group, noise nitrogen oxide group and the control group were 10.3%, 11.5%, 12.3%, 26.7%, 10.3% and 4.1% respectively, and the rate of total hearing loss were 13.7%, 14.6%, 14.6%, 31.1%, 16.9% and 6.5% respectively. Compared with the control group, the rate of simple high-frequency hearing loss and total hearing loss were higher in the other 5 groups(P<0.005). The rate of high-frequency hearing loss in noise group was lower than that in noise benzene series group(P<0.005). The rate of arrhythmia was 20.9%(717/3 434). Arrhythmia was the main type of ECG abnormality in all groups. The rates of arrhythmia in noise group, noise dust group, noise welding dust group, noise benzene series group, noise nitrogen oxide group and control group were 16.9%, 16.6%, 27.9%, 17.8%, 13.8% and 6.9%, respectively. The rate of arrhythmia in noise welding dust group was higher than that in noise group(P<0.005). CONCLUSION: The combined effect of noise and benzene series increases the risk of high-frequency hearing loss in workers. The combined effect of noise and welding dust increases the risk of arrhythmia in workers.

Vertical and horizontal misfit analysis of 3-unit fdp fabricated with different techniques and cad/cam systems

Abstract The aim of this is was evaluate the vertical and horizontal marginal adaptation of 3-unit fixed partial denture frameworks fabricated using different techniques and CAD/CAM systems. A total of 40 framework specimens were fabricated and divided into four groups as follows: lost-wax casting (G1); lost-wax casting with welding (G2); extraoral optical scanning of models (3S/DWOS) (G3); intraoral optical scanning (Cerec Bluecam/Sirona) (G4). A reference model was used to simulate a fixed partial denture with three elements (with a central pontic). The frameworks of G1 and G2 were cast in nickel-chromium (NiCr) alloy, whereas those of G3 and G4 were milled in zirconia. In all groups, vertical and horizontal marginal adaptation (over-contour and under-contour) was evaluated using a three-dimensional optical microscope (Quick Scope, Mitutoyo). The results showed higher vertical marginal misfit in G1 than in the other groups (p<0.001). Regarding horizontal marginal misfit, higher over-contour values occurred in G3 than in the other groups (p<0.001). G3 did not show under-contour at all, whereas the other groups did not differ from each other in this regard (p>0.05). Within the limitations of this study, it can be concluded that lost-wax casting with welding is a viable alternative to the use of CAD/CAM systems to fabricate frameworks of three-unit FPDs, since the techniques yielded similar vertical misfit values. Extra-oral CAD/CAM systems showed the highest horizontal misfit (over-contour) compared to other groups.

Resumo O objetivo deste estudo foi avaliar a adaptação marginal vertical e horizontal de infraestruturas de prótese fixas de três elementos confeccionadas por diferentes técnicas e diferentes sistemas CAD/CAM. Um total de 40 infraestruturas foram confeccionadas e divididas em quatro grupos: fundição por cera perdida (G1); fundição por cera perdida com ponto de solda (G2); escaneamento óptico extraoral para escaneamento do modelo (3S/DWOS); escaneamento óptico intraoral (Cerec Bluecam/Sirona) (G4). Uma matriz metálica foi utilizada para simular uma prótese fixa de três elementos (com pôntico central). As infraestruturas do G1 e G2 foram fundidas em liga metálica de níquel-cromo (NiCr), enquanto que as infraestruturas de G3 e G4 foram fresadas em zircônia. Todos os grupos foram analisados quanto à adaptação marginal vertical e horizontal (sobrecontorno e subcontorno) em microscópio óptico tridimensional (Quick Scope, Mitutoyo). Os resultados apresentaram maiores valores de desadaptação marginal vertical no G1 comparados aos outros grupos (p<0,001). Em relação a desadaptação marginal horizontal, maiores valores de sobrecontorno foram observado no G3 em comparação com os demais grupos (p<0,001). Não foi observado valores de subcontorno para o G3, enquanto que os demais grupos não apresentaram diferença significante para o subcontorno (p> 0,05). Dentro das limitações do presente estudo, pode-se concluir que a técnica convencional após ponto de solda é uma alternativa viável para confecção de infraestruturas de próteses fixas de três elementos comparado ao uso de sistemas CAD/CAM, uma vez que as técnicas apresentaram valores de adaptação marginal vertical similares. Os sistemas CAD/CAM extraoral apresentou o maior desajuste horizontal (sobrecontorno) em comparação com outros grupos.

Welding strength of NiTi wires

ABSTRACT Objective: To identify the appropriate power level for electric welding of three commercial brands of nickel-titanium (NiTi) wires. Methods: Ninety pairs of 0.018-in and 0.017 × 0.025-in NiTi wires were divided into three groups according to their manufacturers - GI (Orthometric, Marília, Brazil), GII (3M OralCare, St. Paul, CA) and GIII (GAC,York, PA) - and welded by electrical resistance. Each group was divided into subgroups of 5 pairs of wires, in which welding was done with different power levels. In GI and GII, power levels of 2.5, 3, 3.5, 4, 4.5 and 5 were used, while in GIII 2.5, 3, 3.5 and 4 were used (each unit of power of the welding machine representing 500W). The pairs of welded wires underwent a tensile strength test on an universal testing machine until rupture and the maximum forces were recorded. Analysis of variance (ANOVA) and post-hoc tests were conducted to determine which subgroup within each brand group had the greatest resistance to rupture. Results: The 2.5 power exhibited the lowest resistance to rupture in all groups (43.75N for GI, 28.41N for GII and 47.57N for GIII) while the 4.0 power provided the highest resistance in GI and GII (97.90N and 99.61N, respectively), while in GIII (79.28N) the highest resistance was achieved with a 3.5 power welding. Conclusions: The most appropriate power for welding varied for each brand, being 4.0 for Orthometric and 3M, and 3.5 for GAC NiTi wires.

RESUMO Objetivo: identificar a potência mais adequada para solda elétrica em três marcas comerciais de fios de níquel-titânio (NiTi). Métodos: noventa pares de fios ortodônticos de NiTi, de dimensões 0,018" e 0,017" × 0,025'', foram soldados por resistência elétrica e distribuídos em três grupos: GI (Orthometric, Marília, São Paulo, Brasil), GII (3M, São José do Rio Preto, São Paulo, Brasil) e GIII (GAC, Yorque, Pensilvânia, Estados Unidos). Cada grupo foi dividido em subgrupos de cinco pares de fios soldados com diferentes níveis de potência. Nos GI e GII, os fios foram soldados com níveis de potência de 2.5, 3, 3.5, 4, 4.5 e 5; enquanto no GIII as potências utilizadas foram de 2.5, 3, 3.5 e 4. Os pares de fios foram submetidos a um teste de tração até sua ruptura, com registro das forças máximas. Análises de variância (ANOVA) e testes post-hoc foram realizados para determinar qual subgrupo, dentro de cada grupo, obteve a maior força de resistência. Resultados: a potência 2.5 exibiu a menor resistência à ruptura para todos os grupos (43,75 N para o GI; 28,41 N para o GII e 47,57 N para o GIII). A potência 4 mostrou maior resistência à ruptura nos GI e GII (97,90 N e 99,61 N, respectivamente), enquanto no GIII (79,28 N) foi a potência 3.5. Conclusões: os níveis de potência mais adequados variaram para as marcas comerciais, sendo identificados como 4 para Orthometric e 3M, e 3.5 para GAC.

Determinación de metales pesados en humos metálicos presentes en ambientes informales de trabajo dedicados a la soldadura / Determination of heavy metals in metal fumes present in informal work environments dedicated to welding

RESUMEN La industria metalmecánica, en especial los procesos de soldadura, es una de las de mayor actividad económica a escala mundial. La transformación y unión de piezas metálicas se emplean en muchas actividades laborales, por ejemplo, la construcción. La soldadura genera alto grado de riesgo a la salud de los trabajadores debido a la emisión de humos metálicos, los cuales poseen una variada composición y concentración de metales tanto pesados como no pesados. Otros factores de riesgo son el tiempo de exposición y las condiciones higiénicas de los lugares de trabajo, los cuales pueden influenciar para que estos efectos sean agudos o crónicos. Algunos de estos abarcan desde afecciones locales como dolores, fatigas, fiebre, hasta esterilidad y, en caso grave, aumenta el riesgo de padecer de cáncer. Con el fin de establecer el riesgo de exposición a metales, este estudio exploratorio evaluó las concentraciones de arsénico (As), cromo (Cr), manganeso (Mn) y plomo (Pb) en 15 empresas en ambientes dedicadas a la soldadura. Como resultado se hallaron valores elevados de Pb, en 13 lugares justo por debajo del valor límite umbral (TLV) de 0,05 mg Pb/m3 de aire y dos por encima del mismo. Mientras que para el Mn, los valores hallados se encuentran por debajo de su TLV (0,2 mg/m3), y los niveles de As y Cr se encuentran muy por debajo de los permitidos. Aun así, la variedad de metales y sus concentraciones en el aire pueden generar posibles afecciones a la salud a mediano y largo plazo. Por lo anterior, se evidencia un inminente riesgo para la salud de los trabajadores dedicados a la soldadura expuestos por los efectos individuales o combinado de los metales inhalados en sus humos.

Summary Metalworking industry, especially welding processes, is one of the most economically active in the world. Transformation and joining of metal parts are used in many labor activities, for example, construction. Welding generates a high degree of risk to workers' health. Due to emission of metallic fumes, which have a varied composition and concentration of both heavy and non-heavy metals. Other risk factors are exposure time and hygienic conditions of workplace, which may influence whether these effects can be acute or chronic. Some affections could be local conditions such as pain, fatigue, fever, to sterility and in serious cases increases the risk of cancer. In order to establish the risk of exposure to metals, this exploratory study evaluated the concentrations of Arsenic (As), Chromium (Cr), Manganese (Mn) and Lead (Pb) in 15 companies in environments dedicated to welding. As a result, elevated Pb values were found at 13 sites just below the threshold limit value (TLV) of 0.05 mg Pb/ m3 of air and 2 above it. Mn values found correspond to below their TLV (0.2 mg/ m3). Levels of As and Cr are well below those allowed. Even so, the variety of metals and their concentrations in the air can generate possible health conditions in the medium and long term. For all of the above reasons, there is an imminent risk to the health of welding workers because of individual or combined Metals effects inhaled in fumes.

A Feasibility study of hepate ctomy with high-frequency electric welding technique / 重庆医学

Objective To explore the safety and reliability of soft tissue high-frequency welding technique for partial hepatectomy in animals and provide evidence for its clinical application.Methods With high-frequency welding technique,partial liver tissues were removed from 10 SD rats.Intraoperative blood loss was recorded.Liver function was detected and wound healing was observed by dissecting the rats one week after operation.Results There was no hemorrhage during the liver resection.The liver function returned to normal after one week and the liver incision recovered well.Conclusion The use of soft tissue high-frequency welding technique for partial partial hepatectomy is basically free of bleeding and is safe and reliable.

Comparative study of NERC-300 high-frequency electric welding device in rat partial hepatectomy / 重庆医学

Objective To contrastively study the effects of NERC-300 high frequency welding device and ultrasonic scalpel in rat partial hepatectomy.Methods Forty-eight rats were divided into the experimental group and control group(n=24).The experimental group applied NERC-300 high frequency welding instrument for conducting partial hepatectomy,while the control group used ultrasonic scalpel.The survival rate,operation time,bleeding volume,working temperature,extent of hepatic thermal damage and change of liver function on 1,3,7 d were compared between the two groups.Results The liver function recovery on 3 d in the experimental group was superior to the control group (P＜0.05).The intra-operative working temperature in the experimental group was lower than that in the control group(P＜0.05).The thermal damage range in the experimental group was lower than that in the control group(P＜0.05).The survival rate,operation time,bleeding volume and liver function change on 1,7 d had no statistical differences between the two groups(P＞0.05).Conclusion NERC-300 high frequency welding device is safe and effective for partial hepatectomy in rat.

Comparative analysis of ceramic flexural strength in co-cr and ni-cr alloys joined by TIG welding and conventional brazing

Aims: The purpose of the present study was to evaluate the flexural strength of specimens made of nickel-chromium(Ni-Cr) and cobalt-chromium (Co-Cr) alloys and joined by tungsten inert gas (TIG) welding and conventional brazing. Ni­Cr and Co­Cr base metal specimens (n = 40, each) were cast and welded by TIG or brazing. The specimens were divided into six groups (2 base metals, four welded specimens). Ceramic systems were applied to the central part of all the specimens. A three-point bending test with a velocity of 0.5 mm/m was performed on the specimens up to the point of the first ceramic bond failure by measuring the flexural strength. Data were analyzed using two-way ANOVA and Bonferroni's tests. Conventional welding showed the lowest flexural strength results for both alloys, while the TIG weld and the control group presented with varying bond strengths for the alloys studied. We concluded that TIG welding was superior to the conventional welding method for both Ni­Cr and Co­Cr alloys with regard to the flexural strength of the ceramic (AU)

Avaliação da resistência flexural em diferentes métodos de soldagem / Evaluation of flexural resistance in different welding methods

O objetivo do presente estudo foi avaliar três diferentes tipos de soldagem: Chama Direta a maçarico (convencional\brasagem), Solda Mista representada por fixação de dois pontos (Solda Elétrica Fixator - Kernit, Brasil), e completada com solda convencional, e o método de Solda a Laser (Soldadora Desktop - Sisma LM 500, Itália). Dois implantes plataforma Bränemark 4.1 mm (Neodent, Curitiba/Brasil) foram fixados em uma matriz de alumínio para simular uma ponte fixa implanto-suportada de três elementos. Os espécimes foram obtidos a partir de um bloco de cera CAD-CAM (Ceramill-Amammgirrbarch). Trinta e duas UCLAs hexágono externo foram fresadas e posteriormente unidas a uma barra pré-fabricada em cera com 2,5mm. Os corpos de prova foram fundidos em liga de cobalto-cromo simulando uma prótese fixa de três elementos. Esses espécimes foram divididos aleatoriamente e separados em três grupos (n=6): grupo A (solda chama direta), grupo B (solda mista), grupo C (solda laser). Os espécimes foram seccionados ao meio e unidos com resina acrílica para simular uma soldagem em prótese fixa. Os corpos foram soldados e tratados de acordo com a proposição. Após a soldagem os corpos de prova foram usinados e levados ao teste de flexão na técnica de três pontos. Os dados foram submetidos aos testes estatísticos de Tukey. Os cálculos estatísticos foram conduzidos adotando-se o nível de significância de 5% (α = 0,05). Houve diferença estatisticamente significativa entre os grupos soldados. Os resultados demonstraram valores mais elevados nos grupos A e B, solda convencional e solda mista, e menor valor no grupo C, solda a laser. No entanto, considerando a metodologia aplicada, a solda a laser mostrou uma menor resistência flexural comparada à soldagem convencional e mista, e a fixação prévia de solda elétrica com complemento de solda convencional (solda mista) não alterou a resistência flexural, produzindo resultado semelhante à solda convencional

The objective of this study was to evaluate three different types of welding, blowtorch; (conventional/brazing), welder Joint; represented by securing two points (Arc Welding Fixator - Kernit, Brazil), and supplemented with conventional welding), and Laser welding method (welder Desktop - Sisma LM 500, Italy). Two implants Bränemark 4.1 mm platform (Neodent, Curitiba/Brazil) were fixed in an aluminum matrix. Specimens were obtained from a CAD-CAM wax block (Ceramill - Amammgirrbarch) were milled 32 UCLAs (external hexagon, Bränemark platform), and subsequently joined to a prefabricated bar also wax 2.5 mm, the specimens were casted in cobalt-chromium alloy. These specimens were randomly divided and separated into 3 groups: group A (welding direct flame), Group B (mixed welding), C (laser welding), with 6 samples for each group. The specimens of each group were cut in half to simulate a fixed prosthesis in welding, and put together with acrylic resin. The bodies were welded and treated according to the statement. After the specimens were welded, they were manually grinded and submitted to the 3 points bending test technique. Data were subjected to statistical tests of Tukey. Statistical calculations were performed adopting the significance level of 5% (α = 0.05), using SPSS 20 (SPSS Inc., Chicago, IL, USA). There were differences between the soldered groups. The data showed the highest values obtained in groups A and B, conventional welding and soldering joint, and lower in group C, the laser welding. However, within the applied methodology, the laser welding showed a lower flexural strength compared to conventional and mixed welding, and that the advance fixing of electric welding, conventional welding complement (mixed welding), does not change its flexural strength, producing results similar to conventional welding

Cancer Risks among Welders and Occasional Welders in a National Population-Based Cohort Study: Canadian Census Health and Environmental Cohort

BACKGROUND: Welders are exposed to many known and suspected carcinogens. An excess lung cancer risk among welders is well established, but whether this is attributable to welding fumes is unclear. Excess risks of other cancers have been suggested, but not established. We investigated welding cancer risks in the population-based Canadian Census Health and Environmental Cohort. METHODS: Among 1.1 million male workers, 12,845 welders were identified using Standard Occupational Classification codes and followed through retrospective linkage of 1991 Canadian Long Form Census and Canadian Cancer Registry (1992–2010) records. Hazard ratios (HRs) were calculated using Cox proportional hazards models based on estimated risks of lung cancer, mesothelioma, and nasal, brain, stomach, kidney, and bladder cancers, and ocular melanoma. Lung cancer histological subtypes and risks by industry group and for occasional welders were examined. Some analyses restricted comparisons to blue-collar workers to minimize effects of potential confounders. RESULTS: Among welders, elevated risks were observed for lung cancer [HR: 1.16, 95% confidence interval (CI): 1.03–1.31], mesothelioma (HR: 1.78, 95% CI: 1.01–3.18), bladder cancer (HR: 1.40, 95% CI: 1.15–1.70), and kidney cancer (HR: 1.30, 95% CI: 1.01–1.67). When restricted to blue-collar workers, lung cancer and mesothelioma risks were attenuated, while bladder and kidney cancer risks increased. CONCLUSION: Excess risks of lung cancer and mesothelioma may be partly attributable to factors including smoking and asbestos. Welding-specific exposures may increase bladder and kidney cancer risks, and particular sources of exposure should be investigated. Studies that are able to disentangle welding effects from smoking and asbestos exposure are needed.

Effect of Preheating on Microstructure and Tensile Properties of Friction Stir Welded AA7075 Aluminium Alloy Joints

ABSTRACT The high strength AA7075 aluminum alloy is commonly used in the aerospace components due to its exclusive mechanical properties like lightweight and high strength. This alloy cannot be welded by fusion welding techniques due to solidification cracking which severely degrade the mechanical properties of the joint. In contrast, through friction stir welding (FSW) process solidification relate defects can be eliminated. Anyhow, the strength of friction stir welded joint is influenced by process parameters and tool parameters. These parameters govern the heat input, metal flow, microstructure evolution and mechanical properties of the weld. In normal welding condition, (without preheating) heat is generated by friction force which is produced between tool and workpiece. In this paper an added heat input through preheating the metal before weld. This preheating temperature effects on microstructure, microhardness and tensile properties of the joints were investigated. From this study the following conclusions are derived. Sufficient heat input should be given to obtain defect free and quality joint. The results showed that, preheating the base metal to 100 °C prior to welding improved the tensile strength and joint efficiency compared to the joints made without preheating.