Determination of cobalt and tungsten in human urine by inductively coupled plasma mass spectrometry / 中华劳动卫生职业病杂志

Objective: To establish a inductively coupled plasma mass spectrometry method for the determination of trace cobalt and tungsten in human urine. Methods: The authors used 1% nitric acid solution as diluent in October-December 2021, the sample dilution factor and internal standard element were optimized by single factor rotation experiment, and the difference between the working curve and the standard curve was compared. Results: The method uses working curve to determine cobalt and tungsten in urine, the linear range of this method was 0.0~10.0 μg/L, the correlation coefficient was 0.999 9, the detection limits respectively were 0.005 μg/L (cobalt) and 0.09 μg/L (tungsten), the recoveries of samples respectively were 87.0%~100.2% (cobalt) and 89.4%~104.8% (tungsten), the relative standard deviations respectively were 0.4%~4.4% (cobalt) and 0.6%~3.8% (tungsten) . Conclusion: A simple and rapid method for determination of cobalt and tungsten in urine has been established. This method has the advantages of simple operation, high sensitivity, low detection limit and good stability. It is suitable for determination of cobalt and tungsten in urine of all kinds of people.

Ct Of Quartz-Tungsten-Halogen And Light-Emitting Diode-Curing Units On The Depth Of Cure And Flexural Strength Of A Nanohybrid Composite Resin: An In Vitro Study

Introduction: Over the years, the demand for esthetic dentistry has grown dramatically and there has been a rapid developmentof new adhesive restorative materials with nanotechnology that can restore the color and characteristics of natural tooth. Topolymerize these materials, light-curing dental materials extensively used are quartz-tungsten-halogen (QTH) and light-emittingdiode (LED)-curing units. Literature search revealed that depth of cure and flexural strength are the most important propertiesof composite resin materials, relevant to the clinical technique of incremental packing and curing.Purpose: The objectives of the present study were to evaluate and compare the depth of cure and flexural strength of ananohybrid composite resin.Materials and Methods: Two light-curing units were selected for this study: QTH (Bonart, Unicorn) and LED (Ivoclar Vivadent,Bluephase® N). The depth of cure was evaluated with scraping technique using digital caliper and flexural strength was evaluatedusing universal testing machine with a crosshead speed of 1 mm/min.Results: Descriptive statistics was employed to measure the mean and standard deviation of the depth of cure and flexuralstrength. Unpaired “t”-test was used to compare the study variables. Statistical significance was fixed at ≤0.05 and LED-curingunit showed significantly greater depth of cure and flexural strength when compared to QTH curing unit.Conclusion: Curing effectiveness of resin composite is dependent on the light-curing unit.

Determination of tungsten and insoluble compounds in the air of workplace by ICP-OES / 中华劳动卫生职业病杂志

Objective@#To establish the method for determination of tungsten and insoluble compounds in the air of workplace by inductively coupled plasma optical emission spectrometry (ICP-OES) .@*Methods@#The tungsten and insoluble compounds were digested by microwave digestion apparatus using nitric acid and hydrofluoric acid, detected by ICP-OES.@*Results@#The linearity of tungsten and insoluble compounds (as tungsten) were good at the range of 0.16-100.0 μg/ml, the minimum quantitation concentration was 0.11 mg/m3, the recovery was ranged from 81.9%-97.1%, the RSD of intra-and inter-batch precision were 0.5%-2.5% and 1.2%-4.4%, respectively.@*Conclusion@#The determination method meet the requirement of analysis and apply to the determination of tungsten and insoluble compounds in the air of workplace.

Electrochemical Dopamine Sensor Based on Multi-Walled Carbon Nanotubes-Tungsten Oxide Nanocomposites / 分析化学

Multi-walled carbon nanotubes-tungsten oxide (MWCNTs-WOx) nanocomposites were fabricated on glassy carbon electrode (GCE) through a simple electrodeposition method,in which WOx were fabricated on MWCNTs. The morphology and constitution were characterized by field emission scanning electron microscopy(SEM) and X-ray photoelectron spectroscopy(XPS). Electrochemical characterization of modified electrode was done by electrochemical impedance spectroscopy (EIS). The cyclic voltammogram (CV)method was adopted to investigate the electrochemical behavior of dopamine (DA) on MWCNTs-WOx-modified glassy carbon electrode, and a new detection method for DA was developed by differential pulse voltammetry (DPV). The results showed that MWCNTs-WOx nanocomposites had obvious electrocatalytic effect on DA in phosphate buffer solution (pH=6.5). Under the optimized experimental conditions, the DA peak current demonstrated a good linear relationship with concentration in the range of 0.05-1.00 mmol/L, and the detection limit was 17 μmol/L(S/N=3). Effects of different experimental parameters on the response current of the modified electrode were investigated,and it was found that the prepared electrochemical sensor displayed good reproducibility,high selectivity and strong anti-interference ability. UA did not interfere with the detection of DA. A new electrochemical method for the quantitative determination of DA was established and successfully applied to the determination of dopamine hydrochloride injection samples.

Determination of tungsten and cobalt in the air of workplace by ICP-OES / 中华劳动卫生职业病杂志

Objective@#To establish the inductively coupled plasma optical emission spectrometry (ICP-OES) method for determination of cobalt and tungsten in the air of workplace.@*Methods@#The cobalt and tungsten were collected by filter membrane and then digested by nitric acid, inductively coupled plasma optical emission spectrometry (ICP-OES) was used for the detection of cobalt and tungsten.@*Results@#The linearity of tungsten was good at the range of 0.01-1 000 μg/ml with a correlation coefficient of 0.999 9, the LOD and LOQ were 0.006 7 μg/ml and 0.022 μg/ml, respectively. The recovery was ranged from 98%-101%, the RSD of intra-and inter-batch precision were 1.1%-3.0% and 2.1%-3.8%, respectively. The linearity of cobalt was good at the range of 0.01-100 μg/ml with a correlation coefficient of 0.999 9, the LOD and LOQ were 0.001 2 μg/ml and 0.044 μg/ml, respectively. The recovery was ranged from 95%-97%, the RSD of intra-and inter-batch precision were 1.1%-2.4% and 1.1%-2.9%, respectively. The sampling efficiency of tungsten and cobalt were higher than 94%.@*Conclusion@#The linear range, sensitivity and precision of the method was suitable for the detection of tungsten and cobalt in the air of workplace.

Study on the establishment of HMLD model and the expression of KL-6/TGF-beta in rat / 中华劳动卫生职业病杂志

Objective@#To establish an animal model of hard metal lung disease (HMLD) in rats, and to screen the indications for diagnosis of HMLD.@*Methods@#The rats were randomly divided into 5 groups, each group included 8 rats: saline group, pure cobalt group, pure tungsten carbide group, silica group and hard metal (HM) group. 10 mg subjects were administered in each group by using the pulmonary endotracheal tube. After 8 week, the lung CT scan and lung tissue pathology were observed, the serum and bronchoalveolar lavage fluid (BALF) were collected for KL-6, TGF-beta1 and TGF-beta2.@*Results@#The lung tissue structure of HM group was destroyed, a large number of nuclear giant cells and epithelial like cells appeared in the stroma, and uncommon CT scan images appeared in the lung. KL-6, TGF-beta1, TGF-beta2 expression in each group was not the same, the difference was statistically significant (P<0.05) . The expression of KL-6 and TGF-beta1 in serum was not identical in all the groups, the difference was statistically significant (P<0.05) . The expression of TGF-beta2 had no significant difference between the groups (P>0.05) .@*Conclusion@#Rats can be successfully established HMLD model, rats in vivo lung CT scan images appear abnormal, which are provided with assistant diagnostic value for HMLD. The expression of KL-6 and TGF-beta2 in serum and BALF on HMLD rats are not highly specific, and TGF-beta1 has reference value in the rat HMLD auxiliary diagnosis.

CT imaging of tungsten oxide nanoparticles (WO3-x@BSA) / 中国医学影像技术

Objective To investigate the value of CT taking WO3-x@BSA nanoparticles as contrast agents.Methods CT values of WO3-x@BSA nanoparticles and the iohexol contrast agents at different concentrations were measured.When the tube voltage was the same,CT values of the tungsten at different concentrations were measured,and the relationship curve of CT values and the concentrations,the tube voltages and CT values were plotted.The animal models were performed to observe CT imaging in vivo and in vitro.WO3-x@BSA nanoparticles were injected through tail vein and intraperitoneally of rats in vivo.In fresh pig liver,WO3-x@BSA nanoparticles were injected by portal vein.Results CT value of the tungsten was higher than the iodine at the same concentration,and the imaging signal of the tungsten was more significant than the iodine.The amount of WO3-x@BSA was less than the iohexol contrast agent reaching to the same CT value.WO3-x@BSA nanoparticles could reach the organs of various tissues in SD rats through different ways and showing the high density sig nal.WO3-x@BSA nanoparticles were also injected into the fresh in-vitro liver of pig,and could diffuse and distribute along with the blood vessels with good CT imaging.Conclusion As a novel CT contrast agent,WO3-x@BSA nanoparticles can be used to get good CT imaging.

CT imaging of tungsten oxide nanoparticles (WO3-x@BSA) / 中国医学影像技术

Objective To investigate the value of CT taking WO3-x@BSA nanoparticles as contrast agents.Methods CT values of WO3-x@BSA nanoparticles and the iohexol contrast agents at different concentrations were measured.When the tube voltage was the same,CT values of the tungsten at different concentrations were measured,and the relationship curve of CT values and the concentrations,the tube voltages and CT values were plotted.The animal models were performed to observe CT imaging in vivo and in vitro.WO3-x@BSA nanoparticles were injected through tail vein and intraperitoneally of rats in vivo.In fresh pig liver,WO3-x@BSA nanoparticles were injected by portal vein.Results CT value of the tungsten was higher than the iodine at the same concentration,and the imaging signal of the tungsten was more significant than the iodine.The amount of WO3-x@BSA was less than the iohexol contrast agent reaching to the same CT value.WO3-x@BSA nanoparticles could reach the organs of various tissues in SD rats through different ways and showing the high density sig nal.WO3-x@BSA nanoparticles were also injected into the fresh in-vitro liver of pig,and could diffuse and distribute along with the blood vessels with good CT imaging.Conclusion As a novel CT contrast agent,WO3-x@BSA nanoparticles can be used to get good CT imaging.

Hard metal lung disease: a case series / Doença pulmonar por metal duro: uma série de casos

ABSTRACT Objective: To describe diagnostic and treatment aspects of hard metal lung disease (HMLD) and to review the current literature on the topic. Methods: This was a retrospective study based on the medical records of patients treated at the Occupational Respiratory Diseases Clinic of the Instituto do Coração, in the city of São Paulo, Brazil, between 2010 and 2013. Results: Of 320 patients treated during the study period, 5 (1.56%) were diagnosed with HMLD. All of those 5 patients were male (mean age, 42.0 ± 13.6 years; mean duration of exposure to hard metals, 11.4 ± 8.0 years). Occupational histories were taken, after which the patients underwent clinical evaluation, chest HRCT, pulmonary function tests, bronchoscopy, BAL, and lung biopsy. Restrictive lung disease was found in all subjects. The most common chest HRCT finding was ground glass opacities (in 80%). In 4 patients, BALF revealed multinucleated giant cells. In 3 patients, lung biopsy revealed giant cell interstitial pneumonia. One patient was diagnosed with desquamative interstitial pneumonia associated with cellular bronchiolitis, and another was diagnosed with a hypersensitivity pneumonitis pattern. All patients were withdrawn from exposure and treated with corticosteroid. Clinical improvement occurred in 2 patients, whereas the disease progressed in 3. Conclusions: Although HMLD is a rare entity, it should always be included in the differential diagnosis of respiratory dysfunction in workers with a high occupational risk of exposure to hard metal particles. A relevant history (clinical and occupational) accompanied by chest HRCT and BAL findings suggestive of the disease might be sufficient for the diagnosis.

RESUMO Objetivo: Descrever aspectos relacionados ao diagnóstico e tratamento de pacientes com doença pulmonar por metal duro (DPMD) e realizar uma revisão da literatura. Métodos: Estudo retrospectivo dos prontuários médicos de pacientes atendidos no Serviço de Doenças Respiratórias Ocupacionais do Instituto do Coração, localizado na cidade de São Paulo, entre 2010 e 2013. Resultados: Entre 320 pacientes atendidos no período do estudo, 5 (1,56%) foram diagnosticados com DPMD. Todos os pacientes eram do sexo masculino, com média de idade de 42,0 ± 13,6 anos e média de tempo de exposição a metal duro de 11,4 ± 8,0 anos. Os pacientes foram submetidos a avaliação clinica, história ocupacional, TCAR de tórax, prova de função pulmonar, broncoscopia com LBA e biópsia pulmonar. Todos apresentaram distúrbio ventilatório restritivo. O achado de imagem à TCAR de tórax mais frequente foi de opacidades em vidro fosco (em 80%). Em 4 pacientes, o LBA revelou presença de células gigantes multinucleadas. Em 3, foi diagnosticada pneumonia intersticial por células gigantes na biópsia pulmonar. Houve o diagnóstico de pneumonia intersticial descamativa associada à bronquiolite celular em 1 paciente e de pneumonite de hipersensibilidade em 1. Todos foram afastados da exposição e tratados com corticoide. Houve melhora em 2 pacientes e progressão da doença em 3. Conclusões: Apesar de ser uma entidade rara, a DPMD deve ser sempre considerada em trabalhadores com risco ocupacional elevado de exposição a metais duros. A história clínica e ocupacional associada a achados em TCAR de tórax e LBA sugestivos da doença podem ser suficientes para o diagnóstico.

The Risk Evaluation of Tungsten Oxide Nanoparticles in Cultured Rat Liver Cells for Its Safe Applications in Nanotechnology

Tungsten (VI) oxide (WO3) nanoparticles (NPs) are used for many industrial purposes in everyday life. However, their effects on human health have not been sufficiently evaluated. Therefore, the present study was designed to investigate the toxicity potentials of various concentrations (0 to 1000 ppm) of WO3 NPs (<100 nm particle size) in cultured primary rat hepatocytes. The results of cell viability assay showed that the higher concentrations of dispersed WO3 NPs (300, 500 and 1000 ppm) caused significant (p<0.05) decreases of cell viability. Also, dose dependent negative alterations were observed in oxidative status and antioxidant capacity levels after the application of WO3 in cultured rat primary hepatocytes. The results of genotoxicity tests revealed that these NPs did not cause significant increases of micronucleated hepatocytes (MNHEPs) but increased 8-oxo-2-deoxyguanosine (8-OH-dG) levels as compared to the control culture.

A survey on light intensity outputs of QTH, cabled and cordless LED light curing units

Light intensity output is one of the determinants for adequate curing of visible light-cured materials. The aim of this survey was to evaluate the light intensity outputs (LIOs) of light curing units (LCUs) in dental clinics of Hospital Universiti Sains Malaysia (HUSM) and School of Dental Sciences, Universiti Sains Malaysia (USM). The respective LIOs of all functioning Quartz Tungsten Halogen (QTH) and Light Emitting Diode (LED) LCUs were tested using two light radiometers. For cordless LED LCUs, the testing procedure was done in situ and after being fully charged. Statistical analysis using Kruskal Wallis and Wilcoxon signed ranks tests were performed to compare the LIOs between groups and between the LIOs of in situ and post-charged cordless LED LCUs, respectively. The level of significance was set at 0.05 (p<0.05). The results revealed that 72.72%, 42.47% and 92% of QTH, cabled LED and cordless LED LCUs exhibited acceptable LIOs, respectively. Data analysis using Kruskal Wallis test showed a statistically significant difference between groups (p<0.05). The intergroup comparisons using multiple Mann Whitney test with Bonferroni correction revealed a significant difference between the LIOs of cordless LED and both QTH and cabled LED (p<0.017). The difference between the LIOs of in situ and post charged cordless LED LCUs was also significant (p<0.05). In conclusion, both QTH and cordless LED LCUs performed better in term of LIOs than cabled LED LCUs. Periodic testing of LCUs is essential to ensure optimal performance.

Influence of radiopaque fillers on physicochemical properties of a model epoxy resin-based root canal sealer

Objective: To verify the influence of radiopaque fillers on an epoxy resin-based sealer. Material and Methods: Experimental sealers were formulated by adding 20%, 40%, 60%, 80%, 100% and 120% of calcium tungstate, ytterbium trifluoride or barium sulphate by weight to an epoxy-resin-base. Setting time, flow, film thickness, radiopacity, sorption, solubility, pH and push-out bond strength were evaluated. Results: The setting time ranged from 373 to 612.66 min, the flow varied from 13.81±0.49 to 22.49±0.37 mm, and the film thickness ranged from 16.67±5.77 to 33.33±11.54 µm. The lowest pH was 5.47±0.53, and the highest was 6.99±0.03. Radiopacity varied from 0.38±0.04 to 2.57±0.21 mmAl and increased with the amount of filler. Calcium tungstate sealers had a higher sorption and solubility than other sealers. There was no significant difference in the push-out bond strength among the fillers at the 120% concentration. CONCLUSION: The inorganic fillers evaluated and their concentrations affect the physicochemical properties of an epoxy resin-based root canal sealer. .

The experiment study of several resin-removal methods on enamel surface / 重庆医学

Objective To observe the effect of several residual adhesive methods on the enamel surface ,and conduct lab evalua-tion .Methods Sixty premolars extracted because of orthodontic treatment .And all the teeth were randomly divided into 3 groups . Group 1:tungsten carbide burs + silicon particles ;Group 2 :ultrasonic scaling + silicon particles ;Group 3:silicon particles ,each with 20 premolars .After underwent several methods ,the surface roughness differences ,operation time were determined and ob-served with the scanning electron microscope .And the result was statistically analyzed .Results There were significant differences in the surface roughness and operation time among the three groups (P<0 .05) ,The scanning electron microscope after polishing showed that the teeth surface had different degrees of injury ,the silica particles group had less superficial scratch .Conclusion The tungsten carbide burs and ultrasonic instrument for debonding before the silica particles had less superficial scratch .

Time Saving Method In Curing Light Cure Composite While Orthodontic Bracket Placement.

The placement of brackets precisely in clinical situations cured by light cured techniques is time consuming. This special technique describes an innovative idea of reducing the curing time and saving the clinical hours for placement of brackets.

Influência de diferentes métodos de limpeza sobre a eficiência decorte e as características morfológicas de fresas Carbide / Influence of different cleaning methods on the cutting efficiency and morphological characteristics of Carbide burs

Introdução: Atualmente, existem muitas dúvidas em relação aos métodos de limpeza de fresas, o que estimula o estudo desses métodos visando maior eficiência e menor prejuízo desses instrumentos rotatórios. Objetivo: Avaliar a influência de métodos de limpeza sobre a eficiência de corte e sobre as características morfológicas de fresas de açoinoxidável de carbeto de tungstênio (carbide). Material e método: Trinta fresas foram divididas em cinco grupos (n = 6), de acordo com o método de limpeza: L1- escova de aço; L2- escova de nylon; L3- ultrassom + água destilada; L4- ultrassom + solução desincrustante; L5- nenhum método de limpeza (controle). As fresas foram utilizadas para o corte de esmalte dental bovino durante seis períodos de 12 minutos cada. Após cada período, as fresas eram limpas (exceto L5) seguindo o protocolo estabelecido para cada grupo. A eficiência de corte foi determinada pelo método da perda de massa e as características morfológicas, por meio de análise fotomicrográfica. Resultado: As médias da quantidade de desgaste após 72 minutos de uso foram: L1 = 0,3558 g; L2 = 0,4275 g; L3 = 0,4652 g; L4 = 0,4396 g, e L5 = 0,4854 g. Houve diferença significante para o tempo de uso (p < 0,001) e o método de limpeza (p < 0,001). O grupo L1 apresentou pior desempenho. Independentemente do grupo experimental, a análise morfológica revelou alterações nas lâminas de corte a partir de 12 minutos, sendo o grupo L1 o mais afetado. Conclusão: O método mais prejudicial à eficiência de corte e que mais alterou as características morfológicas das fresas carbide foi a limpeza com escova de aço.

Introduction: Currently, there are many questions regarding the cleaning methods seeking greater efficiency and less loss of burs. Aim: the aim of this study was to evaluate the influence of cleaning methods on the cutting efficiency and morphological characteristics of stainless steel burs tungsten carbide (carbide). Materials and method: Thirty burs were divided into five groups (n = 5) according with the cleaning method: L1- steel brush, L2- nylon brush, L3- ultrasound + distilled water, L4- ultrasound + descaling solution and L5- no cleaning method (control). Theburs were used for the cutting of bovine enamel during six periods of 12 minutes each. After each period, the burs were cleaned (except L5) following the protocol established for each group. The cutting efficiency was determined by mass loss and morphological characteristics. Result: The average amount of wear after 72 minutes of use were L1 = 0.3558 g; L2 = 0.4275 g; L3 = 0.4652 g; L4 = 0.4396 g e L5 = 0.4854 g; significant differences in the time of use (p < 0.001) and cleaning method (p < 0.001). The L1 group showed the worst performance. Regardless of theexperimental group, morphological analysis revealed alterations in the cutting blades soon after the first 12 minutes, being L1 the most affected group. Conclusion: The cleaning with wire brush was the most damaging method to the cutting efficiency and to the morphology of carbide burs.

Wear of Rotary Instruments: A Pilot Study

The aim of this study was to assess the wear of tungsten carbide burs and round rotary diamond instruments through measurements of rake angle and visual observations respectively under a f ield emission scanning electron microscope. Sixty short and long head pear-shaped tungsten carbide burs and 18 round rotary diamond instruments that had been used to complete 5 and > 10 cavity preparations (n=10/ group) were selected from the 3rd and 4th year dental students, Faculty of Dentistry, University of Malaya. There were two control groups consisting of long and short tungsten carbide burs of ten each. Two-way ANOVA was used to analyse the rake angle data. The data from the two control groups were collectively analysed following multiple paired t-test (p > .05) which showed no significant difference between the two types of tungsten carbide bur (short and long head). The mean rake angle of the control group was significantly higher (p 5 and > 10 cavity preparation groups. The rake angle of the > 10 cavity preparation group was significantly lower than the other two test groups (p 5 and > 10 cavity preparation groups showed blunt diamond particles. In conclusion, wear of tungsten carbide burs and round rotary diamond instruments were evident after repeated use. Wear was more pronounced when instruments were used to prepare more than ten cavities.

Doença pulmonar por metal duro em trabalhador da indústria petrolífera / Hard metal lung disease in an oil industry worker

A doença pulmonar por metal duro é uma pneumonia intersticial por células gigantes relacionada com a exposição à poeira composta por metais duros. Neste artigo é relatado o caso de um profissional da indústria petrolífera, diagnosticado com doença pulmonar por metal duro com base na documentação clínica, radiológica, funcional pulmonar e anatomopatológica.

Hard metal lung disease, which manifests as giant cell interstitial pneumonia, is caused by exposure to hard metal dust. We report the case of an oil industry worker diagnosed with hard metal lung disease. The diagnosis was based on the clinical, radiological and anatomopathological analysis, as well as on pulmonary function testing.

Influence of flowable materials on microleakage of nanofilled and hybrid Class II composite restorations with LED and QTH LCUs.

Background: Class II composite restorations are more frequently being placed with margins apical to the cementoenamel junction (CEJ) and margins within the dentin are prone to microleakage. Aims: This in vitro study was used to evaluate the influence of flowable composite and flowable compomer as gingival liner on microleakage in Class II composite restorations and compare a light-emitting diode (LED) unit with a quartz tungsten halogen (QTH) unit for light-activating composite resins. Materials and Methods: Mesioocclusal and distoocclusal Class II cavity preparations were made in 72 sound extracted premolars. The buccolingual width was 2.5 mm and the gingival margins of all the cavities were placed 1.0 mm apical to the CEJ. The boxes were prepared 1.5 mm deep axially, making 144 slot cavities. Teeth were randomly divided into the following two groups (n = 72): (I) Universal Filtek Supreme XT; Universal Filtek Supreme XT + Flwable Filtek XT and Universal Filtek Supreme XT + Dyract Flow and (II) Filtek Z250; Filtek Z250 + Flwable Filtek XT and Filtek Z250 + Dyract Flow. Flowable materials were injected into the gingival floor of the cavity to a thickness of 1.0 mm. Each increment was cured for 20 s. One-half of the subgroups in each group were cured with QTH and the other half with LED light curing units (LCUs). After 1 week of incubation at 37°C, the specimens were thermocycled (5-55°C, x1500), immersed in 0.5% basic fuchsine dye for 24 h and sectioned and microleakage was evaluated at the gingival margin by two examiners using a 0-3 score scale. The data were analyzed using the Kruskal-Wallis and Mann-Whitney U tests. Results: The groups utilizing flowable liners had significantly less microleakage (P < 0.05). No significant difference was identified between Universal Filtek Supreme XT and Filtek Z250 composites with and without flowable materials. There was no significant between utilizing flowable composite or flowable compomer and between each similar subgroup when polymerized with either the LED or the QTH LCUs. Conclusions: A layer of flowable materials at the gingival floor of Class II composite restorations may be recommended to improve the marginal seal of a restoration.

Fracture strength of different soldered and welded orthodontic joining configurations with and without filling material

The aim of this study was to compare the mechanical strength of different joints made by conventional brazing, TIG and laser welding with and without filling material. Five standardized joining configurations of orthodontic wire in spring hard quality were used: round, cross, 3 mm length, 9 mm length and 7 mm to orthodontic band. The joints were made by five different methods: brazing, tungsten inert gas (TIG) and laser welding with and without filling material. For the original orthodontic wire and for each kind of joint configuration or connecting method 10 specimens were carefully produced, totalizing 240. The fracture strengths were measured with a universal testing machine (Zwick 005). Data were analyzed by ANOVA (p=0.05) and Bonferroni post hoc test (p=0.05). In all cases, brazing joints were ruptured on a low level of fracture strength (186-407 N). Significant differences between brazing and TIG or laser welding (p<0.05, Bonferroni post hoc test) were found in each joint configuration. The highest fracture strength means were observed for laser welding with filling material and 3 mm joint length (998 N). Using filling materials, there was a clear tendency to higher mean values of fracture strength in TIG and laser welding. However, statistically significant differences were found only in the 9-mm long joints (p<0.05, Bonferroni post hoc test). In conclusion, the fracture strength of welded joints was positively influenced by the additional use of filling material. TIG welding was comparable to laser welding except for the impossibility of joining orthodontic wire with orthodontic band.

Color stability of composites subjected to accelerated aging after curing using either a halogen or a light emitting diode source

The purpose of this study was to evaluate, in vitro, the color stability of three composite resins of two different shades (A3 and C3) cured with either a quartz tungsten halogen (QTH) or a light emitting diode (LED) source. Forty specimens (20 x 2 mm) were prepared for each composite (Tetric Ceram®, Heliomolar® and Esthet-X®), being 20 for each shade. In each group, 10 specimens were light-cured using the QTH unit and 10 with the LED source. The shade of the materials was evaluated before and after submitting the specimens to artificial accelerated aging (4 h UV-B/4 h condensing vapor), using a reflection spectrophotometer. deltaE means were calculated and analyzed statistically by 2-way ANOVA and Tukey's test at 5 percent significance level. Both A3 and C3 shades of Esthet-X composite resin showed the lowest color change when cured with the QTH light, while Tetric C3 cured with the QTH light showed the highest color change.

O objetivo deste estudo foi verificar a estabilidade de cor de três compósitos polimerizados com dois tipos de unidades polimerizadoras, luz halógena ou diodo emissor de luz (LED). Quarenta amostras (20 mm de diâmetro por 2 mm de espessura) foram construídas com cada compósito (Tetric Ceram®, Heliomolar® and Esthet-X®), vinte na cor A3 e vinte na cor C3. Dentro de cada grupo, 10 amostras foram polimerizadas com luz halógena e as outras com LED. A cor dos materiais foi verificada antes e depois das amostras serem submetidas ao envelhecimento artificial acelerado (4h UV-B/4h de condensação de vapor), usando um espectrofotômetro de reflexão. As médias deltaE de foram calculadas e analisadas estatisticamente (ANOVA a dois critérios e teste de Tukey, 95 por cento). Os compósitos Esthet-X A3 e C3 demonstraram a menor alteração de cor quando polimerizados com luz halógena enquanto a resina. Tetric C3 apresentou a maior alteração de cor quando polimerizada por essa mesma fonte de luz.