Knoop hardness of dental resin cements: Effect of veneering material and light curing methods

This study evaluated the Knoop hardness of one resin cement (dual-cure mode or light-cure mode) when illuminated directly or through restorative materials-ceramic (HeraCeram) or composite (Artglass)-by two light curing units. Light curing was carried out using a conventional quartz tungsten halogen (QTH) light source (XL2500) for 40 s, and a light emitting diodes (LED) light source (Ultrablue Is) for 40 s. Bovine incisors had their buccal faces flattened and hybridised. on these surfaces, a mould was seated and filled with cement. A disc of the veneering material (1.5 mm thickness) was positioned over this set for light curing. After storage (24 h/37 degrees C), samples (n = 10) were sectioned for hardness (KHN) measurements. Data were submitted to ANOVA and to Tukey's test (alpha = 0.05). In general, light curing with LED resulted in higher hardness values than QTH. Distinct cement behaviour was observed with different veneering material in association with different light curing units (LCUs). (C) 2006 Elsevier Ltd. All rights reserved.

Use of U-isotope disequilibrium to evaluate the weathering rate and fertilizer-derived uranium in São Paulo state, Brazil

The U-disequilibrium method was utilized to evaluate the velocity of alteration of rocks and fertilizer-derived uranium in the Corumbatai River basin, São Paulo state, Brazil. The Corumbatai River basin is affected by the continuous use of fertilizer-derived uranium utilized in sugar cane crops, increasing the dissolved uranium concentration in the Corumbatai River (Santa Terezinha station) in the wet period to 43%. The weathering rate in the Corumbatai River basin utilizing the U-isotope modeling was 0.0265 mm/year (corresponding to 38,000 years to weather 1 m of rock under actual climatic conditions). However, when the inputs of anthropogenic uranium were considered, then a weathering rate of 0.022 mm/year (corresponding to 45,500 years to weather 1 m of rock) was determined. The removed material in the Corumbatai River basin is mainly from two sub-basins (the Cabecas River and Passa Cinco River), where the sandstones weather easier than the siltstones and claystones in the basin.

Fibrin adhesive implant in wound healing repair of dental sockets with topical application of epsilon aminocaproic acid: Histological analysis

The aim of the study was to evaluate wound healing repair of dental sockets after topical application of 5% epsilon-aminocaproic acid (EACA) and the use of fibrin adhesive implant in rats under anticoagulant therapy with warfarin. Sixty Albinus wistar rats were used, divided into three groups of 20. In Group I, the animals were given 0.1 mL/100 mg of 0.9% saline solution per day, beginning 6 days before dental extraction and continuing throughout the experimental period. In Group II, the animals received 0.03 mL of sodium warfarin daily, beginning 6 days before the surgery and continuing until the day of sacrifice; after tooth extractions, the sockets were filled with fibrin adhesive material. In Group III the animals were treated as in Group II, and after extractions, the sockets were irrigated with 5 mL of 5% EACA and filled with the same fibrin adhesive material. All groups presented biological phases of wound healing repair, the differences being evident only in the chronology. The results obtained in Group III were very similar to those of Group I in the last period of wound repair, whereas Group II presented a late chronology compared to the other groups. © 2005 Wiley Periodicals, Inc.

Calcifications in a clear cell mucoepidermoid carcinoma: a case report with histological and immunohistochemical findings

The aim of this study was to report an unusual case of mucoepidermoid carcinoma (MEC) in a 39-year-old woman. The tumor showed a prominent population of clear and intermediate basal cells. Clear cells rarely predominate over other cell types. Such cases are called clear cell variant of MEC. The case also revealed a variable amount of calcified material in the tumor mass. Calcifications are rare in clear cell MEC. These structures were periodic acid- Schiff positive and diastase resistant, excluding glycogen origin. Immunohistochemistry was performed, and the epidermoid component was positive for cytokeratin (CK) 7, CK13, CK14, and CK19. The mucous and clear cells presented mild staining for CK7. Cytokeratins 7, 13, and 19 stained luminal cells, and intermediate cells exhibited positivity for CK7, CK14, and vimentin. The origin of the calcifications is speculated to be the result of dystrophic calcification of the amorphous eosinophilic material secreted by intermediate basal cells.

Influence of Cu(II) in the SrSnO3 crystallization

Perovskite type oxides have been intensively studied due to their interesting optical, electrical, and catalytic properties. Among perovskites the alkaline earth stannates stand out, being strontium stannates (SrSnO3) the most important material in ceramic technology among them due to their wide application as dielectric component. SrSnO3 has also been applied as stable capacitor and humidity sensor. In the present work, SrSnO3:Cu was synthesized by polymeric precursor method and heat treated at 700, 800, and 900 A degrees C for 4 h. After that, the material was characterized by thermal analysis (TG/DTA), X-ray diffraction (XRD), infrared spectroscopy, and UV-vis spectroscopy. Results indicated three thermal decomposition steps and confirmed the presence of strontium carbonate and Cu2+ reduction to Cu+ at higher dopant amounts. XRD patterns indicated that the perovskite crystallization started at 700 A degrees C with strontiatite (SrCO3) and cassiterite (SnO2) as intermediate phases, disappearing at higher temperatures. The amount of secondary phase was reduced with the increase in the Cu concentration.

Effects of a small fish cage farm on zooplankton assemblages (Cladocera and Copepoda: Crustacea) in a sub-tropicalreservoir (SE Brazil).

In Brazil, the environmental impacts of fish cage farming in water reservoirs have not been well studied. As this activity is being increasingly practiced, investigations on the impacts of this practice are strongly needed. The goal of this study was to investigate the effects of a small cage tilapia farm on zooplankton assemblages in an oligo/mesotrophic reservoir (Jurumirim Reservoir, Paranapanema River). Zooplankton, limnological variables, and water samples were obtained trimonthly during a year at two sample sites, one was located adjacent to the cage farm and the control area was located one kilometer away from it. Eighteen species were identified and Cladocera was the dominant group. The same species of microcrustaceans were identified at both sites. Among the ecological attributes studied, only evenness showed a tendency towards being higher in the control site. Significant differences between studied variables in the sites were observed only for material in suspension. The results of the study indicate that, during the studied period, the cage farm did not generate detectable changes in the zooplankton assemblages and their ecological attributes. However, small differences in some limnological variables could be an indication of some environmental changes associated with the fish farm system.

Detection of infectious bronchitis virus in experimentally infected chickens by an antigen-competitive ELISA

An antigen-competitive enzyme-linked immunosorbent assay (Ag-C-ELISA) was developed for the detection of infectious bronchitis virus (IBV) antigens, M41 strain, in tissues from experimentally infected chickens, or in allantoic fluid harvested from inoculated embryonated eggs. The detection limit of IBV in the Ag-C-ELISA was 104.1 median embryo infective doses (EID50)/well. Tracheal and lung samples from chickens vaccinated with 102.5 EID50 of live attenuated infectious bronchitis (H120) vaccine were negative in the direct detection Ag-C-ELISA. The results indicate that the Ag-C-ELISA has the potential to detect IBV, either directly in tissue samples or when combined with the passage of material in embryonated eggs, thereby constituting an alternative method for the diagnosis of IBV.

Structural analyzes of the use of residues of tires in reinforced concrete

The search for an adequate destination to the tires without use is a problem for many countries. The use of tire rubber in concrete through the partial substitution of the small aggregate has for objective the withdrawal of this material of the environment besides serving as alternative material in places that present sand scarcity. However, to use this type of concrete in civil construction it's necessary to verify its structural behavior. The behavior of the adherence enters the bar of armor and the concrete surrounding it has decisive importance with relation to the load capacity of the structures of reinforced concrete. In this context, this work presents, argues and evaluates the results of the experimental studies for determination of the adherence tension according to pulling up assays pull-out normalized for CEB RC6 and also related in the ASTM C-234 in concrete with and without rubber residues. Armors of nominal diameter of 10,0; 12,5 and 16 mm had been used and concrete contend 10% of rubber fibres in substitution to the sand in volume.

Histological evaluation of the bone repair using mineral trioxide aggregate combined to a material carrier

The aim of this study was to present a possible carrier for MTA, monoolein gel, with the objective to maintain this material in the place that was inserted and verify if this procedure is able to optimize its action. The data were evaluated by histomorphometric method and submitted to statistical analysis. The histological responses observed in this study indicate that the MTA is a reliable material and should be considered effective in bone periapical defects and the monoolein gel was capable to maintain the MTA in situ.

Determination of the volume fraction of retained austenite in a 300m steel by heat tinting technique

Applying the Heat Tinting Technique the microestrutural characterization of a 300M steel (medium carbon steel) was accomplished. The steel was austenitized for 20 min to 900°C, followed by holding at 400°C (in the bainitic temperature), with maintenance time of the material in the temperature of 1min, 5min and 30min, aiming at the formation of a multiphase structure. Through the metallographic analysis it is verified that, with the use of this technique, it is possible the determination of the volume fraction of the present phases in the 300M steel, especially in the identification and quantification of the retained austenite. Copyright © 2007 SAE International.

Effectiveness of rotary or manual techniques for removing a 6-year-old filling material

The aim of this study was to evaluate the effectiveness of manual and rotary instrumentation techniques for removing root fillings after different storage times. Twenty-four canals from palatal roots of human maxillary molars were instrumented and filled with gutta-percha and zinc-oxide eugenol-based sealer (Endofill), and were stored in saline for 6 years. Non-aged control specimens were treated in the same manner and stored for 1 week. All canals were retreated using hand files or ProTaper Universal NiTi rotary system. Radiographs were taken to determine the amount of remaining material in the canals. The roots were vertically split, the halves were examined with a clinical microscope and the obtained images were digitized. The images were evaluated with AutoCAD software and the percentage of residual material was calculated. Data were analyzed with two-way ANOVA and Tukey's test at 5% significance level. There was no statistically significant differences (p>0.05) between the manual and rotary techniques for filling material removal regardless the ageing effect on endodontic sealers. When only the age of the filling material was analyzed microscopically, non-aged fillings that remained on the middle third of the canals presented a higher percentage of material remaining (p<0.05) compared to the aged sealers and to the other thirds of the roots. The apical third showed a higher percentage of residual filling material in both radiographic and microscopic analysis when compared to the other root thirds. In conclusion, all canals presented residual filling material after endodontic retreatment procedures. Microscopic analysis was more effective than radiographs for detection of residual filling material.

Tomographic, Histological, and Immunohistochemical Evidences on the Use of N-Butyl-2-Cyanoacrilate for Onlay Graft Fixation in Rabbits

Background: The bone tissue responses to Cyanoacrylate have been described in the literature, but none used N-butyl-2-cyanoacrilate (NB-Cn) for bone graft fixation. Purpose: The aims of the study were: (a) to analyze the bone grafts volume maintenance fixed either with NB-Cn or titanium screw; (b) to assess the incorporation of onlay grafts on perforated recipient bed; and (c) the differences of expression level of tartrate-resistant acid phosphatase (TRAP) protein involved in bone resorption. Materials and Methods: Eighteen New Zealand White rabbits were submitted to calvaria onlay grafting on both sides of the mandible. On one side, the graft was fixed with NB-Cn, while on the other hand the bone graft was secured with an osteosynthesis screw. The computed tomography (CT) was performed just after surgery and at animals sacrifice, after 1 (n=9) and 6weeks (n=9), in order to estimate the bone grafts volume along the experiments. Histological sections of the grafted areas were prepared to evaluate the healing of bone grafts and to assess the expression of TRAP protein. Results: The CT scan showed better volume maintenance of bone grafts fixed with NB-Cn (p≤0.05) compared with those fixed with screws, in both experimental times (analysis of variance). The immunohistochemical evaluation showed that the TRAP expression in a 6-week period was significantly higher compared with the 1-week period, without showing significant difference between the groups (Wilcoxon and Mann-Whitney). Histological analysis revealed that the NB-Cn caused periosteum damage, but provided bone graft stabilization and incorporation similar to the control group. Conclusion: The perforation provided by screw insertion into the graft during fixation may have triggered early revascularization and remodeling to render increased volume loss compared with the experimental group. These results indicate that the NB-Cn possesses equivalent properties to titanium screw to be used as bone fixation material in osteosynthesis. © 2010 Wiley Periodicals, Inc.

Running holograms in azopolymer films

We report investigations on running holograms recorded in an azopolymer film made of a poly(methyl methacrylate) matrix doped with Disperse Red 1. Two-wave mixing experiments were carried out in the symmetrical transmission geometry. A stabilization technique was employed for active control of the phase shift between the real-time hologram and the interference pattern. Depending on the imposed phase shift, a running hologram propagates in the material in the form of an isomerization wave created by a continuous erasing-rewriting process. Diffraction efficiencies and the hologram velocities were measured as functions of the holographic phase shift at the wavelengths 515 and 488 nm. The experimental results were compared to theoretical curves obtained from a simplified model of the isomerization kinetics. The selective contributions of the phase and the amplitude gratings to the whole hologram were also determined. © 2013 Springer-Verlag Berlin Heidelberg.

Direct in situ observation of the electron-driven synthesis of Ag filaments on α-Ag2 WO4 crystals

In this letter, we report, for the first time, the real-time in situ nucleation and growth of Ag filaments on α-Ag2 WO4 crystals driven by an accelerated electron beam from an electronic microscope under high vacuum. We employed several techniques to characterise the material in depth. By using these techniques combined with first-principles modelling based on density functional theory, a mechanism for the Ag filament formation followed by a subsequent growth process from the nano-to micro-scale was proposed. In general, we have shown that an accelerated electron beam from an electronic microscope under high vacuum enables in situ visualisation of Ag filaments with subnanometer resolution and offers great potential for addressing many fundamental issues in materials science, chemistry, physics and other fields of science.

Production of an axial piston: Impacts resulting from the substitution of steel by a polymer-based material

The substitution of steel as a raw material in the production of axial pistons for pressure washers by polyphthalamide, polytetrafluoroethylene and glass fiber-based composite was studied. The new production process with composite consists of only two steps, while the production of the steel piston is to comprise of thirteen steps. This replacement would result in an estimated reduction of 80% of water consumption, 83% of electricity consumption, 73% of the total cost and 88% of the final mass. With regard to the main mechanical properties required for the end product, the composite was found to withstand the critical axial loads and it shows acceptable wear resistance in an environment without lubrication, an additional advantage of this replacement. © 2012 Elsevier Ltd. All rights reserved.