Scanning electron microscope assessment of several resharpening techniques on the cutting edges of gracey curettes

Aim: Treatment of periodontal diseases is based on efficient scaling and root planing (SRP) and adequate maintenance of the patient. The effectiveness of SRP is influenced by operator skill, access to the subgingival area, root anatomy, and the quality and type of instrument used for SRP. The aim of this study was to evaluate the cutting edges of Gracey curettes after manufacturing and after resharpening using several techniques. Methods and Material: The cutting edges of a total of 41 new #5-6 stainless steel Gracey curettes were evaluated blindly using scanning electron microscopy (SEM). The quality of the cutting edges was evaluated blindly by a calibrated examiner using micrographs. Data were analyzed using a Kruskal Wallis test and nonparametric two-way multiple comparisons. Results and Conclusions: Different sharpening techniques had significantly different effects on the sharpeness of cutting edges (p<0.05). Sharpening by passing the lateral face of curettes over a sharpening stone and then a #299 Arkansas stone produced a high frequency of smooth, sharp edges or slightly irregular edges between the lateral and coronal faces of the curettes. Sharpening by passing a blunt stone over the curette's lateral face produced the poorest quality cutting edge (a bevel). Sharpening of the coronal curette face produced extremely irregular cutting edges and non-functional wire edges. Sharpening with rotary devices produced extremely irregular cutting edges.

Microwave-induced fast decalcification of rat bone for electron microscopic analysis: An ultrastructural and cytochemical study

Bone decalcification is a time-consuming process. It takes weeks and preservation of the tissue structure depends on the quality and velocity of the demineralization process. In the present study, a decalcification methodology was adapted using microwaving to accelerate the decalcification of rat bone for electron microscopic analysis. The ultrastructure of the bone decalcified by microwave energy was observed. Wistar rats were perfused with paraformaldehyde and maxillary segments were removed and fixed in glutaraldehyde. Half of specimens were decalcified by conventional treatment with immersion in Warshawsky solution at 4oC during 45 days, and the other half of specimens were placed into the beaker with 20 mL of the Warshawsky solution in ice bath and thereafter submitted to irradiation in a domestic microwave oven (700 maximum power) during 20 s/350 W/±37°C. In the first day, the specimens were irradiated 9 times and stored at 40°C overnight. In the second day, the specimens were irradiated 20 times changing the solution and the ice after each bath. After decalcification, some specimens were postfixed in osmium tetroxide and others in osmium tetroxide and potassium pyroantimonate. The specimens were observed under transmission electron microscopy. The results showed an increase in the decalcification rate in the specimens activated by microwaving and a reduction of total experiment time from 45 days in the conventional method to 48 hours in the microwave-aided method.

Effect of the Rashba and Dresselhaus spin-splitting terms on the electron g factor in semiconductor quantum wells under applied magnetic fields

We use the Ogg-McCombe Hamiltonian together with the Dresselhaus and Rashba spin-splitting terms to find the g factor of conduction electrons in GaAs-(Ga,Al)As semiconductor quantum wells (QWS) (either symmetric or asymmetric) under a magnetic field applied along the growth direction. The combined effects of non-parabolicity, anisotropy and spin-splitting terms are taken into account. Theoretical results are given as functions of the QW width and compared with available experimental data and previous theoretical works. © 2007 Elsevier B.V. All rights reserved.

Scanning electron microscopic study of the in situ effect of salivary stimulation on erosion and abrasion in human and bovine enamel

This in situ study investigated, using scanning electron microscopy, the effect of stimulated saliva on the enamel surface of bovine and human substrates submitted to erosion followed by brushing abrasion immediately or after one hour. During 2 experimental 7-day crossover phases, 9 previously selected volunteers wore intraoral palatal devices, with 12 enamel specimens (6 human and 6 bovine). In the first phase, the volunteers immersed the device for 5 minutes in 150 ml of a cola drink, 4 times a day (8h00, 12h00, 16h00 and 20h00). Immediately after the immersions, no treatment was performed in 4 specimens (ERO), 4 other specimens were immediately brushed (0 min) using a fluoride dentifrice and the device was replaced into the mouth. After 60 min, the other 4 specimens were brushed. In the second phase, the procedures were repeated but, after the immersions, the volunteers stimulated the salivary flow rate by chewing a sugar-free gum for 30 min. Enamel superficial alterations of all specimens were then evaluated using a scanning electron microscope. Enamel prism core dissolution was seen on the surfaces submitted to erosion, while on those submitted to erosion and to abrasion (both at 0 and 60 min) a more homogeneous enamel surface was observed, probably due to the removal of the altered superficial prism layer. For all the other variables - enamel substrate and salivary stimulation the microscopic pattern of the enamel specimens was similar.

Search for long-lived particles decaying into electron or photon pairs with the D0 detector

In this Letter we report on a search for long-lived particles that decay into final states with two electrons or photons. Such long-lived particles arise in a variety of theoretical models, such as hidden valleys and supersymmetry with gauge-mediated breaking. By precisely reconstructing the direction of the electromagnetic shower we are able to probe much longer lifetimes than previously explored. We see no evidence of the existence of such long-lived particles and interpret this search as a quasi model-independent limit on their production cross section, as well as a limit on a long-lived fourth generation quark. © 2008 The American Physical Society.

Description of eggs and nymphal instars of Triatoma baratai Carcavallo and Jurberg, 2000 based on optical and scanning electron microscopy (Hemiptera: Reduviidae: Triatominae)

Triatoma baratai Carcavallo & Jurberg, is a wild (i.e., nonperidomestic) species found in the State of Mato Grosso do Sul (Bodoquena region, county of Bonito), Brazil. Its eggs and nymphs are described here based on optical and scanning electron microscopy. The operculum and exochorion have pentagonal, hexagonal, and heptagonal cells, with small cracks and small random pits. Differences in the eggs and five nymphal instars of T. baratai allow them to be distinguished from the sympatric species Triatoma williami Galvão, Souza & Lima, and from six of the nine members of the Triatoma oliveirai complex. The most useful differentiating characters are in the color, shape of the abdomen, head, and total body length. Keys are provided to separate the eggs and nymphal instars of six of the nine members of the Triatoma oliveirai species complex. Copyright ©2009 Magnolia Press.

Investigation of the metal/porcelain interface in LASER-welded Ni-Cr-Mo alloy

The interface formed between the metal and the porcelain of laser-welded Ni-Cr-Mo alloy was studied on a metallurgical basis. The characterization was carried out by using optical microscope, electron scan microscopy and X-ray dispersive spectroscopy techniques and mechanical three-point flexion tests, in the laser-welded region, with and without porcelain. The union of the porcelain with the alloy is possible only after the oxidation of the metallic surface and the subsequent application of a bonding agent known as opaque. The porcelain applied to the base metal and weld bead showed different behaviours - after the flexion test, the base metal showed cracks, while that in the weld bead broke away completely. It was noted that the region subjected to laser welding had lower adherence to the porcelain than the base metal region, due to microstructural refinement of the weld bead. These results can be shown by the X-ray dispersive spectroscopy carried out on the regions studied. The flexion tests demonstrated that the Ni-Cr-Mo alloy subject to laser welding had significant alterations in its mechanical properties after application of the porcelain.

Monte Carlo and analytical calculation of lateral deflection of proton beams in homogeneous targets

Proton radiation therapy is a precise form of radiation therapy, but the avoidance of damage to critical normal tissues and the prevention of geographical tumor misses require accurate knowledge of the dose delivered to the patient and the verification of his position demand a precise imaging technique. In proton therapy facilities, the X-ray Computed Tomography (xCT) is the preferred technique for the planning treatment of patients. This situation has been changing nowadays with the development of proton accelerators for health care and the increase in the number of treated patients. In fact, protons could be more efficient than xCT for this task. One essential difficulty in pCT image reconstruction systems came from the scattering of the protons inside the target due to the numerous small-angle deflections by nuclear Coulomb fields. The purpose of this study is the comparison of an analytical formulation for the determination of beam lateral deflection, based on Molière's theory and Rutherford scattering with Monte Carlo calculations by SRIM 2008 and MCNPX codes. © 2010 American Institute of Physics.

Scanning electron microscopic evaluation of the root apex of mandibular premolars.

This aim of this study was to evaluate the root apex of mandibular premolars regarding the presence of main and accessory foramina. The root apexes from fifty extracted mandibular single-rooted premolars were examined by scanning electron microscopy (SEM). The apical openings had their diameter measured and were identified as main or accessory foramina. Double blinded and calibrated examiners analyzed the SEM photographs and classified the premolar roots into three types, based on the presence and size of the apical openings. Type I: roots with a single main apical foramen and no accessory foramina; type II: roots with a main foramen and one or more accessory foramina; type III: roots with accessory foramina only. For the first premolar, 16 roots were classified as type I (48.48%), 4 as type II (12.12%) and 13 as type III (39.40%). For the second premolars, 10 roots were classified as type I (58.83%), 3 as type II (17.65%) and 4 as type III (23.52%). The high incidence of roots with accessory foramina only (type III), mainly in the first premolar, warns of the need for caution during working length determination and apical debridement.

Scanning electron microscopy analysis of RinsEndo system and conventional irrigation for debris removal

A new device for irrigation, which presents hydrodynamic activation based on the pressure-suction technology, has recently been introduced to the market: the Rinsendo system. This study compared the efficacy of the Rinsendo system and conventional (manualdynamic) irrigation in the removal of debris from the root canal walls, using scanning electron microscopy (SEM). Twenty mandibular premolars with completely formed roots were selected and randomly divided into group 1 (irrigation with the Rinsendo system) and group 2 (conventional irrigation). The canals were irrigated with 1 ml of saline at each change of instrument. instrumentation started with a #15 K file and continued up to a #40 K file, which was standardized as the working length instrument. Then, the teeth were sectioned in buccolingual direction and the halves were sputter-coated with gold and examined by SEM. The apical, middle and cervical root canal thirds were evaluated, and the results were analyzed statistically by the Mann-Whitney test for comparison between methods, Kruskal-Wallis test for comparison among thirds, and Miller test for individual comparisons. A significance level of 5% was set for all analyses. The results did not show significant differences (p>0.05) between methods at each third and among thirds for each technique analyzed individually. in conclusion, there was no difference in the cleaning ability of the Rinsendo system and conventional irrigation.

Calcium hydroxide intracanal dressing removal with different rotary instruments and irrigating solutions: A scanning electron microscopy study

This study evaluated the efficacy of 2 types of rotary instruments employed in association with sodium hypochlorite (NaOCl) or EDTA in removing calcium hydroxide (CH) residues from root canals dentin walls. Forty-two mandibular human incisors were instrumented with the ProTaper System up to F2 instrument, irrigated with 2.5% NaOCl followed by 17% EDTA and filled with a CH intracanal dressing. After 7 days, the CH dressing was removed using 4 techniques: NiTi rotary instrument size 25, 0.06 taper (K3 Endo) and irrigation with 17% EDTA (Group 1), NiTi rotary F1 instrument (ProTaper) and irrigation with 17% EDTA (Group 2), NiTi rotary instrument size 25, 0.06 taper and irrigation with 2.5% NaOCl (Group 3) and NiTi rotary F1 instrument and irrigation with 2.5% NaOCl (Group 4). Two roots without intracanal dressing were used as negative controls. Teeth were evaluated by scanning electron microscopy, in the cervical and apical canal thirds. None of the techniques removed the CH dressing completely. In the apical and cervical thirds, F1 instrument was better than instrument size 25, 0.06 taper in removing CH residues (p<0.05), regardless of the final irrigating solution. No difference was found between the irrigating solutions in the groups of F1 instrument and of instrument size 25, 0.06 taper (p>0.05). The negative controls had no CH residues on the dentin walls. In conclusion, the ProTaper F1 instrument was better than K3 Endo instrument size 25, 0.06 taper in the removal of CH intracanal medication, regardless of irrigating solution used.

Precipitates segmentation from scanning electron microscope images through machine learning techniques

The presence of precipitates in metallic materials affects its durability, resistance and mechanical properties. Hence, its automatic identification by image processing and machine learning techniques may lead to reliable and efficient assessments on the materials. In this paper, we introduce four widely used supervised pattern recognition techniques to accomplish metallic precipitates segmentation in scanning electron microscope images from dissimilar welding on a Hastelloy C-276 alloy: Support Vector Machines, Optimum-Path Forest, Self Organizing Maps and a Bayesian classifier. Experimental results demonstrated that all classifiers achieved similar recognition rates with good results validated by an expert in metallographic image analysis. © 2011 Springer-Verlag Berlin Heidelberg.

Study of ITO@PMMA composites by transmission electron microscopy

ITO nanowires were synthesized by carbothermal reduction process, using a co-evaporation method, and have controlled size, shape, and chemical composition. The electrical measurements of nanowires showed they have a resistance of about 102 Ω. In order to produce nanocomposites films, nanowires were dispersed in toluene using an ultrasonic cleaner, so the PMMA polymer was added, and the system was kept under agitation up to obtain a clear suspension. The PMMA polymer was filled with 1, 2, 5 and 10% in weight of nanowires, and the films were done by tape casting. The results showed that the electrical resistance of nanocomposites changed by over 7 orders of magnitude by increasing the amount of filler, and using 5 wt% of filler the composite resistance decreased from 1010 Ω to about 104 Ω, which means that percolation threshold of wires occurred at this concentration. This is an interesting result once for nanocomposites filled with ITO nanoparticles is necessary about 18% in weight to obtain percolation. The addition of filler up to 10 wt% decreased the resistance of the composite to 103 Ω, which is a value close to the resistance of wires. The composites were also analyzed by transmission electron microscopy (TEM), and the TEM results are in agreement with the electrical ones about percolation of nanowires. These results are promising once indicates that is possible to produce conductive and transparent in the visible range films by the addition of ITO nanowires in a polymeric matrix using a simple route. © 2011 Materials Research Society.

Passive vibration isolation using axially loaded curved beams

A nonlinear spring element of a vibration isolator should ideally possess high static and low dynamic stiffness. A buckled beam may be a good candidate to fulfil this requirement provided its internal resonance frequencies are high enough to achieve a wide frequency range of isolation. If a straight beam is used, there is a singularity in the force-displacement characteristic. To smooth this characteristic and eliminate the singularity at the buckling point, beams with initial constant curvature along their length are investigated here as an alternative to the buckled straight beam. Their force displacement characteristics are compared with different initial curvature and with a straight buckled beam. The minimum achievable dynamic stiffness with its corresponding static stiffness is compared for different initial curvatures. A case study is considered where the beams are optimized to isolate a one kilogram mass and to achieve a natural frequency of 1 Hz, considering small amplitudes of vibration. Resonance frequencies of the optimized beams for different curvature are presented. It is shown that an order of magnitude reduction in stiffness compared with a linear spring is achievable, while the internal resonance frequencies of the curved beam are high enough to achieve an acceptable frequency range of isolation.

Comparative in vivo study of commercially pure Ti implants with surfaces modified by laser with and without silicate deposition: Biomechanical and scanning electron microscopy analysis

The purpose of this study was to evaluate commercially pure titanium implant surfaces modified by laser beam (LS) and LS associated with sodium silicate (SS) deposition, and compare them with machined surface (MS) and dual acid-etching surfaces (AS) modified. Topographic characterization was performed by scanning electron microscopy-X-ray energy dispersive spectroscopy (SEM-EDX), and by mean roughness measurement before surgery. Thirty rabbits received 60 implants in their right and left tibias. One implant of each surface in each tibia. The implants were removed by reverse torque for vivo biomechanical analysis at 30, 60, and 90 days postoperative. In addition, the surface of the implants removed at 30 days postoperative was analyzed by SEM-EDX. The topographic characterization showed differences between the analyzed surfaces, and the mean roughness values of LS and SS were statistically higher than AS and MS. At 30 days, values removal torque LS and SS groups showed a statistically significant difference (p < 0.05) when compared with MS and AS. At 60 days, groups LS and SS showed statistically significant difference (p < 0.05) when compared with MS. At 90 days, only group SS presented statistically higher (p < 0.05) in comparison with MS. The authors can conclude that physical chemistry properties and topographical of LS and SS implants increases bone-implant interaction and provides higher degree of osseointegration when compared with MS and AS. © 2012 Wiley Periodicals, Inc.