Search results for "Titani"
showing 10 items of 931 documents
Shaping ability of nickel-titanium rotary instruments in simulated S-shaped root canals.
2009
Objective The aim of this study was to compare the shaping ability of 4 nickel-titanium rotary techniques and 1 hand technique in simulated S-shaped curved root canals. Study design Seventy-five simulated double-curved resin root canals were divided into 5 groups (n = 15). The canals were compared at 12 different levels and at 3 different times: before preparation and after preparation to master apical 25 and 35. Data were statistically analyzed by performing 2-by-2 comparisons with the Tukey parametric test of variance analysis using a confidence interval of 95%. Results All of the 75 resin blocks presented transportation of the root canals by transforming the apical curvature into a strai…
Fracture resistance after implantoplasty in three implant-abutment connection designs
2020
Background To assess the effect of implantoplasty and implant-abutment design on the fracture resistance and macroscopic morphology of narrow-diameter (3.5 mm) dental implants. Material and Methods Screw-shaped titanium dental implants (n = 48) were studied in vitro. Three groups (n = 16) were established, based on implant-abutment connection type: external hexagon, internal hexagon and conical. Eight implants from each group were subjected to an implantoplasty procedure; the remaining 8 implants served as controls. Implant wall thickness was recorded. All samples were subjected to a static strength test. Results The mean wall thickness reductions varied between 106.46 and 153.75 µm. The me…
Load-deflection characteristics of superelastic and thermal nickel-titanium wires
2011
SUMMARY The aim of this study was to investigate the mechanical properties of superelastic and thermal nickel–titanium (NiTi) archwires for correct selection of orthodontic wires. Seven different NiTi wires of two different sizes (0.014 and 0.016 inches), commonly used during the alignment phase, were tested. A three-point bending test was carried out to evaluate the load–deflection characteristics. The archwires were subjected to bending at a constant temperature of 37°C and deflections of 2 and 4 mm. Analysis of variance showed that thermal NiTi wires exerted significantly lower working forces than superelastic wires of the same size in all experimental tests (P < 0.05). Wire size had a s…
Titanium Complexes with a Linked Amido−Cyclopentadienyl Ligand and a Bidentate Organyl Group: Synthesis, Structure, and Ethene Polymerization Activity
1998
Titanium complexes containing a linked isopropyl- or benzylamido(tetramethylcyclopentadienyl) ligand C5Me4SiMe2NR (R = iPr, CH2Ph,) and one bidentate organyl group C6H4(CH2NMe2)-2, CH2C6H4(NMe2)-2, and {η5-C5H3(CH2NMe2)-2}Fe(η5-C5H5) were prepared by salt metathesis of the corresponding dichloro complex Ti(η5:η1-C5Me4SiMe2NR)Cl2 with the lithium organyl. Single crystal X-ray structural analysis of Ti(η5:η1-C5Me4SiMe2NCH2Ph)- {C6H4(CH2NMe2)-2}Cl and of Ti(η5:η1-C5Me4SiMe2NiPr){CH2C6H4(NMe2)-2}Cl revealed the presence of intramolecular coordination with square pyramidal geometry around titanium. In the ferrocenyl derivative Ti(η5:η1-C5Me4SiMe2NCH2Ph)[{η5-C5H3(CH2NMe2)-2}Fe(η5-C5H5)]Cl the NMe…
DFT analysis of titanium complexes with oxygen-containing bidentate ligands
2003
Strength of the TiO co-ordinate bond in several titanium complexes with bidentate ligands has been investigated by means of DFT. Mutual interaction of particular donors and their influence on Lewis acidity of the central atom have also been studied. The energy of ligand binding ranges from −19 to −454 kJ/mol, depending on the kind of donors. Calculations confirm that a strong donor, alkoxide anion, co-ordinatively saturates the titanium and makes binding of new ligands less exoenergetic. On the contrary, two oxygen atoms of similar donor number do not have much influence on each other. Strength of the TiO bonds in titanium complexes with certain oxygen-containing bidentate ligands has bee…
Determination of titanium by adsorption voltammetry with 4-(2-pyridylazo) resorcinol
1990
Titanium (IV) forms a complex with 4-(2-pyridylazo) resorcinol (PAR) in weakly acidic solutions. This complex can be used to determine titanium by adsorption voltammetry at a stationary Hg-electrode. The experimental conditions for the determination are described. The current-concentration curve is linear from 0.15–4.8 ng/g. Ti at a deposition time of 3 min, the detection limit lies at 0.1 ng/g. The influence of foreign ions was investigated. The determination can be carried out in the presence of a 1000-fold excess of iron by the standard addition method, albeit with decreased sensitivity.
A study on the adsorption voltammetry of titanium with various heterocyclic azo-compounds
1994
The voltammetric behaviour of various heterocyclic azo-compounds and their Ti-complexes was investigated at a stationary Hg electrode. In moderately acidic solutions Ti(IV) reacts with pyridylazo-compounds (PAR, 5-Br-PADAP, PAN), thiazolylazo-compounds (TAR, 5-Me-TAR, TAN, 4-Me-TAP) and pyrazolylazo-compounds (MDR, ERB) to form Ti-complexes, which are strongly adsorbed onto the Hg-electrode. These complexes are reduced at potentials more negative than those corresponding to the reduction of their respective ligands. The conditions for determining titanium by adsorption voltammetry using TAR and MDR as complexing agents were investigated in detail, as was the influence of foreign ions on the…
Determination of titanium by adsorption-voltammetry with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)-phenol (5-Br-PADAP)
1990
The 1:1 complex between titanium (IV) and 5-Br-PADAP can be used to determine titanium by adsorption voltammetry at a stationary Hg-electrode. The experimental conditions for the determination are described. The detection limit is 3×10−10 mol/l Ti (0.015 ppb). Calibration curves are linear for solutions containing 4×10−10 to 5×10−8 mol/l Ti(IV) and an enrichment time of 3 min. The influence of foreign ions was investigated. The determination can be carried out in the presence of a 5000-fold excess of iron.
Enhanced nanoscopy of individual CsPbBr3 perovskite nanocrystals using dielectric sub-micrometric antennas
2020
We demonstrate an efficient, simple, and low-cost approach for enhanced nanoscopy in individual green emitting perovskite (CsPbBr3) nanocrystals via TiO2 dielectric nanoantenna. The observed three- to five-fold emission enhancement is attributed to near-field effects and emission steering promoted by the coupling between the perovskite nanocrystals and the dielectric sub-micrometric antennas. The dark-field scattering configuration is then exploited for surface-enhanced absorption measurements, showing a large increase in detection sensitivity, leading to the detection of individual nanocrystals. Due to the broadband spectral response of the Mie sub-micrometric antennas, the method can be e…
Klimt artwork: red-pigment material investigation by backscattering Fe-57 Mössbauer spectroscopy, SEM and p-XRF
2017
Material tests were performed on a rediscovered Klimt-artwork "Trompetender Putto". We performed studies on the red colored spots, mainly taken from non-restored parts. MIMOS II Fe-57 Mossbauer spectroscopy (novelty in art-pigment analysis) mainly reveals haematite and crystallized goethite in red colors. Electron microscopy can identify various layers of the original and overpainting of an artwork. The number of layers fluctuates between three and four chemically painted areas. The portable X-ray fluorescence analysis enables to reduce the pigment list to containing mercury (cinnabar), lead, zinc, iron and titanium. Infrared-light-irradiation visualizes the different age of the pigments.