Effect of fluoride-containing solutions on the surface of cast commercially pure titanium

This study evaluated the effects of fluoride-containing solutions on the surface of commercially pure titanium (CP Ti) obtained by casting. CP Ti specimens were fabricated and randomly assigned to 5 groups (n=10): group 1: stored in distilled water at 37 ± 1ºC; group 2: stored in distilled water at 37 ± 1ºC and daily immersed in 0.05% NaF for 3 min; group 3: stored in distilled water at 37 ± 1ºC and daily immersed in 0.2% NaF for 3 min; group 4: stored in distilled water at 37 ± 1ºC; and immersed in 0.05% NaF every 15 days for 3 min; and group 5: stored in distilled water at 37 ± 1ºC and immersed in 0.2% NaF every 15 days for 3 min. Surface roughness was measured with a profilometer immediately after metallographic polishing of the specimens (T0) and at 15-day intervals until completing 60 days of experiment (T15, T30, T45, T60). Data were analyzed statistically by ANOVA and Tukey's test (α=0.05). There was no statistically significant difference (p>0.05) in surface roughness among the solutions. In conclusion, fluoride-containing solutions (pH 7.0) used as mouthwashes do not damage the surface of cast CP Ti and can be used by patients with titanium-based restorations.

Comparative study of chemical and mechanical retentive systems for bonding of indirect composite resin to commercially pure titanium

This study evaluated the effect of chemical and mechanical surface treatments for cast metal alloys on the bond strength of an indirect composite resin (Artglass) to commercially pure titanium (cpTi). Thirty cylindrical metal rods (3 mm diameter x 60 mm long) were cast in grade-1 cpTi and randomly assigned to 6 groups (n=5) according to the received surface treatment: sandblasting; chemical treatment; mechanical treatment - 0.4 mm beads; mechanical treatment - 0.6 mm beads; chemical/mechanical treatment - 0.4 mm; and chemical/mechanical treatment - 0.6 mm beads. Artglass rings (6.0 mm diameter x 2.0 mm thick) were light cured around the cpTi rods, according manufacturer's specifications. The specimens were invested in hard gypsum and their bond strength (in MPa) to the rods was measured at fracture with a universal testing machine at a crosshead speed of 2.0 mm/min and 500 kgf load cell. Data were analyzed statistically by one-way ANOVA and Tukey test (a=5%). The surface treatments differed significantly from each other (p<0.05) regarding the recorded bond strengths. Chemical retention and sandblasting showed statistically similar results to each other (p=0.139) and both had significantly lower bond strengths (p<0.05) than the other treatments. In conclusion, mechanical retention, either associated or not to chemical treatment, provided higher bond strength of the indirect composite resin to cpTi.

Comparative study of two commercially pure titanium casting methods

The interest in using titanium to fabricate removable partial denture (RPD) frameworks has increased, but there are few studies evaluating the effects of casting methods on clasp behavior. OBJECTIVE: This study compared the occurrence of porosities and the retentive force of commercially pure titanium (CP Ti) and cobalt-chromium (Co-Cr) removable partial denture circumferential clasps cast by induction/centrifugation and plasma/vacuum-pressure. MATERIAL AND METHODS: 72 frameworks were cast from CP Ti (n=36) and Co-Cr alloy (n=36; control group). For each material, 18 frameworks were casted by electromagnetic induction and injected by centrifugation, whereas the other 18 were casted by plasma and injected by vacuum-pressure. For each casting method, three subgroups (n=6) were formed: 0.25 mm, 0.50 mm, and 0.75 mm undercuts. The specimens were radiographed and subjected to an insertion/removal test simulating 5 years of framework use. Data were analyzed by ANOVA and Tukey's to compare materials and cast methods (α=0.05). RESULTS: Three of 18 specimens of the induction/centrifugation group and 9 of 18 specimens of plasma/vacuum-pressure cast presented porosities, but only 1 and 7 specimens, respectively, were rejected for simulation test. For Co-Cr alloy, no defects were found. Comparing the casting methods, statistically significant differences (p<0.05) were observed only for the Co-Cr alloy with 0.25 mm and 0.50 mm undercuts. Significant differences were found for the 0.25 mm and 0.75 mm undercuts dependent on the material used. For the 0.50 mm undercut, significant differences were found when the materials were induction casted. CONCLUSION: Although both casting methods produced satisfactory CP Ti RPD frameworks, the occurrence of porosities was greater in the plasma/vacuum-pressure than in the induction/centrifugation method, the latter resulting in higher clasp rigidity, generating higher retention force values.

Storage effect on the acceptability of snacks made of pure amaranth and blends of amaranth and corn or chickpea

Snacks made by extrusion cooking of pure amaranth flour or mixtures of 80 per cent amaranth flour and 20 per centcorn grits or chickpea flour were developed to replace the traditional commercial ones with improved nutritional and functional quality. Pure amaranth snacks and the blended ones were flavored with salty and sweet flavors and evaluated for acceptability using a 9-point hedonic scale. The good acceptance observed for either salty or sweet flavored snacks indicated that they have characteristics to compete with similar commercial products. Acceptability of salty snacks increased with storage time at room temperature in BOPP (polypropylene bi-guided) packs whereas slightly decreased for the sweet ones. This type of storage proved to be very efficient for the conservation of the salty product and also suitable for the sweet ones

Intrahepatic Glissonian Approach for Pure Laparoscopic Left Hemihepatectomy

Background: Recent advances in laparoscopic devices and experience with advanced techniques have increased the indications for laparoscopic liver. Aim: The aim of this work was to present a video with technical aspects of a pure laparoscopic left hemi-hepatectomy (segments 2, 3, and 4) by using the intrahepatic Glissonian approach and control of venous outflow without hilar dissection or the Pringle maneuver. Patient and Method: A 63-year-old woman with a 5-cm solitary liver metastasis was referred for treatment. Four trocars were used. The left lobe was pulled upward and the lesser omentum was divided, exposing Arantius' ligament. This ligament is a useful landmark for the identification of the main left Glissonian pedicle. A small anterior incision was made in front of the hilum, and a large clamp was introduced behind the Arantius' ligament toward the anterior incision, allowing control of the left main sheath. Ischemic discoloration of the left liver was achieved and marked with cautery. The vascular clamp was replaced by a stapler. If ischemic delineation was coincident with a previously marked area, the stapler was fired. The left hepatic vein was dissected and encircled. Parenchymal transection and vascular control of the hepatic veins were accomplished with a Harmonic scalpel and an endoscopic stapling device, as appropriate. All these steps were performed without the Pringle maneuver and without hand assistance. Results: Operative time was 220 minutes with minimum blood loss. Hospital stay was 4 days. Pathology showed free surgical margins. The patient is alive with no signs of recurrence 18 months after the operation. Conclusion: Totally laparoscopic left hemihepatectomy is safe and feasible in selected patients and should be considered for patients with benign or malignant liver neoplasms. The described technique, with the use of the intrahepatic Glissonian approach and control of venous outflow, may facilitate laparoscopic left hemihepatectomy by reducing the technical difficulties in pedicle control and may decrease bleeding during liver transection.

Local atomic structure in tetragonal pure ZrO(2) nanopowders

The local atomic structures around the Zr atom of pure (undoped) ZrO(2) nanopowders with different average crystallite sizes, ranging from 7 to 40 nm, have been investigated. The nanopowders were synthesized by different wet-chemical routes, but all exhibit the high-temperature tetragonal phase stabilized at room temperature, as established by synchrotron radiation X-ray diffraction. The extended X-ray absorption fine structure (EXAFS) technique was applied to analyze the local structure around the Zr atoms. Several authors have studied this system using the EXAFS technique without obtaining a good agreement between crystallographic and EXAFS data. In this work, it is shown that the local structure of ZrO(2) nanopowders can be described by a model consisting of two oxygen subshells (4 + 4 atoms) with different Zr-O distances, in agreement with those independently determined by X-ray diffraction. However, the EXAFS study shows that the second oxygen subshell exhibits a Debye-Waller (DW) parameter much higher than that of the first oxygen subshell, a result that cannot be explained by the crystallographic model accepted for the tetragonal phase of zirconia-based materials. However, as proposed by other authors, the difference in the DW parameters between the two oxygen subshells around the Zr atoms can be explained by the existence of oxygen displacements perpendicular to the z direction; these mainly affect the second oxygen subshell because of the directional character of the EXAFS DW parameter, in contradiction to the crystallographic value. It is also established that this model is similar to another model having three oxygen subshells, with a 4 + 2 + 2 distribution of atoms, with only one DW parameter for all oxygen subshells. Both models are in good agreement with the crystal structure determined by X-ray diffraction experiments.

Structural and magnetic properties of pure and nickel doped SnO(2) nanoparticles

Ni-doped SnO(2) nanoparticles prepared by a polymer precursor method have been characterized structurally and magnetically. Ni doping (up to 10 mol%) does not significantly affect the crystalline structure of SnO(2), but stabilizes smaller particles as the Ni content is increased. A notable solid solution regime up to similar to 3 mol% of Ni, and a Ni surface enrichment for the higher Ni contents are found. The room temperature ferromagnetism with saturation magnetization (MS) similar to 1.2 x 10(-3) emu g(-1) and coercive field (H(C)) similar to 40 Oe is determined for the undoped sample, which is associated with the exchange coupling of the spins of electrons trapped in oxygen vacancies, mainly located on the surface of the particles. This ferromagnetism is enhanced as the Ni content increases up to similar to 3 mol%, where the Ni ions are distributed in a solid solution. Above this Ni content, the ferromagnetism rapidly decays and a paramagnetic behavior is observed. This finding is assigned to the increasing segregation of Ni ions (likely formed by interstitials Ni ions and nearby substitutional sites) on the particle surface, which modifies the magnetic behavior by reducing the available oxygen vacancies and/or the free electrons and favoring paramagnetic behavior.

Chemical characterization and anticorrosion properties of corrosion products formed on pure copper in synthetic rainwater of Rio de Janeiro and Sao Paulo

This work aims to characterize corrosion products formed on copper samples exposed to synthetic rainwater of Rio Janeiro and Sao Paulo. XRD and XPS were employed to determine their composition, while electrochemical techniques were used to evaluate their protective properties. XRD and XPS indicated the thickening of the corrosion layer with time. Electrochemical results showed that the protectiveness of the corrosion layer depends on the solution composition. Based on our findings a corrosion mechanism for copper in simulated rainwater is proposed where the role of NH(4)(+) ions in the cuprite layer partial regeneration is taken into account. (C) 2009 Elsevier Ltd. All rights reserved.

Synthesis of Cyclic Guanidine Intermediates of Anatoxin-a(s) in Both Racemic and Enantiomerically Pure Forms

The alkyl chain of anatoxin-a(s) (cyclic guanidines), which can be used as an intermediate in the total synthesis of anatoxin-a(s), was synthesized in both racemic and enantiomerically pure forms. These enantiomerically pure cyclic compounds can be used as chiral inductors in some reactions. The two racemic routes disclosed herein have the advantages of high overall yield and mild reaction conditions. Both routes proceed through an intermediate 2,3-diaminoacid - an important synthetic scaffold - with good yields. Furthermore, the N,N-dimethyl-2(tosylimino)imidazolidine-4-carboxamide might be obtained from 2-(tosylimino)imidazolidine-4-carboxylic acid followed by selective reduction of the carbonyl functionality. All synthesized compounds were analyzed by mass spectrometry and (1)H NMR and (13)C NMR spectroscopy.

Growth and acidification performance of probiotics in pure culture and co-culture with Streptococcus thermophilus: The effect of inulin

Inulin was used as a prebiotic to improve the quality and consistency of skim milk fermented by co-cultures and pure Cultures of Lactobacillus acidophilus, Lactobacillus rhamnosus, Lactobacillus bulgaricus and Bifidobacterium lactis with Streptococcus thermophilus. We compared, either in the presence or absence of 4 g inulin/100 g, the results of the main kinetic parameters, specifically the generation time (t(g)), the maximum acidification rate (V(max)). and the times to reach V(max) (t(max)), to attain pH 5.0 (t(pH5.0)) and to complete the fermentation (t(pH4.5)). Post-acidification, lactic acid formation and cell counts were also determined and compared, either 1 day after the fermentation was complete or after 7 day storage at 4 degrees C. In general, inulin addition to the milk increased in co-cultures V(max), decreased t(max), t(g) and t(pH4.5), favored post-acidification, exerted a bifidogenic effect, and preserved almost intact cell viability during storage. In addition, S. thermophilus was shown to stimulate the metabolism of the other lactic bacteria. Contrary to co-cultures, most of the effects in pure Cultures were not statistically significant. The most important aspect of this paper is the use of the generation time as a toot to investigate the microbial response to inulin addition. (c) 2009 Elsevier Ltd. All rights reserved.

Sterilization by pure oxygen plasma and by oxygen-hydrogen peroxide plasma: An efficacy study

Plasma is an innovative sterilization method characterized by a low toxicity to operators and patients, and also by its operation at temperatures close to room temperatures. The use of different parameters for this method of sterilization and the corresponding results were analyzed in this study. A low-pressure inductive discharge was used to study the plasma sterilization processes. Oxygen and a mixture of oxygen and hydrogen peroxide were used as plasma source gases. The efficacy of the processes using different combinations of parameters such as plasma-generation method, type of gas, pressure, gas flow rate, temperature, power, and exposure time was evaluated. Two phases were developed for the processes, one using pure oxygen and the other a mixture of gases. Bacillus subtilis var. niger ATCC 9372 (Bacillus atrophaeus) spores inoculated on glass coverslips were used as biological indicators to evaluate the efficacy of the processes. All cycles were carried out in triplicate for different sublethal exposure times to calculate the D value by the enumeration method. The pour-plate technique was used to quantify the spores. D values of between 8 and 3 min were obtained. Best results were achieved at high power levels (350 and 40oW) using pure oxygen, showing that plasma sterilization is a promising alternative to other sterilization methods. (c) 2007 Elsevier B.V. All rights reserved.

Effect of argon purity on mechanical properties, microstructure and fracture mode of commercially pure (cp) Ti and Ti-6Al-4V alloys for ceramometal dental prostheses

Provision of an inert gas atmosphere with high-purity argon gas is recommended for preventing titanium castings from contamination although the effects of the level of argon purity on the mechanical properties and the clinical performance of Ti castings have not yet been investigated. The purpose of this study was to evaluate the effect of argon purity on the mechanical properties and microstructure of commercially pure (cp) Ti and Ti-6Al-4V alloys. The castings were made using either high-purity and/or industrial argon gas. The ultimate tensile strength (UTS), proportional limit (PL), elongation (EL) and microhardness (VHN) at different depths were evaluated. The microstructure of the alloys was also revealed and the fracture mode was analyzed by scanning electron microscopy. The data from the mechanical tests and hardness were subjected to a two-and three-way ANOVA and Tukey`s test (alpha = 0.05). The mean values of mechanical properties were not affected by the argon gas purity. Higher UTS, PL and VHN, and lower EL were observed for Ti-6Al-4V. The microhardness was not influenced by the argon gas purity. The industrial argon gas can be used to cast cp Ti and Ti-6Al-4V.

Comparative analysis of the fit of 3-unit implant-supported frameworks cast in nickel-chromium and cobalt-chromium alloys and commercially pure titanium after casting, laser welding, and simulated porcelain firings

This study compared the vertical misfit of 3-unit implant-supported nickel-chromium (Ni-Cr) and cobalt-chromium (Co-Cr) alloy and commercially pure titanium (cpTi) frameworks after casting as 1 piece, after sectioning and laser welding, and after simulated porcelain firings. The results on the tightened side showed no statistically significant differences. On the opposite side, statistically significant differences were found for Co-Cr alloy (118.64 mu m [SD: 91.48] to 39.90 mu m [SD: 27.13]) and cpTi (118.56 mu m [51.35] to 27.87 mu m [12.71]) when comparing 1-piece to laser-welded frameworks. With both sides tightened, only Co-Cr alloy showed statistically significant differences after laser welding. Ni-Cr alloy showed the lowest misfit values, though the differences were not statistically significantly different. Simulated porcelain firings revealed no significant differences.

Tensile bond strength of cast commercially pure titanium and cast gold-alloy posts and cores cemented with two luting agents

Statement of problem. In vitro studies on the retentive strengths of various cements used to retain posts have reported conflicting results. Purpose. The purpose of this study was to compare the tensile strength of commercially pure titanium and type III cast gold-alloy posts and cores cemented with zinc phosphate or resin cement. Material and methods. Forty-two extracted human canines were endoclontically treated. The root preparations were accomplished using Largo reamers (10 mm in depth and 1.7 mm in diameter). Acrylic resin patterns for the posts and cores were made, and specimens were cast in commercially pure titanium and in type III gold alloy (n=7). Fourteen titanium cast posts and cores were submitted to surface treatment with Kroll acid solution and to scanning electron microscopy (SEM), before and after acid etching. The groups (n=7) were cemented with zinc phosphate cement or resin cement (Panavia F). Tensile strengths were measured in a universal testing machine at a crosshead speed of 0.5 mm/min. The results (Kgf) were statistically analyzed by 2-way ANCIVA (alpha=.05). Results. The 2-way ANOVA indicated that there were no significant differences among the groups tested. Retentive means for zinc phosphate and Panavia F cements were statistically similar. The bond strength was not Influenced by the alloy, the luting material, or the etching treatment. SEM analysis indicated that the etched surfaces were smoother than those that did not receive surface treatment, but this fact did not influence the results. Conclusions. Commercially pure titanium cast posts and cores cemented with zinc phosphate and resin cements demonstrated similar mean tensile retentive values. Retentive values were also similar to mean values recorded for cast gold-alloy posts and cores cemented with zinc phosphate cement and resin cements.

Corrosion behavior of pure titanium in artificial saliva solution

The biocompatibility of commercially pure (cp) titanium stems from its chemical stability within an organism, due to a fine film of impermeable titanium oxide covering the metal surface, which guarantees its resistance to corrosion. Despite its biocompatible characteristic, this material does not promote the formation of a hydroxyapatite layer, therefore, many research groups have sought to alter the material`s surface, introducing modifications that might influence corrosion resistance. The electrochemical behavior of cp Ti, with hydroxyapatite coating and without hydroxyapatite coating, commonly used in implant materials, was investigated using an artificial saliva solution at 25 degrees C and pH=7.4. In the conditions of the study it was observed that the hydroxyapatite layer influences the properties of corrosion resistance. This study of the behavior of cp Ti with and without hydroxyapatite coating, in naturally aerated artificial saliva solution at 25 degrees C, was based on open circuit potential measurements and potentiodynamic polarization curves. At approximately 1x10(-6) A/cm(2) the potential for cp Ti with and without hydroxyapatite coating begins to increase at a faster rate, but at -74mV (SCE) for coated cp Ti and at 180mV (SCE) for uncoated cp Ti the increase in potential begins to slow. This behavior, characterized by a partial stabilization of current density, indicates that in those potential ranges a protective passive film is formed.