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PubMed2002

Simultaneous determination of zirconium and molybdenum by first-derivative spectrophotometry.

A first-derivative spectrophotometric method for the simultaneous determination of Zr and Mo with Alizarin Red S is described. Measurements were made at the zero-crossing wavelengths at 490.5 nm for Zr and 446.0 nm for Mo. The calibration graphs were linear at 0.5-20 and 0.5-13.0 microg ml(-1) for Zr and Mo, respectively. The possible interfering effects of various ions were studied. Only iron was interfered in this system. The validity of the method was examined by using some mixtures of Mo and Zr. The method was applied in different matrix in both presence and absence of some foreign metal ions.

Journal Article↗
PubMed2000

Zirconium - Phosphorus Chemistry: Strategies in Syntheses, Reactivity, Catalysis, and Utility.

Dramatic developments have taken place over the last few years in the chemistry of complexes containing Zr-P bonds and their utilization in organophosphorus chemistry. This review discusses the synthesis and reactivity of compounds containing Zr-P single and double bonds, phosphazirconacycles, and Zr complexes of substituent-free phosphorus. Applications in both stoichiometric and catalytic syntheses provide access to a variety of novel organophosphorus compounds and illustrate the potential of the organometallic approach to the synthesis of main group compounds.

Journal Article↗
PubMed2001

Highly Enantioselective Allylation of Imines with a Chiral Zirconium Catalyst This work was partially supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports, and Culture, Japan. The authors are grateful to Dr. Motoo Shiro (Rigaku Co. Ltd.) for his help in performng the X-ray analysis of compound 3 cd. T.G. thanks the Japan Society for the Promotion of Science (JSPS) for the award of a postdoctoral research fellowship.

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Journal Article↗
PubMed2006

Ceramic implant abutments: cutting efficiency and resultant surface finish by diamond rotary cutting instruments.

STATEMENT OF PROBLEM: There is no information regarding the cutting efficiency and the surface finish produced on ceramic implant abutments when using diamond rotary cutting instruments (DRCIs). PURPOSE: The purpose of this study was to determine which DRCIs are the most efficient in cutting aluminum oxide and zirconium oxide implant abutments and to evaluate which DRCIs create the prepared ceramic abutment with the least surface roughness. MATERIAL AND METHODS: A cutting regimen with a high-speed handpiece, 25 mL/min water spray and a 102.1-g load at the DRCI/ceramic interface was used to section the 4 x 4-mm edge of blocks of aluminum oxide (CerAdapt and Ceramic Esthetic Abutment) and zirconium oxide (Esthetic Zirconium Abutment (Nobel Biocare NB) and ZiReal Post (3i)) provided by the manufacturers. Two different brands of zirconium oxide were tested. Eight DRCIs of different types (Brasseler 2856, 5856, and 6856, Premier 770, TS2000, and Axis 856TSC, 856SC, and 856C) were tested to section each ceramic material 6 times, using a new block and a new DRCI for each test. The surface roughness (Ra value) was measured using a surface profilometer both parallel and perpendicular to the cut surface. Cutting efficiency was measured 3 times for change in weight/length of time (g/sec). The data were analyzed with a 1-way ANOVA and Tukey HSD tests (alpha=.05). RESULTS: For the 3i zirconium oxide, 2 types of DRCIs (Axis 856 TSC and Brasseler 2856) produced a significantly smoother (P<.001 and P<.0001, respectively) surface finish on the shank and tip but not on the start and end. For the NB zirconium oxide, only the Axis 856C consistently produced a significantly smoother (P<.01, P<.0001 and P<.0001, respectively) surface finish on the start, shank, and tip. There was no significant difference in surface roughness of the NB aluminum oxide with use of any of the DRCIs. The Premier 770 was significantly more efficient (P<.0001 for 150 seconds and P<.001 for 300 seconds) in cutting the 3i zirconium oxide. The Premier 770 was significantly more efficient (P<.0001) in cutting the NB zirconium oxide at 150 seconds. The Premier TS2000 was significantly more efficient (P<.0001) at 300 seconds. The Axis 856 TSC was significantly more efficient (P<.0001 for 150 seconds and P<.001 for 300 seconds) in cutting the NB aluminum oxide. CONCLUSION: For a smoother surface finish, Axis 856C should be used for the NB zirconium oxide abutment, and either Axis 856TSC or Brasseler 2856 should be used for the 3i zirconium oxide abutment. To complete gross reduction on the NB and 3i zirconium oxide abutments, Premier 770 and TS2000 were found to perform the best. Gross reduction on the aluminum oxide ceramic abutment from NB was most efficiently performed by Axis 856TSC.

Aluminum Oxide↗
PubMed2006

In vitro evaluation of push-out bond strengths of various luting agents to tooth-colored posts.

STATEMENT OF PROBLEM: Different compositions of tooth-colored posts may influence the bonding capacity of various luting agents to these posts. An appropriate understanding of these interactions is presently unavailable. PURPOSE: This study initially evaluated the effects of various pretreatment procedures on bond strengths to zirconium-oxide posts using a phosphate-methacrylate resin luting agent. Following that investigation, the bond strengths of various luting agents to tribochemically coated glass-fiber-reinforced composite (FRC) resin and zirconium-oxide posts were investigated. MATERIAL AND METHODS: Two hundred zirconium-oxide posts (CosmoPost) divided into 10 groups (n=20) were luted into artificial post spaces prepared with drills provided by the manufacturer. In 4 groups the posts were luted with phosphate-methacrylate resin agent (Panavia F) after receiving one of the following pretreatment procedures: no treatment (control); airborne-particle abrasion; silica coating and silanization with an intraoral airborne-particle-abrasion device (CoJet); or silica coating and silanization with a laboratory airborne-particle-abrasion device in combination with airborne-particle abrasion (Rocatec). The other zirconium-oxide posts in the 6 remaining groups were silica coated (CoJet), silanated, and luted with 1 of 6 different luting agents (Multilink, Variolink, PermaFlo DC, RelyX Unicem, Clearfil Core, and Ketac Cem). Additionally, 60 FRC posts (FRC Postec) were silica coated (CoJet), silanated, and luted with 1 of the 6 resin luting agents (Panavia F, Multilink, Variolink, PermaFlo DC, RelyX, and Clearfil Core). Push-out tests were performed to evaluate the bond strengths between luting agents and posts. Qualitative scanning electron microscopy (SEM) analyses were performed to evaluate the effects of the pretreatment procedures on the surface of the zirconium-oxide posts. Data were analyzed using analysis of variance (ANOVA) followed by the post hoc Tukey B test (alpha=.05). RESULTS: Bond strengths to the posts were significantly affected by the type of luting agent and the type of post (P<.001; 2-way ANOVA). Bond strengths of all luting agents to the FRC posts were significantly higher than to the zirconium-oxide posts (P<.01), except for Multilink and PermaFlo DC, which demonstrated higher bond strength values to the zirconium-oxide posts (P<.001). Pretreatment procedures significantly increased the bond strength of Panavia F to the zirconium-oxide posts (P<.05). SEM analyses revealed distinctive irregularities on the surface of the pretreated zirconium-oxide posts compared to the untreated posts. CONCLUSION: Bond strengths of luting agents to tooth-colored posts are significantly affected by the type of luting agent and the type of post. All investigated pretreatment procedures of zirconium-oxide posts significantly increased the bond strength of Panavia F.

Analysis of Variance↗
PubMedDate not supplied

In vitro tensile bond strength of adhesive cements to new post materials.

PURPOSE: The purpose of this study was to measure the in vitro tensile bond strength of 3 types of adhesive resin cements to stainless steel, titanium, carbon fiber-reinforced resin, and zirconium oxide post materials. MATERIALS AND METHODS: Disks of post materials were polished to 600 grit, air abraded, and ultrasonically cleaned. Zirconium oxide bonding surfaces were pretreated with hydrofluoric acid and silanated. Bis-Core, C&B Metabond, and Panavia cements were bonded to the post specimens and placed in a humidor for 24 hours. Post specimens were debonded in tension. Means and standard deviations (n = 5) were analyzed by 2-way analysis of variance. Tukey-Kramer intervals at the 0.05 significance level were calculated. Failure modes were observed. RESULTS: Panavia 21 provided the highest bond strengths for all types of post materials, ranging from 22 MPa (zirconium oxide) to 37 MPa (titanium). C&B Metabond bonded significantly more strongly to stainless steel (27 MPa) and titanium (22 MPa) than to zirconium oxide (7 MPa). Bis-Core results were the lowest, ranging from 16 MPa (stainless steel) to 8 MPa (zirconium oxide). In most cases, bonds to carbon fiber post materials were weaker than to stainless steel and titanium, but stronger than to zirconium oxide. In general, higher bond strengths resulted in a higher percentage of cohesive failures within the cement. CONCLUSION: Panavia 21 provided the highest bond strengths to all post materials, followed by C&B Metabond. In most cases, adhesive resins had higher bond strengths to stainless steel, titanium, and carbon fiber than to zirconium oxide.

Adhesives↗
PubMed1990

[Comparative studies on the radioactivity of bone cements containing x-ray contrast media and of the contrast media].

Various PMMA bone cements containing zirconium oxide (ZrO2) as an X-ray contrast medium and zirconium oxides of several manufacturers were tested for their radioactivity by means of a gamma spectrometer. All the bone cements tested (Implast, Palacos R, and Sulfix-6) showed a certain degree of radioactivity. The radiation source in the bone cement is the added zirconium oxide, which is polluted by radioactive elements. The examination of various zirconium oxides showed some high radioactive emissions. The risk of radiation-induced cancer seems to be small, because the cements are normally implanted in humans older than 60 years. In view of the fact that these X-ray contrast media remain in the body for decades as components of the bone cement, the radioactive zirconium oxides should be replaced by high-purity radiation-free zirconium oxide or barium sulphate as soon as possible.

Bone Cements↗
PubMed2003

[Development of novel carbon-carbon bond forming reactions using zirconocene complex].

Novel zirconium-mediated carbon-carbon bond-forming reactions were developed. The allylic, gamma-alkoxyallylic, allenyl, and gamma, gamma-dialkoxyallylic zirconium species can be prepared from corresponding ethers under mild conditions through the addition of a zirconocene-butene complex to the carbon-carbon multiple bond of the ethers and subsequent beta-elimination of the alkoxyl group. The gamma,gamma-dialkoxyallylic zirconium species reacts with carbonyl compounds at the beta-position of the zirconium atom like a ketene dialkyl acetal in the presence of stoichiometric amounts of Lewis acid and gave cyclopropane and/or cyclobutane derivatives. Intramolecular reaction of allylic zirconium species with acetal also develops as a ring contraction reaction of carbohydrates and morpholine derivatives. This method is useful for the construction of chiral highly functionalized carbocycles and pyrrolidines. The intramolecular ester transfer reaction through the zirconium-mediated coupling reaction of alkenyl carbamates gave gamma-aminobutyric acid derivatives and pyrrolidine-3-carboxylic acids.

Carbon↗
PubMed1999

The Electrochemistry of Nonaqueous Copper Phthalocyanine Dispersions in the Presence of a Metal Soap Surfactant: A Simple Equilibrium Site Binding Model.

The electrophoretic mobilities of copper phthalocyanine particles, dispersed in isoparaffin solutions containing zirconium octanoate, have been determined using phase-analysis light scattering. All the samples studied contained trace concentrations of water. The mobility values were converted to zeta potentials using the Hückel equation. All the systems studied exhibited a pronounced maximum in zeta potential as the zirconium octanoate concentration increased. The maximum occurred at a bulk zirconium octanoate concentration equivalent to that required for complete coverage of the particles. The zeta potential data were converted to surface charge density values through the use of the Poisson-Boltzmann equation. The latter were in the range 0.4 to 2.5 µC m-2. A simple two equation site binding theory, which considered the dissociation of zirconium octanoate and the subsequent adsorption of ions at a generic surface site, was successfully applied to the surface charge data. It is proposed that the maximum in the zeta potential and surface charge as a function of zirconium octanoate concentration was observed due to the preferential location of ZrO2+ ions at the particle surface, followed by charge neutralization with octanoate anions. It is suggested that water facilitates the dissociation process of the zirconium octanoate, although it does not directly contribute to the surface charge itself. Two plausible qualitative mechanisms are described. The first involves the presence of water at the particle-solution interface, whilst the second considers the formation of micelles in the bulk isoparaffin phase. Copyright 1999 Academic Press.

Journal Article↗
PubMed2004

Reactivity of secondary metallocene alkyls and the question of dormant sites in catalytic alkene polymerization.

The reactivity of [rac-(C2H4(1-indenyl)2)Zr(n-butyl)][MeB(C6F5)3] (4), [rac-(C2H4(1-indenyl)2)Zr(sec-butyl)][MeB(C6F5)3] (5), and [rac-(C2H4(1-indenyl)2)Zr(polypropenyl)][MeB(C6F5)3] with propene, ethene, and hydrogen was studied by low-temperature (<-40 degrees C) 1H and 13C NMR spectroscopy in toluene solutions. In contrast with previous suggestions that 2 degrees zirconium alkyl species such as 5 are dormant sites, these measurements demonstrate reactivity of 2 degrees zirconium alkyls with propene and ethene comparable to the 1 degrees zirconium alkyl species 4 and [rac-(C2H4(1-indenyl)2)Zr(polypropenyl)][MeB(C6F5)3]. Because 2,1-insertion of propene is an infrequent event, these results preclude significant accumulation of catalyst in the form of 2 degrees zirconium alkyls for this metallocene and counterion. The reactivity of 5 with hydrogen is at least 2 orders of magnitude faster than other 1 degrees zirconium alkyls. Such high reactivity accounts for the puzzlingly high fraction of butyl end groups in prior hydrooligomerization studies and implies that catalyst responsivity to H2 as a molecular weight control agent correlates with the regioselectivity of the catalyst.

Alkenes↗
PubMed2004

White wine continuous protein stabilization by packed column.

Protein stabilization is an important stage in the production of white wine. This paper studies white wine protein stabilization using a continuous process with zirconium oxide (powder and pellets) packed in a column. The results show that the total proteins decrease by 50 and 70% for the pellet and powdered zirconium oxides, respectively. Treatment with all zirconium oxides improves wine stability. The effect of the heat regeneration process on both zirconium oxide forms is to increase the adsorption capacity. The wine treated with powdered zirconium oxide after the regeneration is the most effective for preventing protein haze. The protein profile of wine after treatment shows that the 20-50 kDa and 50-70 kDa fractions are the ones removed preferentially, while the 15 kDa fraction and the ones higher than 70 kDa are removed the least. The results show that the protein fraction with a molecular weight of 15 kDa does not affect the protein instability of the wines studied. The protein fraction with a molecular weight higher than 70 kDa seems to influence protein instability. The physicochemical properties of wine after treatment were not affected, and the values obtained were like those of the standardized range.

Adsorption↗
PubMed2004

Exploring CH-activation pathways in bifunctional zirconocene/borane systems.

The dimethylsilanediyl-bridged ansa-zirconocene dichloride 1, that contains a pendent allyl substituent at a Cp-ring, adds HB(C(6)F(5))(2) to the vinyl group to yield the bifunctional zirconocene/borane complex 2. Substituted benzimidazoles were added to the strongly electrophilic borane moiety as protective groups, which allowed subsequent chloride versus -CH(2)SiMe(3) exchange at zirconium to take place by treatment with the respective alkyllithium reagent. Alternatively, the introduction of active sigma-ligands at zirconium is carried out first, followed by the hydroboration reaction. This route was followed for the synthesis of the diphenyl-ansa-zirconocene/borane complex 12. Complex 12 reacts slowly in solution by intramolecular electrophilic attack of the borane at its adjacent Cp-ring, followed by deprotonation using a [Zr]-Ph group to yield the zwitterionic complex 14 featuring a borata-tetrahydroindenyl moiety as part of the ansa-metallocene framework. Complex 14 was characterized by X-ray diffraction. It adds PMe(3) at zirconium to yield 15. Thermolysis of 12 with excess PMe(3) leads to the formation of the (aryne)zirconocene complex 18, which is stabilized by PMe(3) coordination to zirconium and PMe(3) addition to boron. N-Methylbenzimidazole adds to the -B(C(6)F(5))(2) unit of 12 to give the 1:1 adduct 19. Thermolysis of 19 at 80 degrees C in benzene solution in the presence of one additional equivalent of N-methylbenzimidazole results in deprotonation of the substrate to yield the sigma-N-methylbenzimidazolyl zirconium complex 20 (as a mixture of two diastereoisomers). An additional N-methylbenzimidazole ligand is bonded to the B(C(6)F(5))(2) unit in this product.

Journal Article↗
PubMed2006

Bonding of dual-cured resin cement to zirconia ceramic using phosphate acid ester monomer and zirconate coupler.

This study evaluated the shear bond strength between dual-cured resin luting cement and pure zirconium (99.9%) and industrially manufactured yttrium-oxide-partially-stabilized zirconia ceramic, and the effect of MDP (10-methacryloyloxydecyl dihydrogen phosphate) primer (MP) and zirconate coupler (ZC) on bond strength. Two different-shaped pure zirconium and zirconia ceramic specimens were untreated or treated with various primers, including different concentrations of MP containing phosphoric acid ester monomer (MDP) in ethanol, ZC containing a zirconate coupling agent in ethanol, or a mixture of MP and ZC. The specimens were then cemented together with dual-cured resin luting cement (Clapearl DC). Half of the specimens were stored in water at 37 degrees C for 24 h and the other half were thermocycled 10,000 times before shear bond strength testing. The bond strengths of resin luting cement to both the zirconium and zirconia ceramic were enhanced by the application of most MPs, ZCs, and the mixtures of MP and ZC. For the group (MP2.0+ZC1.0) containing 2.0 wt % MP and 1.0 wt % ZC, no significant difference was observed between in shear bond strength before and after thermal cycling for both zirconium and zirconia ceramic (p > 0.05). For the other primers, statistically significant differences in shear bond strength before and after thermal cycling were observed (p < 0.05). The application of the mixture of MP and ZC (MP2.0+ZC1.0) was effective for bonding between zirconia ceramic and dual-cured resin luting cement. This primer may be clinically useful as an adhesive primer for zirconia ceramic restoration.

Biocompatible Materials↗