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PubMed1981

Polymer implant materials with improved X-ray opacity and biocompatibility.

Poly(methyl methacrylate) samples containing 28 wt% inorganic fillers such as zirconium oxide, barium sulphate, zinc oxide, magnesium oxide and tricalcium phosphate were prepared and studied for their suitability as implant materials by physical property tests, X-ray opacity measurement, cell culture, and animal implantations. Addition of inorganic fillers to poly(methyl methacrylate) increased the compressive strength but decreased the transverse strength. Zirconium oxide was found to be most suitable as an X-ray opaque filler, and tricalcium phosphate showed superior biocompatibility when added to poly(methyl methacrylate) in cell culture experiments. The zirconium oxide and tricalcium phosphate composites evoked no greater unfavourable tissue reaction in rats than pure poly(methyl methacrylate). From the physical and biological standpoints zirconium oxide is the radiopaque filler of choice to be incorporated in poly(methyl methacrylate) implant material and addition of tricalcium phosphate could improve it's biocompatibility.

Animals↗
PubMedDate not supplied

A histomorphometric study of tissue interface by laminar implant test in rats.

Study of the implant-tissue interface is one of the fundamental issues in implantology, both odontologic and orthopedic. The characteristics of this interface will influence the success or failure of an implant. The aim of the present study was to evaluate histomorphometrically the capacity of different metals to osseointegrate employing laminar implants of zirconium, titanium, aluminum, and zirconium coated with diamond-like carbon. The experimental model herein allowed for the quantitative evaluation of the tissue-implant interface for different metals. The implants were placed in the tibiae of Wistar rats under anesthesia and allowed to remain in situ for a 30-day period. The interfaces of the zirconium and diamond-like coated zirconium implants exhibited better responses than the interface of titanium implants. Aluminum produced a local toxic effect, evidenced by osteoid formation.

Aluminum↗
PubMed1990

About radioactivity in some PMMA bone cements.

Various bone cements containing zirconium oxide (ZrO2) as X-ray contrast medium were tested for radioactivity by means of a gamma spectrometer. All measured bone cements (PALACOS, IMPLAST, 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. As these X-ray contrast media remain in the body for decades as components of the bone cement, the radioactive zirconium oxides should be substituted by high purity radiation-free zirconium oxide or barium sulfate.

Bone Cements↗
PubMed1994

Culture surfaces coated with various implant materials affect chondrocyte growth and metabolism.

The effect on chondrocyte metabolism of culture surfaces sputter-coated with various materials used for orthopaedic implants was studied and correlated with the stage of cartilage cell maturation. Confluent, fourth-passage chondrocytes from the costochondral resting zone and growth zone of rats were cultured for 6 or 9 days on 24-well plates sputter-coated with ultrathin films of titanium, titanium dioxide, aluminum oxide, zirconium oxide, and calcium phosphate (1.67:1). Corona-discharged tissue culture plastic served as the control. The effect of surface material was examined with regard to cell morphology; cell proliferation (cell number) and DNA synthesis ([3H]thymidine incorporation); RNA synthesis ([3H]uridine incorporation); collagenase-digestible protein, noncollagenase-digestible protein, and percentage of collagen production; and alkaline phosphatase-specific activity, both in the cell layer and in trypsinized chondrocytes. Cell morphology was dependent on surface material; only cells cultured on titanium had an appearance similar to that of cells cultured on plastic. While titanium or titanium dioxide surfaces had no effect on cell number or [3H]thymidine incorporation, aluminum oxide, calcium phosphate, and zirconium oxide surfaces inhibited both parameters. Cells cultured on aluminum oxide, calcium phosphate, zirconium oxide, and titanium dioxide exhibited decreased collagenase-digestible protein, noncollagenase-digestible protein, and percentage of collagen production, but [3H]uridine incorporation was decreased only in those chondrocytes cultured on aluminum oxide, calcium phosphate, or zirconium oxide. Chondrocytes cultured on titanium had greater alkaline phosphatase-specific activity than did cells cultured on plastic, but the incorporation of [3H]uridine and production of collagenase-digestible protein, noncollagenase-digestible protein, and percentage of collagen was comparable. The response of chondrocytes from the growth zone and resting zone to culture surface was comparable, differing primarily in magnitude. Cell maturation-dependent effects were evident when enzyme activity in trypsinized and scraped cells was compared. These results indicate that different surface materials affect chondrocyte metabolism and phenotypic expression in vitro and suggest that implant materials may modulate the phenotypic expression of cells in vivo.

Alkaline Phosphatase↗
PubMed1999

Erbium:YAG laser cataract removal: role of fiber-optic delivery system.

PURPOSE: To review the properties of energy delivery systems and to evaluate the efficiency of zirconium-fluoride-based and sapphire fibers delivering erbium:YAG (Er:YAG) laser energy in a clinical laser cataract surgery system. SETTING: Department of Ophthalmology, Medical College of Virginia Campus of Virginia Commonwealth University, and Veterans Affairs Medical Center, Richmond, Virginia, USA. METHODS: Thirty-two patients had Er:YAG laser cataract extraction. Preoperative visual acuity ranged between finger counting and 20/40 secondary to cataract. The endothelial cell count was measured preoperatively and 6 weeks after surgery. A zirconium-fluoride-based fiber was used in 23 patients and a sapphire fiber in 9 patients. RESULTS: Of the patients examined after 3 months (n = 31), 90.3% (n = 28) had a visual acuity of 20/30 or better and 9.7% (n = 3), of 20/40 or 20/50. Mean endothelial cell loss at 6 weeks was 7.6% +/- 12.8 (SD). Posterior capsule rupture with vitreous loss occurred in 3 cases; 1 was attributed to laser damage to the capsule. Conversion to ultrasound phacoemulsification was required in 13 cases. Suitable fiber materials for Er:YAG laser delivery are sapphire, zirconium fluoride, silica, and germanium oxide. Toxicity of the latter is under investigation. CONCLUSION: The Er:YAG laser emulsified the lens nucleus safely and effectively. These early results include a higher than acceptable posterior capsule rupture rate and reflect the surgeon's learning curve with a new technology. Effective power delivery can be achieved with sapphire- and zirconium-fluoride-based fiber optics through a silica tip. The optimal energy delivery system has not been determined.

Aged↗
PubMed1999

Synthesis and Crystal Structure of Zr(2)Te. Distinctions in Bonding to Isotypic Sc(2)Te and the Relationship to the Structures of Congeneric Hf(2)Te and Zr(2)Se.

Zr(2)Te is accessible by high-temperature synthesis. The structure of the zirconium-rich telluride was determined by means of powder X-ray diffraction to be orthorhombic, Pnma (No. 62), Z = 12, Pearson symbol oP36, a = 1995.0(2) pm, b = 382.36(2) pm, c = 1065.63(9) pm. Pairwise interpenetrating columns of trans-face-shared, centered Zr(9) cuboids, reminiscent of the bcc high-temperature form of zirconium can be recognized as the topologically characteristic structural feature. Tellurium atoms capping the remaining square faces complete the motif of a [Zr(8)Te(4)] double string running parallel [010]. The tellurium atoms are 7-, 8- and 9-fold coordinated by zirconium. The coordination figures represent mono-, bi- and tricapped distorted trigonal prisms, with zirconium atoms capping the square faces of the prisms. Extended Hückel calculations revealed distinctions in bonding in Zr(2)Te and the isotypic Sc(2)Te. According to Mulliken overlap populations, the heteronuclear interactions are similar in both tellurides. However, the lower valence electron concentration available for M-M bonding in Sc(2)Te is reflected in a considerable restriction of the attractive homonuclear interactions to one-dimensional metal cores, whereas in Zr(2)Te M-M bonding regions extend in space. The structure of Zr(2)Te is contrasted with two other types of bcc fragment structures adopted by the congeneric Hf(2)Te and Zr(2)Se. We show that the structural diversity observed for various dimetal chalcogenides is controlled by an intimate interplay of electronic and geometric factors.

Journal Article↗
PubMed2000

Trigonal prismatic vs octahedral coordination geometry: syntheses and structural characterization of hexakis(arylthiolato) zirconate complexes.

Treating [Li(tmeda)]2[Zr(CH3)6] with aryl thiols, HSC6H4-4-R, in a 1:6 stoichiometry in diethyl ether affords excellent yields of [Li(tmeda)]2[Zr(SC6H4-4-R)6], where R = CH3 (1(2-)) or OCH3 (2(2-)) and tmeda denotes N,N,N',N'-tetramethylethylenediamine. These complexes are air-sensitive canary-yellow solids, soluble in hexane, diethyl ether, THF, and acetonitrile, that form yellow single crystals of [Li(tmeda)](2)1 (diethyl ether solution) or [Li(THF)3](2)2 (THF solution) from saturated solutions at -20 degrees C. Both complexes were characterized by X-ray crystallography and consist of a zirconium atom coordinated solely by the sulfur atoms of six aryl thiolate ligands in a nonoctahedral geometry. In each structure the lithium cation coordinates to the three sulfur atoms on the triangular faces of the S6 pseudotrigonal prism. These lithium-sulfur interactions appear to play a role in determining the coordination geometry about the metal center by orienting the sulfur lone pairs of electrons slightly out of the plane defined by the S3 triangular face and tilted away from the zirconium atoms. A likely consequence is the positioning of the sulfur lone pairs of electrons away from orthogonality with the zirconium-sulfur vector, and hence, they are poorly arranged to pi-interact with zirconium. Complex 1(2-) with a twist angle of ca. 9.18 degrees (trigonal prism, 0 degree; octahedron, 60 degrees) agrees with the interpretations of computational studies on d degree complexes, which suggest that a nearly trigonal prismatic geometry is favored when the interaction between metal and ligand is primarily through sigma-bonds. The intrinsically weak pi-donor thiolate ligand is probably converted to a primarily sigma-bonding system by the lithium-sulfur interaction. On the other hand complex 2(2-) with a twist angle of ca. 30.38 degrees is trigonally twisted to the midpoint of the trigonal prismatic-to-octahedral reaction coordinate. In complex 2(2-) the 4-OCH3 group is an electron donor by resonance effects that possibly may lead to the movement away from the expected trigonal prismatic geometry due to either pi-interactions or electrostatics repulsion.

Journal Article↗
PubMed2003

Multigram scale synthesis and characterization of monodisperse tetragonal zirconia nanocrystals.

A new and simple method has been developed to synthesize large quantities of highly monodisperse tetragonal zirconia nanocrystals. In this synthesis, a nonhydrolytic sol-gel reaction between zirconium(IV) isopropoxide and zirconium(IV) chloride at 340 degrees C generated 4 nm sized zirconia nanoparticles. A high-resolution transmission electron microscopic (HRTEM) image showed that the particles have a uniform particle size distribution and that they are highly crystalline. These monodisperse nanoparticles were synthesized without any size selection process. X-ray diffraction studies combined with Rietveld refinement revealed that the ZrO(2) nanocrystals are the high-temperature tetragonal phase, and very close to a cubic phase. When zirconium(IV) bromide is used as a precursor instead of zirconium chloride, zirconia nanoparticles with an average size of 2.9 nm were obtained. The UV-visible absorption spectrum of 4 nm sized zirconia nanoparticles exhibited a strong absorption starting at around 270 nm. A fluorescence spectrum with excitation at 300 nm showed a broad fluorescence band centered around 370 nm. FTIR spectra showed indication of TOPO binding on the ZrO(2) nanoparticle surface. These optical studies also suggest that the nanoparticles are of high quality in terms of narrow particle size distribution and relatively low density of surface trap states.

Journal Article↗
PubMed2000

Ring-opening reactions of oxabicyclic alkene compounds: enantioselective hydride and ethyl additions catalyzed by group 4 metals

Titanium and zirconium catalysts selectively catalyze either the ethyl or hydride addition to [2.2.1] 4, 5-bis(methoxymethyl)-7-oxabicycloheptene (6); the ring-opened products formed depend on catalyst, temperature, alkylaluminum reagent, and the concentration of alkylaluminum. Bis(neoisomenthylindenyl)zirconium dichloride catalyzes the ethyl addition ring-opening of 6 to produce (1R,2S,3S,6R)-2, 3-bis(methoxymethyl)-6-ethylcyclohex-4-enol (7) in 96% ee. Zirconium catalysts catalyze the ring-opening of [3.2.1] 2, 4-dimethyl-3-(benzyloxy)-8-oxabicyclo-6-octene (7) when ethylmagnesium bromide is used as a reagent. Both hydride and ethyl addition products are obtained at all conditions studied. Bis(neoisomenthylindenyl)zirconium dichloride catalyzes the ethyl addition ring-opening of 7 to produce (1S,2R,3S,4S,7S)-2, 4-dimethyl-3-(benzyloxy)-7-ethyl-5-cyclohexen-1-ol (8) in 48% ee.

Journal Article↗
PubMed1992

Evaluation of desferal as a bifunctional chelating agent for labeling antibodies with Zr-89.

Zirconium-desferal was prepared and analysed by TLC, NMR and u.v.-spectroscopy. The stoichiometry of the complex was found to be 1:1. Chelation of desferal, coupled to resin, with 88Zr appeared to be fast and almost quantitative in various buffer systems in a broad pH-range (4-7). A high in vitro stability of the zirconium-desferal complex was observed; less than 0.2% zirconium was lost within 24 h in plasma-solutions.

Antibodies↗
PubMed2006

Evaluation of cutting efficiency of ultrasonic tips used in orthograde endodontic treatment.

The purpose of the present study was to evaluate the cutting efficiency of the three different ultrasonic tips for orthograde endodontic treatment: stainless steel, zirconium nitride-coated, and diamond-coated tips. An ultrasonic handpiece was mounted on a custom-made automated balance, and each tip repeatedly penetrated dental stone blocks to a depth of 3 mm for 10 times. The amount of time taken to penetrate 3 mm of stone was measured. The diamond-coated tips showed significantly greater cutting efficiency than either stainless steel tips or zirconium-nitride coated tips. The stainless steel tips showed initial better cutting efficiency, but over time , there is no significant difference between the cutting efficiency of the stainless steel tips and the zirconium nitride coated tips. The diamond coated tips were the only group that showed breakage in this study.

Calcium Sulfate↗
PubMed2003

Effect of surface conditioning methods on the bond strength of luting cement to ceramics.

OBJECTIVES: This study evaluated the effect of three different surface conditioning methods on the bond strength of a Bis-GMA based luting cement to six commercial dental ceramics. METHODS: Six disc shaped ceramic specimens (glass ceramics, glass infiltrated alumina, glass infiltrated zirconium dioxide reinforced alumina) were used for each test group yielding a total number of 216 specimens. The specimens in each group were randomly assigned to one of the each following treatment conditions: (1) hydrofluoric acid etching, (2) airborne particle abrasion, (3) tribochemical silica coating. The resin composite luting cement was bonded to the conditioned and silanized ceramics using polyethylene molds. All specimens were tested at dry and thermocycled (6.000, 5-55 degrees C, 30 s) conditions. The shear bond strength of luting cement to ceramics was measured in a universal testing machine (1 mm/min). RESULTS: In dry conditions, acid etched glass ceramics exhibited significantly higher results (26.4-29.4 MPa) than those of glass infiltrated alumina ceramics (5.3-18.1 MPa) or zirconium dioxide (8.1 MPa) (ANOVA, P<0.001). Silica coating with silanization increased the bond strength significantly for high-alumina ceramics (8.5-21.8 MPa) and glass infiltrated zirconium dioxide ceramic (17.4 MPa) compared to that of airborne particle abrasion (ANOVA, P<0.001). Thermocycling decreased the bond strengths significantly after all of the conditioning methods tested. SIGNIFICANCE: Bond strengths of the luting cement tested on the dental ceramics following surface conditioning methods varied in accordance with the ceramic types. Hydrofluoric acid gel was effective mostly on the ceramics having glassy matrix in their structures. Roughening the ceramic surfaces with air particle abrasion provided higher bond strengths for high-alumina ceramics and the values increased more significantly after silica coating/silanization.

Acid Etching, Dental↗
PubMed1977

Sensitization with Cr, Ni and Zr salts and allergic type granuloma formation in the guinea pig.

Guinea pigs were sensitized to potassium dichromate, nickel sulfate and sodium zirconium lactate by three methods of immunization in Freund's complete adjuvant: Polak, split adjuvant, and maximization (modified Magnusson and Kligman). These were followed after 2 weeks by weekly intradermal injections of 25 microng of the metal salt. Delayed hypersensitivity-like reactions developed 3 to 12 weeks after initial injection. Reactivity, although strong with an increase in thickness of over 0.7 mm and/or diameter of erythema of over 8 X 8 mm, was frequently transient, the animal losing reactivity on subsequent skin test or after 2 or 3 skin tests. In two-thirds of the experiments using sodium zirconium lactate, delayed hypersensitivity-like reactions at 24 hr developed into nodular lesions which reached peak intensity at 8 days and histologically contained histiocytes with an epithelioid cell appearance and giant cells. In some experiments, sodium zirconium lactate-sensitive animals showed cross reactivity with potassium dichromate, but not with nickel sulfate.

Animals↗
PubMed2005

Structural resistance in immature teeth using root reinforcements in vitro.

The purpose of this study was to evaluate in vitro the efficacy of root reinforcements by light-cured composite resin or zirconium fiber post in simulated immature non-vital teeth. Fifty-six bovine incisors teeth were used for this study. The crown of each tooth was removed in the medium third to obtain a standard length of 30 mm. The specimens were divided into four groups (n = 14): G1) the root canals were instrumented and enlarged to simulate immature non-vital teeth and were reinforced with a light-cured composite resin using a translucent curing post (Luminex system); (G2) the specimens were instrumented, enlarged and they received root reinforcement with zirconium fiber post; G3 (positive control): they received similar treatment to the G1 and G2 groups, but did not receive root reinforcement; G4 (negative control): the roots were not weakened and did not receive reinforcement. Every tooth was submitted to compressive force using an Instron testing machine with an angle of 45 degrees at a speed of 1 mm min(-1) until the fracture. The results showed a markedly increased resistance to fracture in the G1 and G2 (122.38 and 122.08 kg f, respectively). Among the results of G1 and G2 there was not any significant difference (P > 0.05) but they were significantly different from the control groups (P < 0.05). The conclusion is that the use of root reinforcements with zirconium fiber post or composite resin can increase significantly the structural resistance of the weakened teeth, decreasing the risk of the fracture.

Animals↗
PubMed1999

Copper Phthalocyanine-Mica Interactions in Nonaqueous Media.

The interaction forces and adhesion of copper phthalocyanine particles with a mica substrate in isoparaffin were directly measured using an atomic force microscope. The study was conducted primarily to investigate the stabilization mechanism of copper phthalocyanine dispersions in a nonaqueous medium. The nature of the forces was examined in the presence of various concentrations of water and zirconium octanoate, both of which are present at the particle-isoparaffin interface. A weak attraction, as well as a small adhesion, exists between the copper phthalocyanine particles and the mica surface. These interactions are a function of the water content of the hydrocarbon phase and appear to be a result of capillary forces. The addition of zirconium octanoate produces significant short range repulsive forces with no adhesion between the copper phthalocyanine and mica surfaces. The shape of the force against distance curves suggests that the dispersion stability of the copper phthalocyanine arises through steric stabilization by adsorbed zirconium octanoate. The same qualitative interaction behavior was observed when the copper phthalocyanine particle was coated with a layer of polyvinyl acetate latex. Copyright 1999 Academic Press.

Journal Article↗
PubMed2003

A case for asymmetric hydrozirconation.

Hydrozirconation of cis-2-butene with Cp*ZrHCl[N(t-Bu)C(Me)N(Et)], generated in situ through hydrogenolysis of Cp*ZrCl(SiMe2Ph)[N(t-Bu)C(Me)N(Et)] (5), proceeds in high yield to produce a 1:2 mixture of the kinetically stable, diastereomeric sec-butyl complexes, 3a and 3b. Hydrozirconation of trans-2-butene under identical conditions provides a 2:1 mixture of 3a and 3b. Isolation of diastereomerically pure 3a was achieved through reaction of Cp*ZrCl2[N(t-Bu)C(Me)N(Et)] (4) with sec-butyllithium to provide a 2:1 ratio of 3a and 3b, followed by fractional crystallization. Crystallographic analysis of 3a establishes the relative configuration of the sec-butyl group with respect to the chiral zirconium center, thereby permitting construction of diastereomeric transition states that explain the origin of high face selectivity in the hydrozirconation of cis-2-butene. Finally, both iodinative zirconium-carbon bond cleavage and insertion of tert-butyl isocyanide into the zirconium-carbon bond of the sec-butyl group of 3a were found to proceed in high yield and with retention of the secondary alkyl structure. Together, these results provide a critical platform upon which efforts directed toward the asymmetric hydrozirconation of alkenes can be based.

Journal Article↗
PubMed1998

Influence of aging heat treatment on mechanical properties of biomedical Ti-Zr based ternary alloys containing niobium.

Titanium-zirconium based alloys containing a small amount of niobium were investigated in order to evaluate their possible use as biomedical materials. Zirconium, which belongs to the IVa group, is known to have good corrosion resistance and biocompatibility similar to titanium. As the titanium-zirconium system shows a complete solid solution, a wide variation of alloy design is available and large quantities of solid-solution hardening must be possible. Niobium, having a beta-phase stabilizing effect, was chosen as a ternary element in order to control desirably the microstructure. There have been no reports which suggest its harm to a living body. The alloys containing 2% or 3% niobium showed the highest hardness value after aging heat treatment at 773 K. In contrast to this, no alteration of hardness was seen in specimens aged at 1073 K. Through conventional X-ray diffractometry and in situ X-ray analysis using a hot stage, beta-phase precipitation in the A matrix was identified. From the above results, it is concluded that alloys containing 2%-3% niobium are hopeful candidates for new kinds of biomedical alloys, when they are heat treated under suitable conditions.

Journal Article↗
PubMed1979

Evidence that resistance to the calcemic action of parathyroid hormone in rats with acute uremia is caused by phosphate retention.

An animal model was developed to examine the cause of resistance to the calcemic action of PTH in renal failure. Thyroparathyroidectomized (TPTX) rats were repeatedly reinfused with their excreted urine, over a 5-hour period, to produce an acute uremic animal with normal kidneys. Nonuremic controls were infused with equivalent volumes of a simple electrolyte solution. Using this model, we have demonstrated impaired calcemic response to PTH (Lilly Parathyroid Extract, 80 U/100 g) in urine-infused rats compared with electrolyte-infused rats. The final plasma calcium concentrations were 12.0 +/- 0.3 and 14.9 +/- 0.3 mg/dl, respectively (P less than 0.001). The cause of this impaired calcemic response was investigated by reinfusing rats with their own urine that had been pretreated with either activated charcoal or zirconium oxide in two different anionic forms, or urine that had been ultrafiltrated through an Amicon membrane of which the stated molecular-weight cut-off of the smallest pore-size membrane was 500 daltons. It was found that charcoal and ultrafiltration techniques had no effect, whereas the zirconium oxide treatment completely corrected the impaired calcemic response and returned the plasma phosphorus to a concentration similar to that in nonuremic controls. This can be explained by the fact that the principal effect of zirconium oxide on urine is to remove inorganic phosphate. Other groups of TPTX rats given PTH extract were infused with an electrolyte solution containing varying amounts of phosphate up to a maximum similar to the amount that a urine-infused rat would receive. A highly significant inverse relationship was found between the dose of phosphate infused with the electrolyte solution and the measured calcemic response to PTH. This relationship is represented by the following equation: calcium (mg/dl) = 14.84 - 0.139 inorganic phosphate; r = 0.915, P less than 0.001. From these series of studies, we conclude that phosphate retention is the cause of resistance to the calcemic action of PTH extract in this acute uremic model.

Acute Kidney Injury↗