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PubMed2003

Improved bactericidal activity of silver-loaded zirconium phosphate in the presence of Cl- by combining with hydroxyapatite.

Silver-loaded zirconium phosphate (AgZ) was combined with hydroxyapatite (HA) to prepare an antibacterial composite (AgZ/HA) with improved activity in the presence of Cl-. When Escherichia coli cells were deactivated in 154 mM NaCl, the bacterial survival ratio at 90 min for AgZ/HA was 3.9 x 10(-4) compared to 1.2 x 10(-1) for AgZ itself. Because the bactericidal activity of AgZ/HA decreased with increasing phosphate ion up to 10 mM, cell adsorption onto the combined HA moiety probably compensated for the Cl- -induced deterioration in the activity of the silver-based bactericide.

Anti-Bacterial Agents↗
PubMed2003

Synthesis of cubic zirconium and hafnium nitride having Th3P4 structure.

High-pressure synthesis is a powerful method for the preparation of novel materials with high elastic moduli and hardness. Additionally, such materials may exhibit interesting thermal, optoelectronic, semiconductuing, magnetic or superconducting properties. Here, we report on the high-pressure synthesis of zirconium and hafnium nitrides with the stoichiometry M3N4, where M = Zr, Hf. Synthesis experiments were performed in a laser-heated diamond anvil cell at pressures up to 18 GPa and temperatures up to 3,000 K. We observed formation of cubic Zr3N4 and Hf3N4 (c-M3N4) with a Th3P4-structure, where M-cations are eightfold coordinated by N anions. The c-M3N4 phases are the first binary nitrides with such a high coordination number. Both compounds exhibit high bulk moduli around 250 GPa, which indicates high hardness. Moreover, the new nitrides, c-Zr3N4 and c-Hf3N4, may be the first members of a larger group of transition metal and/or lanthanide nitrides with interesting ferromagnetic or superconducting behaviour.

Crystallization↗
PubMed2005

New and versatile routes to zirconium imido dichloride compounds.

Reactions of zirconium dialkyl- or bis(amido)-dichloride complexes "[Zr(CH2SiMe3)2Cl2(Et2O)2]" or [Zr(NMe2)2Cl2(THF)2] with primary alkyl and aryl amines are described. Reaction of "[Zr(CH2SiMe3)2Cl2(Et2O)2]" with RNH2 in THF afforded dimeric [Zr2(mu-NR)2Cl4(THF)4](R=2,6-C6H3iPr2 (1), 2,6-C6H3Me2 (2) or Ph (3)), [Zr2(mu-NR)2Cl4(THF)3](R=tBu (5), iPr (6), CH2Ph (7)), or the "ate" complex [Zr2(mu-NC6F5)2Cl6(THF)2{Li(THF)3}2](4, the LiCl coming from the in situ prepared "[Zr(CH2SiMe3)2Cl2(Et2O)2]"). With [Zr(NMe2)2Cl2(THF)2] the compounds [Zr2(mu-NR)2Cl4(L)x(L')y](R=2,6-C6H3iPr2 (8), 2,6-C6H3Me2 (9), Ph (10) or C6F5 (11); (L)x(L')y=(NHMe2)3(THF), (NHMe2)2(THF)2 or undefined), [Zr2(mu-NtBu)2Cl4(NHMe2)3] (12) and insoluble [Zr(NR)Cl2(NHMe2)]x(R=iPr (13) or CH2Ph (14)) were obtained. Attempts to form monomeric terminal imido compounds by reaction of or with an excess of pyridine led, respectively, to the corresponding dimeric adducts [Zr2(mu-2,6-C6H3Me2)2Cl4(py)4] (15) and [Zr2(mu-NtBu)2Cl4(py)3] (16). The X-ray structures of 1, 2, 4, 8, 12 and 15 have been determined.

Chlorides↗
PubMed2005

A novel transformation of a zirconium imido compound and the development of a new class of N3 donor heteroscorpionate ligand.

Reaction of the dimeric zirconium imido compound [Zr2(mu-NAr)2Cl4(THF)4] with tris(3,5-dimethylpyrazolyl)methyl silane very selectively gave [Zr{(Me2pz)2Si(Me)NAr}Cl3] (1), a highly active pre-catalyst for ethylene polymerisation; a more general and versatile route to N3 donor heteroscorpionate compounds was achieved via the protio ligand (Me2pz)2CHSi(Me)2N(H)iPr for which neutral and cationic organometallic Group 3 and 4 derivatives are reported (Ar = 2,6-C6H(3)iPr2).

Catalysis↗
PubMed2006

Dinitrogen functionalization with bis(cyclopentadienyl) complexes of zirconium and hafnium.

The rich chemistry of substituted bis(cyclopentadienyl)zirconium and hafnium complexes bearing side-on coordinated dinitrogen ligands is highlighted in this Perspective. Our studies in this area were initially motivated by the desire to understand side-on vs. end-on dinitrogen coordination in bimetallic zirconocene and hafnocene N2 compounds. In the cases where eta2,eta2-dinitrogen compounds were isolated, both structural and computational data have established significant imido character in the metal-nitrogen bonds. This additional bonding interaction, which is diminished in end-on complexes bearing both terminal and bridging N2 ligands, facilitates dinitrogen functionalization by non-polar reagents including dihydrogen, carbon-hydrogen bonds and weak Brønsted acids such as water and ethanol. In hafnocene chemistry, where unwanted side-on, end-on isomerization is suppressed, cycloaddition of phenylisocyanate to coordinated N2 has also been accomplished. For N-H bond forming reactions involving H2, kinetic measurements, in addition to isotopic labelling and computational studies, are consistent with dinitrogen functionalization by 1,2-addition involving a highly ordered, four-centred transition structure.

Cyclopentanes↗
PubMed2005

High-resolution neutron-scattering study of slow dynamics of surface water molecules in zirconium oxide.

We have performed a quasielastic neutron-scattering experiment on backscattering spectrometer with sub-mueV resolution to investigate the slow dynamics of surface water in zirconium oxide using the sample studied previously with a time-of-flight neutron spectrometer [E. Mamontov, J. Chem. Phys. 121, 9087 (2004)]. The backscattering measurements in the temperature range of 240-300 K have revealed a translational dynamics slower by another order of magnitude compared to the translational dynamics of the outer hydration layer observed in the time-of-flight experiment. The relaxation function of this slow motion is described by a stretched exponential with the stretch factors between 0.8 and 0.9, indicating a distribution of the relaxation times. The temperature dependence of the average residence time is non-Arrhenius, suggesting that the translational motion studied in this work is more complex than surface jump diffusion previously observed for the molecules of the outer hydration layer. The observed slow dynamics is ascribed to the molecules of the inner hydration layer that form more hydrogen bonds compared to the molecules of the outer hydration layer. Despite being slower by two orders of magnitude, the translational motion of the molecules of the inner hydration layer may have more in common with bulk water compared to the outer hydration layer, the dynamics of which is slower than that of bulk water by just one order of magnitude.

Chemistry, Physical↗
PubMed2005

Influence of framework configuration on the marginal adaptation of zirconium dioxide ceramic anterior four-unit frameworks.

OBJECTIVE: To evaluate the influence of the framework configuration on the marginal adaptation of four-unit anterior fixed partial denture (FPD) frameworks made of partially sintered zirconium dioxide (ZrO2) ceramics. MATERIAL AND METHODS: Forty-eight standardized partially sintered ZrO2 ceramic four-unit FPD frameworks were fabricated using three different CAD/CAM systems: Cercon Smart Ceramics (group CE), Vita YZ/Cerec In-Lab (group YZ/CL), and Xawex (group XA). Two different framework configurations (straight and curved) were manufactured for each group. The marginal adaptation of the frameworks was measured at 60 different points across the entire circumferential margin using a stereomicroscope. Marginal discrepancy values were compared between the two framework designs and between the three test groups using the t-test. The overall level of statistical significance was 5% after correcting the p-values using the Bonferroni-Holm method. RESULTS: The following geometrical means of the marginal discrepancies were obtained for the curved/straight design: group CE, 120.0 microm/88.0 microm; group YZ/CL, 96.8 microm/86.5 microm; and group XA, 147.3 microm/113.4 microm. Significant differences were detected between the straight and curved designs for groups CE (p=0.001) and XA (p=0.003), but not for group YZ/CL (p = 0.225). For both designs, the marginal discrepancies were significantly smaller in group YZ/CL than in group XA. For the curved design, the marginal discrepancies in group YZ/CL were also significantly smaller than those in group CE. CONCLUSIONS: Within the limitations of this study, the framework configuration influences the marginal adaptation of anterior four-unit FPD frameworks that are manufactured from partially sintered ZrO2 ceramics independently of CAD/CAM system.

Ceramics↗
PubMed2003

Long-lived positron emitters zirconium-89 and iodine-124 for scouting of therapeutic radioimmunoconjugates with PET.

Antibody-PET imaging might be of value for the selection of radioimmunotherapy (RIT) candidates to confirm tumor targeting and to estimate radiation doses to tumor and normal tissues. One of the requirements to be set for such a scouting procedure is that the biodistributions of the diagnostic and therapeutic radioimmunoconjugates should be similar. In the present study we evaluated the potential of the positron emitters zirconium-89 ((89)Zr) and iodine-124 ((124)I) for this approach, as these radionuclides have a relatively long half-life that matches with the kinetics of MAbs in vivo (t(1/2) 3.27 and 4.18 days, respectively). After radiolabeling of the head and neck squamous cell carcinoma (HNSCC)-selective chimeric antibody (cMAb) U36, the biodistribution of two diagnostic (cMAb U36-N-sucDf-(89)Zr and cMAb U36-(124)I) and three therapeutic radioimmunoconjugates (cMAb U36-p-SCN-Bz-DOTA-(88)Y-with (88)Y being substitute for (90)Y, cMAb U36-(131)I, and cMAb U36-MAG3-(186)Re) was assessed in mice with HNSCC-xenografts, at 24, 48, and 72 hours after injection. Two patterns of biodistribution were observed, one pattern matching for (89)Zr- and (88)Y-labeled cMAb U36 and one pattern matching for (124)I-, (131)I-, and (186)Re-cMAb U36. The most remarkable differences between both patterns were observed for uptake in tumor and liver. Tumor uptake levels were 23.2 +/- 0.5 and 24.1 +/- 0.7%ID/g for the (89)Zr- and (88)Y-cMAb U36 and 16.0 +/- 0.8, 15.7 +/- 0.79 and 17.1 +/- 1.6%ID/g for (124)I-, (131)I-, and (186)Re-cMAb U36-conjugates, respectively, at 72 hours after injection. For liver these values were 6.9 +/- 0.8 ((89)Zr), 6.2 +/- 0.8 ((88)Y), 1.7 +/- 0.1 ((124)I), 1.6 +/- 0.1 ((131)I), and 2.3 +/- 0.1 ((186)Re), respectively. These preliminary data justify the further development of antibody-PET with (89)Zr-labeled MAbs for scouting of therapeutic doses of (90)Y-labeled MAbs. In such approach (124)I-labeled MAbs are most suitable for scouting of (131)I- and (186)Re-labeled MAbs.

Animals↗
PubMed2002

Root-end fracture during retropreparation: a comparison between zirconium nitride-coated and stainless steel microsurgical ultrasonic instruments.

The purpose of this study was to evaluate a stainless steel (CT-5) and zirconium nitride coated (KiS) microsurgical ultrasonic instrument with regard to possible root-end fracture production during retropreparation. Forty extracted human central incisors were prepared in a crown-down fashion. Canals were obturated with gutta-percha by lateral condensation. Root-ends were resected. Teeth were placed in methylene blue for 48 h and evaluated by three independent evaluators under microscope. Teeth with existing fractures were eliminated from the study. The remaining teeth were randomly divided into two equal groups. Group A was prepared with the CT-5 tip and Group B with the KiS tip. Preparation time was recorded for all roots. The teeth were again immersed in methylene blue for 48 h and reevaluated. No root-end fractures were produced by either the KiS or CT-5 microsurgical ultrasonic instruments.

Apicoectomy↗
PubMed1993

Histomorphometry of initial bone healing around zirconium implants in rats.

Histometric evaluations as a function of time were performed with zirconium implants during the healing period in 10 Wistar rats. The implants (7 mm x 1 mm x 0.1 mm) were placed in the right tibia of the animals. Five rats were killed after 14 days and the remainder were sacrificed 30 days after implantation. The tibiae were resected, radiographed, and embedded in poly(methyl methacrylate). Three cross-sections were obtained transverse to the major axis of each tibia. Osseointegrated tissue thickness, percentage of direct bone-to-implant contact, and osseointegrated tissue volume were evaluated for each specimen. Bone formation was observed on the surface of the implanted strip that was in contact with tibia marrow. This method is proposed for the evaluation of the first stage of healing of bone in contact with different implant materials subjected to various surface treatment.

Animals↗
PubMed2006

Performance of immuno-positron emission tomography with zirconium-89-labeled chimeric monoclonal antibody U36 in the detection of lymph node metastases in head and neck cancer patients.

PURPOSE: Immuno-positron emission tomography (PET), the combination of PET with monoclonal antibodies (mAb), is an attractive option to improve tumor detection and to guide mAb-based therapy. The long-lived positron emitter zirconium-89 ((89)Zr) has ideal physical characteristics for immuno-PET with intact mAbs but has never been used in a clinical setting. In the present feasibility study, we aimed to evaluate the diagnostic imaging performance of immuno-PET with (89)Zr-labeled-chimeric mAb (cmAb) U36 in patients with squamous cell carcinoma of the head and neck (HNSCC), who were at high risk of having neck lymph node metastases. EXPERIMENTAL DESIGN: Twenty HNSCC patients, scheduled to undergo neck dissection with or without resection of the primary tumor, received 75 MBq (89)Zr coupled to the anti-CD44v6 cmAb U36 (10 mg). All patients were examined by computed tomography (CT) and/or magnetic resonance imaging (MRI) and immuno-PET before surgery. Six patients also underwent PET with (18)F-fluoro-2-deoxy-d-glucose. Immuno-PET scans were acquired up to 144 hours after injection. Diagnostic findings were recorded per neck side (left or right) as well as per lymph node level (six levels per side), and compared with histopathologic outcome. For this purpose, the CT/MRI scores were combined and the best of both scores was used for analysis. RESULTS: Immuno-PET detected all primary tumors (n = 17) as well as lymph node metastases in 18 of 25 positive levels (sensitivity 72%) and in 11 of 15 positive sides (sensitivity 73%). Interpretation of immuno-PET was correct in 112 of 121 operated levels (accuracy 93%) and in 19 of 25 operated sides (accuracy 76%). For CT/MRI, sensitivities of 60% and 73% and accuracies of 90% and 80% were found per level and side, respectively. In the six patients with seven tumor-involved neck levels and sides, immuno-PET and (18)F-fluoro-2-deoxy-d-glucose PET gave comparable diagnostic results. CONCLUSION: In this study, immuno-PET with (89)Zr-cmAb U36 performed at least as good as CT/MRI for detection of HNSCC lymph node metastases.

Aged↗
PubMed1991

An evaluation of zirconium oxide brackets: a preliminary laboratory and clinical report.

A pre-production sample of zirconium oxide (ceramic) brackets was examined in this study. A laboratory investigation of the tensile/peel bond strength of the brackets was carried out using two light-cured adhesives (Prismafil and Heliosit) and one chemically-cured adhesive (Delphic). The mode of failure was also investigated using optical and scanning electron microscopy. The bond strengths achieved with Prismafil were statistically significantly (P less than 0.05) lower than Heliosit and Delphic between which no significant differences were found. All samples failed at the bracket-adhesive interface. A clinical test demonstrated the extreme ease of sliding along stainless steel and nickel-titanium archwires, and revealed a low plaque adhesion. The principal disadvantage of these brackets appears to be their off-white highly opaque appearance which in addition to giving poor aesthetics may adversely affect bond strength with light-cured adhesives.

Adhesives↗
PubMed1990

[Effect of zirconium on immunological reactions of T cells and macrophages in mice].

The effects of zirconium (Zr) on T cells and macrophages in mice were studied in vitro using the indexes of immunological reactions, mitogenesis of C3H/HeJ mouse thymocytes induced by PHA and the production of interleukin-1 of C3H/He mouse intraperitoneal macrophages (MIL-1). The mitogenesis of thymocytes induced by PHA when stimulated with Zr solutions at various concentrations or culture supernatants of macrophages stimulated with LPS and Zr, or Zr alone, ware as shown below. 1. The mitogenesis of thymocytes by PHA was enhanced in the presence of Zr at 0.625-2.5 microM, and suppressed in the presence of Zr at 5-10 microM in culture 2. This reaction was enhanced by the addition of supernatants of macrophages stimulated with LPS and Zr. The most activation by LPS and Zr was shown at concentrations of 0.625-1.25 microM in culture, and the degree activated corresponding to 12.5-25 I.U. of MIL-1. 3. On the other hand, this reaction was inhibited by addition of supernatants of macrophages stimulated with Zr alone. From these results, it is suggested that Zr serves various functions such as an activator or inhibitor of T-cell mitogenesis by PHA, and that this may depend upon the Zr concentration in culture. In regard to the effect of Zr on MIL-1 production, Zr may activate this reaction by LPS, and Zr alone may induce MIL-1 production from macrophages.

Animals↗
PubMed2004

In vitro biocompatibility of a new titanium-29niobium-13tantalum-4.6zirconium alloy with osteoblast-like MG63 cells.

BACKGROUND: Titanium-29niobium-13tantalum-4.6zirconium (TiNb) has recently been developed as a new implant material. TiNb is composed of non-toxic elements and has a lower modulus of elasticity than the other titanium alloys. However, its biocompatibility has not been adequately characterized. The aim of this study was to evaluate the biocompatibility of TiNb using an osteoblast-titanium co-culture system. METHODS: MG63 cells were cultured on three kinds of titanium disks: TiNb, pure titanium (pTi), and titanium-6aluminum-4vanadium (TiAl), prepared with two different surfaces, a polished and acid-etched surface and a machined-grooved surface. The surface topography and roughness were evaluated by scanning electron microscopy (SEM). After 48 hours culture, the number of proliferating cells and prostaglandin E2 (PGE2) production in the culture supernatant were determined. RESULTS: There was no significant difference in surface roughness among the three titanium disks with a polished and acid-etched surface. After 48 hours of culture, the number of cells was significantly reduced on pTi and TiAl compared to TiNb and the control. PGE2 production was significantly higher on pTi than on TiAl, TiNb, and the control. We further examined the effect of surface roughness on PGE2 production using machine-grooved titanium disks. While pTi and TiAl stimulated the production of PGE2 depending on surface roughness, roughened TiNb did not affect PGE2 production. CONCLUSIONS: These results suggest that TiNb may exhibit favorable biocompatibility because it has an efficient surface topography for cell proliferation, and the level of PGE2 production does not depend on surface roughness. We conclude that TiNb may be useful as an implant material.

Alloys↗
PubMed2004

Glucose sensor based on glucose oxidase immobilized by zirconium phosphate.

Amperometric glucose sensors were fabricated using glucose oxidase (GOx) entrapped in zirconium hydrogenphosphate (ZrP), and their performance was evaluated. Reportedly, alpha-ZrP is one of the candidates that are expected to improve the stability of enzymes immobilized on solid surfaces. We intercalated GOxs into ZrP (GOx/ZrP), cast the GOx/ZrP suspension in polyvinylalcohol on a platinum electrode, and dried it in a vacuum oven. The morphological layered structure was investigated by scanning electron microscopy. The enzymatic activities, which were determined by open-circuit potentiometric technique, reached the highest when GOxs were immobilized in ZrP at ca. pH 5. In vitro tests showed good linear responses in the 0-25 mM range and the sensitivity of 0.14 nA mM(-1) at 0.4 V vs. Ag/AgCl. The sensors, as made, were stable for more than 3 days within a limited deterioration.

Biosensing Techniques↗
PubMed2005

A single-retainer zirconium dioxide ceramic resin-bonded fixed partial denture for single tooth replacement: a clinical report.

This clinical report describes a treatment for the replacement of a missing mandibular anterior tooth using a cantilever single-retainer resin-bonded fixed partial denture (RBFPD), fabricated from zirconium dioxide (ZrO2) ceramic. No clinical complications were observed at the 2-year 6-month follow-up examination after placement of the ZrO2 ceramic RBFPD, and satisfactory functional and esthetic results were achieved. A treatment modality using a cantilever ZrO2 ceramic RBFPD is an alternative for single anterior tooth replacement. Further clinical studies are required to evaluate the long-term potential of cantilever single-retainer ZrO2 ceramic RBFPDs.

Ceramics↗