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PubMed2005

Design and evolution of copper apatite catalysts for N-arylation of heterocycles with chloro- and fluoroarenes.

We report the preparation of recyclable heterogeneous catalysts, copper-exchanged fluorapatite, and copper-exchanged tert-butoxyapatite by incorporating basic species F-/tBuO- in apatite in situ by coprecipitation and subsequent exchange with Cu(II). These basic copper catalysts catalyzed N-arylation of imidazoles and other heterocycles with chloroarenes and electron-poor fluoroarenes in good to excellent yields. Synthesis and characterization of some of the intermediates of the catalytic cycle gave some insight into the mechanism of the very important organic transformation. The necessity of basic sites for the activation of C-Cl and C-F bonds in the N-arylation of heterocycles with haloarenes is well-established.

Journal Article↗
PubMed2000

Characterization of the transformation from calcium-deficient apatite to beta-tricalcium phosphate.

The structural changes that occur during the transformation of a Ca-deficient apatite, prepared by a wet chemical method, to beta-TCp were investigated. X-ray diffraction (XRD) analysis of as-prepared samples and samples calcined at temperatures between 500 and 1100 degrees C showed that the transformation occurs over the temperature range 710-740 degrees C, under non-equilibrium conditions. The change in crystallite size with increasing calcination/sintering temperature was studied by XRD using the Scherrer formula. Fourier transform infra-red (FTIR) analysis indicated considerable structural change in samples above and below this temperature range. Changes were observed in the hydroxyl, carbonate and phosphate bands as the calcination temperature was increased from 500 to 1100 degrees C. Even once a single beta-TCP phase is obtained at 740 degrees C there remains a considerable amount of structural change at temperatures between 740 and 1100 degrees C. This effect was illustrated by an unusual change in the lattice parameters of the beta-TCP structure and significant changes in the phosphate bands of FTIR spectra as the calcination temperature was increased. The results obtained in this study show that the combined experimental techniques of XRD and FTIR are excellent complimentary methods for characterizing structural changes that occur during phase transformations.

Journal Article↗
PubMed2000

Characterization of the transformation from calcium-deficient apatite to beta-tricalcium phosphate.

The structural changes that occur during the transformation of a Ca-deficient apatite, prepared by a wet chemical method, to beta-TCP were investigated. X-ray diffraction (XRD) analysis of as-prepared samples and samples calcined at temperatures between 500 and 1100 degrees C showed that the transformation occurs over the temperature range 710-740 degrees C, under non-equilibrium conditions. The change in crystallite size with increasing calcination/sintering temperature was studied by XRD using the Scherrer formula. Fourier transform infra-red (FTIR) analysis indicated considerable structural change in samples above and below this temperature range. Changes were observed in the hydroxyl, carbonate and phosphate bands as the calcination temperature was increased from 500 to 1100 degrees C. Even once a single beta-TCP phase is obtained at 740 degrees C there remains a considerable amount of structural change at temperatures between 740 and 1100 degrees C. This effect was illustrated by an unusual change in the lattice parameters of the beta-TCP structure and significant changes in the phosphate bands of the FTIR spectra as the calcination temperature was increased. The results obtained in this study show that the combined experimental techniques of XRD and FTIR are excellent complimentary methods for characterizing structural changes that occur during phase transformations.

Journal Article↗
PubMedDate not supplied

Rheological properties of an apatitic bone cement during initial setting.

One scientific and technological aspect of main importance to the medical profession is to develop injectable calcium phosphate cements (CPCs) to be used through minimally invasive surgery techniques with still suitable mechanical and biodegradable properties. The objective of this research was to study the influence of several technological factors on the injectability of CPCs. This was performed by studying the rheological behavior of the cement pastes during their initial setting. Cement rheology was approached by looking at the creep response of apatitic cements as a function of the shear stress, the liquid-to-solid (L/S) ratio, the temperature and the addition of organic admixtures. Results showed creep experiments to be a finer method to detect characteristic setting times than other established subjective procedures. However, of all transition times detected none but the dough time seems to be of relevant importance when injectability of cement is concerned. Creep experiments also showed that the addition of organic admixtures such as citric acid increased injectability by retarding the hydration time.

Journal Article↗
PubMed2002

The in vitro antibiotic release from anti-washout apatite cement using chitosan.

The in vitro antibiotic release from anti-washout apatite cement using chitosan (aw-AC(chi)) was investigated in a preliminary evaluation. Flomoxef sodium was employed as the antibiotic and was incorporated into the powder phase aw-AC(chi) at up to 10%. The setting times were measured for aw-AC(chi) containing various amounts of flomoxef sodium. X-ray diffraction (XRD) analysis was also conducted for the identification of products. To evaluate the drug release profile, set aw-AC was immersed in saline and the released flomoxef sodium was determined at regular intervals. The setting time was prolonged slightly with the addition of flomoxef sodium. The difference at 10% flomoxef sodium (0% vs. 10%) was not significant (p>0.05), and can be negligible in clinic. The XRD analysis revealed that formation of hydroxyapatite (HAP) from aw-AC(chi) was reduced, even after 24 h, when the aw-AC(chi) contained flomoxef sodium at 8% or more. The flomoxef sodium release from aw-AC(chi) showed the typical profile observed in skeleton type drug delivery system (DDS). Changing the concentration of chitosan can control the rate of drug release from aw-AC. Therefore, we conclude that aw-AC(chi) is a good candidate for potential use as a DDS carrier that may be useful in surgical operations.

Journal Article↗
PubMed2003

Apatite formation on CaO-free polydimethylsiloxane (PDMS)-TiO2 hybrids.

Polydimethylsiloxane (PDMS)-TiO(2) hybrids with PDMS (M=550)/tetraethylorthotitanate molar ratios at 0.27, 0.68 and 1.35, i.e. Si/Ti atomic ratios at 2, 5 and 10 (hybrids PD2, PD5 and PD10, respectively) were prepared by a sol-gel method. Hybrid PD2 formed many cracks. Hybrids PD5 and PD10 were subjected to hot-water treatment 80 degrees C for 7 d. Hybrid PD5 produced cracks, whereas hybrid PD10 was crack-free after the hot-water treatment. Hybrid PD10 took a homogeneous amorphous structure before the hot-water treatment, and precipitated anatase particles 10-20 nm in size after the hot-water treatment. Hybrid PD10 did not form apatite on its surface in a simulated body fluid before the hot-water treatment, but formed it after the hot-water treatment. The obtained hybrid showed elastic deformation as large as 200% after the hot-water treatment. This kind of hybrid could be useful as a new type of bone-repairing material.

Journal Article↗
PubMed2004

Culture of haematopoietic cells in a 3-D bioreactor made of Al2O3 or apatite foam.

Foams of Al2O3 and apatite ceramics with interconnecting pores were produced using a new technique. The surfaces of the ceramics served as substrates for the culture of human peripheral and bone marrow derived stem cells. Up to 27 days the cells were kept in culture where they proliferated and developed into different morphologies consistent with bone marrow cell lines.

Aluminum Oxide↗
PubMed2004

Development of porous ceramics with well-controlled porosities and pore sizes from apatite fibers and their evaluations.

Porous hydroxyapatite (HAp) ceramics possessing well-controlled porosities and pore sizes were developed by firing apatite-fiber compacts mixed with carbon beads and agar. The total porosities could be controlled in the range from 40 to 85% by varying compaction pressure (20-40 MPa), firing temperature (1000-1300 degrees C) and carbon/HAp ratio (0/10-10/10 (w/w)). Most of the pores were regarded as open pores. The pore sizes were mainly affected by the carbon-bead diameter (5, 20 or 150 microm) and partly by the compaction pressure and the firing temperature. The pore sizes of the porous HAp ceramics derived from the carbon beads of 150 microm in diameter were distributed in the two separate ranges of several micrometers and more than 100 microm.

Ceramics↗
PubMed2006

Carbonated apatite-induced arthropathy: a consideration in cases of polyarthritis.

BACKGROUND: A 79-year-old woman was referred for evaluation of her painful and swollen joints. She had a medical history of congestive heart failure, renal insufficiency and peptic ulcer disease. For the past 3 years she had experienced recurrent bouts of debilitating arthritis, lasting approximately 3-4 weeks at a time. The symptoms were most severe in the hands and knees, where the joints were warm, swollen and tender. During each flare-up, the patient was housebound and required therapeutic dosing of nonsteroidal anti-inflammatory drugs and codeine to control joint pain. INVESTIGATIONS: Physical examination, fine-detailed radiographs of the hands, standing radiographs of the knees, arthrocentesis including cell count and gram stain, compensated polarized light microscopy, alizarin-red staining, X-ray diffraction, scanning and transmission electron microscopy with energy dispersive spectrometry, electron microprobe analysis with energy dispersive spectrometry, Fourier transform infrared spectroscopy, and atomic force microscopy. DIAGNOSIS: Carbonated-substituted apatite arthropathy. MANAGEMENT: Both knees were aspirated and large volumes of a straw-colored synovial fluid was removed. The knees were injected with corticosteroid, resulting in excellent symptomatic response.

Aged↗
PubMed2004

Calcium-lead fluoro-vanadinite apatites. II. Equilibrium structures.

The synthetic vanadinites (Pb(x)Ca(10-x))(VO4)6(F(1-2y)O(y) (y))2, 0.57 < x < 9 and 0.10 < y < 0.47, adopt the P6(3)/m apatite structure with 9.7835 (3) < or = a < or = 10.0531 (1) A and 7.0318 (2) < or = c < or = 7.3033 (1) A. The calcium endmember is monoclinic, space group P2(1)/m, with a = 9.7370 (3), b = 9.7358 (4), c = 7.00572 (9) A, gamma = 120.002 (5) degrees. For mixed metal compounds (x not equal to 0) the partitioning of calcium and lead over the AI(4f) and AII(6h) positions is nonstoichiometric, with lead preferentially favouring the larger AII site at a partitioning coefficient kPb(AI/AII) approximately 0.33 for all x < 7. A miscibility gap exists for 2 < x < 3. Trends in crystallographic parameters can be correlated through consideration of the AIO6 metaprism twist angle (phi) that can be used to derive ideal cell parameters from triangular anion networks.

Journal Article↗
PubMed1999

Iodo-oxyapatite, the first example from a new class of modulated apatites.

Iodo-oxyapatite [pentadecacalcium iodide oxide nonaphosphate, Ca(15)(PO(4))(9)IO] was synthesized by a flux method and the structure was solved from single-crystal X-ray data. The crystal structure was refined in the space group P6(3)/m [a = 9.567 (1), c = 20.754 (2) Å and Z = 2] to wR on F of 0.0459. Iodo-oxyapatite has a typical hexagonal apatite structure but the unit cell is tripled along the hexad owing to ordering of the iodide and oxide ions along this direction.

Journal Article↗
PubMed1977

Fibrous apatite grown on modified collagen.

Fibrous apatite has been grown by the enzymatic hydrolysis of calcium beta-glycerophosphate on reconstituted calfskin collagen tapes which had been modified by the addition of a phosphoprotein, phosvitin, in the presence of a cross-linking agent, dimethylsuberimidate. The deposits were identified as a carbonate-bearing hydroxyapatite by x-ray diffraction, and scanning electron micrographs confirmed their fibrous character.

Alkaline Phosphatase↗
PubMed1985

Acute synovitis with intra-articular apatite deposits in an osteoarthritic metacarpophalangeal joint.

A patient was shown to have acute arthritis in a metacarpophalangeal joint, with local calcification indicated by x-rays. Surgical and pathological examinations showed strictly intra-articular apatite crystal deposits and an erosive osteoarthritis. These crystal deposits could account for the synovial inflammation; they are thought to be related to bone fragments embedded in the synovium. The predisposing role of previous local injections of corticosteroids is debatable.

Acute Disease↗
PubMed1996

Surface spectroscopy of apatitic materials: limitations and concerns.

The use of x-ray photoelectron spectroscopy for the study of biological materials has provided mixed results. The experimental difficulties associated with the application of this technique to the study of biological materials include the effects of ultra-high vacuum, x-ray exposure, surface charging, and, for insulating materials, the inherent lack of an intrinsic energy reference. Since most biological materials are insulators, the lack of an intrinsic energy reference complicates one's ability to draw direct comparisons between different studies. In this paper, the results from two different apatites are compared with the results obtained from the use of two conventional techniques for referencing binding energies. The results presented here are referenced only to the Pt Fermi level; no further energy modifications are performed. A comparison with the results of other investigators indicates a large difference in binding energies for all involved core levels. These results indicate that, in the study of insulating materials with x-ray photoelectron spectroscopy, it is essential that all data be acquired under exacting conditions on the same experimental system.

Animals↗
PubMed2000

Increased bone mineral density adjacent to hydroxy-apatite-coated ankle arthroplasty.

We measured bone mineral density (BMD) in patients treated with a unilateral hydroxy-apatite-coated ankle arthroplasty. The study comprised 11 consecutive patients measured preoperatively and postoperatively after 3, 6, and 12 months (group I) and 17 patients measured once at 12 to 82 months follow-up (group II). BMD was measured in the distal tibia adjacent to the prosthesis and in the calcaneus. BMD of the calcaneus was measured bilaterally as an indicator of changes in foot load. In group I BMD was significantly increased in the distal tibia after 6 and 12 months compared to preoperative values. In group II BMD of the distal tibia was significantly higher compared to the non-operated side. No radiolucencies were detected during follow-up in any case. The increase in BMD and the radiographic findings after uncemented ankle arthroplasty indicates that it is being loaded by the prosthesis. This may indicate a well fixed prosthesis.

Absorptiometry, Photon↗
PubMed2001

Study of the maturation of the organic (type I collagen) and mineral (nonstoichiometric apatite) constituents of a calcified tissue (dentin) as a function of location: a Fourier transform infrared microspectroscopic investigation.

Fourier transform infrared microspectroscopy (FTIRM) was used to investigate the organic and mineral phases of a calcified tissue (dentin) as a function of its location from predentin toward enamel. Thin dentin slices (decalcified or not) were fixed in formaldehyde and embedded in glycolmethylmethacrylate (GMA). Fixation did not denature collagen, and GMA did not interact with organic or mineral constituents of dentin. The v1v3 PO4 domain was studied in particular in order to estimate mineral maturity and amide I, II, A, and B to obtain data on protein conformation. The results showed that dentin apatite became increasingly mature (stoichiometric) from the mineralization front toward the enamel, especially through loss of HPO4(2-) groups and vacancies. Moreover, collagen fibrils became less and less hydrated, suggesting that intrafibrillar mineralization partially dehydrated the collagen. Combined study of the organic and mineral fractions of calcified tissues may help clarify their relationships in physiological and pathological tissues.

Adolescent↗
PubMed1993

Clinical evaluation of two-piece apatite dental implants in 189 cases.

A two-piece apatite implant composed of a titanium abutment and a titanium tubular root portion cemented to an outer dense hydroxyapatite (D-HAP) tubular shell by resin cement has been authorized as High Advanced Medical Technology (H.M.A.T.) and applied since December 1987. We will show the success rate and the evaluation of the implants applied through May 1992. A successful implant was considered as one that provides functional comfort with no mobility and the absence of surrounding mucosal inflammation. The number of implants applied during the last 4.5 years was 810 pieces in 189 cases with an overall success rate of 92.5% for the 704 implants with abutment. The extirpation rate has no clear linear association with the duration of the implant or with the patient's age. Most of the extirpations resulted from cases where the patient used a provisional denture during the bone healing period, the time between implantation and abutment cementation. Extirpation rate of implant was high in cases using large maxillary provisional dentures with ten or more missing teeth. It is believed that all implant cases in which large dentures were used frequently contributed to the extirpation. These observations led us to suggest that provisional dentures may be harmful to the implant. When we shifted from the traditional method to the Delay Method 2.5 years ago, no incidence of extirpation was experienced in the mandible, even with the use of provisional dentures. In the maxilla, the Delay Method proved to be effective without the provisional denture. However, the results of the Delay Method with provisional dentures remains to be evaluated. The reason is that too few cases were encountered with large missing teeth to suffice for our observation. This Delay Method (named by us) consists of delaying the insertion of the implant for approximately 2 months after the first socket preparation, until the bone tissue activity has risen. After some adjustment in the prepared socket, the implant is then inserted during the second surgical procedure. We therefore consider this method of potential benefit over the traditional method.

Aged↗