Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Hydroxyapatites”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 919 records · Page 51Linked to original sources
PubMed1979

Analysis of paramagnetic centers in X-ray-irradiated enamel, bone, and carbonate-containing hydroxyapatite by electron spin resonance spectroscopy.

Carbonate-containing hydroxyapatite, enamel, and bone were irradiated by an X-ray and investigated between 77 degrees and 350 degrees K by means of electron spin resonance (ESR) spectroscopy. The ESR spectrum of enamel irradiated at 77 degrees K in vacuum and observed at the same temperature was almost the same as that of the carbonate-containing hydroxyapatite. The temperature dependence of signal intensities confirms a spin-energy exchange between the mineral and organic constituents in bone, but in enamel no or very little spin-energy exchange between the mineral and organic constituents. Considerable similarity among the ESR spectra of enamel, bone, and carbonate-containing apatite was obtained after X-ray irradiation in air at 300 degrees K with both an X-band and a Q-band ESR spectrometer. The Q-band spectrum can be interpreted in terms of two paramagnetic species. One is identified as a CO3(3-) anion radical which has an axial symmetry with g factors of 2.0029 and 1.9972. The other species is found to be centered at g = 2.0019.

Animals↗
PubMed1998

Cell culture approach to biocompatibility evaluation of unconventionally prepared hydroxyapatite.

Hydroxyapatite (HA), Ca10(PO4)6(OH)2 was produced by microwave irradiation of calcium nitrate (CaNO3.4H2O) and di-ammonium phosphate in aqueous solution. The HA formation was confirmed by X-ray diffraction analysis. HA prepared by this unconventional route was subjected to biocompatibility assay by a cell-culture method using the hybridoma cell line AE9D6 in both conventional Dulbecco's modification of Eagle's medium (DMEM) and simulated body fluid (SBF), both supplemented with 5% fetal calf serum. HA synthesised through this unconventional method showed the presence of tricalcium phosphate which can be reduced only after heat treatment at 1150 degrees C. The HA conformed to the X-ray data index file for hydroxyapatite. Biocompatibility assays showed reproducible growth and secretion patterns of cells both in DMEM as well as in SBF, thereby indicating the effectiveness of this method for the production of biocompatible HA.

Animals↗
PubMed1986

Gallium increases bone calcium and crystallite perfection of hydroxyapatite.

Gallium, a group IIIa metal, is known to interact with hydroxyapatite as well as the cellular components of bone. In recent studies we have found gallium to be a potent inhibitor of bone resorption that is clinically effective in controlling cancer-related hypercalcemia as well as the accelerated bone resorption associated with bone metastases. To begin to elucidate gallium's mechanism of action we have examined its effects on bone mineral properties. After short-term (14 days) administration to rats, gallium nitrate produced measurable changes in bone mineral properties. Using atomic absorption spectroscopy, low levels of gallium were noted to preferentially accumulate in regions of active bone formation, 0.54 +/- .07 microgram/mg bone in the metaphyses versus 0.21 +/- .03 microgram/mg bone in the diaphyses, P less than 0.001. The bones of treated animals had increased calcium content measured spectrophotometrically. Rats injected with radiolabeled calcium during gallium treatment had greater 45-calcium content compared to control animals. By wide-angle X-ray analyses, larger and/or more perfect hydroxyapatite was observed. The combined effects of gallium on bone cell function and bone mineral may explain its clinical efficacy in blocking accelerated bone resorption.

Animals↗
PubMed1986

The effects of proteoglycans from different cartilage types on in vitro hydroxyapatite proliferation.

Proteoglycans extracted from nasal and articular cartilages have previously been shown to inhibit hydroxyapatite proliferation in vitro. This study now demonstrates that proteoglycans isolated (dissociatively extracted and reaggregated in vitro) from bovine fetal growth plate and bovine occipital condyle, as well as those from bovine nasal cartilage, all retard hydroxyapatite seeded-growth in vitro. On a weight basis (1 mg/ml), the growth plate proteoglycan preparation had a significantly greater inhibitory effect. The greater inhibitory effect of the growth plate proteoglycans as compared to the other cartilage proteoglycan preparations may be related to the unique properties of the proteoglycans in the growth plate, a tissue that undergoes physiological calcification.

Animals↗
PubMed1991

Hydroxyapatite formation in the presence of proteoglycans of reduced sulfate content: studies in the brachymorphic mouse.

Proteoglycans from the brachymorphic (bm/bm) mouse have a reduced sulfate content due to the impaired activity of adenosine phosphosulfate phosphokinase in these animals. X-ray diffraction and infrared analyses of the mineral from the calcified cartilage of the bm/bm mice demonstrate the presence of significantly larger and more perfect hydroxyapatite crystals of lower carbonate to phosphate content than crystals found in the control animals. No differences were seen in the mineral content, crystallite size, CO3:PO4 ratio, or infrared splitting factors measured in the diaphyseal bone from these animals. Electron microscopic examination similarly shows larger, more disorganized crystals in the bm/bm animals' calcified cartilage as contrasted with controls. In vitro, proteoglycan aggregates from these dwarf mice are shown in a collagen gel-growth system to be less effective inhibitors of hydroxyapatite formation and growth than similarly size sulfated proteoglycans from age-matched control animals. The proteoglycans from the control mice were comparable in inhibitory ability to proteoglycan aggregates extracted from fetal bovine epiphyses. The in vitro and in vivo mineral parameters suggest the importance of sulfate for the interaction between proteoglycans and mineral in growth plate calcification.

Animals↗
PubMed1986

The uptake of lithium ions by synthetic carbonated hydroxyapatite.

Carbonated hydroxyapatites in the presence of F- and Li+ were synthesized. Limited uptake (0.2-1.6 ppm) of Li+ by the apatites was observed, which was proportional to the initially added Li+ and the carbonate concentration of the samples. Fluoride has retarding effect on the Li+ uptake. Li+ causes a decrease in the solubility of carbonated hydroxyapatite.

Animals↗
PubMed2002

Bone ingrowth on a smooth-surfaced hydroxyapatite-coated acetabular cup.

We studied 29 retrieved smooth-surfaced hydroxyapatite (HA)-coated acetabular cups that had been in situ for an average of 54.9 months. The outer surface of all cups carried two circular grooves dividing the smooth surface. The extent of bony in-growth and hydroxyapatite absorption was calculated using a computer imaging system (analySIS-pro 3.0, Soft Imaging System GmbH, Germany). Absorption of HA was seen in all 29 cups. The extent of absorption was, on average, 60.5%. Twenty-five cups showed bony in-growth covering an average of 13.8% of the cup surface. Thirteen cups showed bony in-growth on the smooth surface as well as the circular grooves. On 11 cups, the bony in-growth was confined to the grooves. We found that bony in-growth on the smooth-surfaced HA-coated acetabular cup was minimal. It occurred along the two circular grooves rather than on the smooth surfaces. We conclude that a macro-structure surface enhancing bony in-growth is necessary for the long-term survival of the studied cup.

Acetabulum↗
PubMed2005

Hydroxyapatite scaffolds for bone tissue engineering made by 3D printing.

Nowadays, there is a significant need for synthetic bone replacement materials used in bone tissue engineering (BTE). Rapid prototyping and especially 3D printing is a suitable technique to create custom implants based on medical data sets. 3D printing allows to fabricate scaffolds based on Hydroxyapatite with complex internal structures and high resolution. To determine the in vitro behaviour of cells cultivated on the scaffolds, we designed a special test-part. MC3T3-E1 cells were seeded on the scaffolds and cultivated under static and dynamic setups. Histological evaluation was carried out to characterise the cell ingrowth. In summary, the dynamic cultivation method lead to a stronger population compared to the static cultivation method. The cells proliferated deep into the structure forming close contact to Hydroxyapatite granules.

3T3 Cells↗
PubMed1984

High-resolution hydroxyapatite chromatography of proteins.

Hydroxyapatite chromatography has been used to separate all five isozymes of lactic dehydrogenase, six enzymatically active forms of bovine pancreatic DNase I, and a standard protein mixture. The proteins were eluted with a linear gradient of sodium phosphate. Enzyme activity recoveries were greater than 90%. Packing materials were obtained from commercial fine-particle-sized hydroxyapatite (DNA grade Bio-Gel HTP) by an elutriation procedure. Long columns packed with small crystals were run under low pressure at acceptable flow rates, and were used over prolonged periods.

Bacillus↗
PubMed1984

The interaction of proteins with hydroxyapatite. I. Role of protein charge and structure.

The criteria for elution of proteins from hydroxyapatite columns were examined as a function of (1) protein isoelectric point (22 proteins with isoelectric points between 3.5 and 11.0); (2) ionic nature of eluant (Na salts of PO4, F-, Cl-, SCN-, ClO-4, and CaCl2); and (3) structural differences between related proteins. It was found that proteins can be classified into three groups: (1) basic proteins, which elute at similar, moderate molarities of PO4, F-, Cl-, SCN-, and ClO-4, and low (less than 0.003 M) Ca2+; (2) acidic proteins which elute at about equal moderate molarities of PO4 and F-, but do not elute with Ca2+ and usually not with Cl-; (3) neutral proteins, which elute with PO4, F-, and Cl-, but show a strong anion specificity, and do not elute with Ca2+ or SCN-. Furthermore, individual specific polar groups are not in general crucial to binding or desorption, and variations in structure, other than major loosening, do not influence strongly the pattern of protein-hydroxyapatite interaction.

Chemical Phenomena↗
PubMed1976

Newly synthesized mammalian cell DNA. Separation of Okazaki pieces by thermal chromatography on hydroxyapatite.

The optical melting profile of a fraction of nascent DNA which can be isolated from DNA of logarithmically growing Ehrlich ascites cells by nitrocellullose column chromatography was recorded. In relation to the bulk DNA a slightly lowered Tm and an increased width of the transition was observed. Thermal hydroxyapatite chromatography revealed that melting of the nascent DNA begins at relatively low temperatures in helix regions containing small daughter strand pieces. The pieces were characterized as Okazaki pieces by determining their size and their labeling kinetics during [3H] thymidine pulses. The combination of nitrocellulose chromatography and thermal hydroxyapatite chromatography seems to be suitable for isolating Okazaki pieces.

Animals↗
PubMed1989

Surgical and prosthodontic residual ridge reconstruction with hydroxyapatite.

The ultimate goal of a ridge augmentation procedure is to form a bearing surface for the denture that will provide stability, retention, and support. Residual ridge reconstruction with an implanted material must be based on an understanding of the variations of ridge atrophy. A problem-oriented classification describes the different forms of residual ridges. This classification of similar types of resorbed residual ridges can be used to establish a rational plan of treatment. The proper placement of hydroxyapatite is critical to obtain the desired reconstructed residual ridge. In the mandible, a lingualized placement of the alloplast is suggested. Careful use of an anatomic matrix to support and contain the hydroxyapatite particles eliminates the need for a splint. The surgical stage includes vestibuloplasty and skin grafting to provide the patient with an increased denture-bearing surface. The ridge created in the form of a comma posteriorly enhances retention and stability. The broad residual ridge with an improved interarch relation also enhances the support and provides a better foundation for balanced occlusion.

Alveolar Process↗
PubMed1990

Initial interface between submerged hydroxyapatite-coated titanium alloy implant and mandibular bone after nontapping and tapping insertions in monkeys.

To clarify whether direct bone interface of submerged plasma-sprayed hydroxyapatite-coated implants could be achieved by nontapping insertion, histologic and histometric studies were made on the structure of the interface between the implant and the mandible in two monkeys. All hydroxyapatite-coated implants, whether by nontapping or tapping insertions, were healed with direct bone apposition. No histologic and histometric difference of interface structure was observed between nontapping and tapping insertions.

Alloys↗
PubMed1986

Porous hydroxyapatite ceramics for use in neurosurgical practice.

Hydroxyapatite ceramics have been increasingly used as an inert prosthetic material in the practice of reconstructive surgery and dentistry. However, the use of this material, which has excellent biostability and biocompatibility, has not yet been popular with most neurosurgeons. The purpose of this paper is to describe three kinds of prosthetic devices made of porous hydroxyapatite ceramics that we have found useful in neurosurgical practice.

Biocompatible Materials↗
PubMed1985

Setting properties of bone cement with added synthetic hydroxyapatite.

Synthetic hydroxyapatite powder was added to commercial bone cement to improve its physico-mechanical properties. The study of the setting properties showed the considerable effect of hydroxyapatite (HA) on the polymerization process; in particular statistical treatment of the experimental results revealed a significant relative minimum of the exothermic peak value at HA 5% weight percentage--an effect attributed to the HA 'crumbling' action on the microporosity features. The relationship between the interface (air and monomer bubbles/acrylic resin) versus dough composition was evaluated: the comparison between this last one and the corresponding internal energy variation supports the above hypothesis.

Bone Cements↗
PubMed1986

Structural analysis of hydroxyapatite coatings on titanium.

Hydroxyapatite from two sources was electrophoretically deposited onto flat titanium plate material. Depending upon the deposition conditions various changes in the structure of the ceramic were identified. A well-adhering Ti-P compound was present at the interface. Hydroxyapatite oxygenated to various degrees and tetracalcium phosphate were reproducibly formed in the coating.

Biocompatible Materials↗
PubMed1986

Macropore tissue ingrowth: a quantitative and qualitative study on hydroxyapatite ceramic.

The aim of this study was to obtain more information about macropore tissue ingrowth into the pores of sintered hydroxyapatite implanted in the rat middle ear, for the assessment of the usefulness of this material in reconstructive middle-ear surgery. The exudate filing the pores during the early post-operative period was gradually replaced by equal amounts of fibrous tissue and bone. The percentage of the macropore area occupied by bone was directly correlated with the macropore size. Bone was deposited not only from the pore wall towards the pore centre, but also in the opposite direction. Bonding osteogenesis was demonstrated. At sites of mechanical irritation, the presence of multinucleated cells and proliferatively active mononuclear phagocytes persisted for as long as a year. Under appropriate conditions hydroxyapatite seems to be a promising material for bone substitution in reconstructive middle-ear surgery.

Animals↗