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At least 973 records · Page 54Linked to original sources
PubMed2003

Osteoconductive and hemostatic properties of apatite formed on/in agarose gel as a bone-grafting material.

The biologic behavior of hydroxyapatite formed on/in agarose (HA/agarose) gels with the use of a novel alternate soaking process was compared with commercially available Bone Ject (True-Bone ceramic-collagen combined bone-graft material, Koken, Japan) as a filler for the tooth-extraction sockets of six adult monkeys (Macasa fascicularis). After the monkeys' first premolars were extracted, the defects created were replaced with one of the following materials: (a). HA/agarose created by 12 soaking cycles, (b). HA/agarose created by 9 soaking cycles, (c). Bone Ject, and (d). no material implantation (control). The time of hemostasis in each extraction site was estimated, and the samples were then studied histologically. In the controls, the time of hemostasis was about 5 min. The Bone Ject particles were easily washed out by bleeding, and the time of hemostasis was about 15 min. The HA/agarose gel was densely packed into the bony defect. The hemorrhage from the defects stopped within a few seconds after graft placement. This hemostasis was most likely related to the compactibility and adhesiveness of the material. After 12 weeks of implantation, free Bone Ject particles surrounded by inflammatory cells were observed. The bony defect filled with the HA/agarose gels was completely absorbed and replaced by newly formed bone possessing bone marrow. There was no difference in the biologic behavior of HA/agarose gels created by 9 versus 12 soaking cycles. The present study suggests that HA/agarose gels may play an important role as an alternative biodegradable bone-graft material for autogenous bone in humans.

Animals↗
PubMed1993

Calcific periarthritis of the finger verified by X-ray diffraction of apatite.

The authors describe a 24-year-old woman presenting with swelling and pain of several finger joints. Roentgenograms showed periarticular, calcific deposits at all locations of swelling. One such deposit revealed the presence of hydroxyapatite crystals on X-ray diffraction. After two injections of corticosteroids in and around one deposit its size and density diminished rapidly, whereas the uninjected corresponding site of the other hand showed no initial improvement; after two years no difference was discernible. Under systemic and topic NSAIDs, pain and swelling improved similarly in all joints. In conclusion, periarthritis of the fingers associated with radiopaque deposits responded favourably to NSAID therapy, while local corticosteroid injections showed no additional benefit.

Adult↗
PubMed1976

Radiogenic free radicals in apatite: the influence of fluoride and hydroxide.

Fluor-hydroxyapatites of varying fluoride and hydroxide contents were irradiated by soft x-rays at -188 degrees C and examined by means of electron spin resonance spectroscopy. Variation in fluoride-hydroxide contents affected radical yield and resulted in the observation of two kinds of oxygen anion resonances: a doublet due to hydrogen hyperfine splitting and a singlet. At higher temperatures a spin transfer process became operative which enhanced the oxygen anion radical population. Increasing fluoride content was paralleled by decreasing g-values for the oxygen anion resonances, possibly attributable to increased delocalization of the unpaired spin.

Electron Spin Resonance Spectroscopy↗
PubMed2000

Dentin sialoprotein (DSP) has limited effects on in vitro apatite formation and growth.

Sialoproteins such as bone sialoprotein (BSP) and dentin sialoprotein (DSP) accumulate at the mineralization fronts in bone and dentin, respectively, suggesting they have some function in the mineralization process. BSP, a highly phosphorylated protein rich in polyglutamate repeats, is an effective nucleator of hydroxyapatite (HA) formation in vitro. The present study examines the effect of DSP, a low phosphorylated but related sialoprotein, on the formation and growth of HA. In vitro, in a gelatin gel diffusion system, DSP at low concentrations (<25 microg/ml) slightly increased the yield of HA formed at 3.5 and 5 days, while at higher concentrations (50-100 microg/ml) it slightly inhibited accumulation. Fewer mineral crystals were formed in the presence of high concentrations of DSP but they tended to aggregate (making them appear larger by electron microscopic analysis) than those formed in DSP-free gels. X-ray diffraction line broadening analysis failed to show significant changes in c-axis crystal dimensions with increasing DSP concentration. When HA-seed crystals were coated with DSP before inclusion in the gelatin gel there was a reduction in mineral accumulation relative to HA-seeds which had not been coated with DSP, but the extent of inhibition was significantly less than that seen in this system with other mineralized tissue matrix sialoproteins, such as osteopontin or BSP. The low affinity of DSP for well-characterized seed crystals and the limited effect of this protein on HA formation and growth suggest that the role of DSP in dentin is not primarily that of a mineralization regulator.

Animals↗
PubMed1981

Idiopathic familial chondrocalcinosis due to apatite crystal deposition.

Idiopathic familial chondrocalcinosis was found in five members of a family. The clinical features of the disease were morning stiffness, pain and limitation of motion of the dorsolumbar spine in four of the five members, associated with arthritis of the small joints of the hands in three, shoulder periarthritis in two and costal cartilage pain in one. Radiologically, four of the five patients had multiple intervertebral disk calcifications, mainly located at the nucleus pulposus area. Three of them also had periarticular calcific deposits, associated with costal cartilage calcifications and degenerative changes in the small joints of the hands in two. None of these cases showed cartilage calcification in the knees, public symphysis or triangular ligament of carpus. In the propositus, optical microscopy of a specimen of the second proximal interphalangeal joint obtained by open biopsy showed the presence of multiple calcified areas in the intercellular matrix and chondroid metaplasia with calcification of the matrix in the synovial membrane and capsule. X-ray diffraction studies, energy dispersive analysis, and infrared spectrophotometry of a costal cartilage sample obtained by open biopsy demonstrated the presence of carbonate calcium hydroxyapatite. In this study, no relation was found between HLA antigens, loci A, B and C, and this syndrome due to calcium hydroxyapatite crystal deposition.

Adult↗
PubMed1977

The separation of human serum high density lipoproteins by hydroxy apatite column chromatography. Evidence for the presence of discrete subfractions.

Human serum high density lipoprotein subfractions 2 and 3, isolated by preparative ultracentrifugation after blocking the enzyme phosphatidylcholine: cholesterol acyl transferase, have been subfractionated further by hydroxyapatite column chromatography. From subfraction 2 we reproducibly obtained 5 and from subfraction 3, 6 fractions differing in chemical composition and apolipoprotein content. The fractions eluting at low salt concentrations were composed primarily of apolipoprotein-A polypeptides while those eluting at high salt concentrations consisted primarily of apolipoprotein-C. From all the 11 subfractions only one contained the "arginine-rich" polypeptide. The apolipoprotein-C-containing fractions were richer in triacylglycerol, phospholipids and free cholesterol as compared to the apolipoprotein-A-containing ones. Although small differences of their partial specific volumes existed, the obtained values indicate that all subfractions belonged to the parent density class. The implications of these results to the current view of lipoprotein metabolism are discussed.

Apolipoproteins↗
PubMed1989

Isolation and characterization of human apatite-inducing aortic proteolipid.

A proteolipid, capable of inducing hydroxyapatite in vitro, can be isolated from human aortic calcified lesions, noncalcified lesions, and nonlesion tissue obtained at autopsy. Analysis of the amino acid composition after acid hydrolysis showed all nucleators to be high in the hydrophobic amino acids glycine and alanine. Estimation of the molecular weight of the nucleator, extracted from calcified lesions, by gel filtration and lipid content showed a minimum molecular weight of 469,000 Da. All nucleators were characterized by the presence of acidic phospholipids which may have a role in the mechanism of calcification.

Adult↗
PubMed1980

Characterization of synthetic apatites for bioceramic implants.

Hydroxyapatite has been studied as a substance suitable for surgical substitution of bones and teeth with emphasis on its biocompatibility. The present work tries to identify the characteristics of this material either from the chemico-physical-structural point of view, or from the technological one, evaluating the best performance. By X-ray, i.r., thermal, chemical and SEM analyses, the relationship of different phenomena involved in the sintering was evaluated. Technological tests demonstrated the stability and the workability characteristics. In particular, the influence of CO2 was studied, in connection with the most suitable technique for hydroxyapatite (HAP) sintering, considering the eventual aims and requirements for industrial production.

Ceramics↗
PubMed1984

The behaviour of apatite-based ceramics in relation to the critical 1150 degrees-1250 degrees C temperature range.

Characterization of synthetic calcium phosphates is reported and compared with previous studies. Barium hydroxyapatite was also synthesized. Shrinkage on sintering, water absorption, tensile strength, porosity and X-ray diffraction patterns were studied. Hydroxyapatite and beta-tricalcium phosphate show compositional and mechanical property variation dependent on sintering temperatures. The property change on introduction of barium removes the practical value. X-ray diffraction analysis is considered essential before clinical use due to sensitivity of composition to sintering conditions.

Barium Compounds↗
PubMed1990

Oxidized cellulose mesh. II. Using hydroxy-apatite bone grafting material in the treatment of infrabony defects.

Biodegradable oxidized cellulose mesh has been used in conjunction with hydroxyapatite synthetic bone grafting material to enhance retention of the graft material and to improve post-operative healing of infrabony defects treated surgically. Initially a good healing response was achieved, but there was a tendency for the sites to relapse in the 8 wk following surgery. A tendency to relapse in reconstructive dentistry is well known, and the possible factors which limit the amount of regeneration of tissues are considered. Although there appear to be limitations on the regeneration possible in tissues, the factors that determine these limitations are poorly understood at present.

Alveolar Bone Loss↗
PubMed2004

Ionic modification of calcium phosphate cement viscosity. Part I: hypodermic injection and strength improvement of apatite cement.

A broadening of the indications for which calcium phosphate cements (CPC) can be used, for example, in the field of vertebroplasty, would require injectable and higher strength materials. Unmodified CPC are not injectable due to a filter-pressing effect during injection. In this work we demonstrated that an effective method for improving the injection properties of CPC was by the use of sodium citrate solution as a liquid component. Cement consisting of tetracalcium phosphate (TTCP) and monetite (DCPA) mixed with water up to a powder:liquid ratio (P:L) of 3.3 g/ml had an injectability of approximately 60%. The use of 500 mM trisodium citrate solution instead of water decreased the viscosity of the cement paste to a point, where complete injectability (>95%) through an 800 microm diameter hypodermic needle could be achieved at low loads. The reduction in water demand of the cement effected by the use of sodium citrate enabled high P:L mixes to be formed which were 400% stronger than cements made with water. The effect was less pronounced with compacted cements such that at 9 MPa applied pressure, 58% improvement was obtained and at 50 MPa 36% improvement was measured yielding a cement with a compressive strength of 154 MPa. The liquefying effect of sodium citrate was thought to derive from a strong increase in the surface charge of both the reactants and the product as determined by zeta-potential measurement.

Biocompatible Materials↗
PubMed2006

Chemical composition, crystal size and lattice structural changes after incorporation of strontium into biomimetic apatite.

Recently, strontium (Sr) as ranelate compound has become increasingly popular in the treatment of osteoporosis. However, the lattice structure of bone crystal after Sr incorporation is yet to be extensively reported. In this study, we synthesized strontium-substituted hydroxyapatite (Sr-HA) with different Sr content (0.3%, 1.5% and 15% Sr-HA in mole ratio) to simulate bone crystals incorporated with Sr. The changes in chemical composition and lattice structure of apetite after synthetic incorporation of Sr were evaluated to gain insight into bone crystal changes after incorporation of Sr. X-ray diffraction (XRD) patterns revealed that 0.3% and 1.5% Sr-HA exhibited single phase spectrum, which was similar to that of HA. However, 15% Sr-HA induced the incorporation of HPO4(2-) and more CO3(2-), the crystallinity reduced dramatically. Transmission electron microscopy (TEM) images showed that the crystal length and width of 0.3% and 1.5% Sr-HA increased slightly. Meanwhile, the length and width distribution were broadened and the aspect ratio decreased from 10.68+/-4.00 to 7.28+/-2.80. The crystal size and crystallinity of 15% Sr-HA dropped rapidly, which may suggest that the fundamental crystal structure is changed. The findings from this work indicate that current clinical dosage which usually results in Sr incorporation of below 1.5% may not change chemical composition and lattice structure of bone, while it will broaden the bone crystal size distribution and strengthen the bone.

Biocompatible Materials↗