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PubMed1986

An unusual complication of a myocardial electrode--apatite mantle on the platinum-iridium spurs.

A case of a high excitation threshold that occurred 2 years 5 months after the initial implantation of pacemaker electrodes is described in a girl 4 years 3 months of age. This complication was considered to be due to calcification of the platinum-iridium electrode spurs. The calcified material was shown to be a kind of apatite using the X-ray powder diffraction method. This complication is rare, but it must be kept in mind since battery longevity has markedly improved in recent years.

Apatites↗

PubMed1995

Acute apatite arthritis of the shoulder in a young woman.

We describe the case of a 40-year-old-woman with an acute arthritis of the left shoulder. Synovial fluid aspirated from the joint cavity appeared purulent but contained few leucocytes and no birefringent crystals. It was, however, rich in apatite crystals. A communication between the subacromial bursa and the gleno-humeral cavity through the rotator cuff could be demonstrated by sonography. The acute arthritis was secondary to the intra-articular rupture of a peri-articular calcification.

Acute Disease↗

PubMed1984

Transmission electron microscopic study of calcium phosphate formation in supersaturated solutions seeded with apatite.

The present study examined crystal growth on enamel and synthetic apatite seed surfaces in dilute supersaturated solutions by means of transmission electron microscopy. At all supersaturations, new growth initially appeared on the ends of the seed crystal. In solutions undersaturated with respect to octacalcium phosphate (OCP), this growth was needlelike in appearance. Above the solubility point for OCP, the growth frequently took the form of thin, platelike crystals. The relevance of these findings to precursor phase formation is discussed.

Animals↗

PubMed1984

A comparison of some effects of fluoride on apatite formation in vitro and in vivo.

In a liquid (22 degrees C) saturated with and in contact with powdered bone apatite, the fluoride ion activity was adjusted to 1-10 parts/10(6). Due to the fluorapatite (FAP) supersaturation produced hereby, a rapid formation of this salt occurred leading to a decrease of the concentration of the ions involved. When no more fluoride was available in the liquid, the concentrations of calcium and phosphate increased again, due to dissolution of presumably hydroxyapatite (HAP). Fifty four rats were given either 10, 20, or 40 mg NaF per kg body weight intraperitoneally. The animals were sacrificed from 5 min to 96 h after the injection. The fluoride concentration in plasma increased to a peak, after which it decreased. Plasma calcium decreased and remained low until the fluoride had attained normal levels. The intensity of mineralization of the growing dental hard tissue was monitored on microradiographs. Corresponding to the plasma fluoride peak and the decrease of plasma calcium, a hypermineralized layer was formed while a hypomineralized zone was formed during plasma calcium increase after disappearance of fluoride. Similarities and dissimilarities between the in vitro and the in vivo experiments are discussed.

Animals↗

PubMed1981

ESR of CO2- in X-irradiated tooth enamel and A-type carbonated apatite.

Using both low microwave power and weak magnetic field modulation, we have shown that the asymmetric signal arising in X-irradiated tooth enamel as well as in A-type carbonated apatite exposed to X-rays or to excited oxygen has an orthorhombic character and must be attributed to CO2-. Effectively, the mean values found for the three g-tensor components are comparable to those quoted for this defect in single-crystal specimens of calcite and sodium formate.

Apatites↗

PubMed1981

Crystal growth of calcium apatites in dilute solutions containing fluoride.

The kinetics of seeded crystal growth of calcium apatites were studied in dilute supersaturated solutions at various levels of fluoride concentrations. Initial precipitation rates were enhanced by fluoride concentrations higher than 0.05 ppm. The analytical results are consistent with the precipitation of fluoridated hydroxyapatites, Ca5Fx-(OH)1-x(PO4)3, FHA. The degree of fluoridation, X, appears to be determined by the activity of HF in solution, which varies for the various initial fluoride levels but remains fairly constant during precipitation. Thus the composition of the precipitating phase was the same for a given solution whether 25 or 10 mg of hydroxyapatite was added as seeds. All the experimental results are consistent with the BCF theory, which relates the mean linear rate of growth, RL, to the supersaturation, DS, by the expression RL = C1T(DS-1)1n(DS)tanh(C2/T 1n DS), in which DS is the supersaturation defined by mean molar activities with respect to the precipitating FHA, T the absolute temperature, and C1 and C2 are constants calculated from the experimental results. Consequently, the crystal growth appears to take place in surface kinks and to be controlled by surface diffusion. Since crystal growth in most biological systems takes place at fluoride concentrations within the experimental range used, it seems probable that it occurs along the model advanced in the present investigation.

Apatites↗

PubMed1989

Carbohydrate-controlled precipitation of apatite with coprecipitation of organic molecules in human saliva: stabilizing role of polyols.

Addition of common dietary carbohydrates to Millipore-treated human whole saliva either enhances or inhibits the formation of salivary precipitates, some carbohydrates showing no effect. The purpose of this study was to investigate the precipitation conditions more thoroughly and to elucidate the chemical nature of the precipitates formed. D-Xylose either enhanced precipitation (in long-term incubations) or had no appreciable effect (in 10 minute incubations). Other aldo- and keto-sugars and disaccharides (maltose, sucrose, lactose) generally enhanced precipitation, whereas all polyols (xylitol, D-sorbitol, mannitol, and maltitol) retarded the formation of turbidity in saliva. Xylitol inhibited formation of precipitates also in the presence of D-xylose, dextrans, and starch. Fast protein liquid chromatography (FPLC) of EDTA-soluble pellets obtained by centrifugation of the precipitates produced two major protein fractions (I and II) with a molecular weight of 112,000 and 46,000, respectively. The carbohydrates exerted a selective effect on the relative size of I and II in that polyol incubations resulted in a I to II ratio of 1:3, whereas control incubations (without added sugars) and incubations with other carbohydrates gave ratios of 1:6 to 1:10. Both peaks contained large amounts of acidic amino acids, proline, and glycine. The saliva precipitates contained a substantial portion of a crystalline phase that had the crystal structure of apatite, the individual crystallites being extremely small (less than 1 micron) with a Ca:P ratio of 1.46. The carbohydrates had a similar effect on the overall inorganic composition of the precipitates, but they had a clearly selective effect on the rate of formation of precipitates and on the relative amount of coprecipitating salivary proteins. This selectivity indicates that these carbohydrates, when consumed habitually, may exert different effects on the precipitation of Ca-salts at mineral-deficient enamel and dentine sites.

Adult↗

PubMed1985

Microbeam electron diffraction and lattice fringe studies of defect structures in enamel apatites.

A microbeam diffraction method in transmission electron microscopy has been applied to lattice structural studies of human and shark enamel apatite crystals. The technique allows diffraction patterns to be obtained from very small regions of the specimen (40 nm in diameter) and transfers minimal energy to the sample during analysis. The presence of crystal defects, nonisolated dislocations with the dislocation line positioned perpendicular to the 100-type planes, was observed in the central part of the crystals. Further experiments with acid-etching of crystals containing such defects showed an initial preferential dissolution at the site of these atomic imperfections. The relative abundance of the crystal defects was approximately the same in both human enamel and shark enameloid.

Animals↗

PubMed1987

Two bovine models of osteogenesis imperfecta exhibit decreased apatite crystal size.

In recent years advances have been made in detailing the changes in both collagen and noncollagenous proteins caused by a variety of mutations leading to osteogenesis imperfecta. Much less, however, is known about the mineral phase in the affected bone. In this report, we measured the crystallinity of the apatite in bovine OI bone. Line broadening of the 002 reflection (which estimates changes in the long or c axis of the crystals) and of the 310 reflection (which estimates changes in the thickness of the crystals) both show large decreases (30 and 35% respectively). Transmission electron micrograph measurements indicate that these changes were most probably a result of smaller crystals. No decrease in the ash weight of the bone was observed.

Animals↗

PubMed1999

Relationships among carbonated apatite solubility, crystallite size, and microstrain parameters.

The use of the metastable equilibrium solubility (MES) concept to describe the solubility properties of carbonated apatites (CAPs) and human dental enamel (HE) has been well established in previous studies using a range of CAPs with varying carbonate contents and crystallinities. It was shown in these studies that the mean value of the CAP MES is directly related to the broadening parameter full width at half maximum (FWHM) of the 002 reflection of the X-ray diffraction profile. The apparent solubility of the CAPs increased monotonically with an increase in the broadening of the diffraction peaks, and when this peak broadening was taken into account, carbonate had no additional effect upon the MES. The broadening of the diffraction peaks has been used as an indicator of crystallinity, and is generally influenced by both crystallite size and microstrain. The purpose of the present study was to extract the crystallite size and microstrain parameters separately from the X-ray diffraction peaks and then to determine their relationships to the corresponding MES values. The samples studied were CAPs synthesized by precipitation from Ca(NO3)2 and NaH2PO4 solutions in carbonate containing media at temperatures of 95, 80, and 70 degrees C, and powdered HE. The crystallite size and microstrain parameters were determined simultaneously with the refinement of the structural parameters with the Rietveld method of whole-pattern-fitting structure-refinement. A modified pseudo-Voigt function was used to model the observed peak profiles. The MES distributions for the CAPs and HE were determined by a previously described method. The results of this study showed that the CAPs possessed an MES distribution and therefore provided further support that MES distribution is a common phenomenon, regardless of the method of CAP synthesis. The crystallite size decreased and the microstrain increased with increasing carbonate content and decreasing temperature of synthesis of the CAPs. A plot of the mean of the MES distribution versus the microstrain parameter showed that the apparent solubility of the CAPs and HE correlated very well with the microstrain parameter. On the other hand, a plot of the mean of the MES distribution versus the crystallite size parameter showed a poor correlation between MES and crystallite size. These findings support a view that microstrain, rather than crystallite size, is the dominant factor governing the effective solubility of the CAPs and dental enamel.

Apatites↗

PubMed2001

Relationships involving metastable equilibrium solubility, surface complexes, and crystallite disorder with carbonated apatites.

Previous studies have shown that the metastable equilibrium solubility (MES) behavior of carbonated apatites (CAPs) may be described by a surface complex with the hydroxyapatite (HAP) stoichiometry in the absence of solution fluoride and by that with the fluorapatite (FAP) stoichiometry when appreciable solution fluoride is present. Studies have also shown that the magnitude of the MES is directly related to the crystallinity of the CAP. The aim of the present investigation was to examine the relationship between the CAP MES determined in the presence of solution fluoride and CAP crystallinity and to examine the effect of the change in the stoichiometry of the surface complex (from that of HAP to that of FAP) upon the relationship of the CAP MES to crystallinity. CAP samples were prepared by methods based on the precipitation of CAP from calcium phosphate solutions and the hydrolysis of dicalcium phosphate dihydrate in bicarbonate solutions. From X-ray diffraction experiments, the crystallite microstrain, and the full width at half maximum (FWHM) of the 002 reflection were determined for the CAPs. From CAP MES experiments conducted in the presence of solu tion fluoride, linear plots of the mean MES (i.e., mean pK(FAP)) values vs the crystallinity parameter (i.e., microstrain and FWHM) were obtained that yielded slopes that were essentially the same as those obtained in the absence of solution fluoride (i.e., mean pK(HAP) values vs crystallinity). This parallel finding suggests that the CAP crystallite disorder affects the energetics of the two surface complexes essentially to the same extent and provides new insight into the nature of CAP surface complexes.

Apatites↗

PubMed2003

Effect of fluoride pretreatment on the solubility of synthetic carbonated apatite.

The purpose of this research was to address the following question: How is the solubility of fluoride-pretreated carbonated apatite (CAP) in aqueous acidic media related to the equilibrium solution fluoride and/or the CAP adsorbed fluoride levels? A CAP sample prepared by a precipitation method at 70 degrees C containing approximately 6% carbonate was fluoride-treated (F adsorption from neutral aqueous solutions) to yield a approximately 1000 ppm F CAP and a approximately 3300 ppm F CAP. Metastable equilibrium solubility distributions were determined in acetate buffers at pH 5.0. Solution fluoride, calcium, phosphate, and pH were determined from the equilibrated solutions. The equilibrium solution fluoride levels were extremely low, e.g., as low as approximately 0.10 ppb to approximately 0.30 ppb at 50% dissolved for the two CAP preparations. The approximately 3300 ppm F CAP yielded a lower solubility than the approximately 1000 ppm F CAP (shift in the mean pKHAP value of 1.5-2 units). This can be attributed to the lower solution F(-) for the sample containing approximately 1000 ppm fluoride compared with the approximately 3300 ppm fluoride-containing CAP. These important findings suggest that a fluoride treatment simply may provide an adsorption fluoride depot for subsequent release, providing a solution fluoride effect upon the CAP solubility and not necessarily any intrinsic alteration of the mineral solubility.

Apatites↗

PubMed2003

Metastable equilibrium solubility behavior of carbonated apatite in the presence of solution strontium.

The purpose of this study was to use the concept of metastable equilibrium solubility (MES) to describe the anomalous solubility behavior of carbonated apatite (CAP) in the presence of solution strontium. A CAP sample (4.8 wt% CO(3), synthesized at 70 degrees C) was prepared by precipitation. Baseline MES distributions were determined in a series of 0.1 M acetate buffers containing only calcium and phosphate (no strontium) over a broad range of solution conditions. In order to assess the influence of strontium, MES profiles were then determined in a similar fashion with 20, 30, 40, 50, 60, 70, and 80% of the solution calcium being replaced on an equal molar basis by solution strontium. From the compositions of the equilibrating buffer solutions, ion activity products (IAPs) of the form Ca(10-n)Sr(n)(PO(4))(6)(OH)(2) (n = 0-10) were calculated in an attempt to determine the correct function governing the dissolution of the CAP preparation. The results demonstrate the following important findings: (a) at high solution strontium/calcium ratios (i.e., when 60% or more of the solution calcium was replaced by strontium), the MES profiles in all the experiments were found to be essentially superimposable when the solution IAPs were calculated using the stoichiometry of Ca(6)Sr(4)(PO(4))(6)(OH)(2), and (b), at low solution strontium/calcium ratios (i.e., when 40% or less of the solution calcium was replaced by strontium), the stoichiometry yielding MES data superpositioning was found to be that of hydroxyapatite. When other stoichiometries were assumed, good superpositioning of the data was not possible.

Apatites↗

PubMed2000

Apatite mineralization in teeth of the chiton Acanthopleura echinata.

Raman spectroscopy has been used to demonstrate, for the first time, that calcium mineralization in the core of the major lateral teeth of the chiton Acanthopleura echinata takes place as an ordered process, with crystalline carbonated apatite being the first mineral deposited. Deposition begins at the top of the tooth core, under the so-called tab region, progresses down the interior surface of the tab and lepidocrocite layer, and then extends outwards to the anterior surface. Mineralization is not initiated until the lepidocrocite layer has isolated the core of the tooth from the magnetite cap. The last region to be infiltrated is the anterior basal region of the tooth cusp, immediately above the junction zone. The junction zone is also a region of high ion density, as determined by energy dispersive spectroscopy (EDS) analysis, but we show here for the first time that it is free of mineral deposits, acting instead as a transfer and storage region.

Animals↗

PubMed1998

Human osteoarthritic cartilage matrix vesicles generate both calcium pyrophosphate dihydrate and apatite in vitro.

Calcium crystals in osteoarthritic (OA) joints promote enzymatic degradation of articular tissues. Matrix vesicles provide a nidus for calcium crystal formation in chick epiphyseal and mature porcine articular cartilage. In order to examine a potential role for matrix vesicles from OA cartilage in generating pathologic crystals, we sought to determine whether vesicles derived from human OA cartilage (OAMV) could mineralize; and we characterized the resultant mineral species. OAMV were isolated and examined for alkaline phosphatase (AP) and nucleoside triphosphate pyrophosphohydrolase (NTPPPH) activity. OAMV ATP-dependent and independent mineralization were measured in a radiometric biomineralization assay, and newly formed OAMV crystals were examined using Fourier transform infrared spectroscopy (FTIR) and compensated polarized light microscopy. The mean specific activity of OAMV AP was approximately 6 times higher and NTPPPH activity 11 times lower than that of previously characterized, mature, porcine, articular cartilage vesicles. OAMV progressively precipitated 45Ca over time both in the presence and absence of ATP. The FTIR spectra of mineral formed in ATP-dependent assays most closely resembled the standard spectrum for calcium pyrophosphate dihydrate (CPPD). The FTIR spectra of OAMV mineral formed in the absence of ATP closely resembled apatite. These data support the hypothesis that OAMV may form mineral phases of two key crystals found in degenerating cartilage and provide further evidence for the role of matrix vesicles in pathologic articular cartilage biomineralization.

Aged↗

PubMed2003

Property analysis of ectopic calcification in the carpal tunnel identification of apatite crystals: a case report.

INTRODUCTION: A 64-year-old woman presented with symptoms of subacute exacerbation of a year-long carpal tunnel syndrome that was caused by a large calcified mass in the tunnel. CONCLUSION: The resected mass consisted of very tiny rods, and x-ray diffraction analysis, as well as the component analysis using energy dispersive x-ray microanalysis, revealed the mass to be most compatible with apatite. The back-scattered electron images suggested that precipitation might be a mechanism for development of the calcified mass.

Apatites↗

PubMed2001

Cytological characterization of apatitic calcium phosphate structures in bronchial epithelial tissue cultured from a child with cystic fibrosis (deltaF508).

Patients with cystic fibrosis homozygous for the AF508 mutation have marked disturbances in ion exchanges in a variety of tissues. Alterations in intra- or extracellular levels of Ca2+ and calcifications have been observed in numerous tissues from such patients, although the nature and origin of such calcifications have yet to be elucidated. In this study, we investigated the formation of calcifications in the respiratory tract of a AF508 homozygous child and attempted to establish their origin. Samples of bronchial epithelium from this patient were subjected to cytophysiological analysis ex vivo and in vitro. The defect of targeting of the cystic fibrosis transmembrane conductance regulator (CFTR) to the apical plasma membrane of epithelial cells was verified. Cytochemical and ultrastructural analysis revealed the presence of crystalline aggregates in fine needles in the respiratory tract. Cytochemical analysis, X-ray spectrometry, and electron diffraction showed that these aggregates corresponded to crystals of calcium phosphate in an apatite-like structure. Ultrastructural study of primary cultures of bronchial epithelium showed the presence of calcium phosphate crystals in granules from Golgi apparatus and in mitochondria. These observations indicated that modifications of ionic exchanges due to a defect in targeting of CFTR AF508 to the apical plasma membrane led to the formation of crystals of calcium phosphate in the cytoplasm of pulmonary cells. These crystals could enhance inflammation of the lung in patients with cystic fibrosis.

Apatites↗

PubMed2000

Augmentation of (pedicle) screws with calcium apatite cement in patients with severe progressive osteoporotic spinal deformities: an innovative technique.

Screw augmentation with calcium apatite cement (CAC) was used in seven patients with a progressive osteoporotic spinal deformity. Thirty-nine spinal segments (64 screws) were augmented: 15 anteriorly (three patients) and 24 posteriorly (five patients). Dorsally, hemilaminectomy was performed at the level of all augmented screws to rule out CAC leakage. Autogenous bone graft was applied in all patients to induce fusion. Screw augmentation failure occurred in only one patient: 1 of the 16 ventral augmented screws (5.5%) was still loose after the augmentation procedure. In three other patients, 4 out of 48 augmented dorsal screws (5.5%) showed CAC leakage at the pedicle corpus vertebra level. Pedicle wall damage was present at two levels, while at two other levels no wall damage was found during visualization. No CAC-related complications were observed perioperatively. No implant migration was observed, and fusion was observed in all cases at follow-up examination performed at a mean of 32 months after surgery.

Adult↗