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At least 1,297 records · Page 72Linked to original sources

PubMed2002

Effects of calcium phosphate ceramic bone graft materials on permanent teeth eruption in beagles.

OBJECTIVE: The aim of this study was to evaluate the use of calcium phosphate ceramic (CPC) materials as a potential alternative to autogenous secondary alveolar bone grafting in cleft lip and palate patients who are in mixed dentition. SAMPLE: Four 12-week-old beagles and one 15-week-old beagle were used as subjects. INTERVENTIONS: In each experimental beagle, the third and fourth deciduous premolars were extracted. The sockets were filled with four different CPC materials and sutured. MAIN OUTCOME MEASURES The beagles were fed a soft diet for the following 8 weeks and then sacrificed for clinical, radiological, histological, transmission electron microscope (TEM), and infrared (IR) absorption analysis. RESULTS: All four experimental graft materials allowed normal development and eruption of permanent premolars. In histological sections, small particles of biphasic calcium phosphate (BCP) and carbonate apatite (CO(3)-AP) were resorbed, and large particulate forms served as bone frames in cortical bones. Polymer coated with carbonate apatite (Poly/CO(3)-AP) did not cause inflammation but was pushed away to the soft tissue by erupting teeth. Alginate coated with carbonate apatite (alginate/CO(3)-AP) caused a severe inflammatory reaction to the point of destroying a part of the dental follicle and cortical bone. In TEM, resorption activity by phagocytic cells was observed only in CO(3)-AP. Direct bonding of CO(3)-AP to the bone was observed as the electron-dense interface between bone and CO(3)-AP. CONCLUSION: BCP and CO(3)-AP proved to be suitable as alveolar bone graft materials in areas where tooth eruption occurs. Of the four materials tested, CO(3)-AP produced the best results.

Alginates↗

PubMed1989

Small angle X-ray scattering study on Lingula unguis shell.

Lingula unguis shell yields a diffuse small angle X-ray scattering which is caused mainly by the scattering from particles of apatite. In this study, the distribution of particles smaller than 500A was analyzed using the small angle X-ray scattering technique. The non-linear Guinier plot indicates that the shell contains various sizes of apatite particles ranging about 20-460A. The small granules with size about 20-160A in diameter are located in the marginal part of the shell and progressively larger granules are observed internally towards the central part. The scattering is anisotropic in the lateral and central part, where the apatite crystals highly ordered. The combined analysis of wide and small angle diffraction indicates that the particles are elongated in the c-axis direction and, furthermore, their long axes are arranged almost parallel to the direction of growth in these parts. This suggests that small and isotropic particles are formed in the early stage of mineralization and larger ellipsoidal shaped particles are formed in the later stage of mineralization.

Animals↗

PubMed1988

19F MAS-NMR and solution chemical characterization of the reactions of fluoride with hydroxyapatite and powdered enamel.

Solution chemical and 19F magic angle spinning-nuclear magnetic resonance (MAS-NMR) methods have been utilized to study the effects of fluoride dose, fluoridating pH, and mineral surface area on the dynamics of fluoride reactivity with hydroxyapatite and powdered human dental enamel in vitro. Both solution chemical fluoride uptake and NMR measurements demonstrated that the reaction products of ionic fluoride with apatite include mixtures of FAP, FHAP, and CaF2, with increased amounts of CaF2 promoted by increased F concentration or decreased pH. NMR analysis showed FAP or FHAP as a reaction product of fluoride uptake under all conditions, regardless of whether CaF2 was formed, unambiguously demonstrating fluorite as an additive rather than substitute form of F reactivity. pH stat measurements demonstrated the release of OH- during F reactivity with apatites corresponding to ion exchange formation of FAP/FHAP or dissolution/reprecipitation formation of CaF2. Phosphate release into solution accompanied fluoride uptake under all conditions, including regions where ion exchange predominated. Whereas powdered dental enamel demonstrated fluoride uptake behavior similar to that of synthetic apatite, the resulting reaction products differed as analyzed by 19F MAS-NMR.

Adsorption↗

PubMed1997

Production of artificial urinary stones from natural materials and their physical properties. First results.

Considered from a clinical point of view, all artificial stones known so far are inappropriate for experimental investigations, because they do not correspond to natural urinary stones in shape, physical properties and chemical composition. A special technique has now been developed for the production of biometric artificial stone models. Standard artificial carbonate apatite stones were produced by a coating technique where several layers of a suspension consisting of pure substance were applied around a core. Density and crushing strength of these ball-shaped artificial stones corresponded to natural apatite stones. Experimental chemolitholysis investigations showed comparable results in respect to the dissolution of artificial apatite stones and of natural stones of the same chemical composition. The disintegration behaviour was studied in ESWL tests which revealed a correlation between generator voltage and number of shock waves necessary for complete disintegration. For the first time, an artificial urinary stone has now been produced which is comparable to a natural stone of the same chemical composition not only in shape but also in its physical properties and lysis behaviour. These stones are suitable for use in systemic scientific investigations on disintegration and chemolitholysis.

Apatites↗

PubMed1989

Calcium phosphate mineralization.

Although it is often assumed that the thermodynamically most stable hydroxyapatite is a suitable prototype for biological minerals, it is now generally accepted that other phases such as dicalcium phosphate dihydrate and octacalcium phosphate as well as defect apatites and carbonated apatites may participate. The Constant Composition kinetics method, has been used to show that defect apatites may be formed with non-stoichiometric coefficients that depend upon the pH of the growth medium. Important factors in analyzing these experiments are the initial surface modification and ion exchange processes involving hydrogen and calcium ions following inoculation of the supersaturated solutions. Proteins and other macromolecules which may inhibit the rate of growth of calcium phosphates in supersaturated solutions are able to enhance the nucleation of these phases when immobilized on inert surfaces.

Apatites↗

PubMed1995

Dentin matrix proteins and dentinogenesis.

The precise mechanisms involved in dentinogenesis are not understood; however, the information to date suggests that a number of highly controlled extracellular events are involved. Mature odontoblasts secrete collagen at the cell border into predentin. They synthesize and secrete other non-collagenous proteins (NCPs) at the mineralization front, possibly through odontoblastic processes. A collagen-NCP complex is formed at the predentin-dentin border and apatite crystal initiation and growth takes place. One of the research needs is to uncover the nature of this dentin collagen-NCP complex and to understand how it controls mineralization. At least three dentin specific NCPs are known: phosphophoryn(s), dentin sialoprotein (DSP) and AG1 (Dmp1). Other macromolecules are commonly made by osteoblasts and odontoblasts and participate in bone and dentin formation. Some progress in understanding dentin mineralization has been gained by focusing upon the role of phosphophoryns. These highly phosphorylated proteins are secreted at the mineralization front, where a small portion binds in the gap region of type I collagen fibrils. This portion of phosphoproteins probably initiates formation of plate-like apatite crystals. Additional phosphoryns in higher concentrations bind to the growing apatite crystals and slow their growth, possibly influencing their size and shape. Other areas which need careful investigations are those involving the mechanisms involved in odontoblast differentiation, how the synthesis of the dentin specific NCPs is controlled and the precise roles of these macromolecules in dentinogenesis. Future experimentation will focus on the gene structures for these NCPs and the mechanisms of tissue specific gene regulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Apatites↗

PubMed1997

Oriented and lengthwise growth of octacalcium phosphate on collagenous matrix in vitro.

A correlation among the oriented growth of octacalcium phosphate (OCP), the arrangement of the collagen fibrils in a collagenous matrix and direction of ionic flow was studied in vitro at pH7.0 and at 37 degrees, using two types of collagen disks made from sliced bovine Achilles tendon. Disk A and disk B were made from slices cut perpendicular and parallel to the collagen fibrils, respectively. The products on the collagen fibrils were a mixture of OCP and apatite in the both disks, but the relative amounts of apatite and OCP could not be determined. Short plate-like or flake-like OCP crystals grew parallel to the collagen fibrils and ionic flow on the Ca-side of the disk A. On the contrary, ribbon-like or rectangular OCP crystals grew along the collagen fibrils lying on the disk B. Apatite also grew with the same orientation as OCP in the both cases. The oriented and length-wise growth of OCP crystals on the disk B was ascribed to the arrangement of the collagen fibrils in the disk.

Achilles Tendon↗

PubMed1992

Phase transformation of octacalcium phosphate in vivo and in vitro.

Octacalcium phosphate (OCP) was implanted in both thigh muscle pouches of ddY mice for 3 weeks, and was soaked in a simulated body fluid (SBF) and 1% NaCl solution maintained at 37 degrees C for 1 day, 1 week and 3 weeks. After implantation or soaking, the specimens were characterized by scanning electron microscopic analyses, X-ray diffractometry, and infrared absorption spectroscopy. X-ray diffraction study showed that OCP had been completely transformed to apatite with low crystallinity such as the mouse's femur after a 3-week implantation in the mouse body, and an apatic crystal was formed after soaking in the NaCl solution. The IR absorption spectra revealed that CO3 was incorporated in the apatite formed from OCP in both the mouse body and the NaCl solution, while OCP changed little after soaking in the SBF. It seems that the magnesium ion retards the transformation of OCP to apatite.

Animals↗

PubMed1994

Effect of crystallization on fracture strength of castable glass-ceramics containing two crystals.

The relationship between fracture strength and crystallization in castable glass-ceramics was studied using castable glass-ceramics which contained crystalline apatite and magnesium titanate. Bending strength was increased with increases in crystal phases; 90, 124, 122 and 162 MPa were recorded for as-cast specimens and specimens cerammed at temperatures of 905 degrees, 925 degrees and 945 degrees C, respectively. The results of bending tests suggest that the crystallization of magnesium titanate is more effective than that of apatite in increasing the strength of glass-ceramics. Fracture toughness in specimens reheated at 905 degrees C was doubled compared with as-cast specimens. The apatite particles precipitated during ceramming treatment were thought to be an important factor in increasing both the fracture toughness and crack pinning effect.

Apatites↗

PubMedDate not supplied

Enhancement of bone regeneration and graft material resorption using surface-modified bioactive glass in cortical and human maxillary cystic bone defects.

PURPOSE: Bioactive glass bonds to bone through a calcium phosphate layer that mimics the structure of the mineral phase of bone. Formation of this layer is inhibited in the presence of serum protein. The authors hypothesize that creation of a calcium phosphate layer on the surface of bioactive glass before implantation will enhance bone regeneration and graft material resorption in bone defects. MATERIALS AND METHODS: Bioactive glass particles covered with a layer of amorphous calcium phosphate (BG-ACP), bioactive glass particles covered with a layer of hydroxycarbonate apatite (BG-HCA), and unmodified bioactive glass particles (as a control) were prepared and implanted in cortical bone defects in dogs or in human maxillary cavities. Ungrafted sites were also used as a control. RESULTS: Histomorphometric analyses showed significantly more bone tissue regeneration and graft material resorption in the defects filled with BG-HCA than in those filled with BG-ACP or unmodified bioactive glass (P < .0001). Moreover, measurements of radiographic density of the grafted areas suggested a higher rate of bone regeneration in defects filled with the modified bioactive glass than in those filled with unmodified bioactive glass or in the ungrafted control. Bone formation was significantly greater in defects filled with unmodified bioactive glass particles than in ungrafted defects. DISCUSSION: The enhancement of bone regeneration could be explained by the ability of the apatite layer to facilitate bone adsorption and enhance calcium release, which stimulates osteoblast differentiation and bone formation. CONCLUSION: Results of both the clinical and animal studies suggest that the use of surface-modified bioactive glass covered with a hydroxycarbonate apatite layer has the potential to accelerate bone formation and graft material resorption better than unmodified bioactive glass.

Adsorption↗

PubMed2006

Does the nature of deposited basic calcium phosphate crystals determine clinical course in calcific periarthritis of the shoulder?

OBJECTIVE: Two typical clinical courses of calcific periarthritis in the shoulder are known: acute, with severe inflammation, and chronic, in the form of impingement syndrome with secondary subacromial bursitis. It remains unclear what factors determine these clinical courses. Our objectives were to clarify whether the calcified deposits that occur in both acute and chronic cases are composed of carbonate apatite; and to compare the Ca:P molar ratio in the 2 forms and to determine if there was any correlation in this respect with the intensity of inflammation induced by basic calcium phosphate crystals. METHODS: Ten samples were aspirated from 10 women (ages 42-65 yrs) with acute inflammation. The average time from first attack to aspiration was 2.3 days. A further 10 samples were operatively removed from 10 women (ages 35-58 yrs) with refractory chronic subacromial bursitis, among whom an average of 7.8 months had passed since the onset of symptoms. All samples were analyzed by x-ray diffraction, Fourier transform infrared spectroscopy, and Raman spectroscopy, and Ca:P molar ratios were measured by x-ray fluorescence spectrometry. RESULTS: Calcified deposits from both acute and chronic cases were identified as carbonate apatite, and not hydroxyapatite, octacalcium phosphate, tricalcium phosphate, or dicalcium phosphate dihydrate. The average Ca:P molar ratio of calcified deposits was calculated as 1.71 +/- 0.16 in acute cases and 1.71 +/- 0.16 in chronic cases (statistically nonsignificant). CONCLUSION: Deposits around the shoulder in both acute and chronic calcific periarthritis are composed of carbonate apatite, Ca:P molar ratios being almost identical in the 2 forms. The results suggest that some factor other than the composition of the crystalline deposits may determine clinical course in calcific periarthritis of the shoulder.

Acute Disease↗

PubMed2006

Chemical surface modification of high-strength porous Ti compacts by spark plasma sintering.

The biological properties of a titanium (Ti) implant depend on its surface oxide film. The aims of the present study were to increase the specific surface oxide area on Ti using a porous structure and to study the relationship between the amount of apatite coating in simulated body fluid (SBF) and the actual surface area on titanium powders. Ti powders of 110 microm average diameter were sintered by spark plasma sintering. The sintered compacts had a porosity of 28%, a compressive elastic modulus of 7.9 GPa and an ultimate strength of 112 MPa. The compressive strength of the compacts was increased to 588 MPa by subsequent annealing in a vacuum furnace at 1000 degrees C for 24 h. The sintered compacts were treated with aqueous NaOH solution and subsequently heated at 600 degrees C. The pretreated compacts showed apatite crystal precipitation in SBF. The amounts of precipitates through the compacts were compared with those of the Ti plate substrates subjected to the same chemical pretreatment. It was confirmed that the amounts of precipitates through the compacts were more than one hundred times higher than those on the Ti plates. It was concluded that the metal porous compacts developed may be used as functional materials for immobilizing functional proteins and/or drugs, because the precipitated apatite can adsorbed these substances.

Apatites↗

PubMed1975

[The cell-independent influence on calcification in living bone and in vitro (author's transl)].

While there is no doubt that collagen is an important extra-cellular factor in the calcification of bone tissues, the exact nature of the process remains unclear. It has been explained in turn by the nucleation effect of corresponding lattice distances of apatite and collagen, that is, an oriented crystal overgrowth of the two substances which decreases the energy of nucleus formation, or by conformity between fibril-bundles and calciumphosphate crystal, or by the binding of phosphate to anionic positions of the collagen, as well as by the bone-forming effect of a non-collagen protein which is, however, separable from collagen. Because of their high viscosity proteo-polysaccharides inhibit crystal formation. Alkaline soluble proteo-pholysaccharides, however, appear to promote calcification in vitro and also in tissue of living bone. Lathyrogene and penicillamine impair the cross-linking in the bone collagen; this probably explains their disturbing effect on ossification. Diphosphonates would, like anorganic pyrophosphate, inhibit both the formation and dissolution of apatite crystal. Our research shows, however, that methanie-bis-phosphonate clearly promotes calcification, in vitro and in vivo. In vitro, and probably also in vivo, magnesium inhibits the formation of apatite crystal nucleus. Our research indicates moreover that magnesium also slows down the reduction of calcified bone tissue on account of its inhibiting effect on parathormone emission.

Apatites↗

PubMed1991

Supravital staining of cells in noninflammatory synovial fluids: analysis of the effect of crystals on cell populations.

Leukocyte differential counts are rarely performed on synovial fluids (SF) with low leukocyte (WBC) counts as they have been difficult to do with standard Wright stains. We performed SF analysis including supravital (SV) stains for differential counts on 100 consecutive relatively noninflammatory synovial fluids defined as any SF with less than 2,000 cells/mm3. SV stains gave clear cellular morphology. Monocytes were the most prominent cells in all noninflammatory synovial fluids. Thirty-eight fluids were found to have crystals (monosodium urate (MSU) in 15, calcium pyrophosphate dihydrate (CPPD) in 5, CPPD plus apatite-like crystals in 9, apatite-like clumps alone in 8 and lipid liquid in 1). WBC counts, percentages of polymorphonuclear (PMN) and absolute PMN counts were greatest in fluids with MSU or CPPD crystals. Fluids with apatite-like clumps alone tended to have the lowest WBC counts. The presence of WBC over 500 cells/mm3, over 20% PMN and absolute PMN counts over 250 cells/mm3 should encourage a careful search for crystals, especially MSU, in noninflammatory synovial fluids.

Apatites↗

PubMed1991

[Estimation of the weddellite to whewellite ratio by infrared spectroscopy].

Powder samples of 56 calcium oxalate stones the contents of weddellite, whewellite and apatite of which had been determined by thermogravimetry (TG) were studied by infrared spectroscopy (IR). When the ratio of the weddellite content to the total of weddellite and whewellite (weddellite ratio) calculated using Oka's method on the infrared spectra was compared with that determined previously by TG, the correlation coefficient between these ratios was 0.734. For the 24 calcium oxalate stones the apatite content of which was less than 10%, the correlation coefficient between these ratios was 0.976, although the weddellite ratio calculated using Oka's method was significantly higher than that determined by TG (P less than 0.01). In an attempt to estimate the weddellite to whewellite ratio by IR regardless of the content of apatite, the ratio of the depth of the absorption band at 780 cm-1 (H780) to the depth of the absorption band at 1,320 cm-1 (H1320) was compared with the ratio of the whewellite content to the total of whewellite and weddellite contents determined by TG. The correlation coefficient between these ratios was 0.953. We conclude that the ratio of H780 to H1320 determined from the infrared spectra obtained from a 0.3 to 1 mg powder sample of calcium oxalate stone is useful in the estimation of the weddellite to whewellite ratio.

Apatites↗

PubMed1987

[Alizarin red staining of articular fluids. Comparison of the results with electron microscopy and clinical data].

Coloration of articular fluids with alizarin S red has been proposed as a method of sensitive detection of calcium microcrystals, especially apatite crystals. We are reporting the results of a study of 230 non-selected fluids. The results of the coloration were quantified into negative, slightly positive, moderately positive and strongly positive. Study of X-Rays of the tapped joint and of the hospital file was done in 199 patients. Electron microscope study, of 44 fluid samples, shows that the coloration with alizarin red permits a reliable detection of calcium microcrystals in the articular fluid, only if the strongly positive results are taken into account. But the coloration is not specific for apatite: 5 strongly positive fluids out of 14 contain only, in electron microscopy, crystals of dihydrated calcium pyrophosphate. 10.8% of the stained fluids give a strongly positive result. In two cases, it concerns destructive arthropathies of the shoulder with periarticular calcifications. The other strongly positive results are found in chondrocalcinosis (52 p. cent), in arthrosis (17 p. cent) and in rheumatoid polyarthritis (15 p. cent). As a whole, the results are correlated with age and the degree of radiological destruction. The similar percentage of strongly positive fluids observed in arthrosis and rheumatoid polyarthritis, is not in favor of a specific role of apatite microcrystals in the pathogenesis of arthrosis. Since the majority of strongly positive fluids come from joints which are very destroyed, regardless of the arthropathy concerned (rheumatoid polyarthritis, chondrocalcinosis or arthrosis), it is possible to think that it is mostly the destruction of the sub-chondral bone which explains these results.

Anthraquinones↗

PubMed1989

Morphogenesis of Michaelis-Gutmann bodies in cerebral malacoplakia. An ultrastructural study.

Malacoplakia was found in the brain biopsy specimen from the wall of a cystic lesion in a 4-month-old girl. Ultrastructural study of the Michaelis-Gutmann bodies revealed that the initial stage of calcification appeared to be the deposit of needle-shaped apatite crystals within intracytoplasmic membrane-bound vesicles of histiocytes. Accumulation of apatite crystals and coalescense of calcified vesicles resulted in the formation of large laminated calcospherules. Extracellular Michaelis-Gutmann bodies and apatite crystal-containing matrix vesicles were also noted. Calcified vesicles and the Michaelis-Gutmann bodies were not observed in the phagolysosomes. Bacteria and viral particles were not identified. These findings suggest that matrix and intracytoplasmic membrane-bound vesicles play an important role in the initial stage of the formation of Michaelis-Gutmann bodies and that a mechanism other than bacterial or viral infection may be involved in cerebral malacoplakia.

Apatites↗

PubMed1988

Magnesium action on the stability of fluorapatite.

Fluorapatites with various magnesium contents (Mg-FAp) were synthesized at pH 7.4 and 80 degrees C. The contraction of their c-axis dimensions observed in X-ray diffraction analysis, together with the results of chemical analyses, suggested that Mg2+ ions may substitute into the apatite crystals to a limited extent. The apatites became less well crystallized with increase in magnesium content. At any given magnesium-calcium feed-in molar ratio (Mg/Ca)f, the magnesium uptake by Mg-FAp was higher than that by the corresponding F- -free Mg-HAp. Therefore, the former became amorphous at lower (Mg/Ca)f than the latter. However, in terms of crystallographic considerations, the Mg-FAp synthesized at high (Mg/Ca)f revealed its apatitic features after pyrolysis at 1,000 degrees C, while Mg-HAp displayed the tricalcium phosphate X-ray pattern.

Apatites↗