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At least 703 records · Page 39Linked to original sources
PubMed1997

[Augmentation rhinoplasty with particulate hydroxy apatite artificial bone in 50 cases--a follow-up of 8 years].

To investigate the long term results of the particulate hydroxy apatite (HA) artificial bone in augmentation rhinoplasty, 50 patients were followed up for 8 years after the operation. The clinical study included the patient's self-evaluation and the surgeons' objective evaluation of the operation results, analysis of nasal radiographs for the position, shape of the HA implant and its relation with the nasal bone. The observations show that HA is stable and the long-term results of augmentation rhinoplasty with HA are very good. It is concluded that HA is a new, ideal, bioactive filling material for augmentation rhinoplasty.

Adult↗
PubMed2006

[Experimental study of acellular xenogenic dermal matrix and allogeneic sclera as wrapping materials for hydroxy apatite implantation].

OBJECTIVE: To observe the experimental results and histopathological changes of acellular xenogenic dermal matrix (X-ADM) and allogeneic sclera used as wrapping materials of hydroxy apatite (HA) ocular implants in New Zealand white rabbits. METHODS: Twenty-four rabbits received unilateral eye enucleating and the sockets were implanted with HA spherical implants wrapped with either acellular xenogenic dermal matrix or allogeneic sclera at random. The rabbits were examined for inflammation and implant exposure and sacrificed at 1, 2, 4, 6, 8 and 12 weeks after implantation. The sockets with the grafts were exenterated and the specimens were assessed histopathologically and ultrastructurally with light or transmission electron microscopy for the changes in inflammation reaction and vascularization. RESULTS: Compared to allogeneic sclera at the same stage of implantation, acellular xenogenic dermal matrix demonstrated more active and earlier growth of fibroblasts and new vessels with abundant collagen deposition. There were few inflammatory cells and no rejection was found. CONCLUSION: This experiment showed that the acellular xenogenic dermal matrix, with fast neovascularization and low immunity, can be an ideal material of ocular implant and a good substitute for allogeneic sclera.

Animals↗
PubMed1991

[Gasometric determination of carbon dioxide in carbano-apatites of calcified tissue].

The determination of carbon dioxide in carbonato-apatites is carried out a new gasometric method. Its application, in this paper, concerns the bones of skull and mandibles of Cory's shearwater (Calonectris diomedea borealis) and Mallard (Anas platyrhynchos). The results lead to appreciable differences between some organs of this two species.

Animals↗
PubMed1990

High resolution electron microscopy of young apatite crystals in human fetal enamel.

Apatite crystal growth in enamel has been followed during the secretory stage in 5 month-old human fetuses. The crystals were observed in a high resolution transmission electron microscope operating at 300 kV. This microscope has a Scherzer resolution of 0.19 nm and for each micrograph, the absence of astigmatism and drift was checked with optical diffractograms. Crystals in various stages of growth from approximately 3 to 10 unit cells in thickness could be observed along [0001] and mean value of 1010 zone axes. For growing crystals, a highly ordered atomic structure with an ionic distribution consistent with hydroxyapatite was noted as demonstrated by the correspondence of computer simulated and observed images. Moreover, most of the crystals showed structural defects such as edge dislocations and periodically repeated strain fields created by screw dislocations. The observed dislocations were described by Burgers vectors running parallel to mean value of 1120 axes.

Computer Simulation↗
PubMed1989

[Specific physicochemical properties of apatites. 9. Organic phosphate ester monomer as a source of P].

Reactions of calcium ions and organic phosphate ester monomers were examined at 60 degrees C and 80 degrees C and at various pH. By a modification of the method used for HAp synthesis, calcium acetate was fed into aqueous solution of mechanically stirred mono (methacryloyloxyethyl) acid phosphate. Above a pH of 10, poorly crystallized hydroxyapatite was formed with lower crystallinity than that synthesized with inorganic phosphate as a source of P under the same conditions. This result suggested that phosphate ester and/or decomposed acrylic monomer may inhibit the diffusion of Ca2+ and PO4(3-) and the formation of the apatite crystal. On the other hand, the results of X-ray diffraction, chemical analysis, and infrared absorption analysis suggested that crystalline organic calcium phosphate ester was formed below pH 10, while in synthesis with inorganic phosphate, hydroxyapatite was formed at pH 7.4.

Calcium Phosphates↗
PubMed1989

[Prognosis for the deciduous molars of juvenile dogs after root canal filling using apatite root sealer].

There are various restrictions on the root canal filling of deciduous roots after root canal treatment unlike in the case of permanent teeth, because deciduous molars undergo physiological root resorption with aging. Among the restrictions, it is most important that the root canal filling material be similarly absorbed and disappear along with the deciduous root so that it does not prevent the eruption of the permanent successors. Hardly any of the root canal filling materials currently on the market, however, are suitable for deciduous molars because some of them disappear earlier than the deciduous root without becoming indurated in the root canal, while some delay tooth replacement because they are resorbed with great difficulty, and continue strongly to stimulate the surrounding tissue of the root apex. Root canal filling materials utilizing alpha-TCP and hydroxyapatite with excellent biocompatibility have recently been put on the market by Sankin Kygyo Co. Type-III, in particular, contains only 5% iodoform, causing only very slight stimulation, and is a relatively good product from a practical standpoint, i.e., filling the root canal using a lentulo. Root canal filling was performed immediately after dental pulp extraction from the deciduous mandibular molars of juvenile dogs to determine the feasibility of filling deciduous teeth with root canal filling materials. Three dogs were then observed for sequential changes in the resorption of the deciduous roots, presence/absence of adverse effects on permanent successors, and influence on the process of eruption by means of radiographic examination every week. The results obtained were as follows: 1. The type-III apatite root sealar or Vitapex used for root canal filling was not absorbed, and there was almost no resorption of the root. Thus, the deciduous teeth on the experimental side were ejected and shed. 2. There was no significant difference in the amount of tooth germ formed between the experimental and control sides. 3. The amount of eruption tended to be delayed because of insufficient resorption of the root of the deciduous predecessor, but this tendency was considered to be due to the influence of the timing of root canal filling and individual difference. In the final analysis, no definite conclusions could be drawn.

Animals↗
PubMed1989

[Experimental evaluation of apatite coated implants prepared by the build-up technique].

In this study, apatite coated subperiosteal and endosseous implants were prepared by the build-up technique, that is, dental alloy was cast in the required shape, and a covering of glass was fused onto it. Then hydroxyapatite powder was coated on the surface of the glass coat and hydrostatically pressed to form a compact layer which was then heated. These implant materials were tested by animal experiment to evaluate the applicability for clinical use. The results suggested that endosseous subperiosteal implants are available for maxillary molar parts.

Animals↗
PubMedDate not supplied

Apatite-associated arthropathy: a clinical study of 14 cases and of 2 patients with calcific bursitis.

Fourteen cases of acute calcific periarthritis and 2 cases of acute calcific bursitis are described. All patients had radiologic periarticular calcific deposits. Synovial fluid was available from 8 patients. Hydroxyapatite crystals were positively identified in 1 by x-ray diffraction analysis and by scanning and transmission electron microscopy. Apatite-associated arthropathy likely represents a form of crystal-induced inflammation. Three articular syndromes can be recognized; acute calcific periarthritis, acute (calcific) arthritis and a subacute-to-chronic arthritis resembling osteoarthritis. To improve patient classification, diagnostic criteria are proposed.

Acute Disease↗
PubMed1982

Conversion of amorphous tricalcium phosphate into apatitic tricalcium phosphate.

Precipitated calcium orthophosphate, rapidly prepared in highly supersaturated solutions at pH 9-11, is an amorphous tricalcium orthophosphate (atomic ratio Ca/P = 3/2) of formula Ca9(PO4)6, nH2O. Kept wet at room temperature, this phosphate is hydrolyzed according to the reaction PO4(3-) + H2O leads to HPO4(2-) + OH-; a tricalcium orthophosphate series is then formed, its general formula is Ca9 (HPO4)x (PO4)6-x (OH)x, O less than or equal to x less than or equal to 1. Moreover, the amorphous phosphate is converted into apatitic phosphate at half hydrolysis (x approximately equal to 0.5). The hydrolysis occurs simultaneously with an endothermic effect [delta H = 12.0 +/- 2.0 kJ/mol Ca9(PO4)6], and the conversion with an exothermic effect [delta H = -5.9 +/- 1.0 kJ/mol Ca9(PO4)6].

Calcium Phosphates↗
PubMed1982

Effect of fluoride on crystal growth of calcium apatites in the presence of a salivary inhibitor.

The effect of fluoride on the kinetics of crystal growth of calcium apatites was studied using seed crystals of hydroxyapatite coated with PRP-3, a proline-rich phosphoprotein salivary inhibitor of crystal growth. Initial precipitation rates in the presence of PRP-3, under conditions of partial inhibition, were enhanced by fluoride, effectively counteracting the inhibitory activity of the macromolecule. This rate enhancement is related to an increase in the precipitation driving force, i.e., the degree of supersaturation with respect to the precipitating phase; in this case a fluoridated hydroxyapatite. The growth of this phase takes place at the uncovered crystal growth sites which have been previously shown to be the same sites as the adsorption sites for the protein inhibitors. Explanations based on fluoride activation of secondary crystal growth sites and on the displacement of adsorbed inhibitor by fluoride are not substantiated by the present results. It has been demonstrated that under conditions of maximum coverage of available crystal growth sites by PRP-3, resulting in no apparent crystal growth, measurable crystal growth is observed upon the addition of fluoride (1 ppm). This phenomenon is best explained by the fact that at maximum PRP-3 coverage, a small number (16%) of crystal growth sites remain uncovered, which support an unmeasurable rate of crystal growth. Upon the addition of fluoride, this rate is significantly enhanced. It is suggested that the fraction of uncovered growth sites is related to steric interactions of the PRP-3 molecule in the adsorbed state. Overall, the results presented suggest that fluoride can accelerate crystal growth in an environment such as the enamel surface where the acquired pellicle is formed.

Crystallization↗
PubMed1982

ESR identification of radiation damage in synthetic apatites: a study of the 13C-hyperfine coupling.

Although radiogenic free radicals are widely used as molecular probes in biological calcified tissues, their nature and their location remain controversial. In the present study we have synthesized and irradiated apatites in which 13CO3(2-) ions substitute hydroxyl or phosphate ions in hydroxyapatite. The 13C-couplings show that the carbon-centered radicals are CO2- --rather than CO3(3-)--the locations of which depend on the type of carbonate and the treatment of the sample.

Carbon Isotopes↗
PubMed1982

The effect of proteoglycans of cartilage and over-sulphated polysaccharides on the development of calcium-hydroxy-apatite (CHA) crystal formation in vitro.

A coulometric model system is described which facilitates the quantitative study of the kinetics of transformation of amorphous calcium phosphate (ACP) into calcium-hydroxy-apatite (CHA) crystals. Proteoglycans of high molecular weight and over-sulphated polysaccharides (Arteparon, dextran sulphate) delayed CHA crystal formation. The results have enabled us to characterize the structure activity relationship of inhibitors of CHA formation, and to postulate a general structural requirement for molecules with inhibitory effect. As working mechanism, binding of calcium ions by sulphate groups of polyanions was supposed, which might reversibly impair "the critical nuclei formation", and/or further deposition of calcium ions in the CHA crystals. The clinical, therapeutical significance of the determination of the threshold concentration of different compounds is discussed.

Animals↗
PubMed1983

Influence of radial TEM distortion on the accuracy of lattice parameter determinations of apatites: a comparison of four electron microscopes.

Lattice fringe distances of synthetic hydroxyapatite were measured quantitatively in four different TEM microscopes as a function of the position with respect to the optical axis. Using the accurately known "a" value of this apatite from X-ray diffraction, the maximum radial distortion in the image planes can be determined in various positions. For the Philips EM 400, EM 300 (1) and EM 300 (2) and JEOL 200 CX the maximum radial distortion was found to be 1.0%, 0.8%, 1.5% and 0.5%, respectively. In accurate lattice parameter determinations of mineral and mineral phases in biological tissues by means of TEM; this radial distortion is an important parameter to take into account.

Crystallography↗
PubMed1982

Determination and calibration of crystal lattice images of biological apatites.

Lattice imaging provides detailed information on the mineral phase of calcified tissues. The lattice space distances dhk1 depend directly on the accuracy of the magnification. Using synthetic apatite, K2PtCl6, graphitized C and crocidolite as calibration material the lattice parameters of human enamel have been determined. The relative errors in the mineral dhk1 values using crocidolite, K2PtCl6 and C are 0.6, 1.0 and 3.9 % resp. If hydroxyapatite is employed on the same grid as the enamel specimen, the d-values obtained are very close to the X-ray diffraction data; a reproducibility of 0.8% in a and c lattice parameter determination can be obtained on selected crystallites.

Crystallography↗
PubMed1994

Observations on structural features and characteristics of biological apatite crystals. 9. Observation on dissolution of carious enamel crystals.

In a series of studies to investigate the basic structural features and characteristics of the biological apatite crystals using a transmission electron microscope, we examined the ultrastructure of the human enamel, dentin, and bone crystals through the cross and longitudinal sections at near atomic resolution. Subsequently, using the same approach, we have been able to directly examine the images of the lattice imperfections in the crystal lattices of the human tooth and bone crystals, and the images of the fusion of the crystals. In this research, furthermore, using transmission and scanning electron microscopes, we examined the dissolution of the enamel crystals caused by the carious enamel from the same viewpoint. The material used for the observation of the dissolution of the enamel crystals was obtained from the region which corresponds to the middle layer of the enamel at the portion near the wall of a carious cavity caused by the fissure caries on the occlusal surface of the lower first molars. Small cubes of the materials used for the observation by transmission electron electron microscope were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with the HITACHI H-800H type transmission electron microscope operated at 200 kV. Each crystal was observed at an initial magnification of 300,000 times and at a final magnification of 10,000,000 times and over. The material used for the observation by the scanning electron microscope was the fractured surface obtained from the carious enamel. The fractured carious enamel surfaces were coated with carbon and gold and observed with the HITACHI HHS-2R type scanning electron microscope operated at 25 kV. The crystals were observed at a final magnification of 50,000 times. As a result, we have confirmed that the dissolution of the enamel crystals caused by a caries occurs in the units of "hexagonal cell". We sincerely believe that the electron micrographs shown in this report are the first to show the images of the dissolution of the enamel crystals caused by a caries at near atomic resolution.

Dental Caries↗
PubMed1993

Observations on structural features and characteristics of biological apatite crystals. 8. Observation on fusion of human enamel crystals.

In a series of studies to investigate the basic structural features and characteristics of the biological apatite crystals, using a transmission electron microscope, we examined the ultrastructure of the human enamel, dentin, and bone crystals at near atomic resolution and showed the configuration of the hydroxyapatite structure through the cross and longitudinal sections of the crystals. Subsequently, based on the results of the observations by the authors of the ultrastructure of the tooth and bone, using the same approach, we have been able to directly examine the images of the lattice imperfections in the human tooth and bone crystals, such as the point defect structure, line defect, and face defect, in the crystals. In this report, we describe the images of the crystal fusion obtained by using the same approach from the sections of the human enamel crystals. The materials used for this study were the noncarious enamel from the freshly extracted human erupted lower first molars. The small cubes of the material were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with the HITACHI H-800 H and H-9000 type transmission electron microscopes operated at 200 kV and 300 kV. Each crystal was observed at an initial magnification of 300,000 times and at a final magnification of 10,000,000 times and over. We are, therefore, able to confirm that the fusion between the adjacent crystals can occur at some time during the life history of the human enamel. We sincerely believe that the electron micrographs shown in this report are the first to show the ultrastructures of the crystal fusion in the human enamel crystals at near atomic resolution.

Crystallography↗
PubMed1993

Observations on structural features and characteristics of biological apatite crystals. 6. Observation on lattice imperfection of human tooth and bone crystals. I.

In a series of studies to investigate the basic structural features and characteristics of the biological apatite crystals, using an electron microscope, we examined the ultrastructure of the human enamel, dentin, and bone crystals at near atomic resolution and showed the configuration of the hydroxyapatite structure through the cross and longitudinal sections of the crystals. Subsequently, based on the results of the observations by the authors of the ultrastructure of the tooth and bone, using the same approach, we have been able to directly examine the images of the lattice imperfections in the human enamel, dentin, and bone crystals, such as the point defect structures and dislocations in the crystals. In this report, we describe the image of the point defect structures and line defect structures obtained, using the same approach from the sections of the human enamel, dentin, and bone crystals. The materials used for this study were the noncarious enamel and dentin from the freshly extracted human erupted lower first molars, and bone tissue obtained from the alveolar compact bone. The small cubes of the material were fixed in glutaraldehyde and osmium tetroxide and embedded in epoxy resin using the routine methods. The ultrathin sections were cut with a diamond knife without decalcification. The sections were examined with the HITACHI H-800 H and H-9000 types of transmission electron microscopes operated at 200 kV and 300 kV. Each crystal was observed at the initial magnification of 300,000-500,000 times and at the final magnification of 10,000,000 times and over. We sincerely believe that the electron micrographs shown in this report are the first to show the images of the lattice imperfections in the human enamel, dentin, and bone crystals, such as the point defect and line defect structures, at near atomic resolution.

Alveolar Process↗