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 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

It has been proposed that the formation of a surface apatite layer in vivo on surface active ceramics is an essential condition for chemical bonding between ceramics and bone tissue. To clarify the difference in bone-bonding mechanisms between surface active ceramics and bioresorbable ceramics, two experiments were performed using plates of dense beta-tricalcium phosphate (beta-TCP). First, plates of beta-TCP were implanted subcutaneously in rats for 8 weeks. Surface change due to bioresorption was observed with scanning electron microscopy. Formation of the apatite layer on the surface was investigated using thin-film x-ray diffraction and Fourier transform infrared reflection spectroscopy. Second, plates of beta-TCP were implanted in tibiae of rabbits for 8 and 25 weeks and subjected to the detaching test to measure bone-bonding strength. beta-TCP bonded strongly to bone. Undecalcified sections of the interface of bone and beta-TCP were examined with SEM-EPMA. However, by physicochemical methods, no formation of surface apatite layer was observed. These results suggest that beta-TCP bonds to bone through microanchoring between bone and rough surface of resorbed beta-TCP.
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PMID:Bone bonding mechanism of beta-tricalcium phosphate. 181 21

Histological studies on the effect of lining methods using a alpha-TCP (TC) and a VLC Dycal (LD) were reported previously. In this report, SEM and electron-probe microanalyzer observations were utilized to determine the effects of lining methods. SEM observations were made on longitudinal sections prepared by a freeze fracture method, using 30 vital dog teeth and 5 vital human teeth. In the LD group, several kinds of crystal growth were seen on surfaces of the material and dentinal wall. In the TC group, the exfoliated space area filled up with rod-shaped crystals. An electron-probe microanalyzer was employed to examine the crystal elements observed in the interface or the exfoliated space area. Our findings indicated that lining appeared to fill the gaps with crystal growth, block stimuli which result from bacterial invasion into the dentinal tubules, and reinforce the superficial dentinal zone.
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PMID:Evaluation of lining materials and a new concept for lining: alpha-TCP cement or visible light curing calcium hydroxide composition in composite resin restoration. 181 51

The following results were obtained from the experiment on the five different blocks (HAP, HAP.diopside, diopside, HAP.anorthite and anorthite) which were created as a material of dental implant for in rabbit mandible. Implantation was done on those five blocks under the same condition using pathologic histology, SEM and TEM to see and examine about the changes in the inner surface of each block, the joint condition of new bone and the block, and new bone created around each block and follow its maturing procedure. 1. Much resorption was not seen HAP block even after 48 weeks, with HAP.diopside block, beta-TCP of HAP was resolved, and with HAP.anorthite block, its inner surface was either broken or resolved. Diopside was resolved only in the inner surface, but it was limited only in the Si-rich area. 2. HAP block was created in the long term, and with HAP.anorthite and anorthite block, their inner surface tended to brake apart. In comparison, neither cracking on parting was seen with diopside and HAP.diopside. 3. In two weeks after operation, direct bone was created and attached to diopside with HAP and HAP.diopside, this kind of bone formation was seen in the part of it, and in the rest of the part, the fiber was created. HAP.anorthite and anorthite did not seem to have new bone attached to the direct block. 4. By 4 weeks after the operation, diopside block was surrounded and stabilized by the completed new bone. It took more than 12 weeks for HAP, HAP.diopside, HAP.anorthite and anorthite block to have osteon in the new bone. 5. Crystal lattice created by HAP crystal which appeared in the diopside block, and apatite crystal in the new bone is continuous and arranged in one direction. 6. From above mentioned study results, we can say that diopside is mechanically strong, and because of new bone created along the block surface at an early stage, it is stabilized in the bone soon after the implantation and is the most suitable as a material of dental implant in all the blocks used in this study case.
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PMID:[Experimental studies of healing process on reinforcement ceramic implantation in rabbit mandible]. 213 99

Powder of not-sintered beta-tricalcium phosphate granules was used as capping material in deep cavities of monkey and human teeth. The authors have demonstrated by SEM with E-DAX the dispersion of beta-TCP in the dentinal tubules and in predentin. Histological sections didn't show any inflammation or degeneration of the pulp.
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PMID:[A new lining material, B-tricalcium phosphate MG substitute]. 251 29

Pure hydroxyapatite (HA), pure bioactive glass (BG), and a new series of (HA/BG) composite coatings were plasma-sprayed onto a commercial Ti6A14V substrate. Changes in morphology and phases of these coatings after immersion in Hank's physiologic solution were investigated using XRD and SEM. Results indicated that the as-sprayed BG coating has an essentially amorphous structure with a very rough surface. After 7 days of immersion, the BG surface started to dissolve, and weak XRD peaks of apatite started to develop. Small amounts of CaO, beta-TCP, Ca4P2O5, as well as a glassy film, were found on the as-sprayed pure HA surface, most of which dissolved in 7 days. The XRD intensity of apatite in pure HA slowly increased with immersion time until, on the 10th day, the intensity started to drop, and 10 days later, the intensity rose again. This undiscovered "drop and rise" phenomenon was observed for the HA/BG composite coatings in an even more dramatic way. The presence of HA accelerates the dissolution of bioactive glass.
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PMID:Morphologic variation in plasma-sprayed hydroxyapatite-bioactive glass composite coatings in Hank's solution. 807 83

The aim of the present paper was to study the myopathic bone both from the morphological and structural viewpoints. To this end, samples from 8 patients affected by different neuromuscular diseases (DMD, SMA and CMD) have been examined. Thus, by SEM analysis a quantitative reduction of the trabeculae and an increase in porosity of the myopathic bone were found and also, by diffractometric analysis, the presence of pathologic crystalline phases (beta-TCP and beta-TCP-Mg).
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PMID:Morphological and structural characteristics of the myopathic bone. 812 10

Hydroxyapatites precipitated at pH 7.0 and 9.0 with and without carbonate and with different amounts of magnesium were studied. Mg uptake, Ca/P ratios, and lattice constant data indicate that Mg is incorporated into the apatite lattice. IR spectra demonstrate the formation of B-type carbonate apatites with carbonate substituting for phosphate. Decomposition of carbonate-containing apatites at elevated temperatures up to 1000 degrees C is more gradual for apatites prepared at pH 9.0 than for those prepared at pH 7.0 for which an abrupt loss of carbonate occurs after 600 degrees C. Compounds synthesized without added carbonate partially transform to beta Ca3(PO4)2 (TCP) at about 700 degrees C. Greater transformation to TCP occurs as the Mg incorporation is increased, indicating the insertion of Mg into TCP and consequent stabilization of the TCP. SEM micrographs show increases in the size of crystallites when apatites are precipitated with Mg (in the 0.2-1.5% range), providing further evidence for Mg incorporation into the apatite structure.
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PMID:Magnesium-containing carbonate apatites. 907 68

Previous work has shown that small additions of a phosphate glass (CaO-P2O5) can significantly enhance the sinterability and strength of hydroxyapatite. However, there are no quantitative phase analyses available for these materials which would provide indicators of biocompatibility and resorbability. Similarly, there is little information available about the mechanical properties, especially with high glass additions. In this study, the effects of sintering hydroxyapatite with phosphate glass additions of 2.5, 5, 10, 25, and 50 wt.% are quantified. Each composition was sintered over a range of temperatures, and quantitative phase analysis was carried out using XRD. In addition, the microstructures were studied using RLOM and SEM, and mechanical properties (Vickers hardness, KIC, and MOR) measured. These results may be used to indicate which compositions and processing conditions may provide materials suitable for use in hard tissue replacement. Composites containing up to 10 wt.% glass additions formed dense HA/TCP composite materials possessing flexural strength and fracture toughness values up to 200% those of pure HA. The HA/TCP ratio was strongly dependent on the percentage glass addition. Higher glass additions resulted in composites containing beta-TCP together with large amounts of alpha- or beta-calcium pyrophosphate, and having similar mechanical strengths to pure HA.
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PMID:A quantitative study of the sintering and mechanical properties of hydroxyapatite/phosphate glass composites. 985 84

A model simulating a spiral diaphyseal fracture with butterfly fragments and bone loss was utilized to evaluate an hydroxyapatite/tricalcium phosphate, and collagen composite bone graft substitute in twelve dogs. The resultant grafted and contralateral control femora were tested in torsion at one year. This study examines the histological response to the graft material as well as crack propagation and fracture surface morphology using light microscopy and SEM. SEM and gross evaluation of the grafted bones revealed that 8/12 had fractured through bone outside the osteotomy site and all fractures included bone outside the graft site. No graft material was demonstrated at the points of initiation or termination of fracture for any of the bones. It was apparent that recorticalization had begun to occur at the graft site but the canal had not yet fully formed. The HA/TCP was seen to be tightly bound in tissue which had the appearance of new bone. Bone was found to be in direct apposition to the surface of the ceramic and within pores with no intervening soft tissue. Much of the new bone had remodeled into well organized Haversian systems with some patchy areas of woven bone and osteoid seen with polarized light illumination.
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PMID:Response of canine bone to a synthetic bone graft material. 1014 84

CaO-P(2)O(5) glasses with additions of MgO and CaF(2) were used as a sintering aid of hydroxyapatite, and glass-reinforced hydroxyapatite composites obtained. Glasses promoted significant changes in the microstructure of the composites, namely with the formation of tricalcium phosphate secondary phases, beta and alpha-TCP. Quantitative phase analysis was performed by the Rietveld method using General Structure Analysis Software. Grain size measurements were carried out on SEM photomicrographs, using a planimetric procedure according to ASTM E 112-88. Flexural bending strength was determined from concentric ring-on-ring testing. Flexural bending strength (FBS) of glass-reinforced hydroxyapatite composites was found to be about twice or three times higher than that of unreinforced hydroxyapatite and tended to depend more on porosity and beta and alpha-TCP secondary phases, rather than on grain size. Traces of alpha-tricalcium phosphate significantly enhanced the strength of the composites. Using the rule of mixtures to estimate the zero porosity bending strength, the Duckworth-Knudsen model applied to the composites gave a porosity correction factor, b, with a value of 4.02. Weibull statistics were also used to analyze biaxial strength data and the level of reinforcement obtained by comparing failure probability for the composites and for the unreinforced hydroxyapatite. Lower activation energies for grain growth were observed for the composites compared to unreinforced hydroxyapatite, which should be attributed to the presence of a liquid glassy phase that promotes atomic diffusion during the sintering process.
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PMID:Glass-reinforced hydroxyapatite composites: secondary phase proportions and densification effects on biaxial bending strength. 1049 Jun 90


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