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PubMed1985

Ultrastructural studies of crystal-organic matrix relations in renal stones.

Biochemically the organic matrix of kidney stones contains mucoproteins, mucopolysaccharides, inorganic material and bound water. Morphologically, the organic matrix exists as either amorphous or fibrous forms. We have attempted to critically evaluate results from analytical and morphological studies on stone matrices using light microscopy, histochemistry, x-ray diffraction, scanning electron microscopy, x-ray energy dispersive spectrometry, transmission electron microscopy and selected area electron diffraction. On the surface of calcium oxalate stones, there are usually large masses of randomly deposited calcium oxalate crystals each coated with organic matrix. Transmission electron microscopy shows these large surface crystals are composed of rows of smaller crystallites interleaved by organic matrix in a fairly orderly manner suggesting the crystallites are held together by organic matrix. In the core of a calcium containing stone, the organic matrix frequently exists as concentric laminations alternating as calcium apatite covered fibrous matrix layers and amorphous matrix layers. Transmission electron microscopy suggests that the fibrous area is probably just an area heavily populated by calcium apatite crystallites which give the fibrous appearance while the amorphous area is sparsely populated. Organic matrix richness in stones can be associated with infection and calcium apatite crystal deposition is favored in infection stones.

Apatites↗

PubMed1980

[Identification of the mineral constituents of various salivary calculi by study of their thermal behavior].

Studies of the physicochemical nature of five salivary calculi have shown that they are practically similar. They are composed of a nucleus and a shell which contain an organic phase and two crystalline mineral phases. These two phases are respectively a whitlockite and an apatite: the composition of the last agrees with the general formula: Ca10-(x+y) (PO4) T-(x+y) (CO3) x (HPO4) y (20H,CO3) (Formula: see text). The shell is different from the nucleus by the fact that it is less mineralized than the nucleus. The apatite of the shell contains more carbonate ions than the apatite of the nucleus.

Apatites↗

PubMed1980

Contribution to the physicochemical rationale for the caries reducing effect of fluoride.

The effect of fluoride on the stability of apatites containing Na+ and CO3(2)- ions is described qualitatively. Also the boundaries of the apatite stability field in the quasi-septary system CaO - P2O5 - H2O - Na2O - CO2 - NaF - MX are presented. At these boundaries brushite (or monetite), octocalciumphosphate, calcite and calcium fluoride can become stable solid phases. As a consequence, certain mechanisms for the caries reducing effect of fluoride gain probability over other proposed mechanisms. First, it is likely that endemic fluoride yields more fully mineralized enamel which in turn results in a lower initial rate of the caries process. Second, after eruption the mineral in the tooth superficial layer is bound to accumulate fluoride on the surface of its crystals. This causes a slower rate of the crystal surface dissolution at that site and, hence, a thicker and denser intact superficial layer over the lesion. Finally, the formation of a precipitate of fluorhydroxyapatite and perhaps also of calcium fluoride is promoted in the plaque during cycles of metabolic activity. Subsequent dissolution of the CaF2 and transformation of the fluorhydroxyapatite sets free Ca+ and F- ions. Both of these ions promote the remineralization of the lesion during periods of metabolic rest whereby brushite or monetite are transformed back into apatite.

Apatites↗

PubMed1982

[Thermal stability of carbonates in bone tissue].

The analysis shows that carbonate ions present in the mineral phases of calcified tissues are decomposed in two steps during their ignition. These carbonate ions might be all localised in the phosphate sites of the apatitic structure (B type carbonate apatite). The loss of one important part of carbonate ions at a abnormally low temperature (250 degrees C) might result from an intracristalline reaction between these ions and HPO4(2-) or P2O7(4-) ions present in the apatitic structure.

Animals↗

PubMed1994

[Osteoarthritis with rice bodies rich in calcium microcrystals. 4 cases with ultrastructural study].

Rice bodies are often found in inflammatory joint fluid specimens, especially from rheumatoid arthritis patients, but have rarely been reported in osteoarthritis. We found rice bodies in knee joint fluid specimens from four of 88 patients with osteoarthritis. There were three males and one female. Age ranged from 61 to 86 years. Three patients had slowly progressive knee osteoarthritis and one had rapidly destructive disease. Abundant, recurrent effusions occurred in all four patients despite one to five local corticosteroid injections per patient and radiation synovectomy in two patients. The joint fluid specimens contained 120 to 320 cells/mm3 and large numbers of rice bodies that stained with alizarin red S. Transmission electron microscopy studies showed that the rice bodies were composed of fibrin and contained numerous intra- and extra-cellular calcium crystals composed of apatite alone in two cases and of a combination of apatite and calcium pyrophosphate dihydrate in the two others. Collagen fibers and fragments of bone and cartilage were present in a few rice bodies. Phagocytic cells, type C synoviocytes, chondrocytes and a few inflammatory cells were also seen. These rice bodies composed mainly of fibrin and apatite may have played a role in the pathogenesis of the recurrent joint effusions in our patients.

Aged↗

PubMed1994

Detection of cholesterol associated with calcium mineral using confocal fluorescence microscopy.

BACKGROUND: Cholesterol and calcium are prominant components within human atherosclerotic lesions. Both accumulate predominantly within the central core region of lesions. Because of similarities in some crystallographic faces of cholesterol monohydrate and calcium apatite, it has been previously proposed that deposition of one may nucleate the deposition of the other. EXPERIMENTAL DESIGN: In this study, we have used the technique of confocal fluorescence microscopy to assess the spatial orientation of cholesterol in association with calcium mineral. Localization of cholesterol within mineral was carried out by staining cholesterol with the fluorescent probe, filipin. RESULTS: With this technique, it was possible to localize cholesterol associated with the surface of hydroxyapatite seeds, cholesterol incorporated within calcium phosphate-cholesterol agglomerates produced in vitro, and cholesterol within apatite isolated from human atherosclerotic lesions. CONCLUSIONS: The presence of cholesterol within the center of calcified granules from atherosclerotic plaque suggests that cholesterol or associated lipids may act to nucleate the deposition of apatite. Confocal fluorescence microscopy should be a useful technique by which to study the relationship of cholesterol associated with calcium minerals that occur not only in atherosclerotic blood vessels, but also in gallstones, and calcified cardiac valves.

Apatites↗

PubMedDate not supplied

Biodegradable ceramic-collagen composite implanted in rabbit tibiae.

To develop an artificial bone substitute that would be gradually degraded and replaced by the regenerating natural bone, a carbonate apatite type I atelocollagen (82/12 in v/v%) composite was designed. The carbonate apatite synthesized at 58 degrees C demonstrated a crystallinity similar to that of natural bone. Type I atelocollagen was purified from human umbilical cords. Carbonate apatite-atelocollagen composite rods (diameter 6 mm x height 10 mm) were irradiated by ultraviolet ray (wave length 254 nm) for 4 hr to increase the collagen fibrillar cross links. Rabbit tibiae were dissected to prepare an artificial total bone defect (length 10 mm). The composites and porous hydroxyapatite rods, sintered at 1200 degrees C, were implanted into the defects and the tibiae were fixed by external osseofixators. The implanted composites were gradually degraded in the lesions, and the regenerated bone totally replaced the defects within 6 weeks, while the hydroxyapatite rod implanted lesions were not replaced by bone. No specific histologic abnormalities appeared in either the hydroxyapatite or composite rod implanted lesions.

Animals↗

PubMed1996

Citrate in synovial fluid and its relation to inflammation and crystal presence.

OBJECTIVE: To investigate the role of citrate in the pathophysiology of arthritides with calcium pyrophosphate dihydrate (CPPD) crystals and/or apatite-like material. METHODS: We measured citrate concentrations in the plasma and synovial fluid (SF) of 23 joints whose SF contained these crystals and 33 joints without crystals. The SF originated from 25 joints each of patients with rheumatoid arthritis (RA) and primary osteoarthritis (OA) and 10 patients with various other inflammatory joint diseases. RESULTS: There was significant correlation between citrate concentrations in the SF and plasma with values globally twice as high in the SF as in the plasma. Citrate concentrations in the SF of patients whose SF contained CPPD crystals and/or apatite-like material were not significantly lower than those without crystals. On the other hand, citrate concentrations were significantly lower in the SF of patients with RA and other inflammatory joint diseases versus those with OA. CONCLUSION: We have no evidence that lower amounts of citrate in SF favor the presence of CPPD crystals or apatite-like material. Our results, however, do suggest a complex regulation of the citrate concentration in SF where cellular metabolic processes and citrates arising from the plasma and neighboring tissues probably interact to produce the levels recorded.

Adult↗

PubMed1977

Synovial calcification in a patient with collagen-vascular disease: light and electron microscopic studies.

Unusual articular as well as periarticular calcifications are reported in a patient with collagen-vascular disease. Tiny crystals visible in electron micrographs in synovial membrane and in synovial fluid cell vacuoles resemble apatite and appear most consistent with apatite on electron probe studies. The inflammatory synovial effusion also contained chylomicrons. Other joint diseases associated with synovial calcification or suspected synovial apatite are discussed.

Adult↗

PubMed1997

Stable isotopic analysis of human diet in the Marianas Archipelago, western Pacific.

Proportions of marine vs. terrestrial resources in prehistoric human diets in the southern Mariana Islands (Guam, Rota, Saipan), Micronesia, have been estimated by analysis of stable isotope ratios of carbon and nitrogen in bone collagen and of carbon in apatite. The isotopic composition of marine and terrestrial food resources from the Marianas have also been determined. Experimental evidence shows that collagen carbon isotopes mainly reflect those of dietary protein sources and thus overestimate the contribution of marine animal foods. Marine protein consumption apparently ranges from approximately 20% to approximately 50% on these islands. Experiments also demonstrate the carbon isotope ratio of bone apatite carbonate accurately reflects that of the whole diet. Carbonate carbon isotope data suggest some individuals consumed significant amounts of 13C-enriched (C4) plants or seaweeds. Sugar cane is an indigenous C4 crop and seaweeds are eaten throughout the Pacific, but they have not been considered by archaeologists to have been prehistoric dietary staples. Apatite carbon isotope analysis has apparently identified previously unrecognized prehistoric dietary adaptations in the Mariana Islands, but this must be confirmed by archaeobotanical evidence.

Bone and Bones↗

PubMed1996

Effect of serum proteins on solution-induced surface transformations of bioactive ceramics.

The kinetics of immersion-induced surface transformation reactions of synthetic bone bioactive ceramics were studied in vitro in either protein-free or protein-containing simulated physiological solutions. Both solutions had an ion content similar to that of plasma. Synthetic ceramics used for the study included Ca-deficient hydroxyapatite (CDHA), stoichiometric HA either not well crystallized or well crystallized (s-HA nwc or s-HA wc), oxyhydroxyapatite (OHA), beta-tricalcium phosphate (beta-TCP), and porous coralline HA (I-HA) and calcium carbonate (CC). Only CDHA and nwc s-HA led to immediate precipitation in both protein-free and protein-containing solutions. In contrast, reactions of wc HA and I-HA showed lag times to onset of precipitation in the protein-free solution and a further delay in the presence of proteins. The reactions of nonapatitic ceramics whose lag times in the protein-free solution were longer than those of apatitic, were completely blocked in the presence of proteins within the duration of the experiment (up to 3 days). CDHA and nwc s-HA were the only ceramics that, in the presence of serum proteins, led to the formation of B-type carbonated apatite, typical for calcified tissue apatite.

Animals↗

PubMed1996

Bone bonding behavior of titanium and its alloys when coated with titanium oxide (TiO2) and titanium silicate (Ti5Si3).

It has been proposed that the essential requirement for artificial materials to bond to living bone is the formation of bonelike apatite on their surfaces in the body. Recent studies have shown that titanium hydrogel and silica gel induce apatite formation on their surface in a simulated body fluid. In this study, the influence of titanium oxide and titanium silicate on the bonding of titanium alloys to bone was studied. Rectangular implants (15 x 10 x 2.2 mm) of titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were implanted into the tibial metaphyses of mature rabbits. At 8 and 24 weeks after implantation, the tibiae containing the implants were dissected out and subjected to a detaching testing. The failure load for titanium, Ti-6Al-4V, Ti-6Al-2Nb-Ta, Ti-6Al-4V coated with TiO2, and Ti-6Al-4V coated with Ti5Si3 were, respectively, 0.68 +/- 0.48, 0.22 +/- 0.46, 0.67 +/- 0.59, 2.18 +/- 0.71 and 2.03 +/- 0.41 kgf at 8 weeks, and 2.7 +/- 0.91, 2.58 +/- 1.29, 2.38 +/- 0.41, 3.79 +/- 1.7, and 2.79 +/- 0.87 kgf at 24 weeks after implantation. Histological examination by Giemsa surface staining, CMR, and SEM-EPMA revealed the coated titanium alloy implants directly bonded to bone tissue during early implantation. A Ca-P layer was observed at the interface of the coated implants and the bone. The results of this study indicated that TiO2 and Ti5Si3 can enhance the early bonding of titanium alloys to bone by inducing a Ca-P layer (chemical apatite) on the surface of titanium alloys. It also is suggested that the direct bone contact occurs in relation to the calcium and phosphorus adsorption onto the surface of the titanium passive layer formed during long-term implantation.

Alloys↗

PubMed1997

Bioactivity of titanium treated with hydrogen peroxide solutions containing metal chlorides.

Commercially available pure metallic titanium was chemically treated at 60 degrees C for 24 h with H2O2 solutions containing various metal chlorides to provide titanium with bioactivity, that is, to give it the ability to form a biologically active bone-like apatite layer on the surface. After the chemical treatment the titanium specimens were soaked in a simulated body fluid (the Kokubo solution). Apatite was found to deposit on the specimens treated with the H2O2/TaCl5 and H2O2/SnCl2 solutions. X-ray photoelectron spectroscopic (XPS) study of the specimens treated with those H2O2 solutions indicated that basic Ti-OH groups in titania hydrogel layers on their surfaces were responsible for apatite nucleation and growth.

Body Fluids↗

PubMed1997

Direct bone formation on alumina bead composite.

We have developed a composite (designated ABC), consisting of alumina bead powder as an inorganic filler and bisphenol-alpha-glycidyl methacrylate (Bis-GMA)-based resin as an organic matrix, which allows direct bone formation on its surface in vivo. Alumina bead powder was manufactured by fusing crushed alpha-alumina powder and quenching it. The beads took spherical form 3 microns in average size. According to powder X-ray diffraction and Fourier transform infrared spectroscopy, the alumina bead powder was composed of amorphous and delta-crystal phases of alumina in its main crystal structure. Fused-quenched silica glass-filled composite (SGC) was used as a control. The proportion of filler added to the composites was 70% w/w. Mechanical testing of the ABC indicated that it would be strong enough for use under weight-bearing conditions. No apatite formation was detected on the surfaces of either composite after soaking in simulated body fluid for 28 days in vitro. Histological examination of rat tibiae for up to 8 weeks revealed that ABC bonded to bone directly via a layer of calcium, phosphorus, and alumina with no interposed soft-tissue layer. Moreover, the amount of bone directly apposed to the ABC surface increased with time, whereas with SGC there was poor direct bone formation even at 8 weeks. The precise mechanism of direct bone formation on ABC is as yet unknown but it is possible that changes in the crystallinity of alumina, which is known to be highly biocompatible, contribute to its excellent osteoconductivity in vivo. Although bioactive materials such as Bioglass or apatite and wollastonite-containing glass-ceramic have previously been reported to form bone-like apatite on their surfaces under acellular conditions via simple chemical reactions, ABC does not have such characteristics, and presenting favorable conditions for osteoconduction and tissue calcification may lead to direct bone formation on its surface in vivo.

Aluminum Oxide↗

PubMed1998

In vivo dissolution behavior of various RF magnetron sputtered Ca-P coatings.

Radiofrequency magnetron sputter deposition was used to deposit Ca-P sputter coatings on titanium discs, and these coatings were implanted subcutaneously into the backs of rabbits. Half of the as-sputtered coatings were subjected to additional heat treatment for 2 h at 500 degrees C. X-ray diffraction (XRD) demonstrated that annealing at 500 degrees C changed the amorphous sputtered coating into an amorphous-crystalline apatite structure. Scanning electron microscopic (SEM) examination of the sputtered coatings showed excellent coverage of the substrate surface. Annealing of the 4-microm-thick coatings resulted in the appearance of small cracks. SEM demonstrated that until 4 weeks of implantation, all heat-treated coatings were present and all amorphous coatings were completely or mostly dissolved. Fourier transform infrared spectroscopy showed the formation of carbonate apatite (CO3-AP) on these specimens. Furthermore, XRD analysis showed that these CO3-AP precipitated coatings disappeared after 8 weeks of implantation. On the other hand, SEM inspection of these specimens revealed that the 4-microm heat-treated coating was still partially maintained and that small Ca-P crystals were present on the titanium substrate. On the basis of these results, we conclude that apparently 0.1 microm heat-treated Ca-P sputter coating is of sufficient thicknesses to stimulate carbonate apatite deposition under in vivo conditions.

Animals↗

PubMed1999

Influence of composition and surface characteristics on the in vitro bioactivity of SiO(2)-CaO-P(2)O(5)-MgO sol-gel glasses.

Glasses in the system SiO(2)-CaO-P(2)O(5)-MgO were prepared by the sol-gel method. These glasses featured SiO(2) contents in the range 60-80 mol %, 4 mol % of P(2)O(5), and a CaO/MgO molar ratio of 4. Because of their composition and surface properties, all the glasses showed in vitro bioactivity, as evidenced by the formation of an apatite-like layer on their surface when soaked in an acellular medium with ionic composition similar to human blood plasma. An increase in the CaO content of the glasses also caused an increase in their porosity. Higher porosity facilitated the apatite nucleation on the sample surface during the first days of the in vitro test. On the other hand, those glasses with higher SiO(2) content also showed higher surface area values, as well as higher calcium phosphate layer growth rates. For longer soaking periods, the grown layer was analyzed, revealing a two-phase composition: apatite and whitlockite.

Biocompatible Materials↗

PubMed2000

Effects of amelogenin on the transforming surface microstructures of Bioglass in a calcifying solution.

Topographies of a bioactive glass (45S5 type Bioglass(R)) during 0-4 h of immersion in a supersaturated calcifying solution (SCS) and the SCS containing recombinant porcine amelogenin rP172 (SCS(rP172)) were observed by atomic force microscopy. Other techniques including X-ray diffraction, scanning electron microscopy coupled with energy dispersive X-ray spectroscopy, and transmission electron microscopy were used for some complementary microstructural investigations. The smooth Bioglass surface changed to be very rough after 0.5 h of SCS immersion because of glass network dissolution. Spherical silica-gel particles with diameters of 150-300 nm consisting of substructures of 20-60 nm across had formed on the sample surfaces after 1 h of SCS immersion. The chemisorption of amorphous calcium phosphate and crystallization of nanophase apatite were seen to occur epitaxially on the silica-gel structures during 1-4 h of SCS immersion. During the first 0.5 h of SCS(rP172) immersion, more than 95% of rP172 protein in solution was adsorbed onto the sample surfaces and generated spherical assemblies of 10-60 nm diameters. During 0.5-4 h of SCS(rP172) immersion, the protein assemblies of rP172 remarkably induced the formation of orientated silica-gel plates (approximately 100-nm wide and 50-nm thick) and subsequently of long and thin apatite needle crystals. The recombinant amelogenin rP172-modulated apatite crystals resembled those formed in the early stage of tooth enamel biomineralization, suggesting the functional roles of amelogenins during the oriented growth of enamel crystallites and a great potential for amelogenins in applications designed to fabricate enamel-like calcium phosphate biomaterials.

Adsorption↗

PubMed2001

Bioactive glass-mesoporous silica coatings on Ti6Al4V through enameling and triblock-copolymer-templated sol-gel processing.

The combination of thick glass coatings that can protect Ti6Al4V from corrosion in the body fluids, and mesoporous silica films able to readily induce the formation of apatite when immersed in a simulated body fluid (SBF), has been investigated in this work as a possible route towards more resistant and long-lasting implants. Glasses in the system Si-Ca-Mg-Na-K-P-O with thermal expansion coefficients close to that of Ti6Al4V were prepared and used to coat this alloy by an enameling technique. However, the glasses apt to coat Ti6Al4V exhibited a very limited capacity to induce apatite formation in SBF. In order to enhance their bioactivity, a thin film of mesoporous silica was applied on the exterior of the specimens by spin coating a sol-gel solution. When tested in SBF, these coatings induced apatite formation after 7 days. The mesoporosity of the silica film was created through a triblock-copolymer-templating process. The diameters of the mesochannels could be adjusted by changing the size of the directing agent. A preferred alignment of the mesostructure was observed. The removal of the organic templates could be achieved through a photocalcination treatment, which, compared to conventional thermocalcination, offered several advantages.

Alloys↗