SEARCH · PubMed Health

Results for “Hydroxyapatites”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed1992

Fibroblastic growth and attachment on hydroxyapatite-coated titanium surfaces following the use of various detoxification modalities. Part II: Contaminated hydroxyapatite.

This study evaluated the ability of various chemotherapeutic and mechanical modalities to detoxify endotoxin-contaminated hydroxyapatite-coated dental implant surfaces as determined by the early attachment and growth of human gingival fibroblasts. Hydroxyapatite-coated test strips were contaminated with purified outer membranes of Escherichia coli and treated with citric acid, hydrogen peroxide, stannous fluoride, chlorhexidine gluconate, tetracycline HCl, polymyxin B, a plastic sonic scaler tip, or left untreated (contaminated and sterile controls). Human gingival fibroblasts were then seeded onto the test strips and incubated for 48 hours. The citric acid-treated strips showed greater cell growth than the other treatments. The plastic sonic scaler tip and the polymyxin B-treated samples exhibited greater cell coverage than the sterile control specimens. The use of citric acid and/or a modified plastic sonic scaler tip may be a valuable adjunct when surgical repair of an ailing hydroxyapatite-coated dental implant is contemplated.

Cell Adhesion↗

PubMed1977

Interaction of hydroxyapatite and protein-coated hydroxyapatite with Streptococcus mutans and Streptococcus sanguis.

The present study showed that S. mutans and S. sanguis behaved like negatively-charged particles in their interaction with hydroxyapatite in vitro. Phosphate in the system inhibited bacterial uptake by apatite, whereas calcium increased the uptake. A layer of acidic protein inhibited the uptake of bacteria by hydroxyapatite. The opposite was true when a basic protein was first adsorbed to the apatite. A saliva film on the apatite decreased the uptake of bacteria, supporting the view that acidic proteins are selectively adsorbed by hydroxyapatite from saliva. The results indicate clearly that electrostatic forces may be involved in bacterial interaction with tooth surface.

Adsorption↗

PubMed1992

Fibroblastic growth and attachment on hydroxyapatite-coated titanium surfaces following the use of various detoxification modalities. Part I: Noncontaminated hydroxyapatite.

Hydroxyapatite-coated titanium alloy test strips were treated with chlorhexidine gluconate, stannous fluoride, citric acid, tetracycline HCl, polymyxin B, hydrogen peroxide, and a plastic Cavitron tip: untreated sterile strips served as controls. The strips were incubated with cultured human gingival and periodontal ligament fibroblasts. Image analysis of three photomicrographs of each test strip (original magnification x350) indicated that the tetracycline HCl treatment resulted in significantly greater cellular surface area coverage compared with the other treatments. Citric acid and the plastic Cavitron tip also stimulated cell attachment, although the results from the Cavitron tip were not significantly different from citric acid or the other treatment groups. The remainder of the modalities and the untreated cellular controls experienced similar cellular coverage.

Cell Adhesion↗

PubMed1992

Reaction of bone to HA, carbonate-HA, hydroxyapatite + calcium orthophosphate and to hydroxyapatite + calcium ortho- and pyrophosphate.

Slip cast conical implants of HA, carbonate-HA, calcium orthophosphate/hydroxyapatite and hydroxyapatite/calcium pyrophosphate/calcium orthophosphate with weight ratios 75/25 and 50/30/20 were implanted in rabbit tibia. The bone-implant interfaces were evaluated histologically, by means of SEM/EDX analysis and by push-out test. Thirty-six implanted samples were investigated after 2, 8, and 24 weeks. The triphasic calcium phosphate showed a moderate disintegration. This material showed 2 weeks after implantation a bonding between new bone and implant could be seen in parts of the operation site by SEM. Eight weeks after implantation an intimate relationship between the bone tissue and all specimens of each material was found. After 24 weeks the Ca/P ratio in the bone had reached the Ca/P ratio of mature bone determined by SEM/EDX analysis.

Animals↗

PubMed1992

Experimental hydroxyapatite cement cranioplasty.

Hydroxyapatite cement is a calcium phosphate-based material that when mixed with water forms a dense paste that sets within 15 minutes and isothermically converts in vivo to a microporous hydroxyapatite implant. This cement was used to reconstruct bilateral 2.5-cm-diameter full-thickness critical-sized parietal skull defects in six cats. One side was reconstructed with 100 percent hydroxyapatite cement, and the other with a mixture of 50 percent hydroxyapatite cement and 50 percent ground autogenous bone by weight. These animals were sacrificed at 6 and 12 months after implantation. Positive and negative controls also were prepared. The anatomic contour of the soft tissue overlying all hydroxyapatite cement implants was well maintained, there were no wound infections or structural failures, and the implants were well tolerated histologically. None of the negative (unreconstructed) control defects was completely filled with repair bone, and all positive (methyl methacrylate) controls demonstrated foreign-body giant-cell formation and fibrous encapsulation of the implants. Examination of decalcified and undecalcified sections revealed progressive but variable replacement of the cement by new bone and soft tissue without a change in the shape or volume of the hydroxyapatite cement-reconstructed areas. New bone comprised 77.3 and 64.7 percent of the tissue replacing the hydroxyapatite cement and hydroxyapatite cement-bone implants, respectively. Replacement of the hydroxyapatite cement implants by new bone is postulated to occur by a combination of osteoconduction and implant resorption. These results indicate that further experimental research leading to the possible application of hydroxyapatite cement for full-thickness calvarial defect reconstruction in humans is warranted.

Animals↗

PubMed1976

Hydroxyapatite - a reagent for the separation of free and antibody-bound steroid during the radioimmunoassay.

The use of hydroxyapatite to absorb antibody-bound steroid and thus separate free and antibody-bound steroid during radioimmunoassay has been examined using three steroid antisera (to testosterone, to 17-hydroxyprogesterone and to estradiol-17beta). For all three antisera studied the separation was shown to be independent of length of time in contact with hydroxyapatite (up to 1h); temperature variations from 4 degrees -37 degrees and pH over the range 4.9-8.0. The presence of protein affected the absorption of antibody-bound steroid but this effect could be overcome by the addition of increasing amounts of hydroxyapatite. Further increase in the amount of hydroxyapatite added had no effect on the separation of free and bound steroid. Sodium phosphate buffers of molarity greater than 0.01M eluted antibody-bount steroid from hydroxyapatite, but Tris-HC1 buffers up to molarities of 0.1 M had no effect. Hydroxyapatite when used as a dry powder had the same effects as suspensions. No effect on the cross-reactivities of the antisera used could be demonstrated when hydroxyapatite was used and plasma testosterone assays on 22 plasma samples using hydroxyapatite gave essentially the same results as assays on the plasma using a coated-tube assay. Hydroxyapatite can also be successfully pumped along small bore plastic tubing without settling and can thus be used in automated immunoassay systems.

Estradiol↗

PubMed1992

Osteogenin, a bone morphogenetic protein, adsorbed on porous hydroxyapatite substrata, induces rapid bone differentiation in calvarial defects of adult primates.

Osteogenin, a bone morphogenetic protein, in conjunction with insoluble collagenous bone matrix initiates local endochondral bone differentiation by induction in vivo. This study, by exploiting the affinity of native osteogenin for hydroxyapatite, was designed to construct a delivery system for the expression of the biologic activity of osteogenin in nonhealing calvarial defects of adult primates. After exposure of the calvaria, 64 cranial defects, 25 mm in diameter, were prepared in 16 adult male baboons (Papio ursinus). Defects were implanted with disks of porous nonresorbable and resorbable hydroxyapatite substrata obtained after hydrothermal conversion of calcium carbonate exoskeletons of corals. In each animal, one disk of each hydroxyapatite preparation was treated with osteogenin isolated and purified from baboon bone matrix after sequential chromatography on heparin-Sepharose, hydroxyapatite, and Sephacryl S-200 gel filtration columns. The remaining two defects were implanted with one disk of each hydroxyapatite preparation without osteogenin as control. Histomorphometry on decalcified sections prepared on days 30 and 90 showed superior osteogenesis in osteogenin-treated nonresorbable hydroxyapatite specimens as compared with controls. On day 90, substantial bone formation also had occurred in control nonresorbable hydroxyapatite specimens. On day 90, but not on day 30, significantly greater amounts of bone had formed in osteogenin-treated resorbable specimens as compared with resorbable controls. Overall, resorbable substrata performed poorly when compared with nonresorbable substrata, perhaps due to a premature dissolution of the implants. These results provide evidence that the biologic activity of osteogenin can be restored and delivered by a substratum other than the organic collagenous matrix, inducing rapid bone differentiation in calvarial defects of adult nonhuman primates. The adsorption strategy of osteogenin on porous inorganic nonimmunogenic substrata may help to design appropriate osteogenic delivery systems for craniofacial and orthopedic applications in humans.

Adsorption↗

PubMed1979

SnF2 treatment of enamel, hydroxyapatite or brushite at 37 degrees C and 50 degrees C: an infra-red investigation.

The effect of 4% SnF2 on brushite, hydroxyapatite and powdered bovine enamel applied for short, 15 or 30 minute, periods was investigated using infra-red spectroscopy. It was found that brushite was converted into a fluoridated hydroxyapatite, a reaction which was both time and temperature dependent. The reactions of hydroxyapatite and powdered enamel with SnF2 were similar. There was a drop in the OH- peak intesities. X-ray diffraction analysis of these samples showed that F- ions occupied mainly OH positions in the hydroxyapatite lattice structure. In all reactions an increase in temperature from 37 degrees C to 50 degrees C increased the reaction speed by at least a factor 2. The most probable result of in vivi SnF2 application on sound enamel is the formation of a fluoridated hydroxyapatite together wity stannous complexes and amorphous CaF2. In demineralized areas some of the brushite is converted into a fluoridated hydroxyapatite as is some of the remaining hydroxyapatite. In the more protected area of an enamel lesion these reactions may well continue for some time after the topical fluoride application; Sn2F3PO4 may also therefore be formed.

Animals↗

PubMed1992

Mechanical failure of hydroxyapatite- and polysulfone-coated titanium rods in a weight-bearing canine model.

Three types of material that have shown potential as coatings for orthopaedic implants were studied. Using a weight-bearing canine model, Ti-6A1-4V femoral intramedullary rods coated with (1) sintered titanium beads, (2) plasma-sprayed hydroxyapatite, and (3) silyl coupled polysulfone beads were evaluated for mechanical strength and bone ingrowth. The model was designed to secure optimal prosthetic stability by obtaining maximal bony ingrowth during an initial non-weight-bearing phase, then stressing the implant during a full-weight-bearing phase. None of the rods coated with titanium beads failed. All 17 polysulfone-coated rods failed, 13 of them at the interface between the polysulfone coating and the titanium core. Of 18 rods coated with hydroxyapatite, 15 suffered implant breakdown at the interface between the hydroxyapatite coating and the titanium core. This may be due to dissolution of the plasma-sprayed hydroxyapatite in vivo. Testing of retrieved specimens from both hydroxyapatite- and polysulfone-coated implants showed that the shear strength at the coating-rod interface had decreased to less than 40% of the shear strength at manufacture. Despite mechanical failure, histologic study showed extensive bone ingrowth or apposition onto both the polysulfone and hydroxyapatite coatings.

Animals↗

PubMed1992

Exposed hydroxyapatite orbital implants. Report of six cases.

Six patients with complications of primary or secondary hydroxyapatite implants were studied. Complications included socket infection and/or conjunctival dehiscence. Complications were detected during regular follow-up examinations, and various treatment approaches were used. The hydroxyapatite implant exposure occurred 4 to 6 weeks (mean, 4.5 weeks) after implantation. Three of the six implants were wrapped in preserved donor sclera before implantation. One of the implants showed wide exposure and chronic infection and was removed. In two cases, scleral patch grafts with a conjunctival pedicle graft were performed, resulting in successful coverage of the implant without further conjunctival dehiscence. In one of the patients, a Tenon's conjunctival flap was advanced to cover the defect, and was unsuccessful with the spicules of the hydroxyapatite eroding through the vascular flap after 1 month. Three of the patients demonstrate a persistent conjunctival epithelial defect. These three patients with chronically exposed hydroxyapatite have remained stable with follow-up intervals ranging from 8 to 12 months. Early exposure of hydroxyapatite orbital implants is a potential problem despite meticulous technique. Implant coverage is difficult, although chronic exposure seems to be tolerated often in the hydroxyapatite orbital implant without migration or extrusion.

Adolescent↗

PubMed1992

Heterogeneous synthesis of fluoridated hydroxyapatites.

Fluoridated hydroxyapatites were synthesized with two different modes of fluoride supply: by supplying F(-)-free solution initially, followed by a F(-)-containing solution whose fluoride concentration was stoichiometrically equal to that of fluorapatite; and with the order of supply of these solutions reversed. Both of these heterogeneously synthesized fluoridated hydroxyapatites showed typical calcium phosphate X-ray diffraction patterns; and both had similar total fluoride contents (0.94 +/- 0.02 and 0.99 +/- 0.03 mmol/g, respectively), i.e. half of the maximum fluoride content of fluorapatite. However, they differed considerably in their physico-chemical properties. The former had a wider peak breadth of X-ray diffraction and a lower apparent solubility (Ca = 12.2 +/- 0.7 mmol/l) than the latter (Ca = 19.8 +/- 0.4 mmol/l) at 37 degrees C and pH 4.0. Wavelength dispersive spectroscopy attached to scanning electron microscopy gave clearly different spectra. Electron spectroscopy for chemical analysis of apatite pellets made by pressing and heating showed a slightly larger F1s signal at the crystal surface of the former, although the difference was not marked. These results suggest that two different types of heterogeneous fluoridated hydroxyapatites were formed, hydroxyapatite covered with fluorapatite and fluorapatite covered with hydroxyapatite.

Fluorides↗

PubMed1992

Interface between hydroxyapatite and mandibular human bone tissue.

Samples from intraosseous dental implants, removed from patients for mechanical failures, were examined to analyse the interaction between hydroxyapatite as plasma sprayed coating on titanium supports and human bone. The implantation time varied up to 8 years. No failures had arisen from problems at the interface between the hydroxyapatite coating and bone. The number of samples examined and the implantation times give good statistical conclusions. Histological and microchemical studies showed the good performance and compatibility of this sprayed hydroxyapatite. We present evidence from the best samples which show close bonding with the surrounding bone tissue. New bone is seen all around the coated implant. The composition of the calcium phosphate deposited on the hydroxyapatite and cellular approach were determined, and demonstrate the efficiency of the interaction between this plasma sprayed hydroxyapatite and the bone.

Adhesiveness↗

PubMed1979

The nature of the hydroxyapatite-binding site in salivary acidic proline-rich proteins.

Protein A and C, which are major components of the acidic proline-rich proteins in human saliva, were digested, before or after adsorption to hydroxyapatite, with alkaline phosphatase, trypsin, thermolysin and a proteinase preparation from salivary sediment. The results demonstrate that the binding site is located in the proline-poor N-terminal part of the protein, possibly between residues 3 and 25. Phosphoserine is necessary for maximal adsorption of the proteins to hydroxyapatite. When proteins A and C are adsorbed to hydroxyapatite before proteolytic digestion there is a protection of some of the susceptible bonds in the N-terminal part of the proteins and a gradual removal of the proline-rich C-terminal part. Thermolysin can cleave susceptible bonds in the part of the protein that remains bound to hydroxyapatite, but at least some of the resulting peptides are retained on the mineral. Since the ability of the proteins to inhibit hydroxyapatite formation and to bind calcium is located in the N-terminal proline-poor part, it is possible that these activities are retained after proteolytic digestion of the adsorbed proteins.

Adsorption↗

PubMed1992

Calvarial reconstruction in baboons with porous hydroxyapatite.

The growth of bone into porous hydroxyapatite implanted in nonhealing calvarial defects of adult baboons is evaluated. Seventy-two anterior and posterior calvarial defects, 25 mm in diameter, were prepared in 24 adult male baboons (Papio ursinus). In each animal, one defect was implanted with a disc of porous hydroxyapatite obtained after hydrothermal conversion of the calcium carbonate exoskeleton of coral (genus Goniopora); pores averaged 600 microns in diameter, pore interconnections averaged 260 microns in diameter, and the void fraction was 70% (Interpore 500). Another defect was grafted with autogenous corticocancellous bone harvested from the iliac crest. The third defect was left ungrafted and used as a control. Histology and histomorphometry on nondecalcified and decalcified sections prepared from specimens harvested at 3, 6, and 9 months after surgery showed that substantial bone growth had occurred in the hydroxyapatite implants (p < 0.01 vs bone grafts at 3 mos), culminating in complete penetration of bone within the tridimensional porous spaces. Anterior untreated defects showed greater amounts of bone when compared to posterior defects. The extent of bone growth in hydroxyapatite implants, however, appeared to be independent of the site of surgical implantation. This finding suggests that bone deposition within the porous spaces was a function of the implanted matrix rather than the healing potential of specific regions within the calvaria. Of concern was the presence of nonunions at the hydroxyapatite/calvarial interfaces, despite the often extensive bone deposition within the center of the hydroxyapatite implants. Further studies are required to identify the reasons for nonunion and to evaluate the mechanical performance of the bone-porous matrix complex.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMedDate not supplied

[Chromatography of nucleic acids, proteins and certain phages on granulated hydroxyapatite].

A modification of the classical method of hydroxyapatite synthesis is proposed. The essence of the modification is hydroxyapatite synthesis in the presence of an additional component silicic acid particles. The subsequent steps of the method are modified so, as to retain the intactness of crystals at all the stages of preparation and use of the adsorbent. The final product consists of large spherical agregates (200-250 mu in diameter) and contains about 1% of tightly bound silicic acid. It slightly differs from usual hydroxyapatite in its chromatographic properties. Granulated hydroxyapatite obtained has a high specific capacity and can be repeatedly used in experiments (up to 50 chromatographic cycles). Native high-polymeric T2 phage DNA was practically quantitatively eluated from the column. Conditions for chromatography of some proteins (lysozyme, RNase, DNase) are described. Fractionation and purification of T2 and T3 bacteriophages and TMV are carried out by means of chromatography on granulated hydroxyapatite.

Chromatography↗

PubMed1992

Induction of bone in composites of osteogenin and porous hydroxyapatite in baboons.

A major goal of the combined effort of basic scientists and plastic and reconstructive surgeons is the development of novel bone substitutes based on osteogenic growth and differentiation factors with optimal delivery systems for skeletal repair. Osteogenin is a protein initiator of bone differentiation. The present study examined the osteogenic potential of osteogenin in combination with porous hydroxyapatite replicas obtained after hydrothermal conversion of calcium carbonate exoskeletons of corals. Bovine osteogenin, with an apparent molecular weight of 28 to 42 kDa, purified by hydroxyapatite-Ultrogel adsorption chromatography, heparin-Sepharose affinity chromatography, and HR Sephacryl S-200 molecular sieve chromatography, was delivered into rods of nonresorbable and resorbable hydroxyapatite replicas with an average porosity of 600 microns. A total of 48 rods were bioassayed for osteogenic activity by intramuscular implantation into eight adult baboons (Papio ursinus) as a prerequisite for clinical trials in humans. Bovine osteogenin fractions reconstituted with baboon insoluble collagenous bone matrix were implanted in an additional four adult baboons. Specimens were harvested at 30 and 90 days after implantation and subjected to histomorphometry and alkaline phosphatase activity determination. Differentiation of bone occurred in nonresorbable hydroxyapatite rods, both osteogenin-treated and controls. However, no bone formation was observed in resorbable rods, even in the presence of osteogenin. These results demonstrate that the surface and chemical characteristics of the substratum, independent of the osteogenic stimulus, have a profound influence on the morphogenesis of bone. The demonstration of bone induction in nonhuman primates with porous nonresorbable hydroxyapatite replicas and baboon insoluble collagenous bone matrix reconstituted with bovine osteogenin establishes the therapeutic potential of the principle of bone induction in craniofacial, periodontal, and orthopedic reconstructive surgery.

Analysis of Variance↗

PubMed1978

The interaction of collagenase with hydroxyapatite and related materials and enzymatic properties of the adsorbed enzyme.

The commercial collagenase from Clostridium histolyticum was adsorbed on hydroxyapatite, on bovine femur shaft and on enamel and dentin powders. The substrate specificity of the adsorbed enzyme tested, with chromophore substrate, azocoll and native collagen, differed from that obtained with the soluble enzyme. The adsorption and the substrate specificity was also dependent on the adsorbent used. A pretreatment of hydroxyapatite with chondroitin sulphate, hyaluronate and DNA lowered the adsorption of collagenase. Phosphate ion caused desorption of the enzyme from hydroxyapatite. Sodium fluoride caused partial desorption of the enzyme from hydroxyapatite and enamel and dentin powders. Colangenase adsorbed on root surfaces of teeth liberated hydroxyproline containing material.

Adsorption↗

PubMed1977

Thermal elution chromatography of nucleic acids on hydroxyapatite.

Hydroxyapatite thermal elution chromatography was studied from an empirical standpoint. The dependence of elution temperature on elution buffer concentration was determined for various types of buffer, hydroxyapatite and nucleic acid. The results are analyzed in terms of the proper design and interpretation of thermal elution experiments. The potential for serious artifacts is demonstrated and the means by which they may be avoided is described. Various commercially available hydroxyapatites were tested in conjunction with various aqueous and partially non-aqueous buffer systems. Among the materials tested, potassium phosphate and Bio-Rad HTP were found to constitute the best buffer-hydroxyapatite system for most types of thermal elution study.

Chromatography↗