Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Hydroxyapatites”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

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

At least 829 records · Page 46Linked to original sources
PubMed1996

Interaction of citric acid with hydroxyapatite: surface exchange of ions and precipitation of calcium citrate.

The use of citric acid is efficacious and distinctive in the demineralization of dentinal root surfaces for periodontal regeneration and in the etching and conditioning of enamel or dentin for bonding restorative resins. To decipher the role of citric acid in these applications, it is important that one have a basic understanding of its interaction with synthetic hydroxyapatite. The uptake or removal of citrate ions from aqueous solutions of citric acid (4 to 100 mmol/L, 10 mL) by hydroxyapatite (1 g) was studied at 22 degrees C after a given reaction period (from 3 hr to 11 days) by immediate spectrophotometric monitoring of the concentrations of the filtrates (214 nm). The concentrations of calcium, phosphate, and hydrogen ions were also determined in the same solutions. The interaction: (i) is a time-independent ionic-exchange process with the substrate when the initial acid concentrations are dilute (4 to 12.5 mmol/L), and (ii) is a reactive process that is time-dependent for higher acid concentrations. The exchange process shows an adsorption of about one citrate ion per (100) face of the unit cell of hydroxyapatite for a maximally exchanged surface. The curves representing the reactive process may be quantitatively or qualitatively explained on the basis of the supersaturation of the solutions with respect to calcium citrate and its slow precipitation. The physico-chemical analysis of the needle-shaped birefringent crystals of the precipitate from the supersaturated solutions confirms the precipitate to be Ca3(citrate)2.4H2O.

Acid Etching, Dental↗
PubMedDate not supplied

A clinical study of the hydroxyapatite orbital implant.

The hydroxyapatite orbital implant has been used in the anophthalmic patient to give good motility of the artificial eye and a cosmetic result which matches that of the natural eye. It is thought to reduce the unacceptable complication rate that has been associated with other implants, as its buried, vascularized state deters extrusion and migration of the implant. Eighty consecutive patients were followed, 33 of whom had been referred for primary enucleation or evisceration, and 47 for secondary implant surgery. Thirteen of the secondary patients already had implants in situ. There were 44 males and 36 females in the study. The age range was 2.5 to 72 years with a mean of 36 years. The follow-up time was 2 to 30 months with a mean of 15 months. Twenty patients had been pegged at the time of review. A standardised operative and post-operative protocol was followed. The patients were assessed for the results of the motility of the artificial eye for both smooth pursuit and saccades, and for the cosmetic result. The amount of upper lid sulcus deformity was assessed to give an indication of volume replacement by the implant. The nature of any complications was noted as well as any further surgical procedures undertaken. The results show the hydroxyapatite orbital implant to give good cosmetic results with good motility of the artificial eye and to be associated with a low rate of complications. Drilling of the implant is simple to perform and also not associated with any significant complications. The hydroxyapatite orbital implant can be used successfully not only as a primary but also as a secondary or exchange implant with very few contraindications.

Adolescent↗
PubMed2006

Calcium modulates interactions between bacteria and hydroxyapatite.

Bacterial adhesion onto hydroxyapatite is known to depend on the surface properties of both the biomaterial and the bacterial strain, but less is known about the influence of the composition of the aqueous medium. Here, the adhesion of Streptococcus mutans and 3 different Lactobacilli on powdered hydroxyapatite was shown to change with Ca2+ concentration. The effect depends on the surface properties of each strain. Adhesion of Lactobacillus fermentum and salivarius (and of Streptococcus mutans at low Ca2+) was enhanced with increasing Ca2+ concentration. Lactobacillus casei was efficiently removed by adhesion on hydroxyapatite, even without Ca2+ addition, and the effect of this ion was only marginal. The results are interpreted in terms of Ca2+-mediated adhesion, and relative to the hydrophobic properties of each strain and the electrical properties of the bacterial and solid surfaces (electrophoretic mobility).

Adsorption↗
PubMed2003

Molecular recognition at the protein-hydroxyapatite interface.

Proteins found in mineralized tissues act as nature's crystal engineers, where they play a key role in promoting or inhibiting the growth of minerals such as hydroxyapatite (bones/teeth) and calcium oxalate (kidney stones). Despite their importance in hard-tissue formation and remodeling, and in pathological processes such as stone formation and arterial calcification, there is little known of the protein structure-function relationships that govern hard-tissue engineering. Here we review early studies that have utilized solid-state NMR (ssNMR) techniques to provide in situ secondary-structure determination of statherin and statherin peptides on their biologically relevant hydroxyapatite (HAP) surfaces. In addition to direct structural study, molecular dynamics studies have provided considerable insight into the protein-binding footprint on hydroxyapatite. The molecular insight provided by these studies has also led to the design of biomimetic fusion peptides that utilize nature's crystal-recognition mechanism to display accessible and dynamic bioactive sequences from the HAP surface. These peptides selectively engage adhesion receptors and direct specific outside-in signaling pathway activation in osteoblast-like cells.

Crystallization↗
PubMed2003

Medium-term results of cementless hydroxyapatite-coated primary total hip arthroplasty: a clinical and radiological review.

PURPOSE: To evaluate the clinical and radiological outcomes following cementless primary hydroxyapatite-coated total hip arthroplasty. METHODS: A retrospective study of 69 patients (82 hips) who underwent uncemented hydroxyapatite-coated Anatomic Benoist Girard total hip replacement between October 1991 and October 1995 at our institution was conducted. Patient records were reviewed. All patients were evaluated clinically using the Merle D'Aubigne hip score, and osteointegration was assessed radiographically by analysing the bone implant interface in the 7 zones of Gruen on followup review. RESULTS: The mean follow-up period was 7.3 years. Clinical results were excellent with an improvement seen in clinical score from 9.9 preoperatively to 16.5 at last review. A total of 15% of patients recorded some thigh discomfort, which was intermittent and not functionally limiting, except in 2 cases. There were 3 cases of severe acetabular osteolysis and loosening requiring revision surgery, and 4 cases of localised proximal femoral osteolysis around well-ingrown implants. There were few perioperative complications, with the exception of 5 dislocations of which 3 were recurrent and required a revision procedure. CONCLUSION: Clinical and radiological outcomes following cementless hydroxyapatite-coated total hip arthroplasty were seen to be favourable in this medium-term retrospective study.

Adult↗
PubMed2006

Biocompatability of hydroxyapatite composite as a local drug delivery system.

PURPOSE: To investigate the biocompatibility of hydroxyapatite composite (hydroxyapatite, plaster of Paris, and chitosan) impregnated with gentamicin, fosfomycin, imipenem, or amphotericin B. METHODS: The interactions of the extract from each drug against osteoblast were tested using the methylthiotetrazole test. RESULTS: Extracts from all drugs showed good biocompatibility at concentrations varying from 10 microgram/ml to 1000 microgram/ml. Imipenem and amphotericin B at a concentration of 1000 microgram/ml had a significantly higher percentage of cell viability than the control group. No morphological change of osteoblast was observed in all drug tests at any concentrations. CONCLUSION: The hydroxyapatite composite had a good biocompatibility for carrying gentamicin, fosfomycin, imipenem, or amphotericin B.

Amphotericin B↗
PubMed2006

A knee-sparing distal femoral endoprosthesis using hydroxyapatite-coated extracortical plates. Preliminary results.

We used a knee-sparing distal femoral endoprosthesis in young patients with malignant bone tumours of the distal femur in whom it was possible to resect the tumour and to preserve the distal femoral condyles. The proximal shaft of the endoprosthesis had a coated hydroxyapatite collar, while the distal end had hydroxyapatite-coated extracortical plates to secure it to the small residual femoral condylar fragment. We reviewed the preliminary results of this endoprosthesis in eight patients with primary bone tumours of the distal femur. Their mean age at surgery was 17.years (14 to 21). The mean follow-up was 24 months (20 to 31). At final follow-up the mean flexion at the knee was 102 degrees (20 degrees to 120 degrees) and the mean Musculoskeletal Tumour Society score was 80% (57% to 96.7%). There was excellent osteointegration at the prosthesis-proximal bone interface with formation of new bone around the hydroxyapatite collar. The prosthesis allowed preservation of the knee and achieved a good functional result. Formation of new bone and remodelling at the interface make the implant more secure. Further follow-up is required to determine the long-term structural integrity of the prosthesis.

Adolescent↗
PubMed1997

Repair of the anophthalmic cavity of rats with synthetic hydroxyapatite.

We placed spheres of synthetic hydroxyapatite (calcium chloride combined with sodium phosphate) in the eviscerated or enucleated orbital cavity of rats in order to evaluate the biocompatibility of this material with the orbital cavity. The study was conducted on 50 albino rats, 25 of which were submitted to enucleation and 25 to evisceration of one eye. The animals were sacrificed 7, 15, 21, 30 and 60 days after surgery and the orbital content was submitted to histopathological examination. A reaction of the young granulation tissue type was observed first. The hydroxyapatite was gradually surrounded by a granulomatous macrophage inflammatory response and covered with dense connective tissue that formed a sort of "mesh" septating and supporting progressively smaller blocks of the substance. The same type of reaction was observed in the enucleated and eviscerated cavities. We conclude that synthetic hydroxyapatite is an inert nonallergenic material which is appropriate for volume replacement in the anophthalmic cavity.

Animals↗
PubMed2005

Lack of repair of rat skull critical size defect treated with bovine morphometric protein bound to microgranular bioabsorbable hydroxyapatite.

The ability of a pool of bovine bone morphogenetic proteins bound to synthetic microgranular hydroxyapatite (BMPb-HA) to stimulate bone repair was determined in rat critical size defects. An 8-mm diameter defect was created in the calvaria of 25 rats. In 15 rats, the defects were filled with BMPb-HA homogenized with blood (experimental group), and in 10 rats the defects were filled only with blood clots (control). The calvariae of experimental rats were collected 1, 3 and 6 months after surgery and of the control rats at the end of surgery and 6 months thereafter. The morphometric results obtained in the radiographs showed an absence of new bone formation at 1 and 3 months post-surgery and, histologically, the defects were filled with fibrous connective tissue and numerous foci of a foreign body-type granulomatous reaction around hydroxyapatite agglomerates. At the end of 6 months, the number and size of the granulomatous foci decreased and the area of the defects was reduced by 22% compared to the 0-hour control due to the formation of new bone at their borders, although the mean area was similar to the 6-month control. We conclude that the use of BMPb-HA in the treatment of critical size bone defects of the rat skull leads to the formation of a foreign body-type granulomatous reaction that markedly inhibits new bone formation, suggesting that synthetic microgranular hydroxyapatite does not represent a good carrier for BMP-induced bone formation.

Absorbable Implants↗
PubMed2005

In vivo characterization of titanium implants coated with synthetic hydroxyapatite by electrophoresis.

This study compared in vivo the performances of commercially pure titanium (cp Ti) screw dental implants either uncoated or coated with synthetic hydroxyapatite (HA) by electrophoresis. The HA coating was characterized by scanning electron microscopy, energy dispersive spectroscopy (EDS) and Fourier-transform infrared (FT-IR) spectroscopy. Well-adhered carbonated-hydroxyapatite layers (4- to-8-microm-thick) were obtained. In vivo tests were carried out by insertion of both uncoated and HA-coated implants into rabbit tibiae for 8 or 12 weeks. Histomorphometric analysis was performed by scanning electron microscopy with the aid of image-processing software. Results showed significantly greater bone-implant contact for HA-coated implants (p<0.05) than cp Ti implants. Comparison of bone content inside the screw implants showed no significant differences (p>0.05) between both types of implants, although cp Ti had numerically higher percentage of bone content than HA-coated implants. In conclusion, the HA-coated implants had better performance regarding the bone-implant contact area than the uncoated implants; coating by electrophoresis proved to be a valuable process to coat metallic implants with an osteoconductive material such as hydroxyapatite.

Animals↗
PubMed1994

Histological verification of bone bonding and ingrowth into porous hydroxyapatite spinous process spacer for cervical laminoplasty.

Three spinous processes of the cervical spine and implanted porous hydroxyapatite spacers were removed from a patient with a recurring intramedullary tumor at revisional laminectomy one year after spinous process splitting laminoplasty. Histological examination of undecalcified sections revealed direct bone bonding to the spacer at three of the six bone-hydroxyapatite interfaces. Bone ingrowth was observed up to 400 microns into the implant pores. Fibrous tissue was observed to intervene between the other three bone-hydroxyapatite interfaces. The suspected bone bonding with the spacer on CT scans before the revision was confirmed by the histological findings.

Astrocytoma↗
PubMed1995

The effect of warfarin on the attachment of bone to hydroxyapatite-coated and uncoated porous implants.

The attachment of bone to hydroxyapatite-coated and uncoated porous implants made of cobalt-chromium-molybdenum alloy was investigated with and without postoperative administration of warfarin sodium. The implants were placed transcortically in the femoral diaphysis of adult female goats and were evaluated after three, six, and twelve weeks in situ. Mechanical push-out testing and histological evaluation revealed that the attachment strength and the ingrowth of bone at the bone-implant interface increased with time in situ for both the hydroxyapatite-coated and the uncoated implants. The administration of warfarin significantly impaired both the attachment strength and the ingrowth of bone at twelve weeks. At twelve weeks, the attachment strength and bone ingrowth of the hydroxyapatite-coated implants in the animals that had received warfarin were statistically equal to those of the uncoated implants in the control animals.

Analysis of Variance↗
PubMedDate not supplied

Immobilization of nickel and other metals in contaminated sediments by hydroxyapatite addition.

Batch experiments were conducted to evaluate the ability of hydroxyapatte (HA) to reduce the solubility of metals, including the primary contaminants of concern, Ni and U, from contaminated sediments located on the Department of Energy's Savannah River Site, near Aiken, SC. Hydroxyapatitie was added to the sediments at application rates of 0, 5, 15.8, and 50 g kg-1. After equilibrating in either 0.02 M KCl or 0.01 M CaCl2, the samples were centrifuged and the supernatants filtered prior to metal, dissolved organic C, and PO4 analyses. The treated soils were then air-dried and changes in solid-phase metal distribution were evaluated using sequential extractions and electron-based microanalysis techniques. Hydroxyapatite was effective at reducing the solubility of U and, to a lesser degree, Ni. Hydroxyapatite was also effective in reducing the solubility of Al, Ba, Cd, Co, Mn, and Pb. Sequential extractions indicate that HA transfers such metals from more chemically labile forms, such as the water-soluble and exchangeable fractions, by altering solid-phase speciation in favor of secondary phosphate precipitates. Hydroxyapatite effectiveness was somewhat reduced in the presence of soluble organics that likely increased contaminant metal solubility through complexation. Arsenic and Cr solubility increased with HA addition, suggesting that the increase in pH and competition from PO4 reduced sorption of oxyanion contaminants. Energy dispersive x-ray (EDXA) analysis conducted in the transmission electron microscope (TEM) confirmed that HA amendment sequesters U, Ni, Pb, and possibly other contaminant metals in association with secondary Al-phosphates.

Biocompatible Materials↗
PubMed2006

Collagen-hydroxyapatite composites for hard tissue repair.

Bone is the most implanted tissue after blood. The major solid components of human bone are collagen (a natural polymer, also found in skin and tendons) and a substituted hydroxyapatite (a natural ceramic, also found in teeth). Although these two components when used separately provide a relatively successful mean of augmenting bone growth, the composite of the two natural materials exceeds this success. This paper provides a review of the most common routes to the fabrication of collagen (Col) and hydroxyapatite (HA) composites for bone analogues. The regeneration of diseased or fractured bones is the challenge faced by current technologies in tissue engineering. Hydroxyapatite and collagen composites (Col-HA) have the potential in mimicking and replacing skeletal bones. Both in vivo and in vitro studies show the importance of collagen type, mineralisation conditions, porosity, manufacturing conditions and crosslinking. The results outlined on mechanical properties, cell culturing and de-novo bone growth of these devices relate to the efficiency of these to be used as future bone implants. Solid free form fabrication where a mould can be built up layer by layer, providing shape and internal vascularisation may provide an improved method of creating composite structures.

Animals↗
PubMed2003

Use of a hydroxyapatite orbital implant in a cosmetic corneoscleral prosthesis after enucleation in a horse.

A hydroxyapatite orbital implant was used after enucleation of an eye from a 5-year-old performance horse. A custom-made corneoscleral prosthesis was made and fitted over the hydroxyapatite implant. The implant and surgery were well tolerated. Placement of a cosmetic prosthesis is desired after enucleation of equine eyes to allow horses to return to competition. Synthetic spheres consisting of methylmethacrylate or silicone have been used, although reported complications have included extrusion, infection, and poor cosmetic results. Hydroxyapatite orbital implants made from marine coral allow vascular and fibrous tissue growth from the host orbit into the implant, which decreases the possibility of implant extrusion or infection and allows enhanced healing of defects in the overlying conjunctiva. Extraocular muscle fixation onto the implant permits motility and assists in the prevention of implant extrusion.

Animals↗
PubMed1999

Destructive tophaceous calcium hydroxyapatite tumor of the infratemporal fossa. Case report and review of the literature.

Tophaceous pseudogout is one of the rarest forms of crystal deposition disease, typically presenting as a destructive and invasive mass involving the temporomandibular joint or the infratemporal fossa region in the absence of any other articular manifestations. Previous cases have been assumed to be caused by calcium pyrophosphate dihydrate (CPPD) crystal deposition, based on finding weakly birefringent crystals in the involved tissues. The authors present the unique case of a 65-year-old woman with a destructive and invasive facial mass extending to the middle cranial fossa with microscopic and clinical features consistent with tophaceous pseudogout. High-resolution x-ray crystallographic powder diffraction and Fourier transformed infrared spectroscopy subsequently revealed that the crystals were composed of calcium hydroxyapatite without CPPD. The patient was later found to have primary hyperparathyroidism and mild hypercalcemia. This case demonstrates that tissue deposits of calcium hydroxyapatite can cause a destructive and invasive mass containing weakly birefringent crystals and raises the question of whether previous cases attributed to tophaceous pseudogout resulting from CPPD actually were composed of birefringent calcium hydroxyapatite.

Aged↗
PubMed2002

A novel type of milk calcium has higher calcium bioavailability compared with the hydroxyapatite type of milk calcium.

We prepared a novel type of milk calcium from milk whey, and evaluated its calcium bioavailability as compared with conventional industrial milk calcium obtained from milk whey, which has been reported to be an excellent calcium source. An X-ray diffraction analysis showed that the chemical form of conventional industrial milk calcium from milk whey through the neutralization and precipitation method (NP-MCa) is hydroxyapatite type, and that of a novel type of milk calcium obtained using the ultrafiltration method (UF-MCa) is different from hydroxyapatite. Growing rats were fed either NP-MCa or UF-MCa as the source of calcium for 33 d. The calcium absorption rate in the UF-MCa diet group was significantly higher than that in the NP-MCa diet group. The calcium content of the femur in the UF-MCa diet group was significantly higher than that in the NP-MCa diet group. The breaking force of the excised femur in the UF-MCa diet group was also significantly higher than that in the NP-MCa diet group. The serum calcium level, alkaline phosphatase activity and calcitonin level were not significantly different between the experimental groups, but the PTH level of the serum in the UF-MCa diet group was significantly lower than that in the NP-MCa diet group. These results indicate that the calcium bioavailability of the novel type of milk calcium (UF-MCa) is higher than that of the hydroxyapatite type of milk calcium (NP-MCa).

Alkaline Phosphatase↗
PubMed2001

A case of anaerobic abscessed hydroxyapatite orbital implants.

The purpose of this report is to document an unusual case of implant infection in a patient who had undergone enucleation and hydroxyapatite orbital implant surgery. A 32-year-old woman presented with chronic orbital discomfort and discharge following a history of hydroxyapatite orbital implant surgery at another hospital 4 years previous. She exhibited profuse discharge with a yellow, creamy color and marked conjunctival chemosis. Granulation tissue was noted on the central conjunctival surface. Following the removal of the conjunctival granulation tissue, a central 3x5 mm conjunctival dehiscence was present with exposure of the hydroxyapatite implant. A culture of purulent drainage emanating from the exposed implant showed a growth of Clostridium acetobutylicum. Removal of the orbital implant was done. The implant was noted to be filled with pus. This case suggests that anaerobic infection may be suspected when the granulation tissue is observed and a discharge with a foul odor is found.

Abscess↗