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PubMed1993

Human pulpal response to hydroxyapatite and a calcium hydroxide material as direct capping agents.

Forty maxillary and four mandibular first premolars that were to be extracted for orthodontic reasons were used in this study to evaluate human pulpal response to hydroxyapatite and Dycal as direct capping materials. After the postoperative periods of 2 days, 30 days and, 60 days, teeth were extracted and prepared for the histologic examination. The results of this study showed that hydroxyapatite does not induce hard tissue bridging at the exposure site in human dental pulp. No hard tissue bridging at the exposure site was observed in any of the teeth capped with hydroxyapatite. Moderate infiltration of the inflammatory cells was seen generally in the teeth capped with hydroxyapatite. However, this study has verified that exposed human dental pulp will heal under Dycal application with hard tissue bridging and with none or minimal inflammatory response.

Bicuspid↗
PubMed2004

Influence of fluorapatite on the properties of thermally sprayed hydroxyapatite coatings.

Thermally sprayed hydroxyapatite has been the widely used on orthopaedic prosthesis to induce bone growth and facilitate bone attachment. However, hydroxyapatite has a greater affinity for the formation of an amorphous phase in the thermally sprayed coating that results in the release of excessive amount of mineral ions from the implant coating leading to a saturated environment in the immediate vicinity of the bone cells. Fluorapatite however is highly crystalline and offers the potential for lower mineral ion release by dissolution. Thus study investigates the influence of fluorapatite in a thermally sprayed hydroxyapatite coating. Mechanical blends of fluorapatite with hydroxyapatite were thermally sprayed, characterized with X-ray diffraction, SEM, FTIR, optical microscopy for microstructure, roughness and tested for solubility. Cathodoluminescence microscopy was used to examine the resorbed coating surface. Fluorapatite coatings crystallized more readily and produce a greater coating roughness. The roughness in fluorapatite coatings arises from less flattened droplets that show a tendency for finger formation. Addition of fluorapatite increases coating crystallinity. The use of slower resorbing fluorapatite produces less particle release which favors improved osseointegration. Less change in the surface topography during resorption can be used to an advantage to control the coating surface presented to cells and extra cellular matrix proteins.

Apatites↗
PubMed2005

Characterization of hydroxyapatite films obtained by pulsed-laser deposition on Ti and Ti-6AL-4v substrates.

OBJECTIVES: Pulsed-laser deposition (PLD) is a development process to obtain hydroxyapatite (HA) thin film. It is an alternative to hydroxyapatite deposition techniques usually employed to cover orthopaedic or dental titanium implant surfaces. The aim of this study is to find out the characteristic ratio for Ca/P (1.66) deposit on titanium implant with the PLD process. METHODS: In a preliminary study, the coating parameters of pure and highly crystalline HA on Ti or Ti-6Al-4V substrates were verified by analysing the deposit by Rutherford backscattering spectroscopy (RBS). Ablation parameters to reach a stoichiometric hydroxyapatite composition (ideal Ca/P atomic ratio) and to control the growth of crystalline phases were: 575 degrees C for the substrate temperature, 0.4 mbar H2O vapour pressure in the ablation chamber, the target substrate distance was 40 mm and the deposition time was 120 min. In a second part, the film properties were analysed by means of XRD, SEM, AFM. The coating adhesion of the HA to the substrate was determined with a micro scratch tester. RESULTS: The analysed HA thin films showed a perfect crystallized and textured deposit. Sample observation and surface quality analysis demonstrated a surface roughness and adhesion of the films to the substrates compatible with biological applications. SIGNIFICANCE: These results suggest that pulsed-laser deposition is a suitable technique to obtain crystalline and adherent hydroxyapatite films on Ti or Ti-6Al-4V substrates. The quality of the HA deposit with the PLD process could be an interesting option for coating dental implant.

Alloys↗
PubMed2005

A novel non line-of-sight method for coating hydroxyapatite onto the surfaces of support materials by biomineralization.

A novel method is described for the non line-of-sight coating of hydroxyapatite onto polyurethane reticulated foam and titanium discs. This utilises a biofilm of Serratia sp. NCIMB 40259 which, when challenged with a solution containing calcium chloride and phosphatase substrate, manufactures biofilm-bound material identified as hydroxyapatite by X-ray powder diffraction analysis. Non-invasive magnetic resonance imaging was used to visualize the biofilm coating throughout the foam labyrinth and to measure the thickness of the film within reticulated foam cubes in situ. The film developed within the cube matrices was similar to that measured on the surface of a glass slide. Using LaPO(4) deposition as a model system the metallised biofilm was visualised in two-dimensional slices throughout three-dimensional images acquired by magnetic resonance imaging. A similar encrustation of hydroxyapatite on the surface of biofilm grown on titanium discs was confirmed by scanning electron microscopy. Potential applications for bio-hydroxyapatite as possible bone implant precursors are discussed.

Biofilms↗
PubMed2005

Preparation and characterization of carbonated barium-calcium hydroxyapatite solid solutions.

Particles of carbonated barium-calcium hydroxyapatite solid solutions (BaCaHap) with different Ba/(Ba+Ca) (X(Ba)) atomic ratios were prepared by a wet method at 100 degrees C and characterized by various means. The crystal phases and structures of the products strongly depended on the composition of the starting solution, that is, the Ba/(Ba+Ca) atomic ratio ([X(Ba)]) and H3PO4 concentration ([H3PO4]) in the solution. BaCaHap with X(Ba)0.43 could be prepared at [X(Ba)]0.7 by changing [H3PO4], but could never be obtained at [X(Ba)]=0.8-0.95 regardless of [H3PO4]. The carbonated calcium hydroxyapatite particles prepared at [X(Ba)]=0 were fine and short rod-shaped particles (ca. 14x84 nm). With increasing [X(Ba)] from 0 to 0.8, the particles obtained became large spherical agglomerates. The carbonated barium hydroxyapatite particles formed at [X(Ba)]=1 were long rod-shaped agglomerates (ca. 0.2x2 microm) of fine primary particles. The amount of CO2 adsorbed irreversibly on a series of BaCaHaps showed a minimum at (Ba+Ca)/(P+C) atomic ratio of around 1.56, which agreed well with the minimum cation/P ratio obtained for the other hydroxyapatites, as already reported.

Adsorption↗
PubMed2004

Retention of fluoride ions from aqueous solution using porous hydroxyapatite. Structure and conduction properties.

Synthetic porous calcium hydroxyapatite (noted p-HAp) treated with different fluoride concentrations at room temperature in the presence of carbonate, sodium chloride and phosphate-rich media was investigated. The fluoridation rate of the porous calcium hydroxyapatite was 89% using 1 mol/L [F(-)] solution compared with 30% for crystalline hydroxyapatite (c-HAp). The high specific surface area of p-HAp (235 m(2)g(-1)) compared with c-HAp sample (47 m(2)g(-1)) has an important effect on the removal of fluoride ions from aqueous solution, when p-HAp was treated with high fluoride concentration to produce calcium fluorohydroxyapatite materials. Fluoride adsorption on porous hydroxyapatites (p-HAp) modified their structural and conduction properties.

Durapatite↗
PubMed2005

Analysis of cell-seeded 3-dimensional bone constructs manufactured in vitro with hydroxyapatite granules obtained from red algae.

PURPOSE: Bone tissue engineering is a promising approach for the treatment of defective or lost bone in the maxillofacial region. Biocompatible and biodegradable scaffolds seeded with living cells are used to create functional tissue for load-bearing bone reconstruction. The aim of this study was to manufacture cell-seeded 3-dimensional bone constructs based on hydroxyapatite ceramic granule calcified from red algae and mesenchymal cambial-layer precursor cells. The ability of these cells to grow on hydroxyapatite ceramic was quantitatively investigated to evaluate 3-dimensional bone constructs for their potential use in bone tissue engineering. MATERIALS AND METHODS: Mesenchymal cambial-layer precursor cells were isolated from mandibular periosteum biopsy samples of 3 patients. To manufacture 72 bone constructs, these cells and hydroxyapatite ceramic granules (C GRAFT/Algipore; Clinician's Preference LLC, Golden, CO) were cultivated under osteogenic differentiation conditions in a rotating wall vessel system. After 6 and 21 days, histologic examination and scanning electron microscopy were performed. The absolute DNA content, protein synthesis, and alkaline phosphatase activity were also quantified. The osteoblastic phenotype of the constructs was confirmed by the expression of bone-specific genes (osteocalcin, osteonectin, osteopontin, and core binding factor alpha1) using semiquantitative reverse transcription-polymerase chain reaction and Western blot analysis. RESULTS: Cells within the constructs showed good viability, which was evidenced by an increase in DNA content over the culture period. The decrease in alkaline phosphatase-specific activity could be an indicator of the maturation of cells and the induction of mineralization. The osteoblastic phenotype of the constructs was demonstrated on protein and at the RNA level over the entire culture period. CONCLUSION: We observed a positive effect of hydroxyapatite ceramic granules on mesenchymal cambial-layer precursor cell behavior in cell-seeded 3-dimensional bone constructs, indicating the potential applicability of C GRAFT/Algipore composites in bone tissue engineering.

Blotting, Western↗
PubMed1995

Gadolinium-enhanced magnetic resonance imaging assessment of hydroxyapatite orbital implants.

PURPOSE: Successful prosthesis attachment depends on complete vascularization of porous coralline hydroxyapatite when it is used as an orbital implant. We retrospectively assessed the utility of gadolinium-enhanced magnetic resonance imaging to evaluate and characterize the temporal progression of this fibrovascular process, which has been histologically documented elsewhere. METHODS: Serial T1-weighted gadolinium-enhanced orbital magnetic resonance examinations were performed in five patients receiving hydroxyapatite orbital implants. Retrospective evaluation of the enhancement patterns was performed. Magnetic resonance imaging enhancement patterns guided timing of final drilling for prosthesis fixation. RESULTS: Serial gadolinium-enhanced T1-weighted sequences consistently demonstrated centrally advancing, peripheral enhancement centered on the drilled access channels. Progression over time varied, with the following two patterns demonstrated: (1) rapid peripheral enhancement, which led to diffuse enhancement (three patients); and (2) enhancement limited to the periphery, which failed to advance centrally. CONCLUSIONS: The temporal enhancement seen on magnetic resonance imaging is identical to the histologically proven fibrovascular ingrowth pattern and most likely reflects this process. Magnetic resonance imaging can identify progression of fibrovascular ingrowth into the hydroxyapatite orbital implants and guide surgical planning. It may also identify implants that fail to vascularize, thereby preventing the morbidity encountered by drilling into an avascular hydroxyapatite implant.

Adolescent↗
PubMed2002

Hydroxyapatite and calcium phosphate coatings on aluminium oxide orbital implants.

BACKGROUND: Hydroxyapatite and calcium phosphate have been used as bone graft substitutes as they facilitate and promote tissue ingrowth. We carried out a study to examine uncoated and coated aluminium oxide (alumina) spherical orbital implants and assess whether the coatings influence fibrovascular ingrowth. METHODS: The aluminium oxide spheres (three coated with hydroxyapatite, three coated with calcium metaphosphate and three uncoated) were manufactured at the School of Materials Engineering, Yeungnam University, Kyongsan, Kyongbuk, Korea. The implants were examined macroscopically and with scanning electron microscopy and were analysed chemically by means of x-ray powder diffraction and x-ray fluorescence spectrophotometry. Implantation of three hydroxyapatite-coated, three calcium metaphosphate-coated and three uncoated aluminium oxide spheres was done in nine adult male New Zealand albino rabbits. Implant vascularization was evaluated at 4, 8 and 12 weeks by means of histopathological sectioning. RESULTS: All three types of implant had multiple interconnected pores. The coatings increased the size of the trabeculae from 150 microm to 300 microm. As a result, the pores appeared slightly smaller but still ranged in size from 300 microm to 750 microm, compared to 400 microm to 800 microm in the uncoated implants. The coatings also increased the weight of the implants slightly. The implants were all strong mechanically. They were made up primarily of aluminium oxide. The coated implants contained significant amounts of calcium oxide (a contaminant). There was no clinical difference in the socket response between the three groups. Histopathologically, fibrovascularization occurred uniformly throughout each implant at 4, 8 and 12 weeks after implantation. INTERPRETATION: The hydroxyapatite and calcium metaphosphate coatings did not appear to facilitate or inhibit fibrovascular ingrowth at 4, 8 and 12 weeks. Longer-term studies are need to determine whether the coatings play a role in long-term acceptance and retention of the implants.

Aluminum Oxide↗
PubMed1998

Comparison of hydroxyapatite granules to autogenous bone graft in fusion cages in a goat model.

BACKGROUND: With the increased use of fusion cages to achieve lumbar intervertebral fusion, the question arises as to the potential for bone ingrowth from the host bone through the entire cage. Is it even necessary to have an autogenous graft to achieve total bone incorporation? METHODS: Nine adult male goats had fusion cages implanted into three vertebral bodies. The design was Surgical Dynamics/Ray Fusion Cage, measuring 21 mm x 14 mm. In each animal, one fusion cage was filled with autogenous graft, one with hydroxyapatite, porous granules, and the other with nonporous granules. Amount of new bone formation was determined by backscatter electron microscopy at 3 months post implantation in all animals. RESULTS: The histologic section shows that there was total incorporation in all specimens at 3 months. There was slightly more new bone (43%) with the nonporous granules compared with the porous granules (35%). The amount of residual void space was about the same in all specimens, indicating that the amount of new bone formation was similar and not statistically different in cages filled with hydroxyapatite granules versus granules of autogenous bone. CONCLUSION: This study confirms that total incorporation by ingrowth of new bone can be expected in fusion cages. The amount of ingrowth is about the same for autogenous graft versus hydroxyapatite granules. Apparently, it is not necessary to use bone graft to achieve successful bone incorporation if an acceptable biocompatable lattice, such as hydroxyapatite granules, is used.

Animals↗
PubMed1998

Hydroxyapatite fiber reinforced poly(alpha-hydroxy ester) foams for bone regeneration.

A process has been developed to manufacture biodegradable composite foams of poly(DL-lactic-co-glycolic acid) (PLGA) and hydroxyapatite short fibers for use in bone regeneration. The processing technique allows the manufacture of three-dimensional foam scaffolds and involves the formation of a composite material consisting of a porogen material (either gelatin microspheres or salt particles) and hydroxyapatite short fibers embedded in a PLGA matrix. After the porogen is leached out, an open-cell composite foam remains which has a pore size and morphology defined by the porogen. By changing the weight fraction of the leachable component it was possible to produce composite foams with controlled porosities ranging from 0.47 +/- 0.02 to 0.85 +/- 0.01 (n = 3). Up to a polymer:fiber ratio of 7:6, short hydroxyapatite fibers served to reinforce low-porosity PLGA foams manufactured using gelatin microspheres as a porogen. Foams with a compressive yield strength up to 2.82 +/- 0.63 MPa (n = 3) and a porosity of 0.47 +/- 0.02 (n = 3) were manufactured using a polymer:fiber weight ratio of 7:6. In contrast, high-porosity composite foams (up to 0.81 +/- 0.02, n = 3) suitable for cell seeding were not reinforced by the introduction of increasing quantities of hydroxyapatite short fibers. We were therefore able to manufacture high-porosity foams which may be seeded with cells but which have minimal compressive yield strength, or low porosity foams with enhanced osteoconductivity and compressive yield strength.

Biocompatible Materials↗
PubMed1998

Repair of exposed hydroxyapatite orbital implant by a tarsoconjunctival pedicle flap.

OBJECTIVE: This study aimed to determine a surgical method of management of exposed hydroxyapatite orbital implants. DESIGN: Noncomparative small case series. PARTICIPANTS: Four patients with exposures of hydroxyapatite orbital implants are described. INTERVENTION: A superiorly based tarsoconjunctival pedicle flap is fashioned from the upper eyelid; this flap is inverted and placed over the scleral-covered, exposed hydroxyapatite orbital implant. The flap is divided as a second-stage procedure 4 weeks later. MAIN OUTCOME MEASURE: Mucosal coverage of the previously exposed orbital implant was measured. RESULTS: Four cases are presented with excellent postoperative results at 3 to 18 months' follow-up. CONCLUSION: A suitably fashioned pedicle flap from the upper eyelid is an effective method of managing exposed hydroxyapatite orbital implants.

Adult↗
PubMed2002

The influence of amino acids on the biomineralization of hydroxyapatite in gelatin.

The effects of pH on the calcium phosphate phase, of Tris and of amino acids, such as aspartic acid, glutamic acid, and serine on hydroxyapatite formation and morphology, were studied in double diffusion experiments. In this system, hydroxyapatite was only formed when the pH was around 7.4 or higher for the duration of the reaction. A decrease in pH resulted in the transformation of hydroxyapatite to octacalcium phosphate. Amino acids and Tris or the buffering capacity of Tris have an effect on the morphology of the synthetic hydroxyapatite. The presence of the additive results in spheres consisting of needles, blades or plates depending on the reaction system.

Amino Acids↗
PubMed1997

Efficient downstream processing of maltodextrin phosphorylase from Escherichia coli and stabilization of the enzyme by immobilization onto hydroxyapatite.

Downstream processing by biospecific chromatography of maltodextrin phosphorylase from Escherichia coli, overexpressed in E. coli, was substantially improved by a novel approach using ceramic hydroxyapatite. Wild-type and a less active mutant enzyme were purified from crude bacterial cell extracts in one efficient separation step that yielded phosphorylase in purity > 95% in at least 90% recoveries. At pH 6.9 and 25 degrees C, wild-type and mutant phosphorylases eluted from the hydroxyapatite column at a phosphate concentration of 0.4 M whereas calcium ions failed to displace the enzymes. The dynamic capacity for phosphorylase binding in the presence of bulk proteins was approximately 3 mg enzyme ml-1 matrix. The interaction of E. coli phosphorylase with hydroxyapatite seems to be mediated by surface amino groups, so that the bound enzyme retained almost full catalytic activity. Compared to the soluble enzyme, immobilization onto hydroxyapatite resulted in a more than 30-fold stabilization of wild-type phosphorylase against thermal and proteolytic inactivation and thus could improve the operational stability of phosphorylase during conversion of polysaccharide to glucose 1-phosphate.

Chromatography↗
PubMed1999

Generation of a new protein purification matrix by loading ceramic hydroxyapatite with metal ions--demonstration with poly-histidine tagged green fluorescent protein.

The gene encoding the green fluorescent protein (GFP) from the jellyfish Aequorea victoria, was inserted under transcriptional control of the polyhedrin promoter of the Autographa californica nuclear polyhedrosis virus and expressed in the Spodoptera frugiperda insect cell line Sf9 during viral infection. The baculovirus transfervector pBlueBacHisB was used for constructing the recombinant baculovirus, so that the green fluorescent protein could be tagged with a poly-histidine tail. This fusion protein was utilized as a marker for evaluating the properties of metal ion loaded ceramic hydroxyapatite as a matrix in protein purification. Ceramic hydroxyapatite loaded with Zn(II) was the best choice for purifying this poly-histidine tagged GFP, followed by Fe(III) of the metal ions tested. Ni(II) that is superior especially in many poly-histidine purification systems did not, when loaded to hydroxyapatite, have binding properties comparable to Zn(II) or Fe(III). Elution of poly-histidine tagged GFP was best performed with phosphate buffers or EDTA that could compete with the phosphate molecules in hydroxyapatite or complexly bind the metal ions, respectively.

Animals↗
PubMed1997

Repair of craniofacial defects with hydroxyapatite cement.

PURPOSE: The objective of this study was to evaluate the course of healing of craniofacial bone defects when filled with hydroxyapatite cement and to determine whether adding various percentages by weight of demineralized bone powder to the cement will result in enhanced bone formation. MATERIALS AND METHODS: The model for the study was the canine calvarium. The implants were placed into cranial defects and harvested at 3 or 6 months for qualitative evaluation by light microscopy, microradiography, and quantitative histomorphometry. RESULTS: The implantation of hydroxyapatite cement resulted in characteristic replacement of the material with new bone ingrowth. The addition of demineralized bone powder to the hydroxyapatite cement appeared to improve the handling characteristics of the cement; however, improvement in the replacement of the material by bone was not observed. The implantation of only allogeneic demineralized bone showed limited new bone formation within the defect site. CONCLUSIONS: Hydroxyapatite cement formed an effective osseoconductive scaffold for bone replacement. The addition of demineralized bone powder to the cement to serve as a carrier of osseoinductive factors did not result in additional bone being formed.

Animals↗
PubMed1999

Feasibility of using natural fishbone apatite as a substitute for hydroxyapatite in remediating aqueous heavy metals.

Fishbone, a natural, apatite rich substance, was examined for suitability as a substitute for hydroxyapatite in the sequestering of aqueous divalent heavy metal ions. The fishbone exhibited lower metal removal capacity than pure hydroxyapatite, due primarily to its purity ( approximately 70% apatite equivalent). In other ways the fishbone behaves in a similar manner as pure hydroxyapatite in the sequestration process. It was observed that it can remove all Pb(2+), Cu(2+), Cd(2+) and Ni(2+) to below detectable levels as measured by inductively coupled plasma atomic absorption, and the rate of reaction with either Zn(2+), Ni(2+), or Pb(2+) was also found to be similar to hydroxyapatite. Also, a two level, three variable full factorial design was performed for the Pb/apatite reaction and both apatites performed similarly. The main difference, besides capacity, was on exposure to high (2.4 mM) Pb concentrations. The fishbone removed less of the Pb(2+) than capacity correction predicted.

Animals↗
PubMed2002

Development of hemoglobin aquasomes from spherical hydroxyapatite cores precipitated in the presence of half-generation poly(amidoamine) dendrimer.

Spherical hydroxyapatite cores were prepared by using carboxylic acid terminated half-generation poly(amidoamine) (PAMAM) dendrimer as templates or crystal modifiers. The hydroxyapatite cores were characterized by infrared spectroscopy (IR), X-ray diffraction (XRD) and transmission electron microscopy (TEM). The spherical core formation depended on phosphate saturation, pH of the simulated body fluid (SBF) and rate of crystal growth. Hydroxyapatite so formed was amorphous and a mixture of various calcium phosphates. Ca/P ratio determination which showed phosphate rich apatite formation. Hydroxyapatite ores were coated with a sugar layer followed by hemoglobin to obtain aquasomes. Aquasomes were characterized for size, hemoglobin loading, oxygen-binding characteristics and storage stability. The nanometric sized aquasome formulation could load approximately 13.7 mg hemoglobin per g of core and retained oxygen-affinity and cooperativity and stability for at least 30 days. Formulation efficacy was tested in albino rats and indicated its potential utility as blood-substitute.

Animals↗