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PubMed2001

Preparation of a bone-like apatite foam cement.

The preparation of a porous bone-like calcium deficient apatite implant material was investigated. A novel cement system composed of an equimolar mixture of Ca4(PO4)2O, Ca(HPO4)2 . H2O, and CaCO3 was used. At a liquid/powder ratio of 0.83 ml/g low density open framework foam cements were formed due to the rapid evolution of CO2. The initial product of the reactants was CaHPO4 . H2O which then reacted with Ca4(PO4)O, forming a calcium deficient carbonated apatite, upon soaking of the cement blocks in SBF. Foam-like cements were composed of a plate-like apatite due to epitaxial overgrowth and conversion of the brushite plate precursor. Cylinders of the foam cement were reinforced with an outer layer of a solid apatite cement to form a material suitable for application as a bone-section implant.

Journal Article↗

PubMed2002

A microstructural examination of apatite induced by Bioglass in vitro.

Bioglass, a clinically used bone graft material, has been tested in vitro in a simulated body fluid (SBF) up to four weeks. Apatite crystals were not only found to form on its surface but also in the reaction solutions. The apatite crystals have been examined by high-resolution transmission electron microscopy (TEM). The crystals formed in the solutions appear identical in morphology and structure with those formed on the Bioglass surface. It may be that the soluble Si in the solution serves as the nucleating site for the apatite crystal or that apatite nuclei are released from the Bioglass surface to the solution resulting in crystal growth.

Journal Article↗

PubMed1997

Mechanical properties of carbonated apatite bone mineral substitute: strength, fracture and fatigue behaviour.

The synthesis and properties of carbonated apatite materials have received considerable attention due to their importance for medical and dental applications. Such apatites closely resemble the mineral phase of bone, exhibiting superior osteoconductive and osteogenic properties. When formed at physiological temperature they present significant potential for bone repair and fracture fixation. The present study investigates the mechanical properties of a carbonated apatite cancellous bone cement. Flexural strength was measured in three and four point bending, and the fracture toughness and fatigue crack-growth behaviour was measured using chevron and disc-shaped compact tension specimens. The average flexural strength was found to be approximately 0.468 MPa, and the fracture toughness was approximately 0.14 MPa radical m. Fatigue crack-growth rates exhibited a power law dependence on the applied stress intensity range with a crack growth exponent m=17. The fatigue threshold value was found to be approximately 0.085 MPa radical m. The mechanical properties exhibited by the carbonated apatite were found to be similar to those of other brittle cellular foams. Toughness values and fatigue crack-growth thresholds were compared to other brittle foams, bone and ceramic materials. Implications for structural integrity and longer term reliability are discussed.

Journal Article↗

PubMed2003

Crystallization modifies osteoconductivity in an apatite-mullite glass-ceramic.

The response to implantation of novel apatite glass-ceramics was evaluated using a weight bearing in vivo bone implant model. Five novel glasses with varying calcium to phosphate ratios were cast as short rods and heat-treated to crystallize principally apatite. One glass ceramic had an apatite stoichiometry (Ca : P=1.67); three were phosphate-rich and one calcium-rich. One of the phosphate-rich glasses was also tested in its glassy state to determine the effect of crystallization on the biological response. Rods were implanted into the midshaft of rat femurs and left for 28 days. The femurs were then harvested and processed for scanning electron microscopy, energy dispersive X-ray microanalysis and conventional histology as ground and polished sections. Four of the materials exhibited evidence of osseointegration and osteoconduction. However, there was a marked inflammatory response to one of the phosphate-rich glass-ceramics, and to the non-crystallized glass. Crystallization of the latter significantly improved the bone tissue response. The glass-ceramic with an apatite stoichiometry elicited the most favorable response and merited further study as an osteoconductive bone substitute in maxillofacial and orthopedic surgery.

Journal Article↗

PubMed2005

Structural studies of apatite-type oxide ion conductors doped with cobalt.

A series of Co doped lanthanum silicate apatite-type phases, La9.83Si4.5Co1.5O26, La9.66Si5CoO26, La10Si5CoO26.5 and La8BaCoSi6O26, have been synthesised, and neutron diffraction, EXAFS and XANES used to investigate their structures in detail. All compositions were shown to possess the hexagonal apatite structure, and the results confirmed that cobalt can be doped onto both the La and Si sites within the structure depending on the starting composition. The Co doping is shown to cause considerable local distortions within the apatite structure. In the case of Si site doping two compositions showed anisotropic peak broadening, which has been attributed to incommensurate ordering of oxygen within the apatite channels.

Journal Article↗

PubMed1999

XRD, SEM-EDS, and FTIR studies of in vitro growth of an apatite-like layer on sol-gel glasses.

A glass with a composition (in mole %) of: SiO2 (70), CaO (26), and P2O5 (4) was obtained using a sol-gel method. The in vitro bioactivity of the glass was assessed by determining the changes in surface morphology and composition after soaking in simulated body fluid (SBF) for periods of up to 14 days at 37 degrees C. X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy, and FTIR analyses of the glass surface after different soaking periods in SBF demonstrated the growth of an apatite-like layer on the glass surface. In the first stage, an amorphous calcium phosphate layer was formed; after 7 days this surface consisted of spheres, with diameters ranging between 2 and 15 microm, composed of needle-like apatite crystallites (250 x 100 nm) with a crystallinity similar to that of a biological apatite.

Apatites↗

PubMed1999

In vitro analysis of the stimulation of bone formation by highly bioactive apatite- and wollastonite-containing glass-ceramic: released calcium ions promote osteogenic differentiation in osteoblastic ROS17/2.8 cells.

We analyzed the mechanisms of the efficient bone formation on the osteoconductive surface of apatite- and wollastonite-containing glass-ceramic (AW) by using an in vitro system. AW releases Ca ions and bonds to bone via a submicron-thick hydroxycarbonate apatite (HCA) layer. AW disks were conditioned with simulated body fluid (SBF) to grow HCA layers, and the amount of released Ca ion was regulated by modulating the conditioning time from 24 to 240 h. Surface-transformed AW disks increased alkaline phosphatase (AP) activity in osteoblastic ROS17/2.8 cells by 1.5- to threefold over unconditioned disks. AW disks conditioned for 24 h [AW(24)], which had a homogeneous, submicron-thick apatite layer and increased extracellular ionized Ca concentration ([Ca(2+)](e)) in the culture medium to the greatest extent, enhanced the AP activity the most. High [Ca(2+)](e) promoted osteogenic differentiation in ROS17/2.8 cells: It increased AP activity in a dose-dependent manner by up to 1.6-fold, and up-regulated the expression of AP, osteocalcin (OC), and transforming growth factor-beta1 mRNAs in dose- and time-dependent manners. AW(24) enhanced AP activity in ROS17/2.8 cells as much as AW disks conditioned with SBF containing serum to exhibit in vivo surface-structure changes. AW(24) increased AP activity in ROS17/2.8 cells by 1.6-fold and enhanced the expression of AP and OC mRNAs significantly, compared with sintered hydroxyapatite (HA). After implantation of AW and HA in the distal metaphyses of rabbit femurs, thin, newly formed bone lined with cuboidal, osteoblast-like cells was characteristically observed adjacent to the AW surface within 8 days. These results provide evidence for the hypothesis that AW stimulates bone formation on its surface by increasing [Ca(2+)](e) to promote the HCA layer formation and the differentiation of osteogenic cells.

Animals↗

PubMed1999

Effect of silane treatment and different resin compositions on biological properties of bioactive bone cement containing apatite-wollastonite glass ceramic powder.

In methylmethacrylate (MMA)-based cements containing bioactive particles, polymethylmetacrylate (PMMA) is known to suppress the bioactivity of Bioglass(R) and apatite-wollastonite glass ceramic (AW-GC). Little is known about the effect of different silane treatment methods on the bioactivity of AW-GC. MMA-based cement plates containing dry silanated AW-GC particles and PMMA particles of different molecular weights (12,000-900,000) were immersed in simulated body fluid (SBF). Cements containing PMMA particles of high molecular weight formed an apatite layer on the surface after 24 h. Using PMMA particles with a molecular weight of 60,000 and AW-GC particles silanated with different methods (dry method vs. slurry method), cement plates were made and immersed in SBF. Only cement plates containing dry silanated AW-GC particles showed apatite formation in SBF after 3 days. In vivo implantation in rat tibias of MMA-based cement containing dry silanated AW-GC particles and PMMA particles (molecular weight 900,000) demonstrated an affinity index of 32.1 +/- 15.8% after 8 weeks of implantation compared to 89.4 +/- 10.7% achieved by bisphenol-A-glycidyl methacrylate based cement containing the same bioactive powder. By using a dry method of silane treatment and high molecular weight PMMA particles, the bioactivity of cement based on MMA monomer was achieved; but further effort is needed to improve the mechanical properties of the composite.

Animals↗

PubMed2000

In vitro bone formation on a bone-like apatite layer prepared by a biomimetic process on a bioactive glass-ceramic.

In this study we have investigated the behavior of fetal rat osteoblasts, cultured up to 23 days, on a bioactive apatite-wollastonite (AW) glass-ceramic and on the same material on which a carbonated apatite layer had been formed by a biomimetic process (AWa). At the last day of culture, the specific activity of alkaline phosphatase activity, as determined biochemically, was about 30% greater on AWa compared with AW disks. After the cell layers had been scraped off, scanning electron microscopic (SEM) observations of the materials' surfaces revealed that mineralized bone nodules remained attached to both surfaces but in larger amounts on AWa. X-ray microanalysis indicated the presence of calcium (Ca) and phosphorus (P) in the bone tissue throughout the AWa surface and Ca, P, and silicon (Si) on the AW surface. The AW/ and AWa/bone interfaces also were analyzed after fracturing of the disks. The interfacial analysis showed firm bone bonding to the AW and AWa surfaces, confirmed by the X-ray microanalytic mappings. These results indicate the importance of surface composition in supporting differentiation of osteogenic cells and the subsequent apposition of bone matrix, which allows a strong bond of the bioactive materials to the bone. Furthermore, prefabrication of a biologic apatite layer by a method that mimics biomineralization could find application to bone-repairing materials.

Alkaline Phosphatase↗

PubMed2000

Use of glass slides coated with apatite-collagen complexes for measurement of osteoclastic resorption activity.

This study was designed to evaluate the use of apatite-collagen complexes (ACC) coated onto glass slides for measurement of osteoclastic resorption activity. ACC-coated glass slides were prepared by immersion in beta-glycerophosphate solution for 7-14 days after glass slides coated with type I collagen had been treated with alkaline phosphatase and phosvitin. Osteoclast-containing cell suspensions were prepared from the long bones of 1-day-old rabbits and were seeded in medium 199 (containing 10% FBS) onto ACC-coated glass slides. After allowing the cells to attach for 1.5 h, the glass slides were incubated for periods of up to 96 h. The cells were observed by scanning electron microscopy and cytochemically for tartarate resistant acid phosphatase (TRAP) activity. Some slides were treated with FITC-phalloidin and anti-type I collagen antibody. TRAP-positive multinucleated cells were located in transparent spaces on the glass slides. These spaces did not stain immunohistochemically with anti-type I collagen antibody. Podosome formation was observed in the multinucleated cells facing the edge of the transparent spaces. The scanning electron microscopy demonstrated well-spread large cells located on the flattened surface on apatite particles covering the glass surface. Our results suggest that osteoclasts could resorb the apatite particles and coated collagen on the glass slide. The resorption lacunae appeared as transparent spaces, and the cytoskeleton of resorbing osteoclasts was observed in these spaces. ACC-coated glass slides could be useful for investigating the function and metabolic activities of osteoclasts.

Animals↗

PubMed2001

Effect of added NaHCO3 on the basic properties of apatite cement.

Alternation of a composition of set apatite cement (AC) from carbonate-free apatite (CO3-free AP) to carbonate apatite (CO3-AP) may accelerate replacement of the set AC with bone because CO3-AP can be dissolved much faster than CO3-free AP in the weak acidic solution produced by osteoclasts. In this investigation, NaHCO3 was added to the AC component and the effects of added NaHCO3 on cement-setting behavior and on set mass were studied as an initial step for the fabrication of AC, which can be replaced with bone faster than current AC. When NaHCO3 was added to AC, the resultant set mass contained CO3. Although not all CO3 was incorporated in the set AC, the amount of CO3 incorporated into the set AC increased with the amount of added NaHCO3. Powder X-ray diffraction analysis and Fourier transform infrared spectrometer measurements revealed the formation of B-type CO3-AP. The setting time measured in an incubator at 37 degrees C and 100% relative humidity slowed from 30 to 45 min, indicating that NaHCO3 has an inhibitory effect on AP formation. The diametral tensile strength of the set AC decreased significantly with the addition of NaHCO3. Scanning electron microscopic observation revealed that fine crystals were formed in the set AC when NaHCO3 was added to AC. As a result, the crystallinity indices of the set AC measured using X-ray diffraction and Fourier transform infrared spectroscopy decreased with an increase in the amount of added NaHCO3. The dissolution rate of set AC in weak acid, pH 5.5, increased with the amount of added NaHCO3. We concluded that the formation of B-type CO3-AP and the resulting faster dissolution of set AC in weak acidic solution is preferable for the faster replacement of set AC with bone even though the decreased diametral tensile strength value is a shortcoming.

Apatites↗

PubMed2002

Formation of apatite layers on modified canasite glass-ceramics in simulated body fluid.

Canasite glass-ceramics were modified by either increasing the concentration of calcium in the glass, or by the addition of P2O5. Samples of these novel materials were placed in simulated body fluid (SBF), along with a control material (commercial canasite), for periods ranging from 12 h to 28 days. After immersion, surface analysis was performed using thin film X-ray diffraction, Fourier transform infrared reflection spectroscopy, and scanning electron microscopy equipped with energy dispersive X-ray detectors. The concentrations of sodium, potassium, calcium, silicon, and phosphorus in the SBF solution were measured using inductively coupled plasma emission spectroscopy. No apatite was detected on the surface of commercial canasite, even after 28 days of immersion in SBF. A crystalline apatite layer was formed on the surface of a P2O5-containing canasite after 5 days, and after 3 days for calcium-enriched canasite. Ion release data suggested that the mechanism for apatite deposition was different for P2O5 and non-P2O5-containing glass-ceramics.

Apatites↗

PubMed2002

Bonelike apatite growth on hydroxyapatite-gelatin sponges from simulated body fluid.

In vitro bioactivity of gelatin sponges and hydroxyapatite-enriched gelatin sponges was tested through evaluation of the variations in their composition and morphology after soaking in simulated body fluid (1.5) for periods up to 21 days at 37 degrees C. The presence of hydroxyapatite inside the sponges promotes the deposition of bonelike apatite crystals. The deposits are laid down as spherical aggregates, with mean diameters increasing from about 1-2 microm, after 4 days of soaking in simulated body fluid solution, up to about 3.5 microm in the samples soaked for 21 days. Simultaneously, the relative amount of inorganic phase increases up to about 56% wt, leading to a composite material with a composition quite close to that of bone tissue. The inorganic phase is a poor crystalline carbonated apatite similar to trabecular bone apatite.

Apatites↗

PubMed1988

Quantitative analysis of early in vivo tissue response to synthetic apatite implants.

Studies have shown synthetic calcium phosphates such as hydroxyapatite and beta tricalcium phosphate to be biocompatible in vivo. However, few studies have quantitated histological responses to the implants. The aim of this study was to develop a method for the quantitative assessment of tissue biocompatibility to ceramic materials in vivo and to use this method to compare noncarbonated and carbonated apatite implants. Synthetic sintered apatites of 0, 3, and 6% carbonate by weight were prepared and cut into implants 4 X 4 X 1 mm. These were placed 2 mm into the medial aspect of rat femurs. Following sacrifice at 4 weeks, the femurs were fixed in formalin, demineralized in formic acid, and embedded in glycol methacrylate. Sections were cut on an ultramicrotome set at 1.5 micron and stained with toluidine blue. A point counting technique using standard stereological grids and a low-power microscope was used to measure areas of new bone formation. The width of the connective tissue zone adjacent to muscle was measured using an image analyzer. All implants were well accepted by the host tissues judging from criteria of minimal inflammation and degree of fixation. Results showed an increase in new bone formed in the marrow cavity with increasing carbonate content. This may improve stability of the implant in the host bone, particularly during the initial healing period. A technique which should enable quantitative histological evaluation of different ceramic materials has been developed. The use of this method indicates that further studies are warranted to investigate carbonated apatite as an implant material.

Animals↗

PubMed1990

Study of the mineral-organic linkage in an apatitic reinforced bone cement.

In order to increase mechanical properties of surgical cements, an apatitic filler has been linked to the polymethylmethacrylate (PMMA) matrix. We report here the study of the linkage between the mineral and organic components by a dielectric spectroscopy: Thermally Stimulated Current. First, the mineral-organic interface between apatitic-octocalcic phosphate and hydroxyethylmethacrylate (HEMA) has been investigated. Second, the filler-matrix interface between grafted apatite and PMMA has been examined. It has been shown that the filler is chemically linked to the matrix and stiffens the PMMA bone cement.

Apatites↗

PubMed2003

Biomimetic nano-apatite coating capable of promoting bone ingrowth.

Nano-apatite coating closely mimicking bone mineral was grown directly on titanium soaked in an aqueous solution containing all major inorganic components present in the body, mainly, HCO3(-), Ca(2+), HPO4(2-), and Mg(2+) ions. The removal of HCO3(-) ions from the solution in the form of CO2 resulted in the increase of solution pH. As a consequence of this reaction, the nano-apatite coating was formed on the surface of titanium with composition and structure equivalent to those of bone mineral. The biomimetic nano-apatite was demonstrated to be capable of conducting bone formation and promoting direct bone apposition. This bioactive coating also affected the behavior of human osteoblasts as indicated by their morphologies observed in cell culture study.

Alloys↗

PubMed2003

Surface potential change in bioactive titanium metal during the process of apatite formation in simulated body fluid.

Bioactive titanium metal can be prepared by NaOH and heat treatments that present the metal with a graded bioactive surface layer of amorphous sodium titanate. This study used laser electrophoresis together with transmission electron microscopy (TEM) and energy-dispersive X-ray microanalysis (EDX) to relate the surface potential change of the bioactive titanium metal with its surface structural change in simulated body fluid (SBF). The surface potential of the metal was highly negative immediately after immersion in SBF. With increasing soaking time, the surface potential increased, revealing a maximum positive value, and then decreased to a constant negative value. TEM-EDX showed that immediately after immersion in SBF, the metal surface formed Ti-OH groups by exchanging Na(+) ions in the surface sodium titanate with H3O(+) ions in the fluid. Thereafter, with increasing soaking time the metal surface formed an amorphous calcium titanate, then an amorphous calcium phosphate, and, finally, apatite with bone-like composition and structure. These results indicate that the process of apatite formation on bioactive titanium metal is initiated by the formation of Ti-OH groups with negative charges that interact with calcium ions with positive charges to form calcium titanate. The calcium titanate gains a positive charge and later interacts with phosphate ions with negative charges, forming amorphous calcium phosphate. The amorphous calcium phosphate eventually transforms and stabilizes into bone-like crystalline apatite with a negative charge.

Apatites↗

PubMed2004

In vitro response of osteoblast-like and odontoblast-like cells to unsubstituted and substituted apatites.

Different types of calcium phosphate compounds [calcium-deficient apatite (CDA); beta-tricalcium phosphate (beta-TCP); biphasic calcium phosphate (BCP)] are commercially available for medical and dental applications as bone substitute materials. Most of the reported in vitro studies on cell-material interactions have used osteoblast-like cells. The purpose of this study was to investigate the in vitro response of osteoblast-like (MC3T3-E1) and odontoblast-like (MDPC23) cells on unsubstituted (HA) and substituted (F-substituted) apatites. MC3T3-E1 and MDPC23 were cultured in alpha-modified medium containing 10% fetal bovine serum, ascorbic acid (50 microg/mL) and beta-glycerophosphate (2 mM). The cells were seeded on pellets made from HA, and FAp (with low, medium, and high F concentrations). Cell morphology was observed after 7 and 14 days using scanning electron microscopy (SEM). Cell attachment and differentiation were determined from the DNA content, alkaline phosphatase (ALP) activity, and total collagen content. Pellet surface composition was characterized by using Fourier Transform infrared spectroscopy. MC3T3-E1 and MDPC23 cells on HA were normal in shape and in fusion but not on FAp. Results of this study showed that the pattern of cell proliferation of osteoblast-like cells was different from that of the odontoblast-like cells. This study suggests that cell morphology, fusion, and proliferation on biomaterial surfaces depend on cell type (osteoblast-like vs odontoblast-like cell) and biomaterial composition (unsubstituted vs substituted F-apatites).

Alkaline Phosphatase↗