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PubMed1992

Chemical, physical, and histologic studies on four commercial apatites used for alveolar ridge augmentation.

The purpose of this study was to evaluate four commercial apatite products. Subperiosteal alveolar ridge augmentation was performed on the maxilla of rats by implantation of granules of two dense products and of two porous products, and the tissue response was compared with the material characteristics obtained by chemical analysis and infrared spectrometry. None of the apatites caused osteoinduction or osteoconduction; fibrous encapsulation with multinuclear giant cells was observed around all four types. One of the apatites was fluorapatite and not hydroxylapatite, as claimed by the manufacturer. The tissue response to this implant material was dominated by multinuclear giant cells.

Alveolar Process↗

PubMed1986

The structure of (100) defects in carbonated apatite crystallites: a high resolution electron microscope study.

Planar defects parallel to (100) with an approximate [1/400] displacement vector have been identified by high resolution transmission electron microscopy and by micro-electron diffraction in the center of synthetic carbonated apatite crystallites. Similar intergrowths, 0.8-1.5 nm in width, have been observed in dental enamel, dentin and bone apatite crystallites. Four possible structural models of the defect core are proposed to explain these experimental features, and computer-simulated lattice images of the models are compared with the experimental images. Typical defects were consistent with a two-dimensional octacalcium phosphate inclusion, one unit cell thick, embedded in an apatite matrix.

Apatites↗

PubMed2005

Mineralisation of chitosan scaffolds with nano-apatite formation by double diffusion technique.

The study of inorganic crystal assembly in organic matrices has given rise to increasing interest in various fields of materials science to the natural process of biomineralisation. To mimic the formation of hydroxyapatite as natural bone, a double diffusion technique is utilised in this study to nucleate the hydroxyapatite crystals onto three-dimensional porous polymeric scaffolds. The porous polymer scaffolds were produced from chitosan by a thermally induced lyophilisation technique, which yields highly porous, well-controlled anisotropic open pore architecture. The nucleation of hydroxyapatite crystals was initiated at ambient conditions on the surface of the polymer scaffold, which was in contact with a calcium solution chamber, due to diffusion of phosphate ions through the scaffold. The morphology of the mineralised scaffold as analysed by scanning electron microscopy shows that apatite crystals were not only formed on the surface of the scaffold, but also in the pore channels and attached to the pore walls. The X-ray diffraction and Fourier transformed infrared analyses confirmed the phase purity of the formed apatite crystals. The transmission electron microscopy analysis reveals the microstructure of the entangled nano-apatite in the chitosan polymeric matrix. The in-vitro cytocompatibility tests with osteoblast-like cells (Saos-2) demonstrated that the biomineralised scaffold is a suitable substrate for cell attachment and migration in bone tissue engineering.

Apatites↗

PubMed2006

Effect of ZnO addition on bioactive CaO-SiO2-P2O5-CaF2 glass-ceramics containing apatite and wollastonite.

Some ceramics show bone-bonding ability, i.e. bioactivity. Apatite formation on ceramics is an essential condition to bring about direct bonding to living bone when implanted into bony defects. A controlled surface reaction of the ceramic is an important factor governing the bioactivity and biodegradation of the implanted ceramic. Among bioactive ceramics, glass-ceramic A-W containing apatite and wollastonite shows high bioactivity, as well as high mechanical strength. In this study, glass-ceramics containing zinc oxide were prepared by modification of the composition of the glass-ceramic A-W. Zinc oxide was selected to control the reactivity of the glass-ceramics since zinc is a trace element that shows stimulatory effects on bone formation. Glass-ceramics were prepared by heat treatment of glasses with the general composition: xZnOx(57.0-x)CaOx35.4SiO(2)x7.2P(2)O(5)x0.4CaF(2) (where x=0-14.2mol.%). Addition of ZnO increased the chemical durability of the glass-ceramics, resulting in a decrease in the rate of apatite formation in a simulated body fluid. On the other hand, the release of zinc from the glass-ceramics increased with increasing ZnO content. Addition of ZnO may provide bioactive CaO-SiO(2)-P(2)O(5)-CaF(2) glass-ceramics with the capacity for appropriate biodegradation, as well as enhancement of bone formation.

Apatites↗

PubMed2005

Simple surface modification of poly(epsilon-caprolactone) for apatite deposition from simulated body fluid.

Poly(epsilon-caprolactone) (PCL) with a bone-like apatite layer bound to its surface could be useful as a scaffold for tissue engineering applications. In the present study, the surface of PCL was treated with aqueous NaOH to introduce carboxylate groups onto the surface. The NaOH-treated material was subsequently dipped in aqueous CaCl(2) and K(2)HPO(4).3H(2)O alternately three times to deposit apatite nuclei on the surface. The surface-modified material successfully formed a dense and uniform bone-like surface apatite layer after incubation for 24 h in simulated body fluid with ion concentrations approximately equal to those of human blood plasma.

Absorbable Implants↗

PubMed2005

Plasma-treated nanostructured TiO(2) surface supporting biomimetic growth of apatite.

Although some types of TiO(2) powders and gel-derived films can exhibit bioactivity, plasma-sprayed TiO(2) coatings are always bioinert, thereby hampering wider applications in bone implants. We have successfully produced a bioactive nanostructured TiO(2) surface with grain size smaller than 50 nm using nanoparticle plasma spraying followed by hydrogen plasma immersion ion implantation (PIII). The hydrogen PIII nano-TiO(2) coating can induce bone-like apatite formation on its surface after immersion in a simulated body fluid. In contrast, apatite cannot form on either the as-sprayed TiO(2) surfaces (both <50 nm grain size and >50 nm grain size) or hydrogen-implanted TiO(2) with grain size larger than 50 nm. Hence, both a hydrogenated surface that gives rise to negatively charged functional groups on the surface and small grain size (<50 nm) that enhances surface adsorption are crucial to the growth of apatite. Introduction of surface bioactivity to plasma-sprayed TiO(2) coatings, which are generally recognized to have excellent biocompatibility and corrosion resistance as well as high bonding to titanium alloys, makes them more superior than many current biomedical coatings.

Apatites↗

PubMed2005

Formation of bone-like apatite on organic polymers treated with a silane-coupling agent and a titania solution.

Polyethylene terephthalate (PET), ethylene-vinyl alcohol copolymer (EVOH) and Nylon 6 in plate form were treated with silane-coupling agents, a titanium alkoxide-alcohol solution and a hot HCl solution to form a thin crystalline titanium oxide layer. When placed in a simulated body fluid with ion concentrations nearly equal to those of the human blood plasma, nanosized bone-like apatite formed uniformly on the surfaces of these treated polymers: within 2 days for PET and Nylon 6, and 7 days for EVOH. This indicates that such titania-modified polymers might form bone-like apatite in the living body, and bond to living bone through this apatite layer. Three-dimensional fabrics of these polymer fibers, with open spaces in various sizes, are expected to be useful as bone substitutes, as they will be integrated with the natural bone.

Apatites↗

PubMed2006

Coupled substitution of type A and B carbonate in sodium-bearing apatite.

A suite of Na-bearing type A-B carbonate hydroxyapatites {Ca(10-y)Na(y)[(PO4)(6-y)(CO3)y][(OH)(2-2x)(CO3)x], x approximately = y} has been synthesized at 1200 degrees C and 0.5-1.0 GPa, and investigated by single-crystal X-ray structure and FTIR spectroscopy. Crystal data for the maximum content of carbonate (11.1 wt%) are a = 9.3855(7), c = 6.9142(4) A, space group P6(3)/m, R = 0.023, R(w) = 0.014. Structural accommodation of the substitutions requires local coupling of Na and channel (type A) and phosphate (type B) carbonate ion defects. The type B carbonate ion is located on the sloping faces of the substituted phosphate group, but is inclined at an angle of 53 degrees to the mirror plane. FTIR spectra have minimal nu3 absorption beyond 1500 cm(-1) and dominant nu2 absorption at 873 cm(-1). Synthetic Na-bearing type A-B apatites (with a high content of type A carbonate) are thus similar in both chemical composition and infrared spectra to biological apatites. The latter are reinterpreted as Na-bearing type A-B carbonate apatites with channel carbonate up to 50% of total carbonate.

Apatites↗

PubMed2004

Sintering behavior and apatite formation of diopside prepared by coprecipitation process.

Sintering behavior and bioactivity of diopside, CaMgSi(2)O(6), prepared by a coprecipitation process were examined for its biomedical applicability. As-prepared powder was synthesized by adding aqueous ammonia to an ethanol solution containing Ca(NO(3))(2).4H(2)O, Mg(NO(3))(2).6H(2)O, and Si(OC(2)H(5))(4) and characterized by means of TG-DTA, XRD, and TG-MS. The dried powder was X-ray amorphous and crystallized into diopside at 845.5 degrees C. The glass network formation by SiO(4) tetrahedra was almost completed below 800 degrees C. The bioactivity of the diopside prepared by sintering the compressed powder at 1100 degrees C for 2h was evaluated by immersion of the sintered body in a simulated body fluid (SBF) at 36.5 degrees C. Leaf-like apatite particles were found to be formed on the surface of the sintered body and grew with passage of soaking time. This apatite-forming behavior in the SBF is related to the dissolution of Ca(II) ions from the sintered body in the early stage of immersion. Thus, diopside prepared by the coprecipitation process using the metal alkoxide and the metal salts was found to have an apatite-forming ability.

Apatites↗

PubMed1997

A computer program for correlating dental plaque pH values, cH+, plaque titration, critical pH, resting pH and the solubility of enamel apatite.

A computer program was written in Visual Basic (Microsoft) to calculate (a) the area between a plaque pH curve (as seen after a sucrose rinse) and either a resting pH (around pH 7) or a critical pH value (around 5.5) above at least parts of the pH curve; (b) the solubility of apatite at the pH values in plaque; (c) the area between the plaque pH solubility curve and the apatite solubility at the resting pH/critical pH; (d) the area between plaque cH+ curve and the cH+ value at resting pH/ critical pH; and (e) the area between a plaque pH curve and a cut-off pH value below the curve, e.g. pH 3. It was found that because both the cH+ and the solubility of apatite increased logarithmically with a pH drop, the two latter area functions (d, e) were basically different from those based directly on pH curves. Thus, pH changes around the resting pH value had little effect on areas calculated from concentrations of H+ and solubility. In contrast, a small pH change around pH 4 had a strong impact on both demineralization potential and areas based on cH+. Also, because of the logarithmic nature, demineralization potentials were generally large in comparison to remineralization potentials, a point that has hitherto received little attention.

Apatites↗

PubMed2001

Apatite formed on the surface of plasma-sprayed wollastonite coating immersed in simulated body fluid.

Wollastonite coatings on titanium alloys substrates were prepared by plasma spraying and incubated in simulated body fluids for different periods to investigate the nucleation and growth of apatite on their surface. Surface structural changes of the specimens were analyzed by XRD and IR technologies. SEM and EDS were used to observe surface morphologies and determine the composition of wollastonite coatings before and after immersion in simulated body fluid. The changes in the concentrations of calcium, silicon and phosphorus in the simulated body fluids due to the immersion of the specimens were measured by inductively coupled plasma atomic emission spectroscopy. The results obtained showed that hydroxycarbonate apatite can be formed on the surface of the coating soaked in SBF for 1 day. With longer immersion periods, the coating surface was covered by hydroxycarbonate apatite, which indicated that the wollastonite coating possesses good bioactivity.

Alloys↗

PubMed2002

Carbonate apatite coating on titanium induced rapidly by precalcification.

Chemical treatments have been thought to be promised methods for improving bioactivity of titanium. In this work, the effect of precalcification with boiling saturated Ca(OH)2 solution on bioactivation of titanium was investigated. After precalcification and soaking in supersaturated Ca-P solution (SCP), calcium phosphate rapidly precipitated onto the surfaces of titanium, and after only three days an uniform apatite layer was found up to thickness of a few micrometers. The observation using scanning electron microscopy (SEM) showed that the coating was composed of a number of small crystal grains. The investigation by X-ray energy dispersion spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) indicated that the coating was Ca-deficient carbonate apatite. Based on the analyses for the surfaces and SCP, a mechanism of precipitation of apatite was proposed in thermal dynamics and kinetics.

Apatites↗

PubMed2002

Influence of apatite seeds on the synthesis of calcium phosphate cement.

This preliminary study explores the seeding effect (using crystalline hydroxyapatite particles) on the setting time, compressive strength, phase evolution, and microstructure of calcium phosphate cements (CPC) based on monocalcium phosphate monohydrate and calcium hydroxide. Experimental results showed that the setting time varies from 5 to about 30 min, as the seed concentration increased from 0 to 20 wt%. The compressive strength of CPC increased from 4 to 17 MPa, followed by decrease to 12 MPa, for the same range of seeds content. The CPC transformed to predominantly apatitic structure within 24 h for all the samples, with or without the seeds. However, increase of the seed concentration improved the final crystallinity of the apatite phase, suggesting nucleation and growth effects during precipitation of CPC from the precursor solution. The microstructure of the resulting apatitic cement showed a change from essentially featureless (or glass-like) to thin, elongated plate-like morphology, as seeds concentration increased. Correlation between microstructural evolution and corresponding compressive strength of seeded CPC is investigated.

Apatites↗

PubMed2003

Effect of molecular weight of poly(epsilon-caprolactone) on interpenetrating network structure, apatite-forming ability, and degradability of poly(epsilon-caprolactone)/silica nano-hybrid materials.

The effect of molecular weight of poly(epsilon-caprolactone) (PCL) on the bioactivity of a PCL/silica nano-hybrid containing calcium salt was investigated. Two hybrids were prepared with low and high molecular weight PCLs, respectively, through a sol-gel method. Their bioactivities were evaluated using a simulated body fluid (SBF), which had almost the same ion concentrations with human blood plasma. Fast and uniform nucleation and growth of the apatite crystals were observed to occur all through the hybrid surface when low molecular weight PCL was used, while slow and random nucleation and growth of the apatite crystals were observed to occur when high molecular weight PCL was used, after soaking for 3 days in the SBF. This phenomenon was explained in terms of the distribution and dispersion of silica phase in the hybrid and the ionic activity product of the apatite in the SBF, which were dependent on the free volume and degradation rate of non-bioactive PCL phase, respectively.

Apatites↗

PubMed2003

Sodium silicate gel as a precursor for the in vitro nucleation and growth of a bone-like apatite coating in compact and porous polymeric structures.

In the present work, a new methodology to produce bioactive coatings on the surface of starch-based biodegradable polymers or other polymeric biomaterials is proposed. A sodium silicate gel is employed as an alternative nucleating agent to the more typical bioactive glasses for inducing the formation of a calcium-phosphate (Ca-P) layer. The method has the advantage of being able to coat efficiently both compact materials and porous 3D architectures aimed at being used on tissue replacement applications and as tissue engineering scaffolds. By means of this treatment, it is possible to observe the formation of an apatite-like layer, only after 6 hours of simulated body fluid immersion. For the porous materials, this layer could also be observed inside the pores, clearly covering the cell walls. Furthermore, an increase of the surface hydrophilicity (higher amount of polar groups in the surface) might contribute to the formation of silanol groups that also act as apatite inductors. After 30 days of SBF immersion, the apatite-like films exhibit a partially amorphous nature and the Ca/P ratios became much closer to the value attributed to hydroxyapatite (1.67). The obtained results are very promising for the development of cancellous bone replacement materials and for pre-calcifying bone tissue engineering scaffolds.

Apatites↗

PubMed1997

Atomic force microscopic study of the surface morphology of apatite films deposited by pulsed laser ablation.

Atomic force microscopy (AFM) has been used to study the surface morphology of apatite films deposited on metallic and polyethylene substrates by laser ablation using KrF and transversely excited atmospheric CO2 lasers. The films are found to consist of a smooth apatite coating with macroparticles scattered on the surface. A wide variety of macroparticles, differing in size, shape and roughness, were found and analysed employing the high spatial resolution of AFM (< 1 nm). We have investigated the correlation between the apatite film morphology and the deposition conditions. Of particular importance are laser fluence, gas pressure, the nature of the target and the substrate temperature. We have explained these dependencies on the basis of a theoretical model which includes evaporation and a cluster-type laser ablation mechanism.

Apatites↗

PubMed1998

Crystallization, fluoridation and some properties of apatite thin films prepared through rf-sputtering from CaO-P2O5 glasses.

Using calcium phosphate glass targets with the CaO/P2O5 molar ratios of 1.50-0.50, much lower than the stoichiometric value of 3.3 for hydroxyapatite, thin films of stoichiometric hydroxy-, nonstoichiometric oxyhydroxy- and Ca-deficient oxyhydroxy-apatites were prepared on alumina ceramic substrates by rf-sputtering followed by post-annealing. Based on the present results, a phase diagram for CaO-P2O5 at low temperatures in the ambience of air was depicted for thin films. The ambient H2O vapor had an influence on the phase diagram: Tricalcium phosphate was changed to apatite in the presence of H2O vapor. Dense fluorohydroxyapatite thin films were prepared by fluoridation of those apatite thin films at a low temperature such as 200 degrees C. In the present report, some functional properties of thin films thus prepared were also shown.

Aluminum Oxide↗

PubMed1999

Modulation of apatite crystal growth on Bioglass by recombinant amelogenin.

The effects of a recombinant mouse amelogenin (rM179) on the growth of apatite crystals nucleated on a bioactive glass (45S5 type Bioglass) surface were investigated with a view to gaining a better understanding of the role of amelogenin protein in tooth enamel formation and of its potential application in the design of novel enamel-like biomaterials. Bioglass discs were incubated in phosphate-buffered saline (PBS) to preform a calcium phosphate surface layer and subsequently immersed in blank, bovine serum albumin (BSA)- and rM179-containing supersaturated calcification solutions (SCS(B), SCS(BSA) and SCSrM179), respectively. Calcium phosphate layers formed on all the treated samples and were characterized to be apatite by X-ray diffraction and Fourier transmission infrared spectrophotometry. Under scanning electron microscopy, plate-shaped crystals (approximately 50 nm thick and 300-600 nm across) were observed on the samples after PBS incubation. The crystals grown from SCS(B) were of the typical plate shape except for an increased thickness, while needle-shaped crystals (200-300 nm long and 50-70 nm thick) were precipitated on the SCS(BSA)-immersed samples. Interestingly, it was found that the crystals deposited on the SCSrM179-immersed samples adopted an elongated, curved shape (approximately 500 nm long and approximately 120 nm thick). Further TEM observations showed that the crystals generated by the SCSrM179 immersion appeared to be composed of bundles of lengthwise crystals (15-20 nm thick) orientated parallel to one another, much alike the long and thin crystals observed in the very early stage of enamel formation. The significant modulation by the rM179 protein of apatite crystal growth is quite different from the overall inhibition observed by BSA and most likely is relevant to the specific function of the amelogenin matrix in controlling enamel crystal growth in vivo.

Amelogenin↗