Lídia Ágata de Sena

Physicochemical characterization of two deproteinized bovine xenografts

Calcium phosphate salts, or more specifically hydroxyapatite, are products of great interest in the fields of medical and dental science due to their biocompatibility and osteoconduction property. Deproteinized xenografts are primarily constituted of natural apatites, sintered or not. Variations in the industrial process may affect physicochemical properties and, therefore, the biological outcome. The purpose of this work was to characterize the physical and chemical properties of deproteinized xenogenic biomaterials, Bio-Oss (Geistlich Biomaterials, Wolhuser, Switzerland) and Gen-Ox (Baumer S.A., Brazil), widely used as bone grafts. Scanning electron microscopy, infrared region spectroscopy, X-ray diffraction, thermogravimetry and degradation analysis were conducted. The results show that both materials presented porous granules, composed of crystalline hydroxyapatite without apparent presence of other phases. Bio-Oss presented greater dissolution in Tris-HCl than Gen-Ox in the degradation test, possibly due to the low crystallinity and the presence of organic residues. In conclusion, both commercial materials are hydroxyapatite compounds, Bio-Oss being less crystalline than Gen-Ox and, therefore, more prone to degradation.

Synthesis of magnesium- and manganese-doped hydroxyapatite structures assisted by the simultaneous incorporation of strontium

Samples of crystalline hydroxyapatite (HA) with and without the addition of individual Mg(2+), Mn(2+) and Sr(2+) ions and samples with the addition of all three ions simultaneously were prepared using the precipitation method in an aqueous medium. Chemical, structural, spectroscopic and thermophysical analyses of the synthesized samples were conducted. The obtained results indicate that Sr(2+) ions were easily incorporated into the HA crystal structure, whereas it was difficult to incorporate Mg(2+) and Mn(2+) ions into the HA lattice when these ions were individually introduced into the samples. The synthesis of HA with Mg(2+) or Mn(2+) ions is characterized by the formation of HA with a low concentration of doping elements that is outweighed by the amount of these atoms present in less biocompatible phases that formed simultaneously. However, the incorporation of Sr(2+) along with Mg(2+) and Mn(2+) ions into the samples allowed for the synthesis of HA with considerably higher concentrations of Mg(2+) and Mn(2+) in the crystal lattice.

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.

Surface characterization of dental implants coated with hydroxyapatite by plasma spray and biomimetic process.

Purpose:The aim of this study was to characterize implants coated with hydroxyapatite (HA) using 2 different processes. Materials and Methods:Commercially pure titanium implants were coated with HA using a modified biomimetic process and the plasma spray process. These implants were characterized by scanning electron microscopy, Fourier-transformed infrared spectroscopy, and x-ray photoelectron spectroscopy. Results:The plasma spray process generates a typical rough topography mainly consisting of HA. The HA coating produced by biomimetic process was partially dissolved in water and only a very thin layer of calcium titanate plus calcium phosphate and probably &bgr;-tricalcium phosphate remained. In vitro test showed that both coatings can be considered bioactive. Conclusion:The modified biomimetic process seems to be a simple and low-cost alternative to coat titanium with a high potential of In vitro application.

A study of the physical, chemical and biological properties of TiO2 coatings produced by micro-arc oxidation in a Ca–P-based electrolyte

In this work, a porous and homogeneous titanium dioxide layer was grown on commercially pure titanium substrate using a micro-arc oxidation (MAO) process and Ca–P-based electrolyte. The structure and morphology of the TiO2 coatings were characterized by X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy, and profilometry. The chemical properties were studied using electron dispersive X-ray spectroscopy (SEM–EDS) and X-ray photoelectron spectroscopy. The wettability of the coating was evaluated using contact angle measurements. During the MAO process, Ca and P ions were incorporated into the oxide layer. The TiO2 coating was composed of a mixture of crystalline and amorphous structures. The crystalline part of the sample consisted of a major anatase phase and a minor rutile phase. A cross-sectional image of the coating–substrate interface reveals the presence of voids elongated along the interface. An osteoblast culture was performed to verify the cytocompatibility of the anodized surface. The results of the cytotoxicity tests show satisfactory cell viability of the titanium dioxide films produced in this study.

Influence of processing parameters on structural characteristics of porous calcium phosphate samples: a study using an experimental design method

Synthetic porous ceramics can be used as three-dimensional scaffolds for bone repair. The aim of this work is to correlate process parameters with scaffolds structural characteristics. The factorial 2 level experimental design was chosen to study the effect of the Ca/P ratio (1.58 or 1.67), calcination temperature (1000 or 1150 °C) and porogen content (20 or 40%) on the calcium phosphate samples characteristics. The influence of such parameters was determined by X-ray diffraction, infrared spectroscopy and image analysis. It was observed that phase composition was basically a function of the Ca/P ratio of the raw material. The use of the porogen did not alter the hydroxyapatite (HA)/tricalcium phosphate (TCP) content, but induced changes in the relative content of TCP phase (a or b). It is possible to design a porous sample with defined characteristics, and the model herein used can be considered as having a good predictive power.

Comparative study of hydroxyapatite coatings obtained by Sol-Gel and electrophoresis on titanium sheets

A comparative study of two coating methods on titanium (Ti) substrates, sol-gel and electrophoresis processes, was performed. Before coating, two different surface treatments were employed. The hydroxyapatite (HA) powder were characterized by infrared spectroscopy (FTIR) and X-ray diffraction (XRD) while coated samples were examined by using scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). Both techniques seem to be suitable to coat Ti. A previous surface treatment on metallic titanium seems to be fundamental to enhance coat uniformity and adhesion that was estimated by the adhesive tape test. The decrease in calcination temperature did not affect the coating adhesion.

Effect of Electrophoretic Apatite Coating on Osseointegration of Titanium Dental Implants

This paper discusses the in vivo behavior of HA-coated titanium implants compared with non-coated implants. HA coating was produced by using electrophoresis. Coat ings were characterized using scanning electron microscopy (SEM) and the bone-i mplant contact length was used as the measure of osseointegration. Results show significantly higher percentage of boneimplant contact for hydroxyapatite coated than for non-coated condition. The obtained results allow us to conclude that coating by electrophoresis appears to be an attrac tive process to coat metallic implants with an osteoconductive material like hydroxyapatite, for sm all or medium scale production.

Síntese da hidroxiapatita e refinamento estrutural por difração de raios-x

A sample of hydroxyapatite was synthesized and its crystalline structure was analyzed by X-ray diffraction by means of the Rietveld method. Two functions were used to fit the peak profiles, modified Voigt (TCHZ) and Pearson VII. The occupational factors and lattice parameters obtained by both models show that the sample does not contain relevant cationic substitutions. The interatomic distances from Ca1 to oxygens O1, O2 and O3 were adequate for a pure hydroxyapatite without defect at site Ca1. Besides, the use of multiple lines in planes (300) and (002) associated with the model Pearson VII resulted in good agreement with the TCHZ model with respect to the size-strain effectswith an ellipsoidal shape of crystallites. In conclusion, the procedures adopted in the synthesis of hydroxyapatite produced a pure and crystalline material. The experimental results of transmission electron microscopy confirmed the predicted shape of crystals.

Synthesis and Characterization of Hydroxyapatite on Collagen Gel

Bone is a complex natural composite with the mineral phase (mainly hydroxyapa tite, HA) arranged in a specific way on the type-I collagen fibers. Tissue engineering tries to mimic this structure by carrying out the hydroxyapatite synthesis in the presence of collagen. Several techniques like electron microscopy, x-ray diffraction and infrared s pectroscopy were employed to characterize the materials produced. The synthesis conditions allow the production of a calciumdeficient hydroxyapatite exhibiting nanometric crystals. The prese nce of collagen had little influence on the hydroxyapatite synthesis, slightly reducing the cris tallinity of apatite phase present in the composite. Introduction Synthetic calcium phosphate (CaP) materials have been widely used in medical and dental applications as they possess the ability to promote cellular funct ion, osteoconductivity and, in certain circumstances, may become osteoinductive [1]. Third-generati on biomaterial are being developed to stimulate specific cellular responses [2]. For bone tiss ue engineering, researches concerning scaffolds design have been outstanding [3, 4]. One option deals wit h scaffolds composed by synthetic or natural hydroxyapatite (Ca 10(PO4)6(OH)2, HA) and collagen (Col). The main reason of this choice is the preponderance of these components in the bone tissue, as bone structure is composed by nanocrystals of HA with the c-axis alig ned to the Col fibres in a specific way [5]. The aim of this work was to synthesise nanocrystalline hy drox apatite in the presence of collagen gel in order to produce a HA-Col composite suitable to be used in bone reconstruction. Methods The synthesis methodology followed the route used b y Kikuchi et al. [5]. The composite was prepared by co-precipitation method using a HA-Col weight ratio o f 80:20. The Ca(OH) 2 (99,6 mM) suspension and H3PO4 (59,64 mM) solution were simultaneously dropped wi th aid of peristaltic bombs into a reaction vessel with 25 mL of milliQ water which wa s vigorously stirred. Natural type collagen I was used in the gel form and was added in the H 3PO4 solution. The synthesis temperature was 40 C and the pH was adjusted to the range of 8-9 with ammoni a. After ageing the precipitates for 18 hours, the material was filtered and lyophilised. Following th e same route, another synthesis was prepared without the presence of collagen to compare to the HA-Col composite. The materials obtained were evaluated by using scanning electron microscopy (SE M, Zeiss, DMS 940A), transmission electron Key Engineering Materials Online: 2003-12-15 ISSN: 1662-9795, Vols. 254-256, pp 493-496 doi:10.4028/www.scientific.net/KEM.254-256.493