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http://www.shogun.com.tw2012

2012

Join us for a three day symposium at the Rome Marriott Park Hotel. This international meeting will host top thought leaders who will discuss an array of topics including immediate loading, esthetics, dental implant complications and a half day Biologics forum. Stay up-to-date with the current techniques and treatment options by attending this well anticipated 3-day course. Enrollment will be limited to maintain an environment conductive to learning, so please register now to reserve your place at this outstanding education event.

Normal HA

BoneMedik-S

BoneMedik-s Hydroxyapatite

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Preparation of porous Si-incorporated hydroxyapatite Y.H. Kim, H. Song, D.H. Riu, S.R. Kim, H.J. Kim, J.H. Moon http://www.sciencedirect.com/science/journal/15671739/5/5

1. Introduction

The most important properties with respect to the use of hydroxyapatite as a biomaterial for filling bone defects are depend on the high porosity and the interconnectivity pore system of the materials. A natural coral has a porous structure with all pores interconnected throughout the skeleton and structure resembles that of trabecular bone. Specially, porites genus of natural coral is expected to be an excellent starting material to synthesize porous hydroxyapatite since its microporous structure resembles that of bone. In recent, hydroxyapatite derived from coral has been used extensively in clinical applications. Ion-incorporated hydroxyapatite can be used for a potential biological material in the form of porous body, granule and coating material on metal alloy substrates to improve biocompatibility. Especially, incorporation of silicon into hydroxyapatite structure is of great interest since they play an important role in developing artificial bone. Poter et al. suggested that the incorporation of silicate ions into the hydroxyapatite structure increases the number of defect structures. The defect structures are the specific sites that are most favorable to dissolution. Therefore, by increasing the number of defect sites, the solubility of the hydroxyapatite in a biological fluid is increased, as is its rate of osseointegration. In this study, a porous silicon-incorporated hydroxyapatite has been prepared using natural coral as a calcium source to obtain a biomaterial having an improved biocompatibility. Si-incorporated hydroxyapatite has been prepared by hydrothermal treatment and solvothermal treatment of the natural coral repeatedly.

with distilled water, block of coral was put in 2 M (NH4)2HPO4 in a teflon lined hydrothermal bomb and heated for 16 h at 180°C Then block of coral was transferred into silicon acetate saturated acetone solution and heated for 24 h at 180°C in Teflon lined hydrothermal bomb. For final step, block of coral was immersed in 2 M (NH4)2HPO4 and treated at 200°C for 24 h hydrothermally again. After thoroughly washing with distilled water, block of coral was dried at 90°C. The phase transformations of natural coral at different reaction process were observed using X-ray powder ������������� �������������������������������������was used at the operating condition of 40 kV and 20 ����������������������!!������"���#$����%����&'(–60°at a step size of 0.02°. Microstructure of natural coral was examined using scanning electron microscopy (JEOL, JSM-6700F) and energy dispersive spectroscopy (EDS) was employed for the distribution of silicon ion of the samples. The porosity of the samplewas measured using Archimedes method. The compressive strength was measured using a universal testing machine (Model 4204, Instron Corp., Danvers, MA).

2. Method

A 10g of block of coral was immersed in 100 ml of 4% sodium hypochlorite for one day at room temperature to remove organic component. After thoroughly washing

Abstract A porous silicon-incorporated hydroxyapatite has been prepared using natural coral as a calcium source to obtain a biomaterial having a good biocompatibility. Si-incorporated hydroxyapatite has been prepared by hydrothermal treatment in 2 M (NH4)2HPO4 and solvothermal treatment in silicon acetate saturated acetone solution at 180°C of the natural coral repeatedly. From the XRD analysis, it was confirmed that the single-phase hydroxyapatite containing silicon has formed without revealing the presence of extra phases related to silicon dioxide or other calcium phosphate species. Compressive strength of the porous silicon-incorporated hydroxyapatite was 5.5 MPa and silicon content was ranged from 0.12% to 0.19% by weight. SEM and EDS investigation confirmed the presence of silicon in the framework of hydroxyapatite structure.

Fig. 1. SEM micrograph of natural coral.

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To measure compressive strength, a sample was prepared into a rectangular bar shape with dimensions of 5 mm x5 mm x10 mm and the top and bottom surface of the bars were infiltrated with resin to minimize the edge effects.

3. Results

For application as a bone substituted materials, it is required that the materials possess three dimensionally ��������������;�����"��%�;���<�=���>���&''?G''K��and 50–70% porosity. This is due to porous structure gives advantage of allowing circulation of body fluids and increasing the potential for firm attachment of body tissue. Fig. 1 shows a scanning electron micrograph of the porites coral genus obtained from the coast of Indonesia. Q��� <�=�� ��<���>����<� ���%�� #''?U''K�� ���<� ���!�exhibits a porous structure with all pores interconnected throughout the skeleton and structure resembles that oftrabecular bone. The observed X-ray powder diffraction pattern of the coral sample is indexed for aragonite phase on the basis of JCPDS Card No. 24-2005. The data do not reveal the presence of extra phases related to calcite phase or other oxide species. To improve biocompatibility, silicon incorporation into hydroxyapatite structure has been carried out. First, silicon incorporation has been attempted during hydrothermal treatment of natural coral. 0.5 g of silicon acetate was dissolved in 2 M, 30 ml (NH4)2HPO4 and 3 g of natural coral was dipped into the solution and hydrothermally treated at 200°C. After the treatment, EDS analysis of the sample shows only Ca, P, O and trace of Mg but does not contain Si ions. X-ray powder diffraction data of the sample shows mostly into hydroxyapatite ;��<�� ���� �!<� ���!����� ��� ������������� ;��W<� ��� #$Y�17° and 24° (Fig. 2). his is attributed that silicon ions are easily hydrolyzed in hydrothermal condition and precipitated as silicon related compounds during

hydrothermal treatment. Therefore, using a hydrothermal condition, silicon is hard to incorporate into the hydroxyapatite structure. Second attempt of silicon incorporation has beendone using an organic solvent that silicon can present as ionic state. In detail, conversion of coral into Si-incorporated hydroxyapatite was carried out by repeated treatments of hydrothermal and solvothermal methods.

Fig. 3. XRD patterns of the samples during the conversion process after (a) hydrothermal treatment in 2 M(NH4)2HPO4 , 180°C, 16 h, (b) solvothermal treatment in silicone acetate saturated acetone solution at 180°C, 24 h and (c) hydrothermal treatment in 2(NH4)2HPO4 200°C, 24 h.

Fig. 2. XRD powder diffraction pattern of the sample after hydrothermal treatment in the presence of silicon acetate.

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