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AMORPHOUS CALCIUM PHOSPHATE FOR BI-PHASE CERAMICS PREPARATION

IGIC-BAS. AMORPHOUS CALCIUM PHOSPHATE FOR BI-PHASE CERAMICS PREPARATION. D . Rabadjieva 1 , S . Tepavitcharova 1 , R . Gergulova 1 , R . Titorenkova 2 , E . Dyulgerova 3 , O. Petrov 2 didiarab@svr.igic.bas.bg. 1 Institute of General and Inorganic Chemistry , BAS

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AMORPHOUS CALCIUM PHOSPHATE FOR BI-PHASE CERAMICS PREPARATION

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  1. IGIC-BAS AMORPHOUS CALCIUM PHOSPHATE FOR BI-PHASE CERAMICS PREPARATION D. Rabadjieva1, S. Tepavitcharova1, R. Gergulova1, R. Titorenkova2, E. Dyulgerova3, O. Petrov2 didiarab@svr.igic.bas.bg 1Institute of General and Inorganic Chemistry, BAS 2Instituteof Mineralogy and Crystallography, BAS 3Dental Medicine Faculty, University of Medicine, Sofia November, 2010, Bulgaria

  2. INTRODUCTION Ca10(PO4)6(OH)2 Ca8(PO4)4(HPO4)2.5H2O Ca(HPO4)2.2H2O -Ca3(PO4)2 Ca(H2PO4)2.H2O Ca(HPO4)2 a-Ca3(PO4)2 Ca(H2PO4)2 A C P Ca4(PO4)2О Amorphous Calcium Phosphate November, 2010, Bulgaria

  3. INTRODUCTION CALCIUM ORTHOPHOSPHATES (COPh) Importance forthe Biological system They are the main inorganic component of body hard tissues Biological apatite • Nano-sized • Poorly crystallized • Non-stoichiometric hydroxyapatite • Including Na, K, Mg, Cl, F and CO3 November, 2010, Bulgaria

  4. INTRODUCTION BIOMIMETIC APPROACH Biological mineralization (biomineralization) process of in vivo formation of inorganic minerals Deposition and Growing of Calcium Phosphates in the organic matrix in the body fluids medium November, 2010, Bulgaria

  5. AIMS To study the biomimetic synthesis and transformations of X-ray ACP in conventional, revised and modified with Glycine SBF in order to elucidate some elementary processes of hard tissue mineralization and of the influence of micro-environmental surroundings on synthesis and transformation processes. November, 2010, Bulgaria

  6. EXPERIMENTS BIOMIMETIC SYNTHESIS EXPERIMENTAL CONDITIONS Ca/P = 1.67 pH 11.5 (KOH) Room temperature; Fast mixing Filtering Washing (water : acetone = 1:1) Freezing -18oC SBFc-Cam SBFc-Pm K2HPO4 CaCl2 K2HPO4 November, 2010, Bulgaria

  7. EXPERIMENTS THERMODYNAMIC CALCULATIONS PHREEQCI computer program INPUT pH, toC, Initial solution concentrations DATABASE for K, H of the reaction for complex formation and precipitation CALCULATION DAVIES equations, OUTPUT Precipitation phase Solutions November, 2010, Bulgaria

  8. RESULTS ACP precipitation Compositions of the initial precipitated solid phase Mg Na KCl Ca/PO4 mmol/g 0.13 0.20 0.450.03 1.51 Enamel, Dentin and Bone 0.02 - 0.29 0.22 - 0.392.10-4 - 0.020.03 – 0.11.6–1.7 XRD powder data and IR spectra November, 2010, Bulgaria

  9. RESULTS ACP precipitation Formation of Posner clusters Ca9(PO4)6 covered with hydrated shell CO32- ions from the solution compete with and partially replace the PO43- ions RESULT  Ca vacancies Ca vacancies could be occupied by free Na+, K+ and Mg2+ ionsfrom the solution RESULT CawMgxNayKz(PO4)v(CO3)6v November, 2010, Bulgaria

  10. RESULTS ACP precipitation Thermodynamic calculated saturated indices (SI) SI = lg(IAP/K) where IAP is an ion activity product, and K is a solubility product. November, 2010, Bulgaria

  11. SUMMARY ACP precipitation • Ionic substitution • Co-precipitation • Incorporation of maternal solution • LEAD TO • precipitation of calcium deficient, X-ray amorphous phosphate • mineral composition similar to those in the hard tissues (enamel, dentin, and bone mineral) November, 2010, Bulgaria

  12. EXPERIMENTS BIOMIMETIC TRANSFORMATION • Conditions • SBFc, SBFr, SBFg (~SBFc + Glycine) • 37oC, pH 7.3; • Static regime; Solid/liquid ratio 4 g/l ; • Duration – 1, 2, 4, 6, 24 h, 3, 10, 30 days; • SBF solution changes - after 3-rd day SBF November, 2010, Bulgaria

  13. RESULTS ACP transformation KINETIC STUDIES PO43- Ca2+ Mg2+ Kinetic profile of PO43-, Ca2+ and Mg2+ contents in liquid phases after different maturation times November, 2010, Bulgaria

  14. RESULTS ACP transformation KINETIC STUDIES Ca/PO4 Mg/Ca Kinetic profile of Ca/PO4 and Mg/Ca ratios in solid phases after different maturation times November, 2010, Bulgaria

  15. RESULTS ACP transformation XRD STUDIES XRD powder data of solid phases after different maturation times November, 2010, Bulgaria

  16. RESULTS RESULTS ACP transformation ACP transformation THERMODYNAMIC STUDIES Calculated saturated indices (SI) M(m) - - - 0 0 M(eq) - - - - - - - 0 Pr Mg(OH)2+ Mg3(PO4)2.8H2O + MgCO3.Mg(OH)2.3H2O + CaCO3+ Ca3(PO4)2(am) + Ca8H2(PO4)6.5H2O + Ca9Mg(HPO4)(PO4)6+ Ca10(PO4)6(OH)2+ November, 2010, Bulgaria

  17. SUMMARY ACP transformation ACP transformation ACP transforms into poorly crystalline apatite in the studied SBFs microenvironments. The SBF composition influences the rate of polymorphous phase transformation. Both HCO3- ions and Glycineaccelerate the transformation rates but the effect is more pronounced by SBF with Glycine The phase transformations leaded to changes in the chemical compositions of solid and liquid phases. Thermodynamic simulations reveal that these phenomena could be explained by the processes of dissolution/crystallization/co-crystallization/ion-exchange. November, 2010, Bulgaria

  18. RESULTS Preparation of bi-phase products XRD analysis of the calcinated at 600oC precursor 47.2 wt. % Mg-substituted -TCP and 52.8 wt. % HA 18.1 wt. % Mg-substituted -TCP and 81.9 wt. % HA November, 2010, Bulgaria

  19. BIOMIMETIC APPROACH FOR PREPARATION OF MODIFIED CALCIUM PHOSPHATES • precursor precipitation in SBF; • precursor maturation in SBF; • calcination of the maturated samples at 600oC.

  20. Thank you for your attention

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