Biocompatible Ceramics for Implants Based on Calcium Phosphates
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0951-E12-31
Biocompatible Ceramics for Implants Based on Calcium Phosphates Tatiana V. Safronova1, Valery I. Putlayev1, Alexander G. Veresov2, Anton V. Kuznetsov2, Mikhail A. Shekhirev2, and Kamila A. Agahi3 1 Department of Chemistry, MSU, Leninskie Gory, 1/3, Moscow, 119992, Russian Federation 2 Department of materials science, MSU, Leninskie Gory, 1, Moscow, 119992, Russian Federation 3 Institute of Mechanics, MSU, Leninskie Gory, 1, Moscow, 119992, Russian Federation
ABSTRACT The biocompatible ceramics containing calcium pyrophosphate Ca2P2O7 (β-CPP), as biodegradation phase, has been studied. The data concerning the effect of HAp/monetite (or, CPP) mixture composition on powder compaction and subsequent sintering are presented. The influence of various parameters in microstructure of ceramic composites (HAp/Ca2P2O7 (βCPP)) is discussed. Ceramic materials have been made from mixtures of stoihiometric hydroxyapatite (Hap) powders (Ca/P=1.67) and monetite (CaHPO4, Ca/P=1). Powders of nanosized HAp and monetite were synthesized by means of wet precipitation from aqueous solutions of Ca(NO3)2*4H2O and (NH4)2HPO4 at 60oC and pH=9 for HAp and pH=4-5 for monetite. Component ratio HAp:monetite was varied from 0:100 to 100:0 % with a step of 20% to adjust the level of bioresorption. Powders of raw materials and their mixtures were tested by means of XRD, TG, DTG, SEM, dilatometry. Linear shrinkage, density and microstructure of samples of the ceramics sintered in isothermal conditions at 900, 1000, 1100ûC with the time of holding up to 6 hours were tested. Complicated consequence of phase transformations were established when the mixtures were heated from 20 to 1200oC. The CPP (Ca/P=1, converted from CaHPO4 at 400-500ûC ) reacts with HAp (Ca/P=1.67) and causes an additional weight loss in the region of 600-1050ûC due to solid state reaction leading to tricalcium phosphate (TCP, Ca/P=1.5) formation. Linear shrinkage of HAp compacts at 1100ûC after 6 hours was found to be about 21%; while for Ca2P2O7 formed from monetite, and for the other mixtures - less than 11%. The fabricated ceramics with the phase composition of HAp, CPP and TCP, i.e. with a different content of a degradable phase and different ratio of CPP/TCP, can be treated as a biocompatible bioactive material with a tunable rate and limit of biodegradation. INTRODUCTION Biocompatible ceramics based on calcium phosphates are known to be a prospective material for biomedical applications. HAp (Ca10(PO4)6(OH)2), TCP (Ca3(PO4)2) and CPP are used in clinical medicine due to their biocompatibility [1]. The materials consisted of 100 % phase of HAp have got the highest bioresistance among calcium phosphates. To control the level of biodegradability, the materials should consist of both stable HAp phase and bioresorbable phase. TCP based ceramics or glasses in systems CaO-P2O5-M2O and CaO-P2O5-SiO2-M2O, where М=Na, R [2] are the most studied materials among bioresorbable ones. To the best our
knowledge ceramic composites containing CPP is not under intensive consider
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