Effect of Natural Calcium Phosphate upon the Properties of Apatite-Wollastonite Glass Ceramics PhD Thesis

Transcription

1 University of Pannonia Doctoral School of Chemical Engineering and Materials Science Effect of Natural Calcium Phosphate upon the Properties of Apatite-Wollastonite Glass Ceramics PhD Thesis Prepared by: Annamária Dobrádi Materials Engineer (MSc) Supervisor: Margit Enisz-Bódogh Associate Professor (PhD) University of Pannonia Faculty of Engineering Institute of Materials Engineering 2018

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3 1. INTRODUCTION AND AIM OF RESEARCH The most frequently used biomaterial is hydroxyapatite, which is the main mineral constituent of human bones. Most important feature of calcium phosphate based biomaterials is the ability to build up a direct binding to living bones, therefore they can be used for bone replacement. Clinical applications are limited by their low mechanical strength. However this disadvantage is eliminated by preparing glass ceramics simultaneously containing crystalline apatite and wollastonite phases. Bioactivity of glass ceramics is influenced primarily by the chemical composition of the glass matrix, amount of crystalline hydroxyapatite and β-whitlockite phases, the Ca/P atomic ratio, their distribution, and grain size. Wollastonite accompanying crystalline calcium phosphate phases both promotes the controlled crystallization of apatite, and enhances mechanical properties through its fibrous structure. Hence these products are suitable also for the replacement of load bearing bones. Most of the calcium phosphate based biomaterials are produced from hydroxyapatite obtained by wet chemical process (co-precipitation), as well from β-whitlockite, and there are very few publications dealing with the application of natural calcium phosphates obtained from heat treated animal bones. The advantage of animal bones lies in their composition: they contain all main and trace elements of human bones in the required quantity, ratio, and distribution. Aim of research is the preparation of bioactive glass ceramics and glass ceramics coatings in which a certain part of calcium and phosphor containing components were added by pre-treated and powdered animal bones. Implants incorporating effectively into the human body were prepared from animal bones having similar chemical composition and structure to the human bones, and quality of these implants can easily be fitted to the requirements. Additional advantage is the transformation of wastes into high tech ceramics. 1

4 2. EXPERIMENTAL Although the hydroxyapatite obtained by wet chemical synthesis is highly pure, the process is expensive. Therefore alternative raw materials were searched for to replace the artificial hydroxyapatite. It is obvious to consider pre-treated animal bones as a replacement, for they contain optimum amount and ratio of all main constituents and trace elements. Biomaterials of different compositions were prepared by heat treating of animal bones. The obtained materials contain various amounts of hydroxyapatite, α- and β-whitlockite. Bioactivity of glass ceramics can be controlled by the amount and ratio of these calcium phosphate compounds. Bioactive phase of bio-glass ceramics is usually produced by heat controlled crystallization. In addition to controlled crystallization obtained by heat treatment, biomaterials produced from animal bones were also added to the mixtures, so eight bioactive glass ceramics of different compositions were produced. Phase composition, morphology, bulk density, and porosity of ceramics were always tested. Bioactivity was determined by simulated body fluid treatment of glass ceramics. Mechanical properties were characterized by the measurement of Vickers microhardness, bending strength, and compressive strength. Out of the eight, two compositions were selected by their bioactivity, and these were plasma sprayed onto the surface of metal and ceramic substrates. Phase composition, morphology, porosity, and bioactivity of these coatings were tested the same way as the bulk. Coating thickness and substrate coating boundary were also investigated. 2

5 3. NEW SCIENTIFIC RESULTS 1.) Two- and multiphase biomaterials were produced from natural raw materials. Besides of an amorphous phase, the pre-treated, protein-free animal bone contains mainly hydroxyapatite (77.83 wt%), and less amount of carbonate-hydroxyapatite (3.77 wt%). A material containing higher amount (71.6 wt%) β-whitlockite and less (1.8 wt%) hydroxyapatite is obtained at 965 C, which is higher than the temperature required by the artificial hydroxyapatite ( C). Moreover a material containing higher amount (33.8 wt%) of α-whitlockite is obtained from animal bones at a heat treatment of even higher temperature (1430 C) and rapid cooling. 2.) Similarly to the hydroxyapatite obtained by wet chemical synthesis, the amorphous, poorly crystallized hydroxyapatite of animal bones will also crystallize when heated to about 400 C. 3.) Porosity of glass ceramics is strongly influenced by the grain size and quantity of additives, while the phase composition of additives has less effect to the porosity. Most significant decrease of porosity is obtained by increasing the temperature of heat treatment. Zero porosity products are obtained by an 1100 C sintering of glass ceramics produced from pretreated or sintered animal bones. 4.) Solubility as well as time dependent changes of solubility of hydroxyapatite obtained by wet chemical synthesis are lower, than the solubility of animal bone additives. Amount of calcium dissolved from samples after 21 days submersion into simulated body fluids is decreasing as a function of sintering temperature (decreasing porosity). 3

6 5.) Sintering of pre-treated (PTB) and sintered (SBB) animal bone additives containing samples at C temperature produces bioceramics having the usual dissolution rate. However the additives containing α- whitlockite (HTSBB) give faster dissolving biomaterials. 6.) In line with the hydroxyapatite containing samples, simulated body fluid treatment of the SBB additive containing mainly β-whitlockite results in an apatite formation of higher particle size and wider size distribution on the surface. Smaller and nearly uniform sized apatite particles are formed on the new surface layer of α-whitlockite containing HTSBB additive. In contrast to the alpha phase, this observation confirms a higher crystallization rate of newly formed apatite from β-whitlockite. 7.) The thin apatite layer being formed during the SBF-treatment decreases the Vickers micro-hardness of glass ceramics. The highest decrease is observed at the lowest formation rate, fine grained apatite layer. Due to the dissolution, hardness of glass matrix under the apatite layer will also slightly decrease. 8.) Strength of glass ceramics can be controlled by the additives and the sintering temperature. Higher mechanical strength is obtained by increasing the sintering temperature. Flexural strength of near-zero porosity glass ceramics containing SBB (6/1100 C, MPa) and HTSBB (8/1100 C, MPa) is similar to the dense bones, and it is much higher than the respective values of traditional bioceramics. Bending strength of these samples is almost two times higher as compared to additive-free samples sintered at identical temperatures (41.41 MPa). 4

7 9.) Plasma spraying of bio-glass ceramics containing animal bone additives onto the surface of titanium alloy and stainless steel substrates result in layers of good adhesion, appropriate porosity, and strength. Bioactivity of these layers is almost identical to the bulk materials. 5

8 4. PUBLICATIONS IN THE FIELD OF THE PhD THESIS 4.1. Core publications from the PhD thesis work Publications in international periodicals: 1. Dobrádi, A., Enisz-Bódogh, M., Kovács, K., Balczár I. (2015) Structure and properties of bio-glass ceramics containing natural bones, Ceramics International Dobrádi, A., Enisz-Bódogh, M., Kovács, K., Korim, T. (2016) Biodegradation of bioactive glass ceramics containing natural calcium phosphates, Ceramics International 42, Dobrádi, A., Enisz-Bódogh, M., Kovács, K. (2017) Plasma Spraying of Bioactive Glass Ceramics Containing Bovine Bone, Processing and Application of Ceramics 11 [2] Conference lectures in Hungarian with printed abstracts: 4. Dobrádi, A., Eniszné, B. M. (2014) Kalcium-foszfát tartalmú bioaktív üvegkerámiák előállítása és vizsgálata, Műszaki Kémiai Napok, Veszprém, május Dobrádi, A., Eniszné, B. M. (2014) Természetes eredetű kalcium-foszfát bioanyagok biodegradációja, PhD hallgatók anyagtudományi napja XIV. Veszprém, november Dobrádi, A., Eniszné, B. M. (2015) Természetes eredetű kalcium-foszfát adalék hatása az apatit-wollastonit üvegkerámiák tulajdonságaira, Áthidaló PhD ösztöndíj: Az anyag tulajdonságaitól a felhasználásig természetes alapanyagok és hulladékok hasznosítását megalapozó kutatások Veszprém, február Dobrádi, A., Eniszné, B. M. (2015) Állati csontból nyert Ca-foszfát tartalmú bioanyagok vizsgálata, PhD hallgatók anyagtudományi napja XV. Veszprém, november 16. 6

9 Conference lectures in Hungarian: 8. Dobrádi, A., Eniszné, B. M. (2015) Állati csont adalék hatása bioüvegkerámiák tervezett tulajdonságaira, Üvegipari szakmai konferencia, Veszprém, április Dobrádi, A., Eniszné, B. M. (2016) Természetes eredetű Ca-foszfát adalék a bio-üvegkerámiák tulajdonságaira, Üvegipari szakmai konferencia, Budapest, november 15. Posters and short oral presentations in English: 10. Dobrádi, A., Enisz-Bódogh, M. (2014) The production of bioactive glass ceramics containing synthetic and natural calcium phosphates, Junior EuroMat2014, Switzerland, Lausanne, July Dobrádi, A., Enisz-Bódogh, M., Kovács, K. (2016) Bioactive glass ceramics from animal bones, 91st DKG Annual Meeting and Symposium on High-Performance Ceramic, Germany, Freiberg March English language posters: 12. Dobrádi, A., Enisz-Bódogh, M., Kovács, K. (2014) Bioactive materials manufactured from natural calcium phosphates, Cimtec th International Conference on Modern Materials and Technologies, Italy, Montecatini Terme, June Dobrádi, A., Enisz-Bódogh, M., Kovács, K. (2015) Investigation of bioglass-ceramics containing natural bones, EuroBioMat2015 Germany, Weimar April Dobrádi, A., Kovács, K. (2015) Microstructure of animal-bone derived hydroxyapatite, MCM 2015, Hungary, Eger August Dobrádi, A., Enisz-Bódogh, M., Kovács, K. (2016) Bioactive glass ceramics from natural calcium phosphates, 4th International conference on competitive materials and technology processes, Hungary, Lillafüred October Dobrádi, A., Enisz-Bódogh, M., Kovács, K. (2017) Microstructure and Properties of Plasma Sprayed Bioactive Glass Ceramics Coatings, EuroBioMat2017, Germany, Weimar May

10 17. Dobrádi, A., Enisz-Bódogh, M., Kovács, K. (2017) Microstructure of Bone Derived Bioactive Glass Ceramics Coatings, SCGC 2017 Slovak and Czech Glass Conference & Seminar on Defects in Glass, Slovak Republic, Trencsén Teplice June Dobrádi, A., Enisz-Bódogh, M., Kovács, K. (2017) Microstructure and properties of bioactive glass-ceramics. 15th Conference & Exhibition of the European Ceramic Society (EcerS2017), Hungary, Budapest, July Dobrádi, A., Enisz-Bódogh, M., Kovács, K. (2017) Microstructure of plasma sprayed bioactive coatings. 13th Multinational Congress on Microscopy, Croatia, Rovinj August Hungarian language posters: 20. Dobrádi, A., Eniszné, B. M., Kovács, K. (2015) Hidroxiapatit tartalmú biokerámiák előállítása állati csontból, X. Országos Anyagtudományi Konferencia, Balatonalmádi, október

11 4.2. Related publications from the PhD thesis work Posters and short oral presentations in English: 21. Dobrádi, A., Enisz-Bódogh, M. (2013) Investigation of Calcium Phosphates obtained from animal bones for production of bioactive glass ceramics, ICMSE 2013: International Conference on Materials Science and Engineering, Netherlands, Amsterdam, May Hungarian language posters: 22. Dobrádi, A., Eniszné, B. M. (2013) Állati csontból nyert Ca-foszfátok bioaktív üvegkerámiák gyártásánál való felhasználhatósága, IX. Országos Anyagtudományi Konferencia, Balatonkenese, október