Additive Manufacturing of 3-Dimensional Bioceramic Structures Elaborated By Calcium Phosphate Cement Reactions

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2022-7-26

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Sever, Hüseyin Engin

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Calcium phosphate cements (CPCs) are clinically used in bone related surgical operations for irregular defect filling operations. The cement nature also enables them to be used in additive manufacturing to produce bioceramic structures with irregular shapes and scaffolds with specific geometry, shape and macroporosity, as explored in this thesis. In this study, first a CPC cement precursor, α-tricalcium phosphate (α-TCP or α-Ca3(PO4)2), is synthesized by using two different powder mixtures of CaHPO4:CaCO3 and Ca2P2O7:CaCO3, respectively. The end-product of second mixture found to be more reactive for cement conversion. The cement conversion here implies conversion of α-TCP to biological bone mineral-like phase calcium deficient hydroxyapatite (CDHAp or Ca9(PO4)(HPO4)(OH)) upon water uptake. The synthesized α-TCP powder are combined with two different binder liquid solutions (Pluronic F127:water and sodium Alginate:water) to obtain injectable cement paste. It is observed that α-TCP:Pluronic F127:Water mixture showed better injectability and provided good integrity upon injecting. α-TCP-based and/or hybrid cement pastes were prepared by blending a-TCP:calcium sulfate Hemihydrate (Plaster of Paris, CSH or CaSO4 · 1/2 H2O) and hydration (cement conversion) behavior of those mixtures were examined thoroughly. It is shown that CSH addition delayed hydration of α-TCP. Taking into consideration of preliminary experiments, optimized cement pastes were implemented on Direct-Ink Writing 3D printing process. Scaffolds with different solid compositions (TCP:CSH) were successfully fabricated. As it was expected, addition of CSH did not improve the strength of the scaffolds, however it enabled controlling microporosity for the printed constructs due to dissolution of calcium sulfate phases during cement hydration. The results of this can be expanded to print any irregular shaped CDHAp, by combining CAD-supported 3D.

Subject Keywords

Calcium Phosphate Cement, 3D Printing, Bioceramic Scaffold, Setting Reaction, Injectability of Cements

URI

https://hdl.handle.net/11511/98696

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

H. E. Sever, “Additive Manufacturing of 3-Dimensional Bioceramic Structures Elaborated By Calcium Phosphate Cement Reactions,” M.S. - Master of Science, Middle East Technical University, 2022.