scholarly journals Extrusion-Based 3D Printing of Calcium Magnesium Phosphate Cement Pastes for Degradable Bone Implants

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5197
Author(s):  
Lisa-Marie Götz ◽  
Katharina Holeczek ◽  
Jürgen Groll ◽  
Tomasz Jüngst ◽  
Uwe Gbureck
Keyword(s):  
Structural Changes ◽  
Mechanical Performance ◽  
Ageing Time ◽  
Ammonium Phosphate ◽  
Magnesium Phosphate ◽  
Porous Scaffolds ◽  
Phosphate Solution ◽  
Extrusion Force ◽  
Cement Pastes ◽  
Calcium Magnesium

This study aimed to develop printable calcium magnesium phosphate pastes that harden by immersion in ammonium phosphate solution post-printing. Besides the main mineral compound, biocompatible ceramic, magnesium oxide and hydroxypropylmethylcellulose (HPMC) were the crucial components. Two pastes with different powder to liquid ratios of 1.35 g/mL and 1.93 g/mL were characterized regarding their rheological properties. Here, ageing over the course of 24 h showed an increase in viscosity and extrusion force, which was attributed to structural changes in HPMC as well as the formation of magnesium hydroxide by hydration of MgO. The pastes enabled printing of porous scaffolds with good dimensional stability and enabled a setting reaction to struvite when immersed in ammonium phosphate solution. Mechanical performance under compression was approx. 8–20 MPa as a monolithic structure and 1.6–3.0 MPa for printed macroporous scaffolds, depending on parameters such as powder to liquid ratio, ageing time, strand thickness and distance.

Structural Optimization of Macroporous Magnesium Phosphate Scaffolds and their Cytocompatibility

2011 ◽  
Vol 493-494 ◽  
pp. 813-819 ◽  
Author(s):  
Andrea Ewald ◽  
Bernhard Lochner ◽  
Uwe Gbureck ◽  
Jürgen Groll ◽  
Reinhard Krüger
Keyword(s):  
Compressive Strength ◽  
Mechanical Performance ◽  
Cell Activity ◽  
Ammonium Phosphate ◽  
Cell Number ◽  
Phosphate Solution ◽  
Pu Foam ◽  
Repair Mechanisms ◽  
Sample Characterization ◽  
Polymer Infiltration

Mg-phosphate ceramics have aroused growing interest as bone replacement materials due to their ability to degrade under physiological conditions. To mimic cancelous bone and to promote tissue repair mechanisms a highly macroporous structure with open cells is desired. In this study trimagnesium phosphate (farringtonite, Mg3(PO4)2) and struvite ((NH4)Mg(PO4)·6H2O) scaffolds were developed as open cell foams using the Schwarzwalder-Somers technique and optimized for pore size and mechanical performance. Polyurethane (PU) foam (20-80 ppi) was used as a template. For the optimization of the farringtonite scaffolds, ppi number of the PU foam as well as the technique that was used to remove excess slurry were varied. Sample characterization was done by SEM, XRD and compression testing. For best results were obtained using 60 ppi PU foams leading to a compressive strength of 58 kPa (90 % porosity). Farringtonite scaffolds were modified by either polymer infiltration or transformation into struvite with an ammonium phosphate solution. The pore macrostructure was retained for both of these processes and a reduction of porosity was observed. The microstructure of struvite foams was significantly altered showing larger and more facetted crystals than farringtonite. Mechanical properties substantially improved by transformation into struvite to 730 kPa (68 % porosity). Cytocompatibility was tested using osteoblasts and fibroblasts. Cell number and cell activity (WST) were tested over a period of 3 to 13 days. Farringtonite foams showed a tendency for higher cell numbers than struvite, while the WST activity was similar. Infiltration of farringtonite with PLGA approximately doubled cell number compared to pure farringtonite. In conclusion macroporous Mg-phosphate foams have been successfully produced. Compressive strength of the foams was drastically improved by optimization of pore fineness, transformation to struvite and infiltration with PLGA. The open porous structure was retained and the materials showed good cytocompatibility.

The Hydration of Magnesium Phosphate Cements: Effect of Powder Characteristics on the Reaction Kinetics

2008 ◽  
Vol 591-593 ◽  
pp. 833-838 ◽  
Author(s):  
M. Arlete Carvalho ◽  
Ana M. Segadães
Keyword(s):  
Room Temperature ◽  
Setting Time ◽  
Ammonium Phosphate ◽  
Mineralogical Composition ◽  
Magnesium Phosphate ◽  
Water Addition ◽  
Cement Pastes ◽  
Powder Characteristics ◽  
Magnesia Powder ◽  
Cold Setting

The setting reaction of magnesium phosphate cements starts with water addition to a mixture of ammonium phosphate and magnesium oxide, is very fast and takes place at room temperature (cold setting). Literature shows that controversy is still going on about the reaction mechanism, hence, about the effect on the setting time of factors such as the water/cement ratio or the magnesia specific surface area. This work is focused on the magnesia powder characteristics, which were varied by calcining MgO at temperatures ranging from 900 to 1050°C, for periods of 30 to 60 min. Cement pastes were obtained by mixing MgO and diammonium phosphate with water and setting aids. The pastes were left to set in air and were characterized in terms of mineralogical composition (XRD) and microstructure (SEM). The results obtained show how the combined effect of the magnesia characteristics can be used to control the workability and adjust the setting time.

Phase composition, mechanical performance and in vitro biocompatibility of hydraulic setting calcium magnesium phosphate cement

2010 ◽  
Vol 6 (4) ◽  
pp. 1529-1535 ◽  
Author(s):  
Uwe Klammert ◽  
Tobias Reuther ◽  
Melanie Blank ◽  
Isabelle Reske ◽  
Jake E. Barralet ◽  
...  
Keyword(s):  
Phase Composition ◽  
Mechanical Performance ◽  
Magnesium Phosphate ◽  
In Vitro Biocompatibility ◽  
Calcium Magnesium

scholarly journals In-Vivo Degradation Behavior and Osseointegration of 3D Powder-Printed Calcium Magnesium Phosphate Cement Scaffolds

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 946
Author(s):  
Katharina Kowalewicz ◽  
Elke Vorndran ◽  
Franziska Feichtner ◽  
Anja-Christina Waselau ◽  
Manuel Brueckner ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Bone Substitutes ◽  
Magnesium Phosphate ◽  
Degradation Behavior ◽  
Micro Computed Tomography ◽  
Calcium Magnesium ◽  
Interest In Research ◽  
In Vivo Degradation ◽  
Volume Decrease

Calcium magnesium phosphate cements (CMPCs) are promising bone substitutes and experience great interest in research. Therefore, in-vivo degradation behavior, osseointegration and biocompatibility of three-dimensional (3D) powder-printed CMPC scaffolds were investigated in the present study. The materials Mg225 (Ca0.75Mg2.25(PO4)2) and Mg225d (Mg225 treated with diammonium hydrogen phosphate (DAHP)) were implanted as cylindrical scaffolds (h = 5 mm, Ø = 3.8 mm) in both lateral femoral condyles in rabbits and compared with tricalcium phosphate (TCP). Treatment with DAHP results in the precipitation of struvite, thus reducing pore size and overall porosity and increasing pressure stability. Over 6 weeks, the scaffolds were evaluated clinically, radiologically, with Micro-Computed Tomography (µCT) and histological examinations. All scaffolds showed excellent biocompatibility. X-ray and in-vivo µCT examinations showed a volume decrease and increasing osseointegration over time. Structure loss and volume decrease were most evident in Mg225. Histologically, all scaffolds degraded centripetally and were completely traversed by new bone, in which the remaining scaffold material was embedded. While after 6 weeks, Mg225d and TCP were still visible as a network, only individual particles of Mg225 were present. Based on these results, Mg225 and Mg225d appear to be promising bone substitutes for various loading situations that should be investigated further.

Effect of microcrystalline cellulose on geopolymer and Portland cement pastes mechanical performance

2021 ◽  
Vol 288 ◽  
pp. 123053
Author(s):  
Saulo Rocha Ferreira ◽  
Neven Ukrainczyk ◽  
Keoma Defáveri do Carmo e Silva ◽  
Luiz Eduardo Silva ◽  
Eduardo Koenders
Keyword(s):  
Portland Cement ◽  
Microcrystalline Cellulose ◽  
Mechanical Performance ◽  
Cement Pastes

Improvement of Oxidation Resistance of Graphite Powder Treated with Phosphate

2007 ◽  
Vol 352 ◽  
pp. 133-136 ◽  
Author(s):  
Katsumi Yoshida ◽  
Hideki Hyuga ◽  
Naoki Kondo ◽  
Hideki Kita
Keyword(s):  
Oxidation Resistance ◽  
Graphite Powder ◽  
Magnesium Phosphate ◽  
Phosphate Solution ◽  
Lanthanum Phosphate ◽  
Magnesium Phosphates

Graphite powder was treated with lanthanum, aluminum and magnesium phosphate solution, and oxidation resistance of the obtained graphite powder was evaluated. Oxidation starting temperature and oxidation completion temperature of graphite powder treated with various phosphates were 50-100oC higher than those of as-received graphite powder. Graphite powder treated with small amount of lanthanum phosphate exhibited the higher oxidation starting temperature than graphite powder treated with aluminum and magnesium phosphates. LaP5O14 would partially exited on graphite powder, and protect the edge carbon atoms of graphite and reduce the reactivity of carbon atoms toward oxygen, resulting in improving the oxidation resistance.

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